RFC 3986 Uniform Resource Identifier (URI): Generic Syntax

From aa9051108ed042b0acc138d2aea37a0a3e51610a Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?J=C3=B6rg=20Frings-F=C3=BCrst?= Date: Sat, 13 Jul 2019 18:04:58 +0200 Subject: Remove rfc files --- doc/rfc3986.htm | 3539 ------------------------------------------------------- 1 file changed, 3539 deletions(-) delete mode 100644 doc/rfc3986.htm (limited to 'doc/rfc3986.htm') diff --git a/doc/rfc3986.htm b/doc/rfc3986.htm deleted file mode 100644 index b392007..0000000 --- a/doc/rfc3986.htm +++ /dev/null @@ -1,3539 +0,0 @@ - - - - - - - - - RFC 3986 Uniform Resource Identifier (URI): Generic Syntax - - - - - -
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-[RFCs/IDs] [Plain Text] [From draft-fielding-uri-rfc2396bis]
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- STANDARD
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Network Working Group                                     T. Berners-Lee
-Request for Comments: 3986                                       W3C/MIT
-STD: 66                                                      R. Fielding
-Updates: 1738                                               Day Software
-Obsoletes: 2732, 2396, 1808                                  L. Masinter
-Category: Standards Track                                  Adobe Systems
-                                                            January 2005
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-           Uniform Resource Identifier (URI): Generic Syntax
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-Status of This Memo
-
-   This document specifies an Internet standards track protocol for the
-   Internet community, and requests discussion and suggestions for
-   improvements.  Please refer to the current edition of the "Internet
-   Official Protocol Standards" (STD 1) for the standardization state
-   and status of this protocol.  Distribution of this memo is unlimited.
-
-Copyright Notice
-
-   Copyright (C) The Internet Society (2005).
-
-Abstract
-
-   A Uniform Resource Identifier (URI) is a compact sequence of
-   characters that identifies an abstract or physical resource.  This
-   specification defines the generic URI syntax and a process for
-   resolving URI references that might be in relative form, along with
-   guidelines and security considerations for the use of URIs on the
-   Internet.  The URI syntax defines a grammar that is a superset of all
-   valid URIs, allowing an implementation to parse the common components
-   of a URI reference without knowing the scheme-specific requirements
-   of every possible identifier.  This specification does not define a
-   generative grammar for URIs; that task is performed by the individual
-   specifications of each URI scheme.
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-Berners-Lee, et al.         Standards Track                     [Page 1]
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-RFC 3986                   URI Generic Syntax               January 2005
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-Table of Contents
-
-   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
-       1.1.  Overview of URIs . . . . . . . . . . . . . . . . . . . .  4
-             1.1.1.  Generic Syntax . . . . . . . . . . . . . . . . .  6
-             1.1.2.  Examples . . . . . . . . . . . . . . . . . . . .  7
-             1.1.3.  URI, URL, and URN  . . . . . . . . . . . . . . .  7
-       1.2.  Design Considerations  . . . . . . . . . . . . . . . . .  8
-             1.2.1.  Transcription  . . . . . . . . . . . . . . . . .  8
-             1.2.2.  Separating Identification from Interaction . . .  9
-             1.2.3.  Hierarchical Identifiers . . . . . . . . . . . . 10
-       1.3.  Syntax Notation  . . . . . . . . . . . . . . . . . . . . 11
-   2.  Characters . . . . . . . . . . . . . . . . . . . . . . . . . . 11
-       2.1.  Percent-Encoding . . . . . . . . . . . . . . . . . . . . 12
-       2.2.  Reserved Characters  . . . . . . . . . . . . . . . . . . 12
-       2.3.  Unreserved Characters  . . . . . . . . . . . . . . . . . 13
-       2.4.  When to Encode or Decode . . . . . . . . . . . . . . . . 14
-       2.5.  Identifying Data . . . . . . . . . . . . . . . . . . . . 14
-   3.  Syntax Components  . . . . . . . . . . . . . . . . . . . . . . 16
-       3.1.  Scheme . . . . . . . . . . . . . . . . . . . . . . . . . 17
-       3.2.  Authority  . . . . . . . . . . . . . . . . . . . . . . . 17
-             3.2.1.  User Information . . . . . . . . . . . . . . . . 18
-             3.2.2.  Host . . . . . . . . . . . . . . . . . . . . . . 18
-             3.2.3.  Port . . . . . . . . . . . . . . . . . . . . . . 22
-       3.3.  Path . . . . . . . . . . . . . . . . . . . . . . . . . . 22
-       3.4.  Query  . . . . . . . . . . . . . . . . . . . . . . . . . 23
-       3.5.  Fragment . . . . . . . . . . . . . . . . . . . . . . . . 24
-   4.  Usage  . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
-       4.1.  URI Reference  . . . . . . . . . . . . . . . . . . . . . 25
-       4.2.  Relative Reference . . . . . . . . . . . . . . . . . . . 26
-       4.3.  Absolute URI . . . . . . . . . . . . . . . . . . . . . . 27
-       4.4.  Same-Document Reference  . . . . . . . . . . . . . . . . 27
-       4.5.  Suffix Reference . . . . . . . . . . . . . . . . . . . . 27
-   5.  Reference Resolution . . . . . . . . . . . . . . . . . . . . . 28
-       5.1.  Establishing a Base URI  . . . . . . . . . . . . . . . . 28
-             5.1.1.  Base URI Embedded in Content . . . . . . . . . . 29
-             5.1.2.  Base URI from the Encapsulating Entity . . . . . 29
-             5.1.3.  Base URI from the Retrieval URI  . . . . . . . . 30
-             5.1.4.  Default Base URI . . . . . . . . . . . . . . . . 30
-       5.2.  Relative Resolution  . . . . . . . . . . . . . . . . . . 30
-             5.2.1.  Pre-parse the Base URI . . . . . . . . . . . . . 31
-             5.2.2.  Transform References . . . . . . . . . . . . . . 31
-             5.2.3.  Merge Paths  . . . . . . . . . . . . . . . . . . 32
-             5.2.4.  Remove Dot Segments  . . . . . . . . . . . . . . 33
-       5.3.  Component Recomposition  . . . . . . . . . . . . . . . . 35
-       5.4.  Reference Resolution Examples  . . . . . . . . . . . . . 35
-             5.4.1.  Normal Examples  . . . . . . . . . . . . . . . . 36
-             5.4.2.  Abnormal Examples  . . . . . . . . . . . . . . . 36
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-RFC 3986                   URI Generic Syntax               January 2005
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-   6.  Normalization and Comparison . . . . . . . . . . . . . . . . . 38
-       6.1.  Equivalence  . . . . . . . . . . . . . . . . . . . . . . 38
-       6.2.  Comparison Ladder  . . . . . . . . . . . . . . . . . . . 39
-             6.2.1.  Simple String Comparison . . . . . . . . . . . . 39
-             6.2.2.  Syntax-Based Normalization . . . . . . . . . . . 40
-             6.2.3.  Scheme-Based Normalization . . . . . . . . . . . 41
-             6.2.4.  Protocol-Based Normalization . . . . . . . . . . 42
-   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 43
-       7.1.  Reliability and Consistency  . . . . . . . . . . . . . . 43
-       7.2.  Malicious Construction . . . . . . . . . . . . . . . . . 43
-       7.3.  Back-End Transcoding . . . . . . . . . . . . . . . . . . 44
-       7.4.  Rare IP Address Formats  . . . . . . . . . . . . . . . . 45
-       7.5.  Sensitive Information  . . . . . . . . . . . . . . . . . 45
-       7.6.  Semantic Attacks . . . . . . . . . . . . . . . . . . . . 45
-   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 46
-   9.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 46
-   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 46
-       10.1. Normative References . . . . . . . . . . . . . . . . . . 46
-       10.2. Informative References . . . . . . . . . . . . . . . . . 47
-   A.  Collected ABNF for URI . . . . . . . . . . . . . . . . . . . . 49
-   B.  Parsing a URI Reference with a Regular Expression  . . . . . . 50
-   C.  Delimiting a URI in Context  . . . . . . . . . . . . . . . . . 51
-   D.  Changes from RFC 2396  . . . . . . . . . . . . . . . . . . . . 53
-       D.1.  Additions  . . . . . . . . . . . . . . . . . . . . . . . 53
-       D.2.  Modifications  . . . . . . . . . . . . . . . . . . . . . 53
-   Index  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
-   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 60
-   Full Copyright Statement . . . . . . . . . . . . . . . . . . . . . 61
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-1.  Introduction
-
-   A Uniform Resource Identifier (URI) provides a simple and extensible
-   means for identifying a resource.  This specification of URI syntax
-   and semantics is derived from concepts introduced by the World Wide
-   Web global information initiative, whose use of these identifiers
-   dates from 1990 and is described in "Universal Resource Identifiers
-   in WWW" [RFC1630].  The syntax is designed to meet the
-   recommendations laid out in "Functional Recommendations for Internet
-   Resource Locators" [RFC1736] and "Functional Requirements for Uniform
-   Resource Names" [RFC1737].
-
-   This document obsoletes [RFC2396], which merged "Uniform Resource
-   Locators" [RFC1738] and "Relative Uniform Resource Locators"
-   [RFC1808] in order to define a single, generic syntax for all URIs.
-   It obsoletes [RFC2732], which introduced syntax for an IPv6 address.
-   It excludes portions of RFC 1738 that defined the specific syntax of
-   individual URI schemes; those portions will be updated as separate
-   documents.  The process for registration of new URI schemes is
-   defined separately by [BCP35].  Advice for designers of new URI
-   schemes can be found in [RFC2718].  All significant changes from RFC
-   2396 are noted in Appendix D.
-
-   This specification uses the terms "character" and "coded character
-   set" in accordance with the definitions provided in [BCP19], and
-   "character encoding" in place of what [BCP19] refers to as a
-   "charset".
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-1.1.  Overview of URIs
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-   URIs are characterized as follows:
-
-   Uniform
-
-      Uniformity provides several benefits.  It allows different types
-      of resource identifiers to be used in the same context, even when
-      the mechanisms used to access those resources may differ.  It
-      allows uniform semantic interpretation of common syntactic
-      conventions across different types of resource identifiers.  It
-      allows introduction of new types of resource identifiers without
-      interfering with the way that existing identifiers are used.  It
-      allows the identifiers to be reused in many different contexts,
-      thus permitting new applications or protocols to leverage a pre-
-      existing, large, and widely used set of resource identifiers.
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-   Resource
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-      This specification does not limit the scope of what might be a
-      resource; rather, the term "resource" is used in a general sense
-      for whatever might be identified by a URI.  Familiar examples
-      include an electronic document, an image, a source of information
-      with a consistent purpose (e.g., "today's weather report for Los
-      Angeles"), a service (e.g., an HTTP-to-SMS gateway), and a
-      collection of other resources.  A resource is not necessarily
-      accessible via the Internet; e.g., human beings, corporations, and
-      bound books in a library can also be resources.  Likewise,
-      abstract concepts can be resources, such as the operators and
-      operands of a mathematical equation, the types of a relationship
-      (e.g., "parent" or "employee"), or numeric values (e.g., zero,
-      one, and infinity).
-
-   Identifier
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-      An identifier embodies the information required to distinguish
-      what is being identified from all other things within its scope of
-      identification.  Our use of the terms "identify" and "identifying"
-      refer to this purpose of distinguishing one resource from all
-      other resources, regardless of how that purpose is accomplished
-      (e.g., by name, address, or context).  These terms should not be
-      mistaken as an assumption that an identifier defines or embodies
-      the identity of what is referenced, though that may be the case
-      for some identifiers.  Nor should it be assumed that a system
-      using URIs will access the resource identified: in many cases,
-      URIs are used to denote resources without any intention that they
-      be accessed.  Likewise, the "one" resource identified might not be
-      singular in nature (e.g., a resource might be a named set or a
-      mapping that varies over time).
-
-   A URI is an identifier consisting of a sequence of characters
-   matching the syntax rule named <URI> in Section 3.  It enables
-   uniform identification of resources via a separately defined
-   extensible set of naming schemes (Section 3.1).  How that
-   identification is accomplished, assigned, or enabled is delegated to
-   each scheme specification.
-
-   This specification does not place any limits on the nature of a
-   resource, the reasons why an application might seek to refer to a
-   resource, or the kinds of systems that might use URIs for the sake of
-   identifying resources.  This specification does not require that a
-   URI persists in identifying the same resource over time, though that
-   is a common goal of all URI schemes.  Nevertheless, nothing in this
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-   specification prevents an application from limiting itself to
-   particular types of resources, or to a subset of URIs that maintains
-   characteristics desired by that application.
-
-   URIs have a global scope and are interpreted consistently regardless
-   of context, though the result of that interpretation may be in
-   relation to the end-user's context.  For example, "http://localhost/"
-   has the same interpretation for every user of that reference, even
-   though the network interface corresponding to "localhost" may be
-   different for each end-user: interpretation is independent of access.
-   However, an action made on the basis of that reference will take
-   place in relation to the end-user's context, which implies that an
-   action intended to refer to a globally unique thing must use a URI
-   that distinguishes that resource from all other things.  URIs that
-   identify in relation to the end-user's local context should only be
-   used when the context itself is a defining aspect of the resource,
-   such as when an on-line help manual refers to a file on the end-
-   user's file system (e.g., "file:///etc/hosts").
-
-1.1.1.  Generic Syntax
-
-   Each URI begins with a scheme name, as defined in Section 3.1, that
-   refers to a specification for assigning identifiers within that
-   scheme.  As such, the URI syntax is a federated and extensible naming
-   system wherein each scheme's specification may further restrict the
-   syntax and semantics of identifiers using that scheme.
-
-   This specification defines those elements of the URI syntax that are
-   required of all URI schemes or are common to many URI schemes.  It
-   thus defines the syntax and semantics needed to implement a scheme-
-   independent parsing mechanism for URI references, by which the
-   scheme-dependent handling of a URI can be postponed until the
-   scheme-dependent semantics are needed.  Likewise, protocols and data
-   formats that make use of URI references can refer to this
-   specification as a definition for the range of syntax allowed for all
-   URIs, including those schemes that have yet to be defined.  This
-   decouples the evolution of identification schemes from the evolution
-   of protocols, data formats, and implementations that make use of
-   URIs.
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-   A parser of the generic URI syntax can parse any URI reference into
-   its major components.  Once the scheme is determined, further
-   scheme-specific parsing can be performed on the components.  In other
-   words, the URI generic syntax is a superset of the syntax of all URI
-   schemes.
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-1.1.2.  Examples
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-   The following example URIs illustrate several URI schemes and
-   variations in their common syntax components:
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-      ftp://ftp.is.co.za/rfc/rfc1808.txt
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-      http://www.ietf.org/rfc/rfc2396.txt
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-      ldap://[2001:db8::7]/c=GB?objectClass?one
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-      mailto:John.Doe@example.com
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-      news:comp.infosystems.www.servers.unix
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-      tel:+1-816-555-1212
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-      telnet://192.0.2.16:80/
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-      urn:oasis:names:specification:docbook:dtd:xml:4.1.2
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-1.1.3.  URI, URL, and URN
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-   A URI can be further classified as a locator, a name, or both.  The
-   term "Uniform Resource Locator" (URL) refers to the subset of URIs
-   that, in addition to identifying a resource, provide a means of
-   locating the resource by describing its primary access mechanism
-   (e.g., its network "location").  The term "Uniform Resource Name"
-   (URN) has been used historically to refer to both URIs under the
-   "urn" scheme [RFC2141], which are required to remain globally unique
-   and persistent even when the resource ceases to exist or becomes
-   unavailable, and to any other URI with the properties of a name.
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-   An individual scheme does not have to be classified as being just one
-   of "name" or "locator".  Instances of URIs from any given scheme may
-   have the characteristics of names or locators or both, often
-   depending on the persistence and care in the assignment of
-   identifiers by the naming authority, rather than on any quality of
-   the scheme.  Future specifications and related documentation should
-   use the general term "URI" rather than the more restrictive terms
-   "URL" and "URN" [RFC3305].
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-1.2.  Design Considerations
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-1.2.1.  Transcription
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-   The URI syntax has been designed with global transcription as one of
-   its main considerations.  A URI is a sequence of characters from a
-   very limited set: the letters of the basic Latin alphabet, digits,
-   and a few special characters.  A URI may be represented in a variety
-   of ways; e.g., ink on paper, pixels on a screen, or a sequence of
-   character encoding octets.  The interpretation of a URI depends only
-   on the characters used and not on how those characters are
-   represented in a network protocol.
-
-   The goal of transcription can be described by a simple scenario.
-   Imagine two colleagues, Sam and Kim, sitting in a pub at an
-   international conference and exchanging research ideas.  Sam asks Kim
-   for a location to get more information, so Kim writes the URI for the
-   research site on a napkin.  Upon returning home, Sam takes out the
-   napkin and types the URI into a computer, which then retrieves the
-   information to which Kim referred.
-
-   There are several design considerations revealed by the scenario:
-
-   o  A URI is a sequence of characters that is not always represented
-      as a sequence of octets.
-
-   o  A URI might be transcribed from a non-network source and thus
-      should consist of characters that are most likely able to be
-      entered into a computer, within the constraints imposed by
-      keyboards (and related input devices) across languages and
-      locales.
-
-   o  A URI often has to be remembered by people, and it is easier for
-      people to remember a URI when it consists of meaningful or
-      familiar components.
-
-   These design considerations are not always in alignment.  For
-   example, it is often the case that the most meaningful name for a URI
-   component would require characters that cannot be typed into some
-   systems.  The ability to transcribe a resource identifier from one
-   medium to another has been considered more important than having a
-   URI consist of the most meaningful of components.
-
-   In local or regional contexts and with improving technology, users
-   might benefit from being able to use a wider range of characters;
-   such use is not defined by this specification.  Percent-encoded
-   octets (Section 2.1) may be used within a URI to represent characters
-   outside the range of the US-ASCII coded character set if this
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-   representation is allowed by the scheme or by the protocol element in
-   which the URI is referenced.  Such a definition should specify the
-   character encoding used to map those characters to octets prior to
-   being percent-encoded for the URI.
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-1.2.2.  Separating Identification from Interaction
-
-   A common misunderstanding of URIs is that they are only used to refer
-   to accessible resources.  The URI itself only provides
-   identification; access to the resource is neither guaranteed nor
-   implied by the presence of a URI.  Instead, any operation associated
-   with a URI reference is defined by the protocol element, data format
-   attribute, or natural language text in which it appears.
-
-   Given a URI, a system may attempt to perform a variety of operations
-   on the resource, as might be characterized by words such as "access",
-   "update", "replace", or "find attributes".  Such operations are
-   defined by the protocols that make use of URIs, not by this
-   specification.  However, we do use a few general terms for describing
-   common operations on URIs.  URI "resolution" is the process of
-   determining an access mechanism and the appropriate parameters
-   necessary to dereference a URI; this resolution may require several
-   iterations.  To use that access mechanism to perform an action on the
-   URI's resource is to "dereference" the URI.
-
-   When URIs are used within information retrieval systems to identify
-   sources of information, the most common form of URI dereference is
-   "retrieval": making use of a URI in order to retrieve a
-   representation of its associated resource.  A "representation" is a
-   sequence of octets, along with representation metadata describing
-   those octets, that constitutes a record of the state of the resource
-   at the time when the representation is generated.  Retrieval is
-   achieved by a process that might include using the URI as a cache key
-   to check for a locally cached representation, resolution of the URI
-   to determine an appropriate access mechanism (if any), and
-   dereference of the URI for the sake of applying a retrieval
-   operation.  Depending on the protocols used to perform the retrieval,
-   additional information might be supplied about the resource (resource
-   metadata) and its relation to other resources.
-
-   URI references in information retrieval systems are designed to be
-   late-binding: the result of an access is generally determined when it
-   is accessed and may vary over time or due to other aspects of the
-   interaction.  These references are created in order to be used in the
-   future: what is being identified is not some specific result that was
-   obtained in the past, but rather some characteristic that is expected
-   to be true for future results.  In such cases, the resource referred
-   to by the URI is actually a sameness of characteristics as observed
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-   over time, perhaps elucidated by additional comments or assertions
-   made by the resource provider.
-
-   Although many URI schemes are named after protocols, this does not
-   imply that use of these URIs will result in access to the resource
-   via the named protocol.  URIs are often used simply for the sake of
-   identification.  Even when a URI is used to retrieve a representation
-   of a resource, that access might be through gateways, proxies,
-   caches, and name resolution services that are independent of the
-   protocol associated with the scheme name.  The resolution of some
-   URIs may require the use of more than one protocol (e.g., both DNS
-   and HTTP are typically used to access an "http" URI's origin server
-   when a representation isn't found in a local cache).
-
-1.2.3.  Hierarchical Identifiers
-
-   The URI syntax is organized hierarchically, with components listed in
-   order of decreasing significance from left to right.  For some URI
-   schemes, the visible hierarchy is limited to the scheme itself:
-   everything after the scheme component delimiter (":") is considered
-   opaque to URI processing.  Other URI schemes make the hierarchy
-   explicit and visible to generic parsing algorithms.
-
-   The generic syntax uses the slash ("/"), question mark ("?"), and
-   number sign ("#") characters to delimit components that are
-   significant to the generic parser's hierarchical interpretation of an
-   identifier.  In addition to aiding the readability of such
-   identifiers through the consistent use of familiar syntax, this
-   uniform representation of hierarchy across naming schemes allows
-   scheme-independent references to be made relative to that hierarchy.
-
-   It is often the case that a group or "tree" of documents has been
-   constructed to serve a common purpose, wherein the vast majority of
-   URI references in these documents point to resources within the tree
-   rather than outside it.  Similarly, documents located at a particular
-   site are much more likely to refer to other resources at that site
-   than to resources at remote sites.  Relative referencing of URIs
-   allows document trees to be partially independent of their location
-   and access scheme.  For instance, it is possible for a single set of
-   hypertext documents to be simultaneously accessible and traversable
-   via each of the "file", "http", and "ftp" schemes if the documents
-   refer to each other with relative references.  Furthermore, such
-   document trees can be moved, as a whole, without changing any of the
-   relative references.
-
-   A relative reference (Section 4.2) refers to a resource by describing
-   the difference within a hierarchical name space between the reference
-   context and the target URI.  The reference resolution algorithm,
-
-
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-
-   presented in Section 5, defines how such a reference is transformed
-   to the target URI.  As relative references can only be used within
-   the context of a hierarchical URI, designers of new URI schemes
-   should use a syntax consistent with the generic syntax's hierarchical
-   components unless there are compelling reasons to forbid relative
-   referencing within that scheme.
-
-      NOTE: Previous specifications used the terms "partial URI" and
-      "relative URI" to denote a relative reference to a URI.  As some
-      readers misunderstood those terms to mean that relative URIs are a
-      subset of URIs rather than a method of referencing URIs, this
-      specification simply refers to them as relative references.
-
-   All URI references are parsed by generic syntax parsers when used.
-   However, because hierarchical processing has no effect on an absolute
-   URI used in a reference unless it contains one or more dot-segments
-   (complete path segments of "." or "..", as described in Section 3.3),
-   URI scheme specifications can define opaque identifiers by
-   disallowing use of slash characters, question mark characters, and
-   the URIs "scheme:." and "scheme:..".
-
-1.3.  Syntax Notation
-
-   This specification uses the Augmented Backus-Naur Form (ABNF)
-   notation of [RFC2234], including the following core ABNF syntax rules
-   defined by that specification: ALPHA (letters), CR (carriage return),
-   DIGIT (decimal digits), DQUOTE (double quote), HEXDIG (hexadecimal
-   digits), LF (line feed), and SP (space).  The complete URI syntax is
-   collected in Appendix A.
-
-2.  Characters
-
-   The URI syntax provides a method of encoding data, presumably for the
-   sake of identifying a resource, as a sequence of characters.  The URI
-   characters are, in turn, frequently encoded as octets for transport
-   or presentation.  This specification does not mandate any particular
-   character encoding for mapping between URI characters and the octets
-   used to store or transmit those characters.  When a URI appears in a
-   protocol element, the character encoding is defined by that protocol;
-   without such a definition, a URI is assumed to be in the same
-   character encoding as the surrounding text.
-
-   The ABNF notation defines its terminal values to be non-negative
-   integers (codepoints) based on the US-ASCII coded character set
-   [ASCII].  Because a URI is a sequence of characters, we must invert
-   that relation in order to understand the URI syntax.  Therefore, the
-
-
-
-
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-
-   integer values used by the ABNF must be mapped back to their
-   corresponding characters via US-ASCII in order to complete the syntax
-   rules.
-
-   A URI is composed from a limited set of characters consisting of
-   digits, letters, and a few graphic symbols.  A reserved subset of
-   those characters may be used to delimit syntax components within a
-   URI while the remaining characters, including both the unreserved set
-   and those reserved characters not acting as delimiters, define each
-   component's identifying data.
-
-2.1.  Percent-Encoding
-
-   A percent-encoding mechanism is used to represent a data octet in a
-   component when that octet's corresponding character is outside the
-   allowed set or is being used as a delimiter of, or within, the
-   component.  A percent-encoded octet is encoded as a character
-   triplet, consisting of the percent character "%" followed by the two
-   hexadecimal digits representing that octet's numeric value.  For
-   example, "%20" is the percent-encoding for the binary octet
-   "00100000" (ABNF: %x20), which in US-ASCII corresponds to the space
-   character (SP).  Section 2.4 describes when percent-encoding and
-   decoding is applied.
-
-      pct-encoded = "%" HEXDIG HEXDIG
-
-   The uppercase hexadecimal digits 'A' through 'F' are equivalent to
-   the lowercase digits 'a' through 'f', respectively.  If two URIs
-   differ only in the case of hexadecimal digits used in percent-encoded
-   octets, they are equivalent.  For consistency, URI producers and
-   normalizers should use uppercase hexadecimal digits for all percent-
-   encodings.
-
-2.2.  Reserved Characters
-
-   URIs include components and subcomponents that are delimited by
-   characters in the "reserved" set.  These characters are called
-   "reserved" because they may (or may not) be defined as delimiters by
-   the generic syntax, by each scheme-specific syntax, or by the
-   implementation-specific syntax of a URI's dereferencing algorithm.
-   If data for a URI component would conflict with a reserved
-   character's purpose as a delimiter, then the conflicting data must be
-   percent-encoded before the URI is formed.
-
-
-
-
-
-
-
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-
-
-      reserved    = gen-delims / sub-delims
-
-      gen-delims  = ":" / "/" / "?" / "#" / "[" / "]" / "@"
-
-      sub-delims  = "!" / "$" / "&" / "'" / "(" / ")"
-                  / "*" / "+" / "," / ";" / "="
-
-   The purpose of reserved characters is to provide a set of delimiting
-   characters that are distinguishable from other data within a URI.
-   URIs that differ in the replacement of a reserved character with its
-   corresponding percent-encoded octet are not equivalent.  Percent-
-   encoding a reserved character, or decoding a percent-encoded octet
-   that corresponds to a reserved character, will change how the URI is
-   interpreted by most applications.  Thus, characters in the reserved
-   set are protected from normalization and are therefore safe to be
-   used by scheme-specific and producer-specific algorithms for
-   delimiting data subcomponents within a URI.
-
-   A subset of the reserved characters (gen-delims) is used as
-   delimiters of the generic URI components described in Section 3.  A
-   component's ABNF syntax rule will not use the reserved or gen-delims
-   rule names directly; instead, each syntax rule lists the characters
-   allowed within that component (i.e., not delimiting it), and any of
-   those characters that are also in the reserved set are "reserved" for
-   use as subcomponent delimiters within the component.  Only the most
-   common subcomponents are defined by this specification; other
-   subcomponents may be defined by a URI scheme's specification, or by
-   the implementation-specific syntax of a URI's dereferencing
-   algorithm, provided that such subcomponents are delimited by
-   characters in the reserved set allowed within that component.
-
-   URI producing applications should percent-encode data octets that
-   correspond to characters in the reserved set unless these characters
-   are specifically allowed by the URI scheme to represent data in that
-   component.  If a reserved character is found in a URI component and
-   no delimiting role is known for that character, then it must be
-   interpreted as representing the data octet corresponding to that
-   character's encoding in US-ASCII.
-
-2.3.  Unreserved Characters
-
-   Characters that are allowed in a URI but do not have a reserved
-   purpose are called unreserved.  These include uppercase and lowercase
-   letters, decimal digits, hyphen, period, underscore, and tilde.
-
-      unreserved  = ALPHA / DIGIT / "-" / "." / "_" / "~"
-
-
-
-
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-   URIs that differ in the replacement of an unreserved character with
-   its corresponding percent-encoded US-ASCII octet are equivalent: they
-   identify the same resource.  However, URI comparison implementations
-   do not always perform normalization prior to comparison (see Section
-   6).  For consistency, percent-encoded octets in the ranges of ALPHA
-   (%41-%5A and %61-%7A), DIGIT (%30-%39), hyphen (%2D), period (%2E),
-   underscore (%5F), or tilde (%7E) should not be created by URI
-   producers and, when found in a URI, should be decoded to their
-   corresponding unreserved characters by URI normalizers.
-
-2.4.  When to Encode or Decode
-
-   Under normal circumstances, the only time when octets within a URI
-   are percent-encoded is during the process of producing the URI from
-   its component parts.  This is when an implementation determines which
-   of the reserved characters are to be used as subcomponent delimiters
-   and which can be safely used as data.  Once produced, a URI is always
-   in its percent-encoded form.
-
-   When a URI is dereferenced, the components and subcomponents
-   significant to the scheme-specific dereferencing process (if any)
-   must be parsed and separated before the percent-encoded octets within
-   those components can be safely decoded, as otherwise the data may be
-   mistaken for component delimiters.  The only exception is for
-   percent-encoded octets corresponding to characters in the unreserved
-   set, which can be decoded at any time.  For example, the octet
-   corresponding to the tilde ("~") character is often encoded as "%7E"
-   by older URI processing implementations; the "%7E" can be replaced by
-   "~" without changing its interpretation.
-
-   Because the percent ("%") character serves as the indicator for
-   percent-encoded octets, it must be percent-encoded as "%25" for that
-   octet to be used as data within a URI.  Implementations must not
-   percent-encode or decode the same string more than once, as decoding
-   an already decoded string might lead to misinterpreting a percent
-   data octet as the beginning of a percent-encoding, or vice versa in
-   the case of percent-encoding an already percent-encoded string.
-
-2.5.  Identifying Data
-
-   URI characters provide identifying data for each of the URI
-   components, serving as an external interface for identification
-   between systems.  Although the presence and nature of the URI
-   production interface is hidden from clients that use its URIs (and is
-   thus beyond the scope of the interoperability requirements defined by
-   this specification), it is a frequent source of confusion and errors
-   in the interpretation of URI character issues.  Implementers have to
-   be aware that there are multiple character encodings involved in the
-
-
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-
-   production and transmission of URIs: local name and data encoding,
-   public interface encoding, URI character encoding, data format
-   encoding, and protocol encoding.
-
-   Local names, such as file system names, are stored with a local
-   character encoding.  URI producing applications (e.g., origin
-   servers) will typically use the local encoding as the basis for
-   producing meaningful names.  The URI producer will transform the
-   local encoding to one that is suitable for a public interface and
-   then transform the public interface encoding into the restricted set
-   of URI characters (reserved, unreserved, and percent-encodings).
-   Those characters are, in turn, encoded as octets to be used as a
-   reference within a data format (e.g., a document charset), and such
-   data formats are often subsequently encoded for transmission over
-   Internet protocols.
-
-   For most systems, an unreserved character appearing within a URI
-   component is interpreted as representing the data octet corresponding
-   to that character's encoding in US-ASCII.  Consumers of URIs assume
-   that the letter "X" corresponds to the octet "01011000", and even
-   when that assumption is incorrect, there is no harm in making it.  A
-   system that internally provides identifiers in the form of a
-   different character encoding, such as EBCDIC, will generally perform
-   character translation of textual identifiers to UTF-8 [STD63] (or
-   some other superset of the US-ASCII character encoding) at an
-   internal interface, thereby providing more meaningful identifiers
-   than those resulting from simply percent-encoding the original
-   octets.
-
-   For example, consider an information service that provides data,
-   stored locally using an EBCDIC-based file system, to clients on the
-   Internet through an HTTP server.  When an author creates a file with
-   the name "Laguna Beach" on that file system, the "http" URI
-   corresponding to that resource is expected to contain the meaningful
-   string "Laguna%20Beach".  If, however, that server produces URIs by
-   using an overly simplistic raw octet mapping, then the result would
-   be a URI containing "%D3%81%87%A4%95%81@%C2%85%81%83%88".  An
-   internal transcoding interface fixes this problem by transcoding the
-   local name to a superset of US-ASCII prior to producing the URI.
-   Naturally, proper interpretation of an incoming URI on such an
-   interface requires that percent-encoded octets be decoded (e.g.,
-   "%20" to SP) before the reverse transcoding is applied to obtain the
-   local name.
-
-   In some cases, the internal interface between a URI component and the
-   identifying data that it has been crafted to represent is much less
-   direct than a character encoding translation.  For example, portions
-   of a URI might reflect a query on non-ASCII data, or numeric
-
-
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-
-   coordinates on a map.  Likewise, a URI scheme may define components
-   with additional encoding requirements that are applied prior to
-   forming the component and producing the URI.
-
-   When a new URI scheme defines a component that represents textual
-   data consisting of characters from the Universal Character Set [UCS],
-   the data should first be encoded as octets according to the UTF-8
-   character encoding [STD63]; then only those octets that do not
-   correspond to characters in the unreserved set should be percent-
-   encoded.  For example, the character A would be represented as "A",
-   the character LATIN CAPITAL LETTER A WITH GRAVE would be represented
-   as "%C3%80", and the character KATAKANA LETTER A would be represented
-   as "%E3%82%A2".
-
-3.  Syntax Components
-
-   The generic URI syntax consists of a hierarchical sequence of
-   components referred to as the scheme, authority, path, query, and
-   fragment.
-
-      URI         = scheme ":" hier-part [ "?" query ] [ "#" fragment ]
-
-      hier-part   = "//" authority path-abempty
-                  / path-absolute
-                  / path-rootless
-                  / path-empty
-
-   The scheme and path components are required, though the path may be
-   empty (no characters).  When authority is present, the path must
-   either be empty or begin with a slash ("/") character.  When
-   authority is not present, the path cannot begin with two slash
-   characters ("//").  These restrictions result in five different ABNF
-   rules for a path (Section 3.3), only one of which will match any
-   given URI reference.
-
-   The following are two example URIs and their component parts:
-
-         foo://example.com:8042/over/there?name=ferret#nose
-         \_/   \______________/\_________/ \_________/ \__/
-          |           |            |            |        |
-       scheme     authority       path        query   fragment
-          |   _____________________|__
-         / \ /                        \
-         urn:example:animal:ferret:nose
-
-
-
-
-
-
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-
-
-3.1.  Scheme
-
-   Each URI begins with a scheme name that refers to a specification for
-   assigning identifiers within that scheme.  As such, the URI syntax is
-   a federated and extensible naming system wherein each scheme's
-   specification may further restrict the syntax and semantics of
-   identifiers using that scheme.
-
-   Scheme names consist of a sequence of characters beginning with a
-   letter and followed by any combination of letters, digits, plus
-   ("+"), period ("."), or hyphen ("-").  Although schemes are case-
-   insensitive, the canonical form is lowercase and documents that
-   specify schemes must do so with lowercase letters.  An implementation
-   should accept uppercase letters as equivalent to lowercase in scheme
-   names (e.g., allow "HTTP" as well as "http") for the sake of
-   robustness but should only produce lowercase scheme names for
-   consistency.
-
-      scheme      = ALPHA *( ALPHA / DIGIT / "+" / "-" / "." )
-
-   Individual schemes are not specified by this document.  The process
-   for registration of new URI schemes is defined separately by [BCP35].
-   The scheme registry maintains the mapping between scheme names and
-   their specifications.  Advice for designers of new URI schemes can be
-   found in [RFC2718].  URI scheme specifications must define their own
-   syntax so that all strings matching their scheme-specific syntax will
-   also match the <absolute-URI> grammar, as described in Section 4.3.
-
-   When presented with a URI that violates one or more scheme-specific
-   restrictions, the scheme-specific resolution process should flag the
-   reference as an error rather than ignore the unused parts; doing so
-   reduces the number of equivalent URIs and helps detect abuses of the
-   generic syntax, which might indicate that the URI has been
-   constructed to mislead the user (Section 7.6).
-
-3.2.  Authority
-
-   Many URI schemes include a hierarchical element for a naming
-   authority so that governance of the name space defined by the
-   remainder of the URI is delegated to that authority (which may, in
-   turn, delegate it further).  The generic syntax provides a common
-   means for distinguishing an authority based on a registered name or
-   server address, along with optional port and user information.
-
-   The authority component is preceded by a double slash ("//") and is
-   terminated by the next slash ("/"), question mark ("?"), or number
-   sign ("#") character, or by the end of the URI.
-
-
-
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-
-
-      authority   = [ userinfo "@" ] host [ ":" port ]
-
-   URI producers and normalizers should omit the ":" delimiter that
-   separates host from port if the port component is empty.  Some
-   schemes do not allow the userinfo and/or port subcomponents.
-
-   If a URI contains an authority component, then the path component
-   must either be empty or begin with a slash ("/") character.  Non-
-   validating parsers (those that merely separate a URI reference into
-   its major components) will often ignore the subcomponent structure of
-   authority, treating it as an opaque string from the double-slash to
-   the first terminating delimiter, until such time as the URI is
-   dereferenced.
-
-3.2.1.  User Information
-
-   The userinfo subcomponent may consist of a user name and, optionally,
-   scheme-specific information about how to gain authorization to access
-   the resource.  The user information, if present, is followed by a
-   commercial at-sign ("@") that delimits it from the host.
-
-      userinfo    = *( unreserved / pct-encoded / sub-delims / ":" )
-
-   Use of the format "user:password" in the userinfo field is
-   deprecated.  Applications should not render as clear text any data
-   after the first colon (":") character found within a userinfo
-   subcomponent unless the data after the colon is the empty string
-   (indicating no password).  Applications may choose to ignore or
-   reject such data when it is received as part of a reference and
-   should reject the storage of such data in unencrypted form.  The
-   passing of authentication information in clear text has proven to be
-   a security risk in almost every case where it has been used.
-
-   Applications that render a URI for the sake of user feedback, such as
-   in graphical hypertext browsing, should render userinfo in a way that
-   is distinguished from the rest of a URI, when feasible.  Such
-   rendering will assist the user in cases where the userinfo has been
-   misleadingly crafted to look like a trusted domain name
-   (Section 7.6).
-
-3.2.2.  Host
-
-   The host subcomponent of authority is identified by an IP literal
-   encapsulated within square brackets, an IPv4 address in dotted-
-   decimal form, or a registered name.  The host subcomponent is case-
-   insensitive.  The presence of a host subcomponent within a URI does
-   not imply that the scheme requires access to the given host on the
-   Internet.  In many cases, the host syntax is used only for the sake
-
-
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-
-   of reusing the existing registration process created and deployed for
-   DNS, thus obtaining a globally unique name without the cost of
-   deploying another registry.  However, such use comes with its own
-   costs: domain name ownership may change over time for reasons not
-   anticipated by the URI producer.  In other cases, the data within the
-   host component identifies a registered name that has nothing to do
-   with an Internet host.  We use the name "host" for the ABNF rule
-   because that is its most common purpose, not its only purpose.
-
-      host        = IP-literal / IPv4address / reg-name
-
-   The syntax rule for host is ambiguous because it does not completely
-   distinguish between an IPv4address and a reg-name.  In order to
-   disambiguate the syntax, we apply the "first-match-wins" algorithm:
-   If host matches the rule for IPv4address, then it should be
-   considered an IPv4 address literal and not a reg-name.  Although host
-   is case-insensitive, producers and normalizers should use lowercase
-   for registered names and hexadecimal addresses for the sake of
-   uniformity, while only using uppercase letters for percent-encodings.
-
-   A host identified by an Internet Protocol literal address, version 6
-   [RFC3513] or later, is distinguished by enclosing the IP literal
-   within square brackets ("[" and "]").  This is the only place where
-   square bracket characters are allowed in the URI syntax.  In
-   anticipation of future, as-yet-undefined IP literal address formats,
-   an implementation may use an optional version flag to indicate such a
-   format explicitly rather than rely on heuristic determination.
-
-      IP-literal = "[" ( IPv6address / IPvFuture  ) "]"
-
-      IPvFuture  = "v" 1*HEXDIG "." 1*( unreserved / sub-delims / ":" )
-
-   The version flag does not indicate the IP version; rather, it
-   indicates future versions of the literal format.  As such,
-   implementations must not provide the version flag for the existing
-   IPv4 and IPv6 literal address forms described below.  If a URI
-   containing an IP-literal that starts with "v" (case-insensitive),
-   indicating that the version flag is present, is dereferenced by an
-   application that does not know the meaning of that version flag, then
-   the application should return an appropriate error for "address
-   mechanism not supported".
-
-   A host identified by an IPv6 literal address is represented inside
-   the square brackets without a preceding version flag.  The ABNF
-   provided here is a translation of the text definition of an IPv6
-   literal address provided in [RFC3513].  This syntax does not support
-   IPv6 scoped addressing zone identifiers.
-
-
-
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-
-
-   A 128-bit IPv6 address is divided into eight 16-bit pieces.  Each
-   piece is represented numerically in case-insensitive hexadecimal,
-   using one to four hexadecimal digits (leading zeroes are permitted).
-   The eight encoded pieces are given most-significant first, separated
-   by colon characters.  Optionally, the least-significant two pieces
-   may instead be represented in IPv4 address textual format.  A
-   sequence of one or more consecutive zero-valued 16-bit pieces within
-   the address may be elided, omitting all their digits and leaving
-   exactly two consecutive colons in their place to mark the elision.
-
-      IPv6address =                            6( h16 ":" ) ls32
-                  /                       "::" 5( h16 ":" ) ls32
-                  / [               h16 ] "::" 4( h16 ":" ) ls32
-                  / [ *1( h16 ":" ) h16 ] "::" 3( h16 ":" ) ls32
-                  / [ *2( h16 ":" ) h16 ] "::" 2( h16 ":" ) ls32
-                  / [ *3( h16 ":" ) h16 ] "::"    h16 ":"   ls32
-                  / [ *4( h16 ":" ) h16 ] "::"              ls32
-                  / [ *5( h16 ":" ) h16 ] "::"              h16
-                  / [ *6( h16 ":" ) h16 ] "::"
-
-      ls32        = ( h16 ":" h16 ) / IPv4address
-                  ; least-significant 32 bits of address
-
-      h16         = 1*4HEXDIG
-                  ; 16 bits of address represented in hexadecimal
-
-   A host identified by an IPv4 literal address is represented in
-   dotted-decimal notation (a sequence of four decimal numbers in the
-   range 0 to 255, separated by "."), as described in [RFC1123] by
-   reference to [RFC0952].  Note that other forms of dotted notation may
-   be interpreted on some platforms, as described in Section 7.4, but
-   only the dotted-decimal form of four octets is allowed by this
-   grammar.
-
-      IPv4address = dec-octet "." dec-octet "." dec-octet "." dec-octet
-
-      dec-octet   = DIGIT                 ; 0-9
-                  / %x31-39 DIGIT         ; 10-99
-                  / "1" 2DIGIT            ; 100-199
-                  / "2" %x30-34 DIGIT     ; 200-249
-                  / "25" %x30-35          ; 250-255
-
-   A host identified by a registered name is a sequence of characters
-   usually intended for lookup within a locally defined host or service
-   name registry, though the URI's scheme-specific semantics may require
-   that a specific registry (or fixed name table) be used instead.  The
-   most common name registry mechanism is the Domain Name System (DNS).
-   A registered name intended for lookup in the DNS uses the syntax
-
-
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-
-
-   defined in Section 3.5 of [RFC1034] and Section 2.1 of [RFC1123].
-   Such a name consists of a sequence of domain labels separated by ".",
-   each domain label starting and ending with an alphanumeric character
-   and possibly also containing "-" characters.  The rightmost domain
-   label of a fully qualified domain name in DNS may be followed by a
-   single "." and should be if it is necessary to distinguish between
-   the complete domain name and some local domain.
-
-      reg-name    = *( unreserved / pct-encoded / sub-delims )
-
-   If the URI scheme defines a default for host, then that default
-   applies when the host subcomponent is undefined or when the
-   registered name is empty (zero length).  For example, the "file" URI
-   scheme is defined so that no authority, an empty host, and
-   "localhost" all mean the end-user's machine, whereas the "http"
-   scheme considers a missing authority or empty host invalid.
-
-   This specification does not mandate a particular registered name
-   lookup technology and therefore does not restrict the syntax of reg-
-   name beyond what is necessary for interoperability.  Instead, it
-   delegates the issue of registered name syntax conformance to the
-   operating system of each application performing URI resolution, and
-   that operating system decides what it will allow for the purpose of
-   host identification.  A URI resolution implementation might use DNS,
-   host tables, yellow pages, NetInfo, WINS, or any other system for
-   lookup of registered names.  However, a globally scoped naming
-   system, such as DNS fully qualified domain names, is necessary for
-   URIs intended to have global scope.  URI producers should use names
-   that conform to the DNS syntax, even when use of DNS is not
-   immediately apparent, and should limit these names to no more than
-   255 characters in length.
-
-   The reg-name syntax allows percent-encoded octets in order to
-   represent non-ASCII registered names in a uniform way that is
-   independent of the underlying name resolution technology.  Non-ASCII
-   characters must first be encoded according to UTF-8 [STD63], and then
-   each octet of the corresponding UTF-8 sequence must be percent-
-   encoded to be represented as URI characters.  URI producing
-   applications must not use percent-encoding in host unless it is used
-   to represent a UTF-8 character sequence.  When a non-ASCII registered
-   name represents an internationalized domain name intended for
-   resolution via the DNS, the name must be transformed to the IDNA
-   encoding [RFC3490] prior to name lookup.  URI producers should
-   provide these registered names in the IDNA encoding, rather than a
-   percent-encoding, if they wish to maximize interoperability with
-   legacy URI resolvers.
-
-
-
-
-
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- 
-RFC 3986                   URI Generic Syntax               January 2005
-
-
-3.2.3.  Port
-
-   The port subcomponent of authority is designated by an optional port
-   number in decimal following the host and delimited from it by a
-   single colon (":") character.
-
-      port        = *DIGIT
-
-   A scheme may define a default port.  For example, the "http" scheme
-   defines a default port of "80", corresponding to its reserved TCP
-   port number.  The type of port designated by the port number (e.g.,
-   TCP, UDP, SCTP) is defined by the URI scheme.  URI producers and
-   normalizers should omit the port component and its ":" delimiter if
-   port is empty or if its value would be the same as that of the
-   scheme's default.
-
-3.3.  Path
-
-   The path component contains data, usually organized in hierarchical
-   form, that, along with data in the non-hierarchical query component
-   (Section 3.4), serves to identify a resource within the scope of the
-   URI's scheme and naming authority (if any).  The path is terminated
-   by the first question mark ("?") or number sign ("#") character, or
-   by the end of the URI.
-
-   If a URI contains an authority component, then the path component
-   must either be empty or begin with a slash ("/") character.  If a URI
-   does not contain an authority component, then the path cannot begin
-   with two slash characters ("//").  In addition, a URI reference
-   (Section 4.1) may be a relative-path reference, in which case the
-   first path segment cannot contain a colon (":") character.  The ABNF
-   requires five separate rules to disambiguate these cases, only one of
-   which will match the path substring within a given URI reference.  We
-   use the generic term "path component" to describe the URI substring
-   matched by the parser to one of these rules.
-
-      path          = path-abempty    ; begins with "/" or is empty
-                    / path-absolute   ; begins with "/" but not "//"
-                    / path-noscheme   ; begins with a non-colon segment
-                    / path-rootless   ; begins with a segment
-                    / path-empty      ; zero characters
-
-      path-abempty  = *( "/" segment )
-      path-absolute = "/" [ segment-nz *( "/" segment ) ]
-      path-noscheme = segment-nz-nc *( "/" segment )
-      path-rootless = segment-nz *( "/" segment )
-      path-empty    = 0<pchar>
-
-
-
-
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- 
-RFC 3986                   URI Generic Syntax               January 2005
-
-
-      segment       = *pchar
-      segment-nz    = 1*pchar
-      segment-nz-nc = 1*( unreserved / pct-encoded / sub-delims / "@" )
-                    ; non-zero-length segment without any colon ":"
-
-      pchar         = unreserved / pct-encoded / sub-delims / ":" / "@"
-
-   A path consists of a sequence of path segments separated by a slash
-   ("/") character.  A path is always defined for a URI, though the
-   defined path may be empty (zero length).  Use of the slash character
-   to indicate hierarchy is only required when a URI will be used as the
-   context for relative references.  For example, the URI
-   <mailto:fred@example.com> has a path of "fred@example.com", whereas
-   the URI <foo://info.example.com?fred> has an empty path.
-
-   The path segments "." and "..", also known as dot-segments, are
-   defined for relative reference within the path name hierarchy.  They
-   are intended for use at the beginning of a relative-path reference
-   (Section 4.2) to indicate relative position within the hierarchical
-   tree of names.  This is similar to their role within some operating
-   systems' file directory structures to indicate the current directory
-   and parent directory, respectively.  However, unlike in a file
-   system, these dot-segments are only interpreted within the URI path
-   hierarchy and are removed as part of the resolution process (Section
-   5.2).
-
-   Aside from dot-segments in hierarchical paths, a path segment is
-   considered opaque by the generic syntax.  URI producing applications
-   often use the reserved characters allowed in a segment to delimit
-   scheme-specific or dereference-handler-specific subcomponents.  For
-   example, the semicolon (";") and equals ("=") reserved characters are
-   often used to delimit parameters and parameter values applicable to
-   that segment.  The comma (",") reserved character is often used for
-   similar purposes.  For example, one URI producer might use a segment
-   such as "name;v=1.1" to indicate a reference to version 1.1 of
-   "name", whereas another might use a segment such as "name,1.1" to
-   indicate the same.  Parameter types may be defined by scheme-specific
-   semantics, but in most cases the syntax of a parameter is specific to
-   the implementation of the URI's dereferencing algorithm.
-
-3.4.  Query
-
-   The query component contains non-hierarchical data that, along with
-   data in the path component (Section 3.3), serves to identify a
-   resource within the scope of the URI's scheme and naming authority
-   (if any).  The query component is indicated by the first question
-   mark ("?") character and terminated by a number sign ("#") character
-   or by the end of the URI.
-
-
-
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- 
-RFC 3986                   URI Generic Syntax               January 2005
-
-
-      query       = *( pchar / "/" / "?" )
-
-   The characters slash ("/") and question mark ("?") may represent data
-   within the query component.  Beware that some older, erroneous
-   implementations may not handle such data correctly when it is used as
-   the base URI for relative references (Section 5.1), apparently
-   because they fail to distinguish query data from path data when
-   looking for hierarchical separators.  However, as query components
-   are often used to carry identifying information in the form of
-   "key=value" pairs and one frequently used value is a reference to
-   another URI, it is sometimes better for usability to avoid percent-
-   encoding those characters.
-
-3.5.  Fragment
-
-   The fragment identifier component of a URI allows indirect
-   identification of a secondary resource by reference to a primary
-   resource and additional identifying information.  The identified
-   secondary resource may be some portion or subset of the primary
-   resource, some view on representations of the primary resource, or
-   some other resource defined or described by those representations.  A
-   fragment identifier component is indicated by the presence of a
-   number sign ("#") character and terminated by the end of the URI.
-
-      fragment    = *( pchar / "/" / "?" )
-
-   The semantics of a fragment identifier are defined by the set of
-   representations that might result from a retrieval action on the
-   primary resource.  The fragment's format and resolution is therefore
-   dependent on the media type [RFC2046] of a potentially retrieved
-   representation, even though such a retrieval is only performed if the
-   URI is dereferenced.  If no such representation exists, then the
-   semantics of the fragment are considered unknown and are effectively
-   unconstrained.  Fragment identifier semantics are independent of the
-   URI scheme and thus cannot be redefined by scheme specifications.
-
-   Individual media types may define their own restrictions on or
-   structures within the fragment identifier syntax for specifying
-   different types of subsets, views, or external references that are
-   identifiable as secondary resources by that media type.  If the
-   primary resource has multiple representations, as is often the case
-   for resources whose representation is selected based on attributes of
-   the retrieval request (a.k.a., content negotiation), then whatever is
-   identified by the fragment should be consistent across all of those
-   representations.  Each representation should either define the
-   fragment so that it corresponds to the same secondary resource,
-   regardless of how it is represented, or should leave the fragment
-   undefined (i.e., not found).
-
-
-
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- 
-RFC 3986                   URI Generic Syntax               January 2005
-
-
-   As with any URI, use of a fragment identifier component does not
-   imply that a retrieval action will take place.  A URI with a fragment
-   identifier may be used to refer to the secondary resource without any
-   implication that the primary resource is accessible or will ever be
-   accessed.
-
-   Fragment identifiers have a special role in information retrieval
-   systems as the primary form of client-side indirect referencing,
-   allowing an author to specifically identify aspects of an existing
-   resource that are only indirectly provided by the resource owner.  As
-   such, the fragment identifier is not used in the scheme-specific
-   processing of a URI; instead, the fragment identifier is separated
-   from the rest of the URI prior to a dereference, and thus the
-   identifying information within the fragment itself is dereferenced
-   solely by the user agent, regardless of the URI scheme.  Although
-   this separate handling is often perceived to be a loss of
-   information, particularly for accurate redirection of references as
-   resources move over time, it also serves to prevent information
-   providers from denying reference authors the right to refer to
-   information within a resource selectively.  Indirect referencing also
-   provides additional flexibility and extensibility to systems that use
-   URIs, as new media types are easier to define and deploy than new
-   schemes of identification.
-
-   The characters slash ("/") and question mark ("?") are allowed to
-   represent data within the fragment identifier.  Beware that some
-   older, erroneous implementations may not handle this data correctly
-   when it is used as the base URI for relative references (Section
-   5.1).
-
-4.  Usage
-
-   When applications make reference to a URI, they do not always use the
-   full form of reference defined by the "URI" syntax rule.  To save
-   space and take advantage of hierarchical locality, many Internet
-   protocol elements and media type formats allow an abbreviation of a
-   URI, whereas others restrict the syntax to a particular form of URI.
-   We define the most common forms of reference syntax in this
-   specification because they impact and depend upon the design of the
-   generic syntax, requiring a uniform parsing algorithm in order to be
-   interpreted consistently.
-
-4.1.  URI Reference
-
-   URI-reference is used to denote the most common usage of a resource
-   identifier.
-
-      URI-reference = URI / relative-ref
-
-
-
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- 
-RFC 3986                   URI Generic Syntax               January 2005
-
-
-   A URI-reference is either a URI or a relative reference.  If the
-   URI-reference's prefix does not match the syntax of a scheme followed
-   by its colon separator, then the URI-reference is a relative
-   reference.
-
-   A URI-reference is typically parsed first into the five URI
-   components, in order to determine what components are present and
-   whether the reference is relative.  Then, each component is parsed
-   for its subparts and their validation.  The ABNF of URI-reference,
-   along with the "first-match-wins" disambiguation rule, is sufficient
-   to define a validating parser for the generic syntax.  Readers
-   familiar with regular expressions should see Appendix B for an
-   example of a non-validating URI-reference parser that will take any
-   given string and extract the URI components.
-
-4.2.  Relative Reference
-
-   A relative reference takes advantage of the hierarchical syntax
-   (Section 1.2.3) to express a URI reference relative to the name space
-   of another hierarchical URI.
-
-      relative-ref  = relative-part [ "?" query ] [ "#" fragment ]
-
-      relative-part = "//" authority path-abempty
-                    / path-absolute
-                    / path-noscheme
-                    / path-empty
-
-   The URI referred to by a relative reference, also known as the target
-   URI, is obtained by applying the reference resolution algorithm of
-   Section 5.
-
-   A relative reference that begins with two slash characters is termed
-   a network-path reference; such references are rarely used.  A
-   relative reference that begins with a single slash character is
-   termed an absolute-path reference.  A relative reference that does
-   not begin with a slash character is termed a relative-path reference.
-
-   A path segment that contains a colon character (e.g., "this:that")
-   cannot be used as the first segment of a relative-path reference, as
-   it would be mistaken for a scheme name.  Such a segment must be
-   preceded by a dot-segment (e.g., "./this:that") to make a relative-
-   path reference.
-
-
-
-
-
-
-
-
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- 
-RFC 3986                   URI Generic Syntax               January 2005
-
-
-4.3.  Absolute URI
-
-   Some protocol elements allow only the absolute form of a URI without
-   a fragment identifier.  For example, defining a base URI for later
-   use by relative references calls for an absolute-URI syntax rule that
-   does not allow a fragment.
-
-      absolute-URI  = scheme ":" hier-part [ "?" query ]
-
-   URI scheme specifications must define their own syntax so that all
-   strings matching their scheme-specific syntax will also match the
-   <absolute-URI> grammar.  Scheme specifications will not define
-   fragment identifier syntax or usage, regardless of its applicability
-   to resources identifiable via that scheme, as fragment identification
-   is orthogonal to scheme definition.  However, scheme specifications
-   are encouraged to include a wide range of examples, including
-   examples that show use of the scheme's URIs with fragment identifiers
-   when such usage is appropriate.
-
-4.4.  Same-Document Reference
-
-   When a URI reference refers to a URI that is, aside from its fragment
-   component (if any), identical to the base URI (Section 5.1), that
-   reference is called a "same-document" reference.  The most frequent
-   examples of same-document references are relative references that are
-   empty or include only the number sign ("#") separator followed by a
-   fragment identifier.
-
-   When a same-document reference is dereferenced for a retrieval
-   action, the target of that reference is defined to be within the same
-   entity (representation, document, or message) as the reference;
-   therefore, a dereference should not result in a new retrieval action.
-
-   Normalization of the base and target URIs prior to their comparison,
-   as described in Sections 6.2.2 and 6.2.3, is allowed but rarely
-   performed in practice.  Normalization may increase the set of same-
-   document references, which may be of benefit to some caching
-   applications.  As such, reference authors should not assume that a
-   slightly different, though equivalent, reference URI will (or will
-   not) be interpreted as a same-document reference by any given
-   application.
-
-4.5.  Suffix Reference
-
-   The URI syntax is designed for unambiguous reference to resources and
-   extensibility via the URI scheme.  However, as URI identification and
-   usage have become commonplace, traditional media (television, radio,
-   newspapers, billboards, etc.) have increasingly used a suffix of the
-
-
-
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- 
-RFC 3986                   URI Generic Syntax               January 2005
-
-
-   URI as a reference, consisting of only the authority and path
-   portions of the URI, such as
-
-      www.w3.org/Addressing/
-
-   or simply a DNS registered name on its own.  Such references are
-   primarily intended for human interpretation rather than for machines,
-   with the assumption that context-based heuristics are sufficient to
-   complete the URI (e.g., most registered names beginning with "www"
-   are likely to have a URI prefix of "http://").  Although there is no
-   standard set of heuristics for disambiguating a URI suffix, many
-   client implementations allow them to be entered by the user and
-   heuristically resolved.
-
-   Although this practice of using suffix references is common, it
-   should be avoided whenever possible and should never be used in
-   situations where long-term references are expected.  The heuristics
-   noted above will change over time, particularly when a new URI scheme
-   becomes popular, and are often incorrect when used out of context.
-   Furthermore, they can lead to security issues along the lines of
-   those described in [RFC1535].
-
-   As a URI suffix has the same syntax as a relative-path reference, a
-   suffix reference cannot be used in contexts where a relative
-   reference is expected.  As a result, suffix references are limited to
-   places where there is no defined base URI, such as dialog boxes and
-   off-line advertisements.
-
-5.  Reference Resolution
-
-   This section defines the process of resolving a URI reference within
-   a context that allows relative references so that the result is a
-   string matching the <URI> syntax rule of Section 3.
-
-5.1.  Establishing a Base URI
-
-   The term "relative" implies that a "base URI" exists against which
-   the relative reference is applied.  Aside from fragment-only
-   references (Section 4.4), relative references are only usable when a
-   base URI is known.  A base URI must be established by the parser
-   prior to parsing URI references that might be relative.  A base URI
-   must conform to the <absolute-URI> syntax rule (Section 4.3).  If the
-   base URI is obtained from a URI reference, then that reference must
-   be converted to absolute form and stripped of any fragment component
-   prior to its use as a base URI.
-
-
-
-
-
-
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- 
-RFC 3986                   URI Generic Syntax               January 2005
-
-
-   The base URI of a reference can be established in one of four ways,
-   discussed below in order of precedence.  The order of precedence can
-   be thought of in terms of layers, where the innermost defined base
-   URI has the highest precedence.  This can be visualized graphically
-   as follows:
-
-         .----------------------------------------------------------.
-         |  .----------------------------------------------------.  |
-         |  |  .----------------------------------------------.  |  |
-         |  |  |  .----------------------------------------.  |  |  |
-         |  |  |  |  .----------------------------------.  |  |  |  |
-         |  |  |  |  |       <relative-reference>       |  |  |  |  |
-         |  |  |  |  `----------------------------------'  |  |  |  |
-         |  |  |  | (5.1.1) Base URI embedded in content   |  |  |  |
-         |  |  |  `----------------------------------------'  |  |  |
-         |  |  | (5.1.2) Base URI of the encapsulating entity |  |  |
-         |  |  |         (message, representation, or none)   |  |  |
-         |  |  `----------------------------------------------'  |  |
-         |  | (5.1.3) URI used to retrieve the entity            |  |
-         |  `----------------------------------------------------'  |
-         | (5.1.4) Default Base URI (application-dependent)         |
-         `----------------------------------------------------------'
-
-5.1.1.  Base URI Embedded in Content
-
-   Within certain media types, a base URI for relative references can be
-   embedded within the content itself so that it can be readily obtained
-   by a parser.  This can be useful for descriptive documents, such as
-   tables of contents, which may be transmitted to others through
-   protocols other than their usual retrieval context (e.g., email or
-   USENET news).
-
-   It is beyond the scope of this specification to specify how, for each
-   media type, a base URI can be embedded.  The appropriate syntax, when
-   available, is described by the data format specification associated
-   with each media type.
-
-5.1.2.  Base URI from the Encapsulating Entity
-
-   If no base URI is embedded, the base URI is defined by the
-   representation's retrieval context.  For a document that is enclosed
-   within another entity, such as a message or archive, the retrieval
-   context is that entity.  Thus, the default base URI of a
-   representation is the base URI of the entity in which the
-   representation is encapsulated.
-
-
-
-
-
-
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- 
-RFC 3986                   URI Generic Syntax               January 2005
-
-
-   A mechanism for embedding a base URI within MIME container types
-   (e.g., the message and multipart types) is defined by MHTML
-   [RFC2557].  Protocols that do not use the MIME message header syntax,
-   but that do allow some form of tagged metadata to be included within
-   messages, may define their own syntax for defining a base URI as part
-   of a message.
-
-5.1.3.  Base URI from the Retrieval URI
-
-   If no base URI is embedded and the representation is not encapsulated
-   within some other entity, then, if a URI was used to retrieve the
-   representation, that URI shall be considered the base URI.  Note that
-   if the retrieval was the result of a redirected request, the last URI
-   used (i.e., the URI that resulted in the actual retrieval of the
-   representation) is the base URI.
-
-5.1.4.  Default Base URI
-
-   If none of the conditions described above apply, then the base URI is
-   defined by the context of the application.  As this definition is
-   necessarily application-dependent, failing to define a base URI by
-   using one of the other methods may result in the same content being
-   interpreted differently by different types of applications.
-
-   A sender of a representation containing relative references is
-   responsible for ensuring that a base URI for those references can be
-   established.  Aside from fragment-only references, relative
-   references can only be used reliably in situations where the base URI
-   is well defined.
-
-5.2.  Relative Resolution
-
-   This section describes an algorithm for converting a URI reference
-   that might be relative to a given base URI into the parsed components
-   of the reference's target.  The components can then be recomposed, as
-   described in Section 5.3, to form the target URI.  This algorithm
-   provides definitive results that can be used to test the output of
-   other implementations.  Applications may implement relative reference
-   resolution by using some other algorithm, provided that the results
-   match what would be given by this one.
-
-
-
-
-
-
-
-
-
-
-
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- 
-RFC 3986                   URI Generic Syntax               January 2005
-
-
-5.2.1.  Pre-parse the Base URI
-
-   The base URI (Base) is established according to the procedure of
-   Section 5.1 and parsed into the five main components described in
-   Section 3.  Note that only the scheme component is required to be
-   present in a base URI; the other components may be empty or
-   undefined.  A component is undefined if its associated delimiter does
-   not appear in the URI reference; the path component is never
-   undefined, though it may be empty.
-
-   Normalization of the base URI, as described in Sections 6.2.2 and
-   6.2.3, is optional.  A URI reference must be transformed to its
-   target URI before it can be normalized.
-
-5.2.2.  Transform References
-
-   For each URI reference (R), the following pseudocode describes an
-   algorithm for transforming R into its target URI (T):
-
-      -- The URI reference is parsed into the five URI components
-      --
-      (R.scheme, R.authority, R.path, R.query, R.fragment) = parse(R);
-
-      -- A non-strict parser may ignore a scheme in the reference
-      -- if it is identical to the base URI's scheme.
-      --
-      if ((not strict) and (R.scheme == Base.scheme)) then
-         undefine(R.scheme);
-      endif;
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
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- 
-RFC 3986                   URI Generic Syntax               January 2005
-
-
-      if defined(R.scheme) then
-         T.scheme    = R.scheme;
-         T.authority = R.authority;
-         T.path      = remove_dot_segments(R.path);
-         T.query     = R.query;
-      else
-         if defined(R.authority) then
-            T.authority = R.authority;
-            T.path      = remove_dot_segments(R.path);
-            T.query     = R.query;
-         else
-            if (R.path == "") then
-               T.path = Base.path;
-               if defined(R.query) then
-                  T.query = R.query;
-               else
-                  T.query = Base.query;
-               endif;
-            else
-               if (R.path starts-with "/") then
-                  T.path = remove_dot_segments(R.path);
-               else
-                  T.path = merge(Base.path, R.path);
-                  T.path = remove_dot_segments(T.path);
-               endif;
-               T.query = R.query;
-            endif;
-            T.authority = Base.authority;
-         endif;
-         T.scheme = Base.scheme;
-      endif;
-
-      T.fragment = R.fragment;
-
-5.2.3.  Merge Paths
-
-   The pseudocode above refers to a "merge" routine for merging a
-   relative-path reference with the path of the base URI.  This is
-   accomplished as follows:
-
-   o  If the base URI has a defined authority component and an empty
-      path, then return a string consisting of "/" concatenated with the
-      reference's path; otherwise,
-
-
-
-
-
-
-
-
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- 
-RFC 3986                   URI Generic Syntax               January 2005
-
-
-   o  return a string consisting of the reference's path component
-      appended to all but the last segment of the base URI's path (i.e.,
-      excluding any characters after the right-most "/" in the base URI
-      path, or excluding the entire base URI path if it does not contain
-      any "/" characters).
-
-5.2.4.  Remove Dot Segments
-
-   The pseudocode also refers to a "remove_dot_segments" routine for
-   interpreting and removing the special "." and ".." complete path
-   segments from a referenced path.  This is done after the path is
-   extracted from a reference, whether or not the path was relative, in
-   order to remove any invalid or extraneous dot-segments prior to
-   forming the target URI.  Although there are many ways to accomplish
-   this removal process, we describe a simple method using two string
-   buffers.
-
-   1.  The input buffer is initialized with the now-appended path
-       components and the output buffer is initialized to the empty
-       string.
-
-   2.  While the input buffer is not empty, loop as follows:
-
-       A.  If the input buffer begins with a prefix of "../" or "./",
-           then remove that prefix from the input buffer; otherwise,
-
-       B.  if the input buffer begins with a prefix of "/./" or "/.",
-           where "." is a complete path segment, then replace that
-           prefix with "/" in the input buffer; otherwise,
-
-       C.  if the input buffer begins with a prefix of "/../" or "/..",
-           where ".." is a complete path segment, then replace that
-           prefix with "/" in the input buffer and remove the last
-           segment and its preceding "/" (if any) from the output
-           buffer; otherwise,
-
-       D.  if the input buffer consists only of "." or "..", then remove
-           that from the input buffer; otherwise,
-
-       E.  move the first path segment in the input buffer to the end of
-           the output buffer, including the initial "/" character (if
-           any) and any subsequent characters up to, but not including,
-           the next "/" character or the end of the input buffer.
-
-   3.  Finally, the output buffer is returned as the result of
-       remove_dot_segments.
-
-
-
-
-
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- 
-RFC 3986                   URI Generic Syntax               January 2005
-
-
-   Note that dot-segments are intended for use in URI references to
-   express an identifier relative to the hierarchy of names in the base
-   URI.  The remove_dot_segments algorithm respects that hierarchy by
-   removing extra dot-segments rather than treat them as an error or
-   leaving them to be misinterpreted by dereference implementations.
-
-   The following illustrates how the above steps are applied for two
-   examples of merged paths, showing the state of the two buffers after
-   each step.
-
-      STEP   OUTPUT BUFFER         INPUT BUFFER
-
-       1 :                         /a/b/c/./../../g
-       2E:   /a                    /b/c/./../../g
-       2E:   /a/b                  /c/./../../g
-       2E:   /a/b/c                /./../../g
-       2B:   /a/b/c                /../../g
-       2C:   /a/b                  /../g
-       2C:   /a                    /g
-       2E:   /a/g
-
-      STEP   OUTPUT BUFFER         INPUT BUFFER
-
-       1 :                         mid/content=5/../6
-       2E:   mid                   /content=5/../6
-       2E:   mid/content=5         /../6
-       2C:   mid                   /6
-       2E:   mid/6
-
-   Some applications may find it more efficient to implement the
-   remove_dot_segments algorithm by using two segment stacks rather than
-   strings.
-
-      Note: Beware that some older, erroneous implementations will fail
-      to separate a reference's query component from its path component
-      prior to merging the base and reference paths, resulting in an
-      interoperability failure if the query component contains the
-      strings "/../" or "/./".
-
-
-
-
-
-
-
-
-
-
-
-
-
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- 
-RFC 3986                   URI Generic Syntax               January 2005
-
-
-5.3.  Component Recomposition
-
-   Parsed URI components can be recomposed to obtain the corresponding
-   URI reference string.  Using pseudocode, this would be:
-
-      result = ""
-
-      if defined(scheme) then
-         append scheme to result;
-         append ":" to result;
-      endif;
-
-      if defined(authority) then
-         append "//" to result;
-         append authority to result;
-      endif;
-
-      append path to result;
-
-      if defined(query) then
-         append "?" to result;
-         append query to result;
-      endif;
-
-      if defined(fragment) then
-         append "#" to result;
-         append fragment to result;
-      endif;
-
-      return result;
-
-   Note that we are careful to preserve the distinction between a
-   component that is undefined, meaning that its separator was not
-   present in the reference, and a component that is empty, meaning that
-   the separator was present and was immediately followed by the next
-   component separator or the end of the reference.
-
-5.4.  Reference Resolution Examples
-
-   Within a representation with a well defined base URI of
-
-      http://a/b/c/d;p?q
-
-   a relative reference is transformed to its target URI as follows.
-
-
-
-
-
-
-
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- 
-RFC 3986                   URI Generic Syntax               January 2005
-
-
-5.4.1.  Normal Examples
-
-      "g:h"           =  "g:h"
-      "g"             =  "http://a/b/c/g"
-      "./g"           =  "http://a/b/c/g"
-      "g/"            =  "http://a/b/c/g/"
-      "/g"            =  "http://a/g"
-      "//g"           =  "http://g"
-      "?y"            =  "http://a/b/c/d;p?y"
-      "g?y"           =  "http://a/b/c/g?y"
-      "#s"            =  "http://a/b/c/d;p?q#s"
-      "g#s"           =  "http://a/b/c/g#s"
-      "g?y#s"         =  "http://a/b/c/g?y#s"
-      ";x"            =  "http://a/b/c/;x"
-      "g;x"           =  "http://a/b/c/g;x"
-      "g;x?y#s"       =  "http://a/b/c/g;x?y#s"
-      ""              =  "http://a/b/c/d;p?q"
-      "."             =  "http://a/b/c/"
-      "./"            =  "http://a/b/c/"
-      ".."            =  "http://a/b/"
-      "../"           =  "http://a/b/"
-      "../g"          =  "http://a/b/g"
-      "../.."         =  "http://a/"
-      "../../"        =  "http://a/"
-      "../../g"       =  "http://a/g"
-
-5.4.2.  Abnormal Examples
-
-   Although the following abnormal examples are unlikely to occur in
-   normal practice, all URI parsers should be capable of resolving them
-   consistently.  Each example uses the same base as that above.
-
-   Parsers must be careful in handling cases where there are more ".."
-   segments in a relative-path reference than there are hierarchical
-   levels in the base URI's path.  Note that the ".." syntax cannot be
-   used to change the authority component of a URI.
-
-      "../../../g"    =  "http://a/g"
-      "../../../../g" =  "http://a/g"
-
-
-
-
-
-
-
-
-
-
-
-
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- 
-RFC 3986                   URI Generic Syntax               January 2005
-
-
-   Similarly, parsers must remove the dot-segments "." and ".." when
-   they are complete components of a path, but not when they are only
-   part of a segment.
-
-      "/./g"          =  "http://a/g"
-      "/../g"         =  "http://a/g"
-      "g."            =  "http://a/b/c/g."
-      ".g"            =  "http://a/b/c/.g"
-      "g.."           =  "http://a/b/c/g.."
-      "..g"           =  "http://a/b/c/..g"
-
-   Less likely are cases where the relative reference uses unnecessary
-   or nonsensical forms of the "." and ".." complete path segments.
-
-      "./../g"        =  "http://a/b/g"
-      "./g/."         =  "http://a/b/c/g/"
-      "g/./h"         =  "http://a/b/c/g/h"
-      "g/../h"        =  "http://a/b/c/h"
-      "g;x=1/./y"     =  "http://a/b/c/g;x=1/y"
-      "g;x=1/../y"    =  "http://a/b/c/y"
-
-   Some applications fail to separate the reference's query and/or
-   fragment components from the path component before merging it with
-   the base path and removing dot-segments.  This error is rarely
-   noticed, as typical usage of a fragment never includes the hierarchy
-   ("/") character and the query component is not normally used within
-   relative references.
-
-      "g?y/./x"       =  "http://a/b/c/g?y/./x"
-      "g?y/../x"      =  "http://a/b/c/g?y/../x"
-      "g#s/./x"       =  "http://a/b/c/g#s/./x"
-      "g#s/../x"      =  "http://a/b/c/g#s/../x"
-
-   Some parsers allow the scheme name to be present in a relative
-   reference if it is the same as the base URI scheme.  This is
-   considered to be a loophole in prior specifications of partial URI
-   [RFC1630].  Its use should be avoided but is allowed for backward
-   compatibility.
-
-      "http:g"        =  "http:g"         ; for strict parsers
-                      /  "http://a/b/c/g" ; for backward compatibility
-
-
-
-
-
-
-
-
-
-
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- 
-RFC 3986                   URI Generic Syntax               January 2005
-
-
-6.  Normalization and Comparison
-
-   One of the most common operations on URIs is simple comparison:
-   determining whether two URIs are equivalent without using the URIs to
-   access their respective resource(s).  A comparison is performed every
-   time a response cache is accessed, a browser checks its history to
-   color a link, or an XML parser processes tags within a namespace.
-   Extensive normalization prior to comparison of URIs is often used by
-   spiders and indexing engines to prune a search space or to reduce
-   duplication of request actions and response storage.
-
-   URI comparison is performed for some particular purpose.  Protocols
-   or implementations that compare URIs for different purposes will
-   often be subject to differing design trade-offs in regards to how
-   much effort should be spent in reducing aliased identifiers.  This
-   section describes various methods that may be used to compare URIs,
-   the trade-offs between them, and the types of applications that might
-   use them.
-
-6.1.  Equivalence
-
-   Because URIs exist to identify resources, presumably they should be
-   considered equivalent when they identify the same resource.  However,
-   this definition of equivalence is not of much practical use, as there
-   is no way for an implementation to compare two resources unless it
-   has full knowledge or control of them.  For this reason,
-   determination of equivalence or difference of URIs is based on string
-   comparison, perhaps augmented by reference to additional rules
-   provided by URI scheme definitions.  We use the terms "different" and
-   "equivalent" to describe the possible outcomes of such comparisons,
-   but there are many application-dependent versions of equivalence.
-
-   Even though it is possible to determine that two URIs are equivalent,
-   URI comparison is not sufficient to determine whether two URIs
-   identify different resources.  For example, an owner of two different
-   domain names could decide to serve the same resource from both,
-   resulting in two different URIs.  Therefore, comparison methods are
-   designed to minimize false negatives while strictly avoiding false
-   positives.
-
-   In testing for equivalence, applications should not directly compare
-   relative references; the references should be converted to their
-   respective target URIs before comparison.  When URIs are compared to
-   select (or avoid) a network action, such as retrieval of a
-   representation, fragment components (if any) should be excluded from
-   the comparison.
-
-
-
-
-
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- 
-RFC 3986                   URI Generic Syntax               January 2005
-
-
-6.2.  Comparison Ladder
-
-   A variety of methods are used in practice to test URI equivalence.
-   These methods fall into a range, distinguished by the amount of
-   processing required and the degree to which the probability of false
-   negatives is reduced.  As noted above, false negatives cannot be
-   eliminated.  In practice, their probability can be reduced, but this
-   reduction requires more processing and is not cost-effective for all
-   applications.
-
-   If this range of comparison practices is considered as a ladder, the
-   following discussion will climb the ladder, starting with practices
-   that are cheap but have a relatively higher chance of producing false
-   negatives, and proceeding to those that have higher computational
-   cost and lower risk of false negatives.
-
-6.2.1.  Simple String Comparison
-
-   If two URIs, when considered as character strings, are identical,
-   then it is safe to conclude that they are equivalent.  This type of
-   equivalence test has very low computational cost and is in wide use
-   in a variety of applications, particularly in the domain of parsing.
-
-   Testing strings for equivalence requires some basic precautions.
-   This procedure is often referred to as "bit-for-bit" or
-   "byte-for-byte" comparison, which is potentially misleading.  Testing
-   strings for equality is normally based on pair comparison of the
-   characters that make up the strings, starting from the first and
-   proceeding until both strings are exhausted and all characters are
-   found to be equal, until a pair of characters compares unequal, or
-   until one of the strings is exhausted before the other.
-
-   This character comparison requires that each pair of characters be
-   put in comparable form.  For example, should one URI be stored in a
-   byte array in EBCDIC encoding and the second in a Java String object
-   (UTF-16), bit-for-bit comparisons applied naively will produce
-   errors.  It is better to speak of equality on a character-for-
-   character basis rather than on a byte-for-byte or bit-for-bit basis.
-   In practical terms, character-by-character comparisons should be done
-   codepoint-by-codepoint after conversion to a common character
-   encoding.
-
-   False negatives are caused by the production and use of URI aliases.
-   Unnecessary aliases can be reduced, regardless of the comparison
-   method, by consistently providing URI references in an already-
-   normalized form (i.e., a form identical to what would be produced
-   after normalization is applied, as described below).
-
-
-
-
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- 
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-
-
-   Protocols and data formats often limit some URI comparisons to simple
-   string comparison, based on the theory that people and
-   implementations will, in their own best interest, be consistent in
-   providing URI references, or at least consistent enough to negate any
-   efficiency that might be obtained from further normalization.
-
-6.2.2.  Syntax-Based Normalization
-
-   Implementations may use logic based on the definitions provided by
-   this specification to reduce the probability of false negatives.
-   This processing is moderately higher in cost than character-for-
-   character string comparison.  For example, an application using this
-   approach could reasonably consider the following two URIs equivalent:
-
-      example://a/b/c/%7Bfoo%7D
-      eXAMPLE://a/./b/../b/%63/%7bfoo%7d
-
-   Web user agents, such as browsers, typically apply this type of URI
-   normalization when determining whether a cached response is
-   available.  Syntax-based normalization includes such techniques as
-   case normalization, percent-encoding normalization, and removal of
-   dot-segments.
-
-6.2.2.1.  Case Normalization
-
-   For all URIs, the hexadecimal digits within a percent-encoding
-   triplet (e.g., "%3a" versus "%3A") are case-insensitive and therefore
-   should be normalized to use uppercase letters for the digits A-F.
-
-   When a URI uses components of the generic syntax, the component
-   syntax equivalence rules always apply; namely, that the scheme and
-   host are case-insensitive and therefore should be normalized to
-   lowercase.  For example, the URI <HTTP://www.EXAMPLE.com/> is
-   equivalent to <http://www.example.com/>.  The other generic syntax
-   components are assumed to be case-sensitive unless specifically
-   defined otherwise by the scheme (see Section 6.2.3).
-
-6.2.2.2.  Percent-Encoding Normalization
-
-   The percent-encoding mechanism (Section 2.1) is a frequent source of
-   variance among otherwise identical URIs.  In addition to the case
-   normalization issue noted above, some URI producers percent-encode
-   octets that do not require percent-encoding, resulting in URIs that
-   are equivalent to their non-encoded counterparts.  These URIs should
-   be normalized by decoding any percent-encoded octet that corresponds
-   to an unreserved character, as described in Section 2.3.
-
-
-
-
-
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- 
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-
-
-6.2.2.3.  Path Segment Normalization
-
-   The complete path segments "." and ".." are intended only for use
-   within relative references (Section 4.1) and are removed as part of
-   the reference resolution process (Section 5.2).  However, some
-   deployed implementations incorrectly assume that reference resolution
-   is not necessary when the reference is already a URI and thus fail to
-   remove dot-segments when they occur in non-relative paths.  URI
-   normalizers should remove dot-segments by applying the
-   remove_dot_segments algorithm to the path, as described in
-   Section 5.2.4.
-
-6.2.3.  Scheme-Based Normalization
-
-   The syntax and semantics of URIs vary from scheme to scheme, as
-   described by the defining specification for each scheme.
-   Implementations may use scheme-specific rules, at further processing
-   cost, to reduce the probability of false negatives.  For example,
-   because the "http" scheme makes use of an authority component, has a
-   default port of "80", and defines an empty path to be equivalent to
-   "/", the following four URIs are equivalent:
-
-      http://example.com
-      http://example.com/
-      http://example.com:/
-      http://example.com:80/
-
-   In general, a URI that uses the generic syntax for authority with an
-   empty path should be normalized to a path of "/".  Likewise, an
-   explicit ":port", for which the port is empty or the default for the
-   scheme, is equivalent to one where the port and its ":" delimiter are
-   elided and thus should be removed by scheme-based normalization.  For
-   example, the second URI above is the normal form for the "http"
-   scheme.
-
-   Another case where normalization varies by scheme is in the handling
-   of an empty authority component or empty host subcomponent.  For many
-   scheme specifications, an empty authority or host is considered an
-   error; for others, it is considered equivalent to "localhost" or the
-   end-user's host.  When a scheme defines a default for authority and a
-   URI reference to that default is desired, the reference should be
-   normalized to an empty authority for the sake of uniformity, brevity,
-   and internationalization.  If, however, either the userinfo or port
-   subcomponents are non-empty, then the host should be given explicitly
-   even if it matches the default.
-
-   Normalization should not remove delimiters when their associated
-   component is empty unless licensed to do so by the scheme
-
-
-
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- 
-RFC 3986                   URI Generic Syntax               January 2005
-
-
-   specification.  For example, the URI "http://example.com/?" cannot be
-   assumed to be equivalent to any of the examples above.  Likewise, the
-   presence or absence of delimiters within a userinfo subcomponent is
-   usually significant to its interpretation.  The fragment component is
-   not subject to any scheme-based normalization; thus, two URIs that
-   differ only by the suffix "#" are considered different regardless of
-   the scheme.
-
-   Some schemes define additional subcomponents that consist of case-
-   insensitive data, giving an implicit license to normalizers to
-   convert this data to a common case (e.g., all lowercase).  For
-   example, URI schemes that define a subcomponent of path to contain an
-   Internet hostname, such as the "mailto" URI scheme, cause that
-   subcomponent to be case-insensitive and thus subject to case
-   normalization (e.g., "mailto:Joe@Example.COM" is equivalent to
-   "mailto:Joe@example.com", even though the generic syntax considers
-   the path component to be case-sensitive).
-
-   Other scheme-specific normalizations are possible.
-
-6.2.4.  Protocol-Based Normalization
-
-   Substantial effort to reduce the incidence of false negatives is
-   often cost-effective for web spiders.  Therefore, they implement even
-   more aggressive techniques in URI comparison.  For example, if they
-   observe that a URI such as
-
-      http://example.com/data
-
-   redirects to a URI differing only in the trailing slash
-
-      http://example.com/data/
-
-   they will likely regard the two as equivalent in the future.  This
-   kind of technique is only appropriate when equivalence is clearly
-   indicated by both the result of accessing the resources and the
-   common conventions of their scheme's dereference algorithm (in this
-   case, use of redirection by HTTP origin servers to avoid problems
-   with relative references).
-
-
-
-
-
-
-
-
-
-
-
-
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- 
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-
-
-7.  Security Considerations
-
-   A URI does not in itself pose a security threat.  However, as URIs
-   are often used to provide a compact set of instructions for access to
-   network resources, care must be taken to properly interpret the data
-   within a URI, to prevent that data from causing unintended access,
-   and to avoid including data that should not be revealed in plain
-   text.
-
-7.1.  Reliability and Consistency
-
-   There is no guarantee that once a URI has been used to retrieve
-   information, the same information will be retrievable by that URI in
-   the future.  Nor is there any guarantee that the information
-   retrievable via that URI in the future will be observably similar to
-   that retrieved in the past.  The URI syntax does not constrain how a
-   given scheme or authority apportions its namespace or maintains it
-   over time.  Such guarantees can only be obtained from the person(s)
-   controlling that namespace and the resource in question.  A specific
-   URI scheme may define additional semantics, such as name persistence,
-   if those semantics are required of all naming authorities for that
-   scheme.
-
-7.2.  Malicious Construction
-
-   It is sometimes possible to construct a URI so that an attempt to
-   perform a seemingly harmless, idempotent operation, such as the
-   retrieval of a representation, will in fact cause a possibly damaging
-   remote operation.  The unsafe URI is typically constructed by
-   specifying a port number other than that reserved for the network
-   protocol in question.  The client unwittingly contacts a site running
-   a different protocol service, and data within the URI contains
-   instructions that, when interpreted according to this other protocol,
-   cause an unexpected operation.  A frequent example of such abuse has
-   been the use of a protocol-based scheme with a port component of
-   "25", thereby fooling user agent software into sending an unintended
-   or impersonating message via an SMTP server.
-
-   Applications should prevent dereference of a URI that specifies a TCP
-   port number within the "well-known port" range (0 - 1023) unless the
-   protocol being used to dereference that URI is compatible with the
-   protocol expected on that well-known port.  Although IANA maintains a
-   registry of well-known ports, applications should make such
-   restrictions user-configurable to avoid preventing the deployment of
-   new services.
-
-
-
-
-
-
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- 
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-
-
-   When a URI contains percent-encoded octets that match the delimiters
-   for a given resolution or dereference protocol (for example, CR and
-   LF characters for the TELNET protocol), these percent-encodings must
-   not be decoded before transmission across that protocol.  Transfer of
-   the percent-encoding, which might violate the protocol, is less
-   harmful than allowing decoded octets to be interpreted as additional
-   operations or parameters, perhaps triggering an unexpected and
-   possibly harmful remote operation.
-
-7.3.  Back-End Transcoding
-
-   When a URI is dereferenced, the data within it is often parsed by
-   both the user agent and one or more servers.  In HTTP, for example, a
-   typical user agent will parse a URI into its five major components,
-   access the authority's server, and send it the data within the
-   authority, path, and query components.  A typical server will take
-   that information, parse the path into segments and the query into
-   key/value pairs, and then invoke implementation-specific handlers to
-   respond to the request.  As a result, a common security concern for
-   server implementations that handle a URI, either as a whole or split
-   into separate components, is proper interpretation of the octet data
-   represented by the characters and percent-encodings within that URI.
-
-   Percent-encoded octets must be decoded at some point during the
-   dereference process.  Applications must split the URI into its
-   components and subcomponents prior to decoding the octets, as
-   otherwise the decoded octets might be mistaken for delimiters.
-   Security checks of the data within a URI should be applied after
-   decoding the octets.  Note, however, that the "%00" percent-encoding
-   (NUL) may require special handling and should be rejected if the
-   application is not expecting to receive raw data within a component.
-
-   Special care should be taken when the URI path interpretation process
-   involves the use of a back-end file system or related system
-   functions.  File systems typically assign an operational meaning to
-   special characters, such as the "/", "\", ":", "[", and "]"
-   characters, and to special device names like ".", "..", "...", "aux",
-   "lpt", etc.  In some cases, merely testing for the existence of such
-   a name will cause the operating system to pause or invoke unrelated
-   system calls, leading to significant security concerns regarding
-   denial of service and unintended data transfer.  It would be
-   impossible for this specification to list all such significant
-   characters and device names.  Implementers should research the
-   reserved names and characters for the types of storage device that
-   may be attached to their applications and restrict the use of data
-   obtained from URI components accordingly.
-
-
-
-
-
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- 
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-
-
-7.4.  Rare IP Address Formats
-
-   Although the URI syntax for IPv4address only allows the common
-   dotted-decimal form of IPv4 address literal, many implementations
-   that process URIs make use of platform-dependent system routines,
-   such as gethostbyname() and inet_aton(), to translate the string
-   literal to an actual IP address.  Unfortunately, such system routines
-   often allow and process a much larger set of formats than those
-   described in Section 3.2.2.
-
-   For example, many implementations allow dotted forms of three
-   numbers, wherein the last part is interpreted as a 16-bit quantity
-   and placed in the right-most two bytes of the network address (e.g.,
-   a Class B network).  Likewise, a dotted form of two numbers means
-   that the last part is interpreted as a 24-bit quantity and placed in
-   the right-most three bytes of the network address (Class A), and a
-   single number (without dots) is interpreted as a 32-bit quantity and
-   stored directly in the network address.  Adding further to the
-   confusion, some implementations allow each dotted part to be
-   interpreted as decimal, octal, or hexadecimal, as specified in the C
-   language (i.e., a leading 0x or 0X implies hexadecimal; a leading 0
-   implies octal; otherwise, the number is interpreted as decimal).
-
-   These additional IP address formats are not allowed in the URI syntax
-   due to differences between platform implementations.  However, they
-   can become a security concern if an application attempts to filter
-   access to resources based on the IP address in string literal format.
-   If this filtering is performed, literals should be converted to
-   numeric form and filtered based on the numeric value, and not on a
-   prefix or suffix of the string form.
-
-7.5.  Sensitive Information
-
-   URI producers should not provide a URI that contains a username or
-   password that is intended to be secret.  URIs are frequently
-   displayed by browsers, stored in clear text bookmarks, and logged by
-   user agent history and intermediary applications (proxies).  A
-   password appearing within the userinfo component is deprecated and
-   should be considered an error (or simply ignored) except in those
-   rare cases where the 'password' parameter is intended to be public.
-
-7.6.  Semantic Attacks
-
-   Because the userinfo subcomponent is rarely used and appears before
-   the host in the authority component, it can be used to construct a
-   URI intended to mislead a human user by appearing to identify one
-   (trusted) naming authority while actually identifying a different
-   authority hidden behind the noise.  For example
-
-
-
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- 
-RFC 3986                   URI Generic Syntax               January 2005
-
-
-      ftp://cnn.example.com&story=breaking_news@10.0.0.1/top_story.htm
-
-   might lead a human user to assume that the host is 'cnn.example.com',
-   whereas it is actually '10.0.0.1'.  Note that a misleading userinfo
-   subcomponent could be much longer than the example above.
-
-   A misleading URI, such as that above, is an attack on the user's
-   preconceived notions about the meaning of a URI rather than an attack
-   on the software itself.  User agents may be able to reduce the impact
-   of such attacks by distinguishing the various components of the URI
-   when they are rendered, such as by using a different color or tone to
-   render userinfo if any is present, though there is no panacea.  More
-   information on URI-based semantic attacks can be found in [Siedzik].
-
-8.  IANA Considerations
-
-   URI scheme names, as defined by <scheme> in Section 3.1, form a
-   registered namespace that is managed by IANA according to the
-   procedures defined in [BCP35].  No IANA actions are required by this
-   document.
-
-9.  Acknowledgements
-
-   This specification is derived from RFC 2396 [RFC2396], RFC 1808
-   [RFC1808], and RFC 1738 [RFC1738]; the acknowledgements in those
-   documents still apply.  It also incorporates the update (with
-   corrections) for IPv6 literals in the host syntax, as defined by
-   Robert M. Hinden, Brian E. Carpenter, and Larry Masinter in
-   [RFC2732].  In addition, contributions by Gisle Aas, Reese Anschultz,
-   Daniel Barclay, Tim Bray, Mike Brown, Rob Cameron, Jeremy Carroll,
-   Dan Connolly, Adam M. Costello, John Cowan, Jason Diamond, Martin
-   Duerst, Stefan Eissing, Clive D.W. Feather, Al Gilman, Tony Hammond,
-   Elliotte Harold, Pat Hayes, Henry Holtzman, Ian B. Jacobs, Michael
-   Kay, John C. Klensin, Graham Klyne, Dan Kohn, Bruce Lilly, Andrew
-   Main, Dave McAlpin, Ira McDonald, Michael Mealling, Ray Merkert,
-   Stephen Pollei, Julian Reschke, Tomas Rokicki, Miles Sabin, Kai
-   Schaetzl, Mark Thomson, Ronald Tschalaer, Norm Walsh, Marc Warne,
-   Stuart Williams, and Henry Zongaro are gratefully acknowledged.
-
-10.  References
-
-10.1.  Normative References
-
-   [ASCII]    American National Standards Institute, "Coded Character
-              Set -- 7-bit American Standard Code for Information
-              Interchange", ANSI X3.4, 1986.
-
-
-
-
-
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- 
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-
-
-   [RFC2234]  Crocker, D. and P. Overell, "Augmented BNF for Syntax
-              Specifications: ABNF", RFC 2234, November 1997.
-
-   [STD63]    Yergeau, F., "UTF-8, a transformation format of
-              ISO 10646", STD 63, RFC 3629, November 2003.
-
-   [UCS]      International Organization for Standardization,
-              "Information Technology - Universal Multiple-Octet Coded
-              Character Set (UCS)", ISO/IEC 10646:2003, December 2003.
-
-10.2.  Informative References
-
-   [BCP19]    Freed, N. and J. Postel, "IANA Charset Registration
-              Procedures", BCP 19, RFC 2978, October 2000.
-
-   [BCP35]    Petke, R. and I. King, "Registration Procedures for URL
-              Scheme Names", BCP 35, RFC 2717, November 1999.
-
-   [RFC0952]  Harrenstien, K., Stahl, M., and E. Feinler, "DoD Internet
-              host table specification", RFC 952, October 1985.
-
-   [RFC1034]  Mockapetris, P., "Domain names - concepts and facilities",
-              STD 13, RFC 1034, November 1987.
-
-   [RFC1123]  Braden, R., "Requirements for Internet Hosts - Application
-              and Support", STD 3, RFC 1123, October 1989.
-
-   [RFC1535]  Gavron, E., "A Security Problem and Proposed Correction
-              With Widely Deployed DNS Software", RFC 1535,
-              October 1993.
-
-   [RFC1630]  Berners-Lee, T., "Universal Resource Identifiers in WWW: A
-              Unifying Syntax for the Expression of Names and Addresses
-              of Objects on the Network as used in the World-Wide Web",
-              RFC 1630, June 1994.
-
-   [RFC1736]  Kunze, J., "Functional Recommendations for Internet
-              Resource Locators", RFC 1736, February 1995.
-
-   [RFC1737]  Sollins, K. and L. Masinter, "Functional Requirements for
-              Uniform Resource Names", RFC 1737, December 1994.
-
-   [RFC1738]  Berners-Lee, T., Masinter, L., and M. McCahill, "Uniform
-              Resource Locators (URL)", RFC 1738, December 1994.
-
-   [RFC1808]  Fielding, R., "Relative Uniform Resource Locators",
-              RFC 1808, June 1995.
-
-
-
-
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- 
-RFC 3986                   URI Generic Syntax               January 2005
-
-
-   [RFC2046]  Freed, N. and N. Borenstein, "Multipurpose Internet Mail
-              Extensions (MIME) Part Two: Media Types", RFC 2046,
-              November 1996.
-
-   [RFC2141]  Moats, R., "URN Syntax", RFC 2141, May 1997.
-
-   [RFC2396]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
-              Resource Identifiers (URI): Generic Syntax", RFC 2396,
-              August 1998.
-
-   [RFC2518]  Goland, Y., Whitehead, E., Faizi, A., Carter, S., and D.
-              Jensen, "HTTP Extensions for Distributed Authoring --
-              WEBDAV", RFC 2518, February 1999.
-
-   [RFC2557]  Palme, J., Hopmann, A., and N. Shelness, "MIME
-              Encapsulation of Aggregate Documents, such as HTML
-              (MHTML)", RFC 2557, March 1999.
-
-   [RFC2718]  Masinter, L., Alvestrand, H., Zigmond, D., and R. Petke,
-              "Guidelines for new URL Schemes", RFC 2718, November 1999.
-
-   [RFC2732]  Hinden, R., Carpenter, B., and L. Masinter, "Format for
-              Literal IPv6 Addresses in URL's", RFC 2732, December 1999.
-
-   [RFC3305]  Mealling, M. and R. Denenberg, "Report from the Joint
-              W3C/IETF URI Planning Interest Group: Uniform Resource
-              Identifiers (URIs), URLs, and Uniform Resource Names
-              (URNs): Clarifications and Recommendations", RFC 3305,
-              August 2002.
-
-   [RFC3490]  Faltstrom, P., Hoffman, P., and A. Costello,
-              "Internationalizing Domain Names in Applications (IDNA)",
-              RFC 3490, March 2003.
-
-   [RFC3513]  Hinden, R. and S. Deering, "Internet Protocol Version 6
-              (IPv6) Addressing Architecture", RFC 3513, April 2003.
-
-   [Siedzik]  Siedzik, R., "Semantic Attacks: What's in a URL?",
-              April 2001, <http://www.giac.org/practical/gsec/
-              Richard_Siedzik_GSEC.pdf>.
-
-
-
-
-
-
-
-
-
-
-
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- 
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-
-
-Appendix A.  Collected ABNF for URI
-
-   URI           = scheme ":" hier-part [ "?" query ] [ "#" fragment ]
-
-   hier-part     = "//" authority path-abempty
-                 / path-absolute
-                 / path-rootless
-                 / path-empty
-
-   URI-reference = URI / relative-ref
-
-   absolute-URI  = scheme ":" hier-part [ "?" query ]
-
-   relative-ref  = relative-part [ "?" query ] [ "#" fragment ]
-
-   relative-part = "//" authority path-abempty
-                 / path-absolute
-                 / path-noscheme
-                 / path-empty
-
-   scheme        = ALPHA *( ALPHA / DIGIT / "+" / "-" / "." )
-
-   authority     = [ userinfo "@" ] host [ ":" port ]
-   userinfo      = *( unreserved / pct-encoded / sub-delims / ":" )
-   host          = IP-literal / IPv4address / reg-name
-   port          = *DIGIT
-
-   IP-literal    = "[" ( IPv6address / IPvFuture  ) "]"
-
-   IPvFuture     = "v" 1*HEXDIG "." 1*( unreserved / sub-delims / ":" )
-
-   IPv6address   =                            6( h16 ":" ) ls32
-                 /                       "::" 5( h16 ":" ) ls32
-                 / [               h16 ] "::" 4( h16 ":" ) ls32
-                 / [ *1( h16 ":" ) h16 ] "::" 3( h16 ":" ) ls32
-                 / [ *2( h16 ":" ) h16 ] "::" 2( h16 ":" ) ls32
-                 / [ *3( h16 ":" ) h16 ] "::"    h16 ":"   ls32
-                 / [ *4( h16 ":" ) h16 ] "::"              ls32
-                 / [ *5( h16 ":" ) h16 ] "::"              h16
-                 / [ *6( h16 ":" ) h16 ] "::"
-
-   h16           = 1*4HEXDIG
-   ls32          = ( h16 ":" h16 ) / IPv4address
-   IPv4address   = dec-octet "." dec-octet "." dec-octet "." dec-octet
-
-
-
-
-
-
-
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- 
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-
-
-   dec-octet     = DIGIT                 ; 0-9
-                 / %x31-39 DIGIT         ; 10-99
-                 / "1" 2DIGIT            ; 100-199
-                 / "2" %x30-34 DIGIT     ; 200-249
-                 / "25" %x30-35          ; 250-255
-
-   reg-name      = *( unreserved / pct-encoded / sub-delims )
-
-   path          = path-abempty    ; begins with "/" or is empty
-                 / path-absolute   ; begins with "/" but not "//"
-                 / path-noscheme   ; begins with a non-colon segment
-                 / path-rootless   ; begins with a segment
-                 / path-empty      ; zero characters
-
-   path-abempty  = *( "/" segment )
-   path-absolute = "/" [ segment-nz *( "/" segment ) ]
-   path-noscheme = segment-nz-nc *( "/" segment )
-   path-rootless = segment-nz *( "/" segment )
-   path-empty    = 0<pchar>
-
-   segment       = *pchar
-   segment-nz    = 1*pchar
-   segment-nz-nc = 1*( unreserved / pct-encoded / sub-delims / "@" )
-                 ; non-zero-length segment without any colon ":"
-
-   pchar         = unreserved / pct-encoded / sub-delims / ":" / "@"
-
-   query         = *( pchar / "/" / "?" )
-
-   fragment      = *( pchar / "/" / "?" )
-
-   pct-encoded   = "%" HEXDIG HEXDIG
-
-   unreserved    = ALPHA / DIGIT / "-" / "." / "_" / "~"
-   reserved      = gen-delims / sub-delims
-   gen-delims    = ":" / "/" / "?" / "#" / "[" / "]" / "@"
-   sub-delims    = "!" / "$" / "&" / "'" / "(" / ")"
-                 / "*" / "+" / "," / ";" / "="
-
-Appendix B.  Parsing a URI Reference with a Regular Expression
-
-   As the "first-match-wins" algorithm is identical to the "greedy"
-   disambiguation method used by POSIX regular expressions, it is
-   natural and commonplace to use a regular expression for parsing the
-   potential five components of a URI reference.
-
-   The following line is the regular expression for breaking-down a
-   well-formed URI reference into its components.
-
-
-
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- 
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-
-
-      ^(([^:/?#]+):)?(//([^/?#]*))?([^?#]*)(\?([^#]*))?(#(.*))?
-       12            3  4          5       6  7        8 9
-
-   The numbers in the second line above are only to assist readability;
-   they indicate the reference points for each subexpression (i.e., each
-   paired parenthesis).  We refer to the value matched for subexpression
-   <n> as $<n>.  For example, matching the above expression to
-
-      http://www.ics.uci.edu/pub/ietf/uri/#Related
-
-   results in the following subexpression matches:
-
-      $1 = http:
-      $2 = http
-      $3 = //www.ics.uci.edu
-      $4 = www.ics.uci.edu
-      $5 = /pub/ietf/uri/
-      $6 = <undefined>
-      $7 = <undefined>
-      $8 = #Related
-      $9 = Related
-
-   where <undefined> indicates that the component is not present, as is
-   the case for the query component in the above example.  Therefore, we
-   can determine the value of the five components as
-
-      scheme    = $2
-      authority = $4
-      path      = $5
-      query     = $7
-      fragment  = $9
-
-   Going in the opposite direction, we can recreate a URI reference from
-   its components by using the algorithm of Section 5.3.
-
-Appendix C.  Delimiting a URI in Context
-
-   URIs are often transmitted through formats that do not provide a
-   clear context for their interpretation.  For example, there are many
-   occasions when a URI is included in plain text; examples include text
-   sent in email, USENET news, and on printed paper.  In such cases, it
-   is important to be able to delimit the URI from the rest of the text,
-   and in particular from punctuation marks that might be mistaken for
-   part of the URI.
-
-   In practice, URIs are delimited in a variety of ways, but usually
-   within double-quotes "http://example.com/", angle brackets
-   <http://example.com/>, or just by using whitespace:
-
-
-
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- 
-RFC 3986                   URI Generic Syntax               January 2005
-
-
-      http://example.com/
-
-   These wrappers do not form part of the URI.
-
-   In some cases, extra whitespace (spaces, line-breaks, tabs, etc.) may
-   have to be added to break a long URI across lines.  The whitespace
-   should be ignored when the URI is extracted.
-
-   No whitespace should be introduced after a hyphen ("-") character.
-   Because some typesetters and printers may (erroneously) introduce a
-   hyphen at the end of line when breaking it, the interpreter of a URI
-   containing a line break immediately after a hyphen should ignore all
-   whitespace around the line break and should be aware that the hyphen
-   may or may not actually be part of the URI.
-
-   Using <> angle brackets around each URI is especially recommended as
-   a delimiting style for a reference that contains embedded whitespace.
-
-   The prefix "URL:" (with or without a trailing space) was formerly
-   recommended as a way to help distinguish a URI from other bracketed
-   designators, though it is not commonly used in practice and is no
-   longer recommended.
-
-   For robustness, software that accepts user-typed URI should attempt
-   to recognize and strip both delimiters and embedded whitespace.
-
-   For example, the text
-
-      Yes, Jim, I found it under "http://www.w3.org/Addressing/",
-      but you can probably pick it up from <ftp://foo.example.
-      http://www.ics.uci.edu/pub/
-      ietf/uri/historical.html#WARNING>.
-
-   contains the URI references
-
-      http://www.w3.org/Addressing/
-      ftp://foo.example.com/rfc/
-      http://www.ics.uci.edu/pub/ietf/uri/historical.html#WARNING
-
-
-
-
-
-
-
-
-
-
-
-
-
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- 
-RFC 3986                   URI Generic Syntax               January 2005
-
-
-Appendix D.  Changes from RFC 2396
-
-D.1.  Additions
-
-   An ABNF rule for URI has been introduced to correspond to one common
-   usage of the term: an absolute URI with optional fragment.
-
-   IPv6 (and later) literals have been added to the list of possible
-   identifiers for the host portion of an authority component, as
-   described by [RFC2732], with the addition of "[" and "]" to the
-   reserved set and a version flag to anticipate future versions of IP
-   literals.  Square brackets are now specified as reserved within the
-   authority component and are not allowed outside their use as
-   delimiters for an IP literal within host.  In order to make this
-   change without changing the technical definition of the path, query,
-   and fragment components, those rules were redefined to directly
-   specify the characters allowed.
-
-   As [RFC2732] defers to [RFC3513] for definition of an IPv6 literal
-   address, which, unfortunately, lacks an ABNF description of
-   IPv6address, we created a new ABNF rule for IPv6address that matches
-   the text representations defined by Section 2.2 of [RFC3513].
-   Likewise, the definition of IPv4address has been improved in order to
-   limit each decimal octet to the range 0-255.
-
-   Section 6, on URI normalization and comparison, has been completely
-   rewritten and extended by using input from Tim Bray and discussion
-   within the W3C Technical Architecture Group.
-
-D.2.  Modifications
-
-   The ad-hoc BNF syntax of RFC 2396 has been replaced with the ABNF of
-   [RFC2234].  This change required all rule names that formerly
-   included underscore characters to be renamed with a dash instead.  In
-   addition, a number of syntax rules have been eliminated or simplified
-   to make the overall grammar more comprehensible.  Specifications that
-   refer to the obsolete grammar rules may be understood by replacing
-   those rules according to the following table:
-
-
-
-
-
-
-
-
-
-
-
-
-
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- 
-RFC 3986                   URI Generic Syntax               January 2005
-
-
-   +----------------+--------------------------------------------------+
-   | obsolete rule  | translation                                      |
-   +----------------+--------------------------------------------------+
-   | absoluteURI    | absolute-URI                                     |
-   | relativeURI    | relative-part [ "?" query ]                      |
-   | hier_part      | ( "//" authority path-abempty /                  |
-   |                | path-absolute ) [ "?" query ]                    |
-   |                |                                                  |
-   | opaque_part    | path-rootless [ "?" query ]                      |
-   | net_path       | "//" authority path-abempty                      |
-   | abs_path       | path-absolute                                    |
-   | rel_path       | path-rootless                                    |
-   | rel_segment    | segment-nz-nc                                    |
-   | reg_name       | reg-name                                         |
-   | server         | authority                                        |
-   | hostport       | host [ ":" port ]                                |
-   | hostname       | reg-name                                         |
-   | path_segments  | path-abempty                                     |
-   | param          | *<pchar excluding ";">                           |
-   |                |                                                  |
-   | uric           | unreserved / pct-encoded / ";" / "?" / ":"       |
-   |                |  / "@" / "&" / "=" / "+" / "$" / "," / "/"       |
-   |                |                                                  |
-   | uric_no_slash  | unreserved / pct-encoded / ";" / "?" / ":"       |
-   |                |  / "@" / "&" / "=" / "+" / "$" / ","             |
-   |                |                                                  |
-   | mark           | "-" / "_" / "." / "!" / "~" / "*" / "'"          |
-   |                |  / "(" / ")"                                     |
-   |                |                                                  |
-   | escaped        | pct-encoded                                      |
-   | hex            | HEXDIG                                           |
-   | alphanum       | ALPHA / DIGIT                                    |
-   +----------------+--------------------------------------------------+
-
-   Use of the above obsolete rules for the definition of scheme-specific
-   syntax is deprecated.
-
-   Section 2, on characters, has been rewritten to explain what
-   characters are reserved, when they are reserved, and why they are
-   reserved, even when they are not used as delimiters by the generic
-   syntax.  The mark characters that are typically unsafe to decode,
-   including the exclamation mark ("!"), asterisk ("*"), single-quote
-   ("'"), and open and close parentheses ("(" and ")"), have been moved
-   to the reserved set in order to clarify the distinction between
-   reserved and unreserved and, hopefully, to answer the most common
-   question of scheme designers.  Likewise, the section on
-   percent-encoded characters has been rewritten, and URI normalizers
-   are now given license to decode any percent-encoded octets
-
-
-
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- 
-RFC 3986                   URI Generic Syntax               January 2005
-
-
-   corresponding to unreserved characters.  In general, the terms
-   "escaped" and "unescaped" have been replaced with "percent-encoded"
-   and "decoded", respectively, to reduce confusion with other forms of
-   escape mechanisms.
-
-   The ABNF for URI and URI-reference has been redesigned to make them
-   more friendly to LALR parsers and to reduce complexity.  As a result,
-   the layout form of syntax description has been removed, along with
-   the uric, uric_no_slash, opaque_part, net_path, abs_path, rel_path,
-   path_segments, rel_segment, and mark rules.  All references to
-   "opaque" URIs have been replaced with a better description of how the
-   path component may be opaque to hierarchy.  The relativeURI rule has
-   been replaced with relative-ref to avoid unnecessary confusion over
-   whether they are a subset of URI.  The ambiguity regarding the
-   parsing of URI-reference as a URI or a relative-ref with a colon in
-   the first segment has been eliminated through the use of five
-   separate path matching rules.
-
-   The fragment identifier has been moved back into the section on
-   generic syntax components and within the URI and relative-ref rules,
-   though it remains excluded from absolute-URI.  The number sign ("#")
-   character has been moved back to the reserved set as a result of
-   reintegrating the fragment syntax.
-
-   The ABNF has been corrected to allow the path component to be empty.
-   This also allows an absolute-URI to consist of nothing after the
-   "scheme:", as is present in practice with the "dav:" namespace
-   [RFC2518] and with the "about:" scheme used internally by many WWW
-   browser implementations.  The ambiguity regarding the boundary
-   between authority and path has been eliminated through the use of
-   five separate path matching rules.
-
-   Registry-based naming authorities that use the generic syntax are now
-   defined within the host rule.  This change allows current
-   implementations, where whatever name provided is simply fed to the
-   local name resolution mechanism, to be consistent with the
-   specification.  It also removes the need to re-specify DNS name
-   formats here.  Furthermore, it allows the host component to contain
-   percent-encoded octets, which is necessary to enable
-   internationalized domain names to be provided in URIs, processed in
-   their native character encodings at the application layers above URI
-   processing, and passed to an IDNA library as a registered name in the
-   UTF-8 character encoding.  The server, hostport, hostname,
-   domainlabel, toplabel, and alphanum rules have been removed.
-
-   The resolving relative references algorithm of [RFC2396] has been
-   rewritten with pseudocode for this revision to improve clarity and
-   fix the following issues:
-
-
-
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-
-
-   o  [RFC2396] section 5.2, step 6a, failed to account for a base URI
-      with no path.
-
-   o  Restored the behavior of [RFC1808] where, if the reference
-      contains an empty path and a defined query component, the target
-      URI inherits the base URI's path component.
-
-   o  The determination of whether a URI reference is a same-document
-      reference has been decoupled from the URI parser, simplifying the
-      URI processing interface within applications in a way consistent
-      with the internal architecture of deployed URI processing
-      implementations.  The determination is now based on comparison to
-      the base URI after transforming a reference to absolute form,
-      rather than on the format of the reference itself.  This change
-      may result in more references being considered "same-document"
-      under this specification than there would be under the rules given
-      in RFC 2396, especially when normalization is used to reduce
-      aliases.  However, it does not change the status of existing
-      same-document references.
-
-   o  Separated the path merge routine into two routines: merge, for
-      describing combination of the base URI path with a relative-path
-      reference, and remove_dot_segments, for describing how to remove
-      the special "." and ".." segments from a composed path.  The
-      remove_dot_segments algorithm is now applied to all URI reference
-      paths in order to match common implementations and to improve the
-      normalization of URIs in practice.  This change only impacts the
-      parsing of abnormal references and same-scheme references wherein
-      the base URI has a non-hierarchical path.
-
-Index
-
-   A
-      ABNF  11
-      absolute  27
-      absolute-path  26
-      absolute-URI  27
-      access  9
-      authority  17, 18
-
-   B
-      base URI  28
-
-   C
-      character encoding  4
-      character  4
-      characters  8, 11
-      coded character set  4
-
-
-
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- 
-RFC 3986                   URI Generic Syntax               January 2005
-
-
-   D
-      dec-octet  20
-      dereference  9
-      dot-segments  23
-
-   F
-      fragment  16, 24
-
-   G
-      gen-delims  13
-      generic syntax  6
-
-   H
-      h16  20
-      hier-part  16
-      hierarchical  10
-      host  18
-
-   I
-      identifier  5
-      IP-literal  19
-      IPv4  20
-      IPv4address  19, 20
-      IPv6  19
-      IPv6address  19, 20
-      IPvFuture  19
-
-   L
-      locator  7
-      ls32  20
-
-   M
-      merge  32
-
-   N
-      name  7
-      network-path  26
-
-   P
-      path  16, 22, 26
-         path-abempty  22
-         path-absolute  22
-         path-empty  22
-         path-noscheme  22
-         path-rootless  22
-      path-abempty  16, 22, 26
-      path-absolute  16, 22, 26
-      path-empty  16, 22, 26
-
-
-
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- 
-RFC 3986                   URI Generic Syntax               January 2005
-
-
-      path-rootless  16, 22
-      pchar  23
-      pct-encoded  12
-      percent-encoding  12
-      port  22
-
-   Q
-      query  16, 23
-
-   R
-      reg-name  21
-      registered name  20
-      relative  10, 28
-      relative-path  26
-      relative-ref  26
-      remove_dot_segments  33
-      representation  9
-      reserved  12
-      resolution  9, 28
-      resource  5
-      retrieval  9
-
-   S
-      same-document  27
-      sameness  9
-      scheme  16, 17
-      segment  22, 23
-         segment-nz  23
-         segment-nz-nc  23
-      sub-delims  13
-      suffix  27
-
-   T
-      transcription  8
-
-   U
-      uniform  4
-      unreserved  13
-      URI grammar
-         absolute-URI  27
-         ALPHA  11
-         authority  18
-         CR  11
-         dec-octet  20
-         DIGIT  11
-         DQUOTE  11
-         fragment  24
-         gen-delims  13
-
-
-
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- 
-RFC 3986                   URI Generic Syntax               January 2005
-
-
-         h16  20
-         HEXDIG  11
-         hier-part  16
-         host  19
-         IP-literal  19
-         IPv4address  20
-         IPv6address  20
-         IPvFuture  19
-         LF  11
-         ls32  20
-         OCTET  11
-         path  22
-         path-abempty  22
-         path-absolute  22
-         path-empty  22
-         path-noscheme  22
-         path-rootless  22
-         pchar  23
-         pct-encoded  12
-         port  22
-         query  24
-         reg-name  21
-         relative-ref  26
-         reserved  13
-         scheme  17
-         segment  23
-         segment-nz  23
-         segment-nz-nc  23
-         SP  11
-         sub-delims  13
-         unreserved  13
-         URI  16
-         URI-reference  25
-         userinfo  18
-      URI  16
-      URI-reference  25
-      URL  7
-      URN  7
-      userinfo  18
-
-
-
-
-
-
-
-
-
-
-
-
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- 
-RFC 3986                   URI Generic Syntax               January 2005
-
-
-Authors' Addresses
-
-   Tim Berners-Lee
-   World Wide Web Consortium
-   Massachusetts Institute of Technology
-   77 Massachusetts Avenue
-   Cambridge, MA  02139
-   USA
-
-   Phone: +1-617-253-5702
-   Fax:   +1-617-258-5999
-   EMail: timbl@w3.org
-   URI:   http://www.w3.org/People/Berners-Lee/
-
-
-   Roy T. Fielding
-   Day Software
-   5251 California Ave., Suite 110
-   Irvine, CA  92617
-   USA
-
-   Phone: +1-949-679-2960
-   Fax:   +1-949-679-2972
-   EMail: fielding@gbiv.com
-   URI:   http://roy.gbiv.com/
-
-
-   Larry Masinter
-   Adobe Systems Incorporated
-   345 Park Ave
-   San Jose, CA  95110
-   USA
-
-   Phone: +1-408-536-3024
-   EMail: LMM@acm.org
-   URI:   http://larry.masinter.net/
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-Berners-Lee, et al.         Standards Track                    [Page 60]
- 
-RFC 3986                   URI Generic Syntax               January 2005
-
-
-Full Copyright Statement
-
-   Copyright (C) The Internet Society (2005).
-
-   This document is subject to the rights, licenses and restrictions
-   contained in BCP 78, and except as set forth therein, the authors
-   retain all their rights.
-
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-
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-   ipr@ietf.org.
-
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-Acknowledgement
-
-   Funding for the RFC Editor function is currently provided by the
-   Internet Society.
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-
-
-
-Berners-Lee, et al.         Standards Track                    [Page 61]
- 
-
-
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