< draft-fielding-uri-syntax-02.txt		draft-fielding-uri-syntax-03.txt >
	Network Working Group T. Berners-Lee, MIT/LCS		Network Working Group T. Berners-Lee, MIT/LCS
	INTERNET-DRAFT R. Fielding, U.C. Irvine		INTERNET-DRAFT R. Fielding, U.C. Irvine
	draft-fielding-uri-syntax-02 L. Masinter, Xerox Corporation		draft-fielding-uri-syntax-03 L. Masinter, Xerox Corporation
	Expires six months after publication date March 4, 1998		Expires six months after publication date June 4, 1998
	Uniform Resource Identifiers (URI): Generic Syntax		Uniform Resource Identifiers (URI): Generic Syntax
	Status of this Memo		Status of this Memo
	This document is an Internet-Draft. Internet-Drafts are working		This document is an Internet-Draft. Internet-Drafts are working
	documents of the Internet Engineering Task Force (IETF), its areas,		documents of the Internet Engineering Task Force (IETF), its areas,
	and its working groups. Note that other groups may also distribute		and its working groups. Note that other groups may also distribute
	working documents as Internet-Drafts.		working documents as Internet-Drafts.
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	months and may be updated, replaced, or obsoleted by other		months and may be updated, replaced, or obsoleted by other
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	as reference material or to cite them other than as ``work in		as reference material or to cite them other than as ``work in
	progress.''		progress.''
	To learn the current status of any Internet-Draft, please check the		To view the entire list of current Internet-Drafts, please check the
	``1id-abstracts.txt'' listing contained in the Internet-Drafts		"1id-abstracts.txt" listing contained in the Internet-Drafts Shadow
	Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net		Directories on ftp.is.co.za (Africa), ftp.nordu.net (Northern
	(Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East		Europe), ftp.nis.garr.it (Southern Europe), munnari.oz.au (Pacific
	Coast), or ftp.isi.edu (US West Coast).		Rim), ftp.ietf.org (US East Coast), or ftp.isi.edu (US West Coast).
	Instructions to RFC Editor: This document will obsolete RFC 1738 and		Instructions to RFC Editor: This document will obsolete RFC 1738 and
	RFC 1808. If the new version of the MHTML proposed standard is		RFC 1808. If the new version of the MHTML proposed standard is
	ready for publication at the same time as this document, please		ready for publication at the same time as this document, please
	change all references to RFC 2110 to refer to its new version.		change all references to RFC 2110 to refer to its new version.
	Copyright Notice		Copyright Notice
	Copyright (C) The Internet Society (1998). All Rights Reserved.		Copyright (C) The Internet Society (1998). All Rights Reserved.
	Abstract		Abstract
	A Uniform Resource Identifier (URI) is a compact string of characters		A Uniform Resource Identifier (URI) is a compact string of characters
	for identifying an abstract or physical resource. This document		for identifying an abstract or physical resource. This document
	defines the general syntax of URIs, including both absolute and		defines the generic syntax of URI, including both absolute and
	relative forms, and guidelines for their use; it revises and replaces		relative forms, and guidelines for their use; it revises and replaces
	the generic definitions in RFC 1738 and RFC 1808.		the generic definitions in RFC 1738 and RFC 1808.
			This document defines a grammar that is a superset of all valid URI,
			such that an implementation can parse the common components of a URI
			reference without knowing the scheme-specific requirements of every
			possible identifier type. This document does not define a generative
			grammar for URI; that task will be performed by the individual
			specifications of each URI scheme.
	1. Introduction		1. Introduction
	Uniform Resource Identifiers (URIs) provide a simple and extensible		Uniform Resource Identifiers (URI) provide a simple and extensible
	means for identifying a resource. This specification of URI syntax		means for identifying a resource. This specification of URI syntax
	and semantics is derived from concepts introduced by the World Wide		and semantics is derived from concepts introduced by the World Wide
	Web global information initiative, whose use of such objects dates		Web global information initiative, whose use of such objects dates
	from 1990 and is described in "Universal Resource Identifiers in WWW"		from 1990 and is described in "Universal Resource Identifiers in WWW"
	[RFC1630]. The specification of URIs is designed to meet the		[RFC1630]. The specification of URI is designed to meet the
	recommendations laid out in "Functional Recommendations for Internet		recommendations laid out in "Functional Recommendations for Internet
	Resource Locators" [RFC1736] and "Functional Requirements for Uniform		Resource Locators" [RFC1736] and "Functional Requirements for Uniform
	Resource Names" [RFC1737].		Resource Names" [RFC1737].
	This document updates and merges "Uniform Resource Locators"		This document updates and merges "Uniform Resource Locators"
	[RFC1738] and "Relative Uniform Resource Locators" [RFC1808] in		[RFC1738] and "Relative Uniform Resource Locators" [RFC1808] in
	order to define a single, general syntax for all URIs. It excludes		order to define a single, generic syntax for all URI. It excludes
	those portions of RFC 1738 that defined the specific syntax of		those portions of RFC 1738 that defined the specific syntax of
	individual URL schemes; those portions will be updated as separate		individual URL schemes; those portions will be updated as separate
	documents, as will the process for registration of new URI schemes.		documents, as will the process for registration of new URI schemes.
	This document does not discuss the issues and recommendation for		This document does not discuss the issues and recommendation for
	dealing with characters outside of the US-ASCII character set		dealing with characters outside of the US-ASCII character set
	[ASCII]; those recommendations are discussed in a separate document.		[ASCII]; those recommendations are discussed in a separate document.
	All significant changes from the prior RFCs are noted in Appendix G.		All significant changes from the prior RFCs are noted in Appendix G.
	1.1 Overview of URIs		1.1 Overview of URI
	URIs are characterized by the following definitions:		URI are characterized by the following definitions:
	Uniform		Uniform
	Uniformity provides several benefits: it allows different types		Uniformity provides several benefits: it allows different types
	of resource identifiers to be used in the same context, even		of resource identifiers to be used in the same context, even
	when the mechanisms used to access those resources may differ;		when the mechanisms used to access those resources may differ;
	it allows uniform semantic interpretation of common syntactic		it allows uniform semantic interpretation of common syntactic
	conventions across different types of resource identifiers; it		conventions across different types of resource identifiers; it
	allows introduction of new types of resource identifiers		allows introduction of new types of resource identifiers
	without interfering with the way that existing identifiers are		without interfering with the way that existing identifiers are
	used; and, it allows the identifiers to be reused in many		used; and, it allows the identifiers to be reused in many
	skipping to change at line 102 ¶		skipping to change at line 109 ¶
	The resource is the conceptual mapping to an entity or set of		The resource is the conceptual mapping to an entity or set of
	entities, not necessarily the entity which corresponds to that		entities, not necessarily the entity which corresponds to that
	mapping at any particular instance in time. Thus, a resource		mapping at any particular instance in time. Thus, a resource
	can remain constant even when its content---the entities to		can remain constant even when its content---the entities to
	which it currently corresponds---changes over time, provided		which it currently corresponds---changes over time, provided
	that the conceptual mapping is not changed in the process.		that the conceptual mapping is not changed in the process.
	Identifier		Identifier
	An identifier is an object that can act as a reference to		An identifier is an object that can act as a reference to
	something that has identity. In the case of URIs, the object		something that has identity. In the case of URI, the object
	is a sequence of characters with a restricted syntax.		is a sequence of characters with a restricted syntax.
	Having identified a resource, a system may perform a variety of		Having identified a resource, a system may perform a variety of
	operations on the resource, as might be characterized by such words		operations on the resource, as might be characterized by such words
	as `access', `update', `replace', or `find attributes'.		as `access', `update', `replace', or `find attributes'.
	1.2. URI, URL, and URN		1.2. URI, URL, and URN
	A URI can be further classified as a locator, a name, or both. The		A URI can be further classified as a locator, a name, or both. The
	term "Uniform Resource Locator" (URL) refers to the subset of URI		term "Uniform Resource Locator" (URL) refers to the subset of URI
	that identify resources via a representation of their primary access		that identify resources via a representation of their primary access
	mechanism (e.g., their network "location"), rather than identifying		mechanism (e.g., their network "location"), rather than identifying
	the resource by name or by some other attribute(s) of that resource.		the resource by name or by some other attribute(s) of that resource.
	The term "Uniform Resource Name" (URN) refers to the subset of URI		The term "Uniform Resource Name" (URN) refers to the subset of URI
	that are required to remain globally unique and persistent even when		that are required to remain globally unique and persistent even when
	the resource ceases to exist or becomes unavailable.		the resource ceases to exist or becomes unavailable.
	The URI scheme (Section 3.1) defines the namespace of the URI, and		The URI scheme (Section 3.1) defines the namespace of the URI, and
	thus may further restrict the syntax and semantics of identifiers		thus may further restrict the syntax and semantics of identifiers
	using that scheme. This specification defines those elements of the		using that scheme. This specification defines those elements of the
	URI syntax which are either required of all URI schemes or are common		URI syntax that are either required of all URI schemes or are common
	to many URI schemes. It thus defines the syntax and semantics that		to many URI schemes. It thus defines the syntax and semantics that
	are needed to implement a scheme-independent parsing mechanism for		are needed to implement a scheme-independent parsing mechanism for
	URI references, such that the scheme-dependent handling of a URI can		URI references, such that the scheme-dependent handling of a URI can
	be postponed until the scheme-dependent semantics are needed. We use		be postponed until the scheme-dependent semantics are needed. We use
	the term URL below when describing syntax or semantics that only		the term URL below when describing syntax or semantics that only
	apply to locators.		apply to locators.
	Although many URL schemes are named after protocols, this does not		Although many URL schemes are named after protocols, this does not
	imply that the only way to access the URL's resource is via the named		imply that the only way to access the URL's resource is via the named
	protocol. Gateways, proxies, caches, and name resolution services		protocol. Gateways, proxies, caches, and name resolution services
	might be used to access some resources, independent of the protocol		might be used to access some resources, independent of the protocol
	of their origin, and the resolution of some URLs may require the use		of their origin, and the resolution of some URL may require the use
	of more than one protocol (e.g., both DNS and HTTP are typically used		of more than one protocol (e.g., both DNS and HTTP are typically used
	to access an "http" URL's resource when it can't be found in a local		to access an "http" URL's resource when it can't be found in a local
	cache).		cache).
	A URN differs from a URL in that it's primary purpose is persistent		A URN differs from a URL in that it's primary purpose is persistent
	labeling of a resource with an identifier. That identifier is drawn		labeling of a resource with an identifier. That identifier is drawn
	from one of a set of defined namespaces, each of which has its own		from one of a set of defined namespaces, each of which has its own
	set name structure and assignment procedures. The "urn" scheme has		set name structure and assignment procedures. The "urn" scheme has
	been reserved to establish the requirements for a standardized URN		been reserved to establish the requirements for a standardized URN
	namespace, as defined in "URN Syntax" [RFC2141] and its related		namespace, as defined in "URN Syntax" [RFC2141] and its related
	specifications.		specifications.
	Most of the examples in this specification demonstrate URLs, since		Most of the examples in this specification demonstrate URL, since
	they allow the most varied use of the syntax and often have a		they allow the most varied use of the syntax and often have a
	hierarchical namespace. A parser of the URI syntax is capable of		hierarchical namespace. A parser of the URI syntax is capable of
	parsing both URL and URN references as a generic URI; once the scheme		parsing both URL and URN references as a generic URI; once the scheme
	is determined, the scheme-specific parsing can be performed on the		is determined, the scheme-specific parsing can be performed on the
	generic URI components. In other words, the URI syntax is a superset		generic URI components. In other words, the URI syntax is a superset
	of the syntax of all URI schemes.		of the syntax of all URI schemes.
	1.3. Example URIs		1.3. Example URI
	The following examples illustrate URIs which are in common use.		The following examples illustrate URI that are in common use.
	ftp://ftp.is.co.za/rfc/rfc1808.txt		ftp://ftp.is.co.za/rfc/rfc1808.txt
	-- ftp scheme for File Transfer Protocol services		-- ftp scheme for File Transfer Protocol services
	gopher://spinaltap.micro.umn.edu/00/Weather/California/Los%20Angeles		gopher://spinaltap.micro.umn.edu/00/Weather/California/Los%20Angeles
	-- gopher scheme for Gopher and Gopher+ Protocol services		-- gopher scheme for Gopher and Gopher+ Protocol services
	http://www.math.uio.no/faq/compression-faq/part1.html		http://www.math.uio.no/faq/compression-faq/part1.html
	-- http scheme for Hypertext Transfer Protocol services		-- http scheme for Hypertext Transfer Protocol services
	mailto:mduerst@ifi.unizh.ch		mailto:mduerst@ifi.unizh.ch
	-- mailto scheme for electronic mail addresses		-- mailto scheme for electronic mail addresses
	news:comp.infosystems.www.servers.unix		news:comp.infosystems.www.servers.unix
	-- news scheme for USENET news groups and articles		-- news scheme for USENET news groups and articles
	telnet://melvyl.ucop.edu/		telnet://melvyl.ucop.edu/
	-- telnet scheme for interactive services via the TELNET Protocol		-- telnet scheme for interactive services via the TELNET Protocol
	1.4. Hierarchical URIs and Relative Forms		1.4. Hierarchical URI and Relative Forms
	An absolute identifier refers to a resource independent of the		An absolute identifier refers to a resource independent of the
	context in which the identifier is used. In contrast, a relative		context in which the identifier is used. In contrast, a relative
	identifier refers to a resource by describing the difference within a		identifier refers to a resource by describing the difference within a
	hierarchical namespace between the current context and an absolute		hierarchical namespace between the current context and an absolute
	identifier of the resource.		identifier of the resource.
	Some URI schemes support a hierarchical naming system, where the		Some URI schemes support a hierarchical naming system, where the
	hierarchy of the name is denoted by a "/" delimiter separating the		hierarchy of the name is denoted by a "/" delimiter separating the
	components in the scheme. This document defines a scheme-independent		components in the scheme. This document defines a scheme-independent
	`relative' form of URI reference that can be used in conjunction with		`relative' form of URI reference that can be used in conjunction with
	a `base' URI (of a hierarchical scheme) to produce another URI. The		a `base' URI (of a hierarchical scheme) to produce another URI. The
	syntax of hierarchical URIs is described in Section 3; the relative		syntax of hierarchical URI is described in Section 3; the relative
	URI calculation is described in Section 5.		URI calculation is described in Section 5.
	1.5. URI Transcribability		1.5. URI Transcribability
	The URI syntax was designed with global transcribability as one of		The URI syntax was designed with global transcribability as one of
	its main concerns. A URI is a sequence of characters from a very		its main concerns. A URI is a sequence of characters from a very
	limited set, i.e. the letters of the basic Latin alphabet, digits,		limited set, i.e. the letters of the basic Latin alphabet, digits,
	and a few special characters. A URI may be represented in a		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		variety of ways: e.g., ink on paper, pixels on a screen, or a
	sequence of octets in a coded character set. The interpretation of		sequence of octets in a coded character set. The interpretation of
	skipping to change at line 219 ¶		skipping to change at line 226 ¶
	for the research site on a napkin. Upon returning home, Sam takes		for the research site on a napkin. Upon returning home, Sam takes
	out the napkin and types the URI into a computer, which then		out the napkin and types the URI into a computer, which then
	retrieves the information to which Kim referred.		retrieves the information to which Kim referred.
	There are several design concerns revealed by the scenario:		There are several design concerns revealed by the scenario:
	o A URI is a sequence of characters, which is not always		o A URI is a sequence of characters, which is not always
	represented as a sequence of octets.		represented as a sequence of octets.
	o A URI may be transcribed from a non-network source, and thus		o A URI may be transcribed from a non-network source, and thus
	should consist of characters which are most likely to be able		should consist of characters that are most likely to be able
	to be typed into a computer, within the constraints imposed by		to be typed into a computer, within the constraints imposed by
	keyboards (and related input devices) across languages and		keyboards (and related input devices) across languages and
	locales.		locales.
	o A URI often needs to be remembered by people, and it is easier		o A URI often needs to be remembered by people, and it is easier
	for people to remember a URI when it consists of meaningful		for people to remember a URI when it consists of meaningful
	components.		components.
	These design concerns are not always in alignment. For example, it		These design concerns are not always in alignment. For example, it
	is often the case that the most meaningful name for a URI component		is often the case that the most meaningful name for a URI component
	would require characters which cannot be typed into some systems.		would require characters that cannot be typed into some systems.
	The ability to transcribe the resource identifier from one medium to		The ability to transcribe the resource identifier from one medium to
	another was considered more important than having its URI consist		another was considered more important than having its URI consist
	of the most meaningful of components. In local and regional		of the most meaningful of components. In local and regional
	contexts and with improving technology, users might benefit from		contexts and with improving technology, users might benefit from
	being able to use a wider range of characters; such use is not		being able to use a wider range of characters; such use is not
	defined in this document.		defined in this document.
	1.6. Syntax Notation and Common Elements		1.6. Syntax Notation and Common Elements
	This document uses two conventions to describe and define the syntax		This document uses two conventions to describe and define the syntax
	skipping to change at line 261 ¶		skipping to change at line 268 ¶
	The second convention is a BNF-like grammar, used to define the		The second convention is a BNF-like grammar, used to define the
	formal URI syntax. The grammar is that of [RFC822], except that		formal URI syntax. The grammar is that of [RFC822], except that
	"|" is used to designate alternatives. Briefly, rules are separated		"|" is used to designate alternatives. Briefly, rules are separated
	from definitions by an equal "=", indentation is used to continue a		from definitions by an equal "=", indentation is used to continue a
	rule definition over more than one line, literals are quoted with "",		rule definition over more than one line, literals are quoted with "",
	parentheses "(" and ")" are used to group elements, optional elements		parentheses "(" and ")" are used to group elements, optional elements
	are enclosed in "[" and "]" brackets, and elements may be preceded		are enclosed in "[" and "]" brackets, and elements may be preceded
	with <n>* to designate n or more repetitions of the following		with <n>* to designate n or more repetitions of the following
	element; n defaults to 0.		element; n defaults to 0.
	Unlike many specifications which use a BNF-like grammar to define the		Unlike many specifications that use a BNF-like grammar to define the
	bytes (octets) allowed by a protocol, the URI grammar is defined in		bytes (octets) allowed by a protocol, the URI grammar is defined in
	terms of characters. Each literal in the grammar corresponds to the		terms of characters. Each literal in the grammar corresponds to the
	character it represents, rather than to the octet encoding of that		character it represents, rather than to the octet encoding of that
	character in any particular coded character set. How a URI is		character in any particular coded character set. How a URI is
	represented in terms of bits and bytes on the wire is dependent upon		represented in terms of bits and bytes on the wire is dependent upon
	the character encoding of the protocol used to transport it, or the		the character encoding of the protocol used to transport it, or the
	charset of the document which contains it.		charset of the document which contains it.
	The following definitions are common to many elements:		The following definitions are common to many elements:
	skipping to change at line 291 ¶		skipping to change at line 298 ¶
	digit = "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" |		digit = "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" |
	"8" | "9"		"8" | "9"
	alphanum = alpha | digit		alphanum = alpha | digit
	The complete URI syntax is collected in Appendix A.		The complete URI syntax is collected in Appendix A.
	2. URI Characters and Escape Sequences		2. URI Characters and Escape Sequences
	URIs consist of a restricted set of characters, primarily chosen to		URI consist of a restricted set of characters, primarily chosen to
	aid transcribability and usability both in computer systems and in		aid transcribability and usability both in computer systems and in
	non-computer communications. Characters used conventionally as		non-computer communications. Characters used conventionally as
	delimiters around URIs were excluded. The restricted set of		delimiters around URI were excluded. The restricted set of
	characters consists of digits, letters, and a few graphic symbols		characters consists of digits, letters, and a few graphic symbols
	were chosen from those common to most of the character encodings		were chosen from those common to most of the character encodings
	and input facilities available to Internet users.		and input facilities available to Internet users.
			uric = reserved | unreserved | escaped
	Within a URI, characters are either used as delimiters, or to		Within a URI, characters are either used as delimiters, or to
	represent strings of data (octets) within the delimited portions.		represent strings of data (octets) within the delimited portions.
	Octets are either represented directly by a character (using the		Octets are either represented directly by a character (using the
	US-ASCII character for that octet [ASCII]) or by an escape encoding.		US-ASCII character for that octet [ASCII]) or by an escape encoding.
	This representation is elaborated below.		This representation is elaborated below.
	2.1 URIs and non-ASCII characters		2.1 URI and non-ASCII characters
	The relationship between URIs and characters has been a source of		The relationship between URI and characters has been a source of
	confusion for characters that are not part of US-ASCII. To describe		confusion for characters that are not part of US-ASCII. To describe
	the relationship, it is useful to distinguish between a "character"		the relationship, it is useful to distinguish between a "character"
	(as a distinguishable semantic entity) and an "octet" (an 8-bit		(as a distinguishable semantic entity) and an "octet" (an 8-bit
	byte). There are two mappings, one from URI characters to octets,		byte). There are two mappings, one from URI characters to octets,
	and a second from octets to original characters:		and a second from octets to original characters:
	URI character sequence->octet sequence->original character sequence		URI character sequence->octet sequence->original character sequence
	A URI is represented as a sequence of characters, not as a sequence		A URI is represented as a sequence of characters, not as a sequence
	of octets. That is because URIs might be "transported" by means that		of octets. That is because URI might be "transported" by means that
	are not through a computer network, e.g., printed on paper, read		are not through a computer network, e.g., printed on paper, read
	over the radio, etc.		over the radio, etc.
	A URI scheme may define a mapping from URI characters to octets;		A URI scheme may define a mapping from URI characters to octets;
	whether this is done depends on the scheme. Commonly, within a		whether this is done depends on the scheme. Commonly, within a
	delimited component of a URI, a sequence of characters may be		delimited component of a URI, a sequence of characters may be
	used to represent a sequence of octets. For example, the character		used to represent a sequence of octets. For example, the character
	"a" represents the octet 97 (decimal), while the character sequence		"a" represents the octet 97 (decimal), while the character sequence
	"%", "0", "a" represents the octet 10 (decimal).		"%", "0", "a" represents the octet 10 (decimal).
	skipping to change at line 353 ¶		skipping to change at line 362 ¶
	however, the situation is more difficult. Internet protocols that		however, the situation is more difficult. Internet protocols that
	transmit octet sequences intended to represent character sequences		transmit octet sequences intended to represent character sequences
	are expected to provide some way of identifying the charset used,		are expected to provide some way of identifying the charset used,
	if there might be more than one [RFC2277]. However, there is		if there might be more than one [RFC2277]. However, there is
	currently no provision within the generic URI syntax to accomplish		currently no provision within the generic URI syntax to accomplish
	this identification. An individual URI scheme may require a single		this identification. An individual URI scheme may require a single
	charset, define a default charset, or provide a way to indicate the		charset, define a default charset, or provide a way to indicate the
	charset used.		charset used.
	It is expected that a systematic treatment of character encoding		It is expected that a systematic treatment of character encoding
	within URIs will be developed as a future modification of this		within URI will be developed as a future modification of this
	specification.		specification.
	2.2. Reserved Characters		2.2. Reserved Characters
	Many URIs include components consisting of or delimited by, certain		Many URI include components consisting of or delimited by, certain
	special characters. These characters are called "reserved", since		special characters. These characters are called "reserved", since
	their usage within the URI component is limited to their reserved		their usage within the URI component is limited to their reserved
	purpose. If the data for a URI component would conflict with the		purpose. If the data for a URI component would conflict with the
	reserved purpose, then the conflicting data must be escaped before		reserved purpose, then the conflicting data must be escaped before
	forming the URI.		forming the URI.
	reserved = ";" | "/" | "?" | ":" | "@" | "&" | "=" | "+" |		reserved = ";" | "/" | "?" | ":" | "@" | "&" | "=" | "+" |
	"$" | ","		"$" | ","
	The "reserved" syntax class above refers to those characters which		The "reserved" syntax class above refers to those characters that
	are allowed within a URI, but which may not be allowed within a		are allowed within a URI, but which may not be allowed within a
	particular component of the generic URI syntax; they are used as		particular component of the generic URI syntax; they are used as
	delimiters of the components described in Section 3.		delimiters of the components described in Section 3.
	Characters in the "reserved" set are not reserved in all contexts.		Characters in the "reserved" set are not reserved in all contexts.
	The set of characters actually reserved within any given URI		The set of characters actually reserved within any given URI
	component is defined by that component. In general, a character is		component is defined by that component. In general, a character is
	reserved if the semantics of the URI changes if the character is		reserved if the semantics of the URI changes if the character is
	replaced with its escaped US-ASCII encoding.		replaced with its escaped US-ASCII encoding.
	2.3. Unreserved Characters		2.3. Unreserved Characters
	Data characters which are allowed in a URI but do not have a reserved		Data characters that are allowed in a URI but do not have a reserved
	purpose are called unreserved. These include upper and lower case		purpose are called unreserved. These include upper and lower case
	letters, decimal digits, and a limited set of punctuation marks and		letters, decimal digits, and a limited set of punctuation marks and
	symbols.		symbols.
	unreserved = alphanum | mark		unreserved = alphanum | mark
	mark = "-" | "_" | "." | "!" | "~" | "*" | "'" | "(" | ")"		mark = "-" | "_" | "." | "!" | "~" | "*" | "'" | "(" | ")"
	Unreserved characters can be escaped without changing the semantics		Unreserved characters can be escaped without changing the semantics
	of the URI, but this should not be done unless the URI is being used		of the URI, but this should not be done unless the URI is being used
	in a context which does not allow the unescaped character to appear.		in a context that does not allow the unescaped character to appear.
	2.4. Escape Sequences		2.4. Escape Sequences
	Data must be escaped if it does not have a representation using an		Data must be escaped if it does not have a representation using an
	unreserved character; this includes data that does not correspond		unreserved character; this includes data that does not correspond
	to a printable character of the US-ASCII coded character set, or		to a printable character of the US-ASCII coded character set, or
	that corresponds to any US-ASCII character that is disallowed, as		that corresponds to any US-ASCII character that is disallowed, as
	explained below.		explained below.
	2.4.1. Escaped Encoding		2.4.1. Escaped Encoding
	skipping to change at line 419 ¶		skipping to change at line 428 ¶
	escaped = "%" hex hex		escaped = "%" hex hex
	hex = digit | "A" | "B" | "C" | "D" | "E" | "F" |		hex = digit | "A" | "B" | "C" | "D" | "E" | "F" |
	"a" | "b" | "c" | "d" | "e" | "f"		"a" | "b" | "c" | "d" | "e" | "f"
	2.4.2. When to Escape and Unescape		2.4.2. When to Escape and Unescape
	A URI is always in an "escaped" form, since escaping or unescaping		A URI is always in an "escaped" form, since escaping or unescaping
	a completed URI might change its semantics. Normally, the only		a completed URI might change its semantics. Normally, the only
	time escape encodings can safely be made is when the URI is being		time escape encodings can safely be made is when the URI is being
	created from its component parts; each component may have its own		created from its component parts; each component may have its own
	set of characters which are reserved, so only the mechanism		set of characters that are reserved, so only the mechanism
	responsible for generating or interpreting that component can		responsible for generating or interpreting that component can
	determine whether or not escaping a character will change its		determine whether or not escaping a character will change its
	semantics. Likewise, a URI must be separated into its components		semantics. Likewise, a URI must be separated into its components
	before the escaped characters within those components can be safely		before the escaped characters within those components can be safely
	decoded.		decoded.
	In some cases, data that could be represented by an unreserved		In some cases, data that could be represented by an unreserved
	character may appear escaped; for example, some of the unreserved		character may appear escaped; for example, some of the unreserved
	"mark" characters are automatically escaped by some systems. If the		"mark" characters are automatically escaped by some systems. If the
	given URI scheme defines a canonicalization algorithm, then		given URI scheme defines a canonicalization algorithm, then
	skipping to change at line 445 ¶		skipping to change at line 454 ¶
	being the escape indicator, it must be escaped as "%25" in order to		being the escape indicator, it must be escaped as "%25" in order to
	be used as data within a URI. Implementers should be careful not to		be used as data within a URI. Implementers should be careful not to
	escape or unescape the same string more than once, since unescaping		escape or unescape the same string more than once, since unescaping
	an already unescaped string might lead to misinterpreting a percent		an already unescaped string might lead to misinterpreting a percent
	data character as another escaped character, or vice versa in the		data character as another escaped character, or vice versa in the
	case of escaping an already escaped string.		case of escaping an already escaped string.
	2.4.3. Excluded US-ASCII Characters		2.4.3. Excluded US-ASCII Characters
	Although they are disallowed within the URI syntax, we include here		Although they are disallowed within the URI syntax, we include here
	a description of those US-ASCII characters which have been excluded		a description of those US-ASCII characters that have been excluded
	and the reasons for their exclusion.		and the reasons for their exclusion.
	The control characters in the US-ASCII coded character set are not		The control characters in the US-ASCII coded character set are not
	used within a URI, both because they are non-printable and because		used within a URI, both because they are non-printable and because
	they are likely to be misinterpreted by some control mechanisms.		they are likely to be misinterpreted by some control mechanisms.
	control = <US-ASCII coded characters 00-1F and 7F hexadecimal>		control = <US-ASCII coded characters 00-1F and 7F hexadecimal>
	The space character is excluded because significant spaces may		The space character is excluded because significant spaces may
	disappear and insignificant spaces may be introduced when URIs are		disappear and insignificant spaces may be introduced when URI are
	transcribed or typeset or subjected to the treatment of		transcribed or typeset or subjected to the treatment of
	word-processing programs. Whitespace is also used to delimit URIs		word-processing programs. Whitespace is also used to delimit URI
	in many contexts.		in many contexts.
	space = <US-ASCII coded character 20 hexadecimal>		space = <US-ASCII coded character 20 hexadecimal>
	The angle-bracket "<" and ">" and double-quote (") characters are		The angle-bracket "<" and ">" and double-quote (") characters are
	excluded because they are often used as the delimiters around URIs		excluded because they are often used as the delimiters around URI
	in text documents and protocol fields. The character "#" is		in text documents and protocol fields. The character "#" is
	excluded because it is used to delimit a URI from a fragment		excluded because it is used to delimit a URI from a fragment
	identifier in URI references (Section 4). The percent character "%"		identifier in URI references (Section 4). The percent character "%"
	is excluded because it is used for the encoding of escaped		is excluded because it is used for the encoding of escaped
	characters.		characters.
	delims = "<" | ">" | "#" | "%" | <">		delims = "<" | ">" | "#" | "%" | <">
	Other characters are excluded because gateways and other transport		Other characters are excluded because gateways and other transport
	agents are known to sometimes modify such characters, or they are		agents are known to sometimes modify such characters, or they are
	used as delimiters.		used as delimiters.
	unwise = "{" | "}" | "|" | "\" | "^" | "[" | "]" | "`"		unwise = "{" | "}" | "|" | "\" | "^" | "[" | "]" | "`"
	Data corresponding to excluded characters must be escaped in order		Data corresponding to excluded characters must be escaped in order
	to be properly represented within a URI.		to be properly represented within a URI.
	3. URI Syntactic Components		3. URI Syntactic Components
	The URI syntax is dependent upon the scheme. In general, absolute		The URI syntax is dependent upon the scheme. In general, absolute
	URIs are written as follows:		URI are written as follows:
	<scheme>:<scheme-specific-part>		<scheme>:<scheme-specific-part>
	An absolute URI contains the name of the scheme being used (<scheme>)		An absolute URI contains the name of the scheme being used (<scheme>)
	followed by a colon (":") and then a string (the <scheme-specific-		followed by a colon (":") and then a string (the <scheme-specific-
	part>) whose interpretation depends on the scheme.		part>) whose interpretation depends on the scheme.
	The URI syntax does not require that the scheme-specific-part have		The URI syntax does not require that the scheme-specific-part have
	any general structure or set of semantics which is common among all		any general structure or set of semantics which is common among all
	URIs. However, a subset of URIs do share a common syntax for		URI. However, a subset of URI do share a common syntax for
	representing hierarchical relationships within the namespace. This		representing hierarchical relationships within the namespace. This
	"generic-URI" syntax consists of a sequence of four main components:		"generic URI" syntax consists of a sequence of four main components:
	<scheme>://<authority><path>?<query>		<scheme>://<authority><path>?<query>
	each of which, except <scheme>, may be absent from a particular URI.		each of which, except <scheme>, may be absent from a particular URI.
	For example, some URI schemes do not allow an <authority> component,		For example, some URI schemes do not allow an <authority> component,
	and others do not use a <query> component.		and others do not use a <query> component.
	absoluteURI = generic-URI | opaque-URI		absoluteURI = scheme ":" ( hier_part | opaque_part )
	opaque-URI = scheme ":" *uric
	generic-URI = scheme ":" relativeURI
	The separation of the URI grammar into <generic-URI> and <opaque-URI>
	is redundant, since both rules will successfully parse any string of
	<uric> characters. The distinction is simply to clarify that a
	parser of relative URI references (Section 5) will view a URI as a
	generic-URI, whereas a handler of absolute references need only view
	it as an opaque-URI.
	URIs which are hierarchical in nature use the slash "/" character for		URI that are hierarchical in nature use the slash "/" character for
	separating hierarchical components. For some file systems, a "/"		separating hierarchical components. For some file systems, a "/"
	character (used to denote the hierarchical structure of a URI) is the		character (used to denote the hierarchical structure of a URI) is the
	delimiter used to construct a file name hierarchy, and thus the URI		delimiter used to construct a file name hierarchy, and thus the URI
	path will look similar to a file pathname. This does NOT imply that		path will look similar to a file pathname. This does NOT imply that
	the resource is a file or that the URI maps to an actual filesystem		the resource is a file or that the URI maps to an actual filesystem
	pathname.		pathname.
			hier_part = ( net_path | abs_path ) [ "?" query ]
			net_path = "//" authority [ abs_path ]
			abs_path = "/" path_segments
			URI that do not make use of the slash "/" character for separating
			hierarchical components are considered opaque by the generic URI
			parser.
			opaque_part = uric_no_slash *uric
			uric_no_slash = unreserved | escaped | ";" | "?" | ":" | "@" |
			"&" | "=" | "+" | "$" | ","
			We use the term <path> to refer to both the <abs_path> and
			<opaque_part> constructs, since they are mutually exclusive for any
			given URI and can be parsed as a single component.
	3.1. Scheme Component		3.1. Scheme Component
	Just as there are many different methods of access to resources,		Just as there are many different methods of access to resources,
	there are a variety of schemes for identifying such resources. The		there are a variety of schemes for identifying such resources. The
	URI syntax consists of a sequence of components separated by reserved		URI syntax consists of a sequence of components separated by reserved
	characters, with the first component defining the semantics for the		characters, with the first component defining the semantics for the
	remainder of the URI string.		remainder of the URI string.
	Scheme names consist of a sequence of characters beginning with a		Scheme names consist of a sequence of characters beginning with a
	lower case letter and followed by any combination of lower case		lower case letter and followed by any combination of lower case
	letters, digits, plus ("+"), period ("."), or hyphen ("-"). For		letters, digits, plus ("+"), period ("."), or hyphen ("-"). For
	resiliency, programs interpreting URIs should treat upper case		resiliency, programs interpreting URI should treat upper case
	letters as equivalent to lower case in scheme names (e.g., allow		letters as equivalent to lower case in scheme names (e.g., allow
	"HTTP" as well as "http").		"HTTP" as well as "http").
	scheme = alpha *( alpha | digit | "+" | "-" | "." )		scheme = alpha *( alpha | digit | "+" | "-" | "." )
	Relative URI references are distinguished from absolute URIs in that		Relative URI references are distinguished from absolute URI in that
	they do not begin with a scheme name. Instead, the scheme is		they do not begin with a scheme name. Instead, the scheme is
	inherited from the base URI, as described in Section 5.2.		inherited from the base URI, as described in Section 5.2.
	3.2. Authority Component		3.2. Authority Component
	Many URI schemes include a top hierarchical element for a naming		Many URI schemes include a top hierarchical element for a naming
	authority, such that the namespace defined by the remainder of the		authority, such that the namespace defined by the remainder of the
	URI is governed by that authority. This authority component is		URI is governed by that authority. This authority component is
	typically defined by an Internet-based server or a scheme-specific		typically defined by an Internet-based server or a scheme-specific
	registry of naming authorities.		registry of naming authorities.
	skipping to change at line 597 ¶		skipping to change at line 614 ¶
	server = [ [ userinfo "@" ] hostport ]		server = [ [ userinfo "@" ] hostport ]
	The user information, if present, is followed by a commercial		The user information, if present, is followed by a commercial
	at-sign "@".		at-sign "@".
	userinfo = *( unreserved | escaped |		userinfo = *( unreserved | escaped |
	";" | ":" | "&" | "=" | "+" | "$" | "," )		";" | ":" | "&" | "=" | "+" | "$" | "," )
	Some URL schemes use the format "user:password" in the userinfo		Some URL schemes use the format "user:password" in the userinfo
	field. This practice is NOT RECOMMENDED, because the passing of		field. This practice is NOT RECOMMENDED, because the passing of
	authentication information in clear text (such as URIs) has proven to		authentication information in clear text (such as URI) has proven to
	be a security risk in almost every case where it has been used.		be a security risk in almost every case where it has been used.
	The host is a domain name of a network host, or its IPv4 address as		The host is a domain name of a network host, or its IPv4 address as
	a set of four decimal digit groups separated by ".". Literal IPv6		a set of four decimal digit groups separated by ".". Literal IPv6
	addresses are not supported.		addresses are not supported.
	hostport = host [ ":" port ]		hostport = host [ ":" port ]
	host = hostname | IPv4address		host = hostname | IPv4address
	hostname = *( domainlabel "." ) toplabel [ "." ]		hostname = *( domainlabel "." ) toplabel [ "." ]
	domainlabel = alphanum | alphanum *( alphanum | "-" ) alphanum		domainlabel = alphanum | alphanum *( alphanum | "-" ) alphanum
	skipping to change at line 640 ¶		skipping to change at line 657 ¶
	number may optionally be supplied, in decimal, separated from the		number may optionally be supplied, in decimal, separated from the
	host by a colon. If the port is omitted, the default port number is		host by a colon. If the port is omitted, the default port number is
	assumed.		assumed.
	3.3. Path Component		3.3. Path Component
	The path component contains data, specific to the authority (or the		The path component contains data, specific to the authority (or the
	scheme if there is no authority component), identifying the resource		scheme if there is no authority component), identifying the resource
	within the scope of that scheme and authority.		within the scope of that scheme and authority.
	path = [ "/" ] path_segments		path = [ abs_path | opaque_part ]
	path_segments = segment *( "/" segment )		path_segments = segment *( "/" segment )
	segment = *pchar *( ";" param )		segment = *pchar *( ";" param )
	param = *pchar		param = *pchar
	pchar = unreserved | escaped |		pchar = unreserved | escaped |
	":" | "@" | "&" | "=" | "+" | "$" | ","		":" | "@" | "&" | "=" | "+" | "$" | ","
	The path may consist of a sequence of path segments separated by a		The path may consist of a sequence of path segments separated by a
	single slash "/" character. Within a path segment, the characters		single slash "/" character. Within a path segment, the characters
	skipping to change at line 671 ¶		skipping to change at line 688 ¶
	query = *uric		query = *uric
	Within a query component, the characters ";", "/", "?", ":", "@",		Within a query component, the characters ";", "/", "?", ":", "@",
	"&", "=", "+", ",", and "$" are reserved.		"&", "=", "+", ",", and "$" are reserved.
	4. URI References		4. URI References
	The term "URI-reference" is used here to denote the common usage of		The term "URI-reference" is used here to denote the common usage of
	a resource identifier. A URI reference may be absolute or relative,		a resource identifier. A URI reference may be absolute or relative,
	and may have additional information attached in the form of a		and may have additional information attached in the form of a
	fragment identifier. However, "the URI" which results from such a		fragment identifier. However, "the URI" that results from such a
	reference includes only the absolute URI after the fragment		reference includes only the absolute URI after the fragment
	identifier (if any) is removed and after any relative URI is		identifier (if any) is removed and after any relative URI is
	resolved to its absolute form. Although it is possible to limit		resolved to its absolute form. Although it is possible to limit
	the discussion of URI syntax and semantics to that of the absolute		the discussion of URI syntax and semantics to that of the absolute
	result, most usage of URIs is within general URI references, and it		result, most usage of URI is within general URI references, and it
	is impossible to obtain the URI from such a reference without also		is impossible to obtain the URI from such a reference without also
	parsing the fragment and resolving the relative form.		parsing the fragment and resolving the relative form.
	URI-reference = [ absoluteURI | relativeURI ] [ "#" fragment ]		URI-reference = [ absoluteURI | relativeURI ] [ "#" fragment ]
	The syntax for relative URIs is a shortened form of that for absolute		The syntax for relative URI is a shortened form of that for absolute
	URIs, where some prefix of the URI is missing and certain path		URI, where some prefix of the URI is missing and certain path
	components ("." and "..") have a special meaning when interpreting a		components ("." and "..") have a special meaning when interpreting a
	relative path. The relative URI syntax is defined in Section 5.		relative path. The relative URI syntax is defined in Section 5.
	4.1. Fragment Identifier		4.1. Fragment Identifier
	When a URI reference is used to perform a retrieval action on the		When a URI reference is used to perform a retrieval action on the
	identified resource, the optional fragment identifier, separated from		identified resource, the optional fragment identifier, separated from
	the URI by a crosshatch ("#") character, consists of additional		the URI by a crosshatch ("#") character, consists of additional
	reference information to be interpreted by the user agent after the		reference information to be interpreted by the user agent after the
	retrieval action has been successfully completed. As such, it is not		retrieval action has been successfully completed. As such, it is not
	part of a URI, but is often used in conjunction with a URI.		part of a URI, but is often used in conjunction with a URI.
	fragment = *uric		fragment = *uric
	The semantics of a fragment identifier is a property of the data		The semantics of a fragment identifier is a property of the data
	resulting from a retrieval action, regardless of the type of URI used		resulting from a retrieval action, regardless of the type of URI used
	in the reference. Therefore, the format and interpretation of		in the reference. Therefore, the format and interpretation of
	fragment identifiers is dependent on the media type [RFC2046] of the		fragment identifiers is dependent on the media type [RFC2046] of the
	retrieval result. The character restrictions described in Section 2		retrieval result. The character restrictions described in Section 2
	for URIs also apply to the fragment in a URI-reference. Individual		for URI also apply to the fragment in a URI-reference. Individual
	media types may define additional restrictions or structure within		media types may define additional restrictions or structure within
	the fragment for specifying different types of "partial views" that		the fragment for specifying different types of "partial views" that
	can be identified within that media type.		can be identified within that media type.
	A fragment identifier is only meaningful when a URI reference is		A fragment identifier is only meaningful when a URI reference is
	intended for retrieval and the result of that retrieval is a document		intended for retrieval and the result of that retrieval is a document
	for which the identified fragment is consistently defined.		for which the identified fragment is consistently defined.
	4.2. Same-document References		4.2. Same-document References
	A URI reference which does not contain a URI is a reference to the		A URI reference that does not contain a URI is a reference to the
	current document. In other words, an empty URI reference within a		current document. In other words, an empty URI reference within a
	document is interpreted as a reference to the start of that document,		document is interpreted as a reference to the start of that document,
	and a reference containing only a fragment identifier is a reference		and a reference containing only a fragment identifier is a reference
	to the identified fragment of that document. Traversal of such a		to the identified fragment of that document. Traversal of such a
	reference should not result in an additional retrieval action.		reference should not result in an additional retrieval action.
	However, if the URI reference occurs in a context that is always		However, if the URI reference occurs in a context that is always
	intended to result in a new request, as in the case of HTML's FORM		intended to result in a new request, as in the case of HTML's FORM
	element, then an empty URI reference represents the base URI of the		element, then an empty URI reference represents the base URI of the
	current document and should be replaced by that URI when transformed		current document and should be replaced by that URI when transformed
	into a request.		into a request.
	4.3. Parsing a URI Reference		4.3. Parsing a URI Reference
	A URI reference is typically parsed according to the four main		A URI reference is typically parsed according to the four main
	components and fragment identifier in order to determine what		components and fragment identifier in order to determine what
	components are present and whether the reference is relative or		components are present and whether the reference is relative or
	absolute. The individual components are then parsed for their		absolute. The individual components are then parsed for their
	subparts and to verify their validity. A reference is parsed as if		subparts and, if not opaque, to verify their validity.
	it is a generic-URI, even though it might be considered opaque by
	later processes.
	Although the BNF defines what is allowed in each component, it is		Although the BNF defines what is allowed in each component, it is
	ambiguous in terms of differentiating between an authority component		ambiguous in terms of differentiating between an authority component
	and a path component that begins with two slash characters. The		and a path component that begins with two slash characters. The
	greedy algorithm is used for disambiguation: the left-most matching		greedy algorithm is used for disambiguation: the left-most matching
	rule soaks up as much of the URI reference string as it is capable of		rule soaks up as much of the URI reference string as it is capable of
	matching. In other words, the authority component wins.		matching. In other words, the authority component wins.
	Readers familiar with regular expressions should see Appendix B for a		Readers familiar with regular expressions should see Appendix B for a
	concrete parsing example and test oracle.		concrete parsing example and test oracle.
	5. Relative URI References		5. Relative URI References
	It is often the case that a group or "tree" of documents has been		It is often the case that a group or "tree" of documents has been
	constructed to serve a common purpose; the vast majority of URIs in		constructed to serve a common purpose; the vast majority of URI in
	these documents point to resources within the tree rather than		these documents point to resources within the tree rather than
	outside of it. Similarly, documents located at a particular site		outside of it. Similarly, documents located at a particular site
	are much more likely to refer to other resources at that site than		are much more likely to refer to other resources at that site than
	to resources at remote sites.		to resources at remote sites.
	Relative addressing of URLs allows document trees to be partially		Relative addressing of URI allows document trees to be partially
	independent of their location and access scheme. For instance, it is		independent of their location and access scheme. For instance, it is
	possible for a single set of hypertext documents to be simultaneously		possible for a single set of hypertext documents to be simultaneously
	accessible and traversable via each of the "file", "http", and "ftp"		accessible and traversable via each of the "file", "http", and "ftp"
	schemes if the documents refer to each other using relative URIs.		schemes if the documents refer to each other using relative URI.
	Furthermore, such document trees can be moved, as a whole, without		Furthermore, such document trees can be moved, as a whole, without
	changing any of the relative references. Experience within the WWW		changing any of the relative references. Experience within the WWW
	has demonstrated that the ability to perform relative referencing		has demonstrated that the ability to perform relative referencing
	is necessary for the long-term usability of embedded URLs.		is necessary for the long-term usability of embedded URI.
	relativeURI = net_path | abs_path | rel_path		The syntax for relative URI takes advantage of the <hier_part> syntax
			of <absoluteURI> (Section 3) in order to express a reference that is
			relative to the namespace of another hierarchical URI.
	A relative reference beginning with two slash characters is termed a		relativeURI = ( net_path | abs_path | rel_path ) [ "?" query ]
	network-path reference. Such references are rarely used.
	net_path = "//" authority [ abs_path ]		A relative reference beginning with two slash characters is termed a
			network-path reference, as defined by <net_path> in Section 3. Such
			references are rarely used.
	A relative reference beginning with a single slash character is		A relative reference beginning with a single slash character is
	termed an absolute-path reference.		termed an absolute-path reference, as defined by <abs_path> in
			Section 3.
	abs_path = "/" rel_path
	A relative reference which does not begin with a scheme name or a		A relative reference that does not begin with a scheme name or a
	slash character is termed a relative-path reference.		slash character is termed a relative-path reference.
	rel_path = [ path_segments ] [ "?" query ]		rel_path = rel_segment [ abs_path ]
			rel_segment = 1*( unreserved | escaped |
			";" | "@" | "&" | "=" | "+" | "$" | "," )
	Within a relative-path reference, the complete path segments "." and		Within a relative-path reference, the complete path segments "." and
	".." have special meanings: "the current hierarchy level" and "the		".." have special meanings: "the current hierarchy level" and "the
	level above this hierarchy level", respectively. Although this is		level above this hierarchy level", respectively. Although this is
	very similar to their use within Unix-based filesystems to indicate		very similar to their use within Unix-based filesystems to indicate
	directory levels, these path components are only considered special		directory levels, these path components are only considered special
	when resolving a relative-path reference to its absolute form		when resolving a relative-path reference to its absolute form
	(Section 5.2).		(Section 5.2).
	Authors should be aware that a path segment which contains a colon		Authors should be aware that a path segment which contains a colon
	character cannot be used as the first segment of a relative URI path		character cannot be used as the first segment of a relative URI path
	(e.g., "this:that"), because it would be mistaken for a scheme name.		(e.g., "this:that"), because it would be mistaken for a scheme name.
	It is therefore necessary to precede such segments with other		It is therefore necessary to precede such segments with other
	segments (e.g., "./this:that") in order for them to be referenced as		segments (e.g., "./this:that") in order for them to be referenced as
	a relative path.		a relative path.
	It is not necessary for all URIs within a given scheme to be		It is not necessary for all URI within a given scheme to be
	restricted to the generic-URI syntax, since the hierarchical		restricted to the <hier_part> syntax, since the hierarchical
	properties of that syntax are only necessary when relative URIs are		properties of that syntax are only necessary when relative URI are
	used within a particular document. Documents can only make use of		used within a particular document. Documents can only make use of
	relative URIs when their base URI fits within the generic-URI syntax.		relative URI when their base URI fits within the <hier_part> syntax.
	It is assumed that any document which contains a relative reference		It is assumed that any document which contains a relative reference
	will also have a base URI that obeys the syntax. In other words,		will also have a base URI that obeys the syntax. In other words,
	relative URIs cannot be used within a document that has an unsuitable		relative URI cannot be used within a document that has an unsuitable
	base URI.		base URI.
	Some URI schemes do not allow a hierarchical syntax matching the		Some URI schemes do not allow a hierarchical syntax matching the
	generic-URI syntax, and thus cannot use relative references.		<hier_part> syntax, and thus cannot use relative references.
	5.1. Establishing a Base URI		5.1. Establishing a Base URI
	The term "relative URI" implies that there exists some absolute "base		The term "relative URI" implies that there exists some absolute "base
	URI" against which the relative reference is applied. Indeed, the		URI" against which the relative reference is applied. Indeed, the
	base URI is necessary to define the semantics of any relative URI		base URI is necessary to define the semantics of any relative URI
	reference; without it, a relative reference is meaningless. In order		reference; without it, a relative reference is meaningless. In order
	for relative URIs to be usable within a document, the base URI of		for relative URI to be usable within a document, the base URI of
	that document must be known to the parser.		that document must be known to the parser.
	The base URI of a document can be established in one of four ways,		The base URI of a document can be established in one of four ways,
	listed below in order of precedence. The order of precedence can be		listed below in order of precedence. The order of precedence can be
	thought of in terms of layers, where the innermost defined base URI		thought of in terms of layers, where the innermost defined base URI
	has the highest precedence. This can be visualized graphically as:		has the highest precedence. This can be visualized graphically as:
	.----------------------------------------------------------.		.----------------------------------------------------------.
	| .----------------------------------------------------. |		| .----------------------------------------------------. |
	| | .----------------------------------------------. | |		| | .----------------------------------------------. | |
	skipping to change at line 893 ¶		skipping to change at line 913 ¶
	5.1.4. Default Base URI		5.1.4. Default Base URI
	If none of the conditions described in Sections 5.1.1--5.1.3 apply,		If none of the conditions described in Sections 5.1.1--5.1.3 apply,
	then the base URI is defined by the context of the application.		then the base URI is defined by the context of the application.
	Since this definition is necessarily application-dependent, failing		Since this definition is necessarily application-dependent, failing
	to define the base URI using one of the other methods may result in		to define the base URI using one of the other methods may result in
	the same content being interpreted differently by different types of		the same content being interpreted differently by different types of
	application.		application.
	It is the responsibility of the distributor(s) of a document		It is the responsibility of the distributor(s) of a document
	containing relative URIs to ensure that the base URI for that		containing relative URI to ensure that the base URI for that
	document can be established. It must be emphasized that relative		document can be established. It must be emphasized that relative
	URIs cannot be used reliably in situations where the document's		URI cannot be used reliably in situations where the document's
	base URI is not well-defined.		base URI is not well-defined.
	5.2. Resolving Relative References to Absolute Form		5.2. Resolving Relative References to Absolute Form
	This section describes an example algorithm for resolving URI		This section describes an example algorithm for resolving URI
	references which might be relative to a given base URI.		references that might be relative to a given base URI.
	The base URI is established according to the rules of Section 5.1 and		The base URI is established according to the rules of Section 5.1 and
	parsed into the four main components as described in Section 3.		parsed into the four main components as described in Section 3.
	Note that only the scheme component is required to be present in the		Note that only the scheme component is required to be present in the
	base URI; the other components may be empty or undefined. A		base URI; the other components may be empty or undefined. A
	component is undefined if its preceding separator does not appear in		component is undefined if its preceding separator does not appear in
	the URI reference; the path component is never undefined, though it		the URI reference; the path component is never undefined, though it
	may be empty. The base URI's query component is not used by the		may be empty. The base URI's query component is not used by the
	resolution algorithm and may be discarded.		resolution algorithm and may be discarded.
	skipping to change at line 928 ¶		skipping to change at line 948 ¶
	query components are undefined, then it is a reference to the		query components are undefined, then it is a reference to the
	current document and we are done. Otherwise, the reference URI's		current document and we are done. Otherwise, the reference URI's
	query and fragment components are defined as found (or not found)		query and fragment components are defined as found (or not found)
	within the URI reference and not inherited from the base URI.		within the URI reference and not inherited from the base URI.
	3) If the scheme component is defined, indicating that the reference		3) If the scheme component is defined, indicating that the reference
	starts with a scheme name, then the reference is interpreted as an		starts with a scheme name, then the reference is interpreted as an
	absolute URI and we are done. Otherwise, the reference URI's		absolute URI and we are done. Otherwise, the reference URI's
	scheme is inherited from the base URI's scheme component.		scheme is inherited from the base URI's scheme component.
			Due to a loophole in prior specifications [RFC1630], some parsers
			allow the scheme name to be present in a relative URI if it is the
			same as the base URI scheme. Unfortunately, this can conflict
			with the correct parsing of non-hierarchical URI. For backwards
			compatibility, an implementation may work around such references
			by removing the scheme if it matches that of the base URI and the
			scheme is known to always use the <hier_part> syntax. The parser
			can then continue with the steps below for the remainder of the
			reference components. Validating parsers should mark such a
			misformed relative reference as an error.
	4) If the authority component is defined, then the reference is a		4) If the authority component is defined, then the reference is a
	network-path and we skip to step 7. Otherwise, the reference		network-path and we skip to step 7. Otherwise, the reference
	URI's authority is inherited from the base URI's authority		URI's authority is inherited from the base URI's authority
	component, which will also be undefined if the URI scheme does not		component, which will also be undefined if the URI scheme does not
	use an authority component.		use an authority component.
	5) If the path component begins with a slash character ("/"), then		5) If the path component begins with a slash character ("/"), then
	the reference is an absolute-path and we skip to step 7.		the reference is an absolute-path and we skip to step 7.
	6) If this step is reached, then we are resolving a relative-path		6) If this step is reached, then we are resolving a relative-path
	skipping to change at line 1025 ¶		skipping to change at line 1056 ¶
	reference's query component from its path component before merging		reference's query component from its path component before merging
	the base and reference paths in step 6 above. This may result in		the base and reference paths in step 6 above. This may result in
	a loss of information if the query component contains the strings		a loss of information if the query component contains the strings
	"/../" or "/./".		"/../" or "/./".
	Resolution examples are provided in Appendix C.		Resolution examples are provided in Appendix C.
	6. URI Normalization and Equivalence		6. URI Normalization and Equivalence
	In many cases, different URI strings may actually identify the		In many cases, different URI strings may actually identify the
	identical resource. For example, the host names used in URLs are		identical resource. For example, the host names used in URL are
	actually case insensitive, and the URL <http://www.XEROX.com> is		actually case insensitive, and the URL <http://www.XEROX.com> is
	equivalent to <http://www.xerox.com>. In general, the rules for		equivalent to <http://www.xerox.com>. In general, the rules for
	equivalence and definition of a normal form, if any, are scheme		equivalence and definition of a normal form, if any, are scheme
	dependent. When a scheme uses elements of the common syntax, it		dependent. When a scheme uses elements of the common syntax, it
	will also use the common syntax equivalence rules, namely that the		will also use the common syntax equivalence rules, namely that the
	scheme and hostname are case insensitive and a URL with an explicit		scheme and hostname are case insensitive and a URL with an explicit
	":port", where the port is the default for the scheme, is equivalent		":port", where the port is the default for the scheme, is equivalent
	to one where the port is elided.		to one where the port is elided.
	7. Security Considerations		7. Security Considerations
	skipping to change at line 1054 ¶		skipping to change at line 1085 ¶
	resource in question. A specific URI scheme may include additional		resource in question. A specific URI scheme may include additional
	semantics, such as name persistence, if those semantics are required		semantics, such as name persistence, if those semantics are required
	of all naming authorities for that scheme.		of all naming authorities for that scheme.
	It is sometimes possible to construct a URL such that an attempt to		It is sometimes possible to construct a URL such that an attempt to
	perform a seemingly harmless, idempotent operation, such as the		perform a seemingly harmless, idempotent operation, such as the
	retrieval of an entity associated with the resource, will in fact		retrieval of an entity associated with the resource, will in fact
	cause a possibly damaging remote operation to occur. The unsafe URL		cause a possibly damaging remote operation to occur. The unsafe URL
	is typically constructed by specifying a port number other than that		is typically constructed by specifying a port number other than that
	reserved for the network protocol in question. The client		reserved for the network protocol in question. The client
	unwittingly contacts a site which is in fact running a different		unwittingly contacts a site that is in fact running a different
	protocol. The content of the URL contains instructions which, when		protocol. The content of the URL contains instructions that, when
	interpreted according to this other protocol, cause an unexpected		interpreted according to this other protocol, cause an unexpected
	operation. An example has been the use of gopher URLs to cause an		operation. An example has been the use of a gopher URL to cause an
	unintended or impersonating message to be sent via a SMTP server.		unintended or impersonating message to be sent via a SMTP server.
	Caution should be used when using any URL which specifies a port		Caution should be used when using any URL that specifies a port
	number other than the default for the protocol, especially when it		number other than the default for the protocol, especially when it
	is a number within the reserved space.		is a number within the reserved space.
	Care should be taken when URLs contain escaped delimiters for a		Care should be taken when a URL contains escaped delimiters for a
	given protocol (for example, CR and LF characters for telnet		given protocol (for example, CR and LF characters for telnet
	protocols) that these are not unescaped before transmission. This		protocols) that these are not unescaped before transmission. This
	might violate the protocol, but avoids the potential for such		might violate the protocol, but avoids the potential for such
	characters to be used to simulate an extra operation or parameter		characters to be used to simulate an extra operation or parameter
	in that protocol, which might lead to an unexpected and possibly		in that protocol, which might lead to an unexpected and possibly
	harmful remote operation to be performed.		harmful remote operation to be performed.
	It is clearly unwise to use a URL that contains a password which is		It is clearly unwise to use a URL that contains a password which is
	intended to be secret. In particular, the use of a password within		intended to be secret. In particular, the use of a password within
	the 'userinfo' component of a URL is strongly disrecommended except		the 'userinfo' component of a URL is strongly disrecommended except
	skipping to change at line 1155 ¶		skipping to change at line 1186 ¶
	Cambridge, MA 02139		Cambridge, MA 02139
	Fax: +1(617)258-8682		Fax: +1(617)258-8682
	EMail: timbl@w3.org		EMail: timbl@w3.org
	Roy T. Fielding		Roy T. Fielding
	Department of Information and Computer Science		Department of Information and Computer Science
	University of California, Irvine		University of California, Irvine
	Irvine, CA 92697-3425		Irvine, CA 92697-3425
	Fax: +1(714)824-1715		Fax: +1(949)824-1715
	EMail: fielding@ics.uci.edu		EMail: fielding@ics.uci.edu
	Larry Masinter		Larry Masinter
	Xerox PARC		Xerox PARC
	3333 Coyote Hill Road		3333 Coyote Hill Road
	Palo Alto, CA 94034		Palo Alto, CA 94034
	Fax: +1(415)812-4333		Fax: +1(415)812-4333
	EMail: masinter@parc.xerox.com		EMail: masinter@parc.xerox.com
	Appendices		Appendices
	A. Collected BNF for URIs		A. Collected BNF for URI
	URI-reference = [ absoluteURI | relativeURI ] [ "#" fragment ]		URI-reference = [ absoluteURI | relativeURI ] [ "#" fragment ]
	absoluteURI = generic-URI | opaque-URI		absoluteURI = scheme ":" ( hier_part | opaque_part )
	opaque-URI = scheme ":" *uric		relativeURI = ( net_path | abs_path | rel_path ) [ "?" query ]
	generic-URI = scheme ":" relativeURI
			hier_part = ( net_path | abs_path ) [ "?" query ]
			opaque_part = uric_no_slash *uric
			uric_no_slash = unreserved | escaped | ";" | "?" | ":" | "@" |
			"&" | "=" | "+" | "$" | ","
	relativeURI = net_path | abs_path | rel_path
	net_path = "//" authority [ abs_path ]		net_path = "//" authority [ abs_path ]
	abs_path = "/" rel_path		abs_path = "/" path_segments
	rel_path = [ path_segments ] [ "?" query ]		rel_path = rel_segment [ abs_path ]
			rel_segment = 1*( unreserved | escaped |
			";" | "@" | "&" | "=" | "+" | "$" | "," )
	scheme = alpha *( alpha | digit | "+" | "-" | "." )		scheme = alpha *( alpha | digit | "+" | "-" | "." )
	authority = server | reg_name		authority = server | reg_name
	reg_name = 1*( unreserved | escaped | "$" | "," |		reg_name = 1*( unreserved | escaped | "$" | "," |
	";" | ":" | "@" | "&" | "=" | "+" )		";" | ":" | "@" | "&" | "=" | "+" )
	server = [ [ userinfo "@" ] hostport ]		server = [ [ userinfo "@" ] hostport ]
	userinfo = *( unreserved | escaped |		userinfo = *( unreserved | escaped |
	";" | ":" | "&" | "=" | "+" | "$" | "," )		";" | ":" | "&" | "=" | "+" | "$" | "," )
	hostport = host [ ":" port ]		hostport = host [ ":" port ]
	host = hostname | IPv4address		host = hostname | IPv4address
	hostname = *( domainlabel "." ) toplabel [ "." ]		hostname = *( domainlabel "." ) toplabel [ "." ]
	domainlabel = alphanum | alphanum *( alphanum | "-" ) alphanum		domainlabel = alphanum | alphanum *( alphanum | "-" ) alphanum
	toplabel = alpha | alpha *( alphanum | "-" ) alphanum		toplabel = alpha | alpha *( alphanum | "-" ) alphanum
	IPv4address = 1*digit "." 1*digit "." 1*digit "." 1*digit		IPv4address = 1*digit "." 1*digit "." 1*digit "." 1*digit
	port = *digit		port = *digit
	path = [ "/" ] path_segments		path = [ abs_path | opaque_part ]
	path_segments = segment *( "/" segment )		path_segments = segment *( "/" segment )
	segment = *pchar *( ";" param )		segment = *pchar *( ";" param )
	param = *pchar		param = *pchar
	pchar = unreserved | escaped |		pchar = unreserved | escaped |
	":" | "@" | "&" | "=" | "+" | "$" | ","		":" | "@" | "&" | "=" | "+" | "$" | ","
	query = *uric		query = *uric
	fragment = *uric		fragment = *uric
	skipping to change at line 1235 ¶		skipping to change at line 1273 ¶
	"j" | "k" | "l" | "m" | "n" | "o" | "p" | "q" | "r" |		"j" | "k" | "l" | "m" | "n" | "o" | "p" | "q" | "r" |
	"s" | "t" | "u" | "v" | "w" | "x" | "y" | "z"		"s" | "t" | "u" | "v" | "w" | "x" | "y" | "z"
	upalpha = "A" | "B" | "C" | "D" | "E" | "F" | "G" | "H" | "I" |		upalpha = "A" | "B" | "C" | "D" | "E" | "F" | "G" | "H" | "I" |
	"J" | "K" | "L" | "M" | "N" | "O" | "P" | "Q" | "R" |		"J" | "K" | "L" | "M" | "N" | "O" | "P" | "Q" | "R" |
	"S" | "T" | "U" | "V" | "W" | "X" | "Y" | "Z"		"S" | "T" | "U" | "V" | "W" | "X" | "Y" | "Z"
	digit = "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" |		digit = "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" |
	"8" | "9"		"8" | "9"
	B. Parsing a URI Reference with a Regular Expression		B. Parsing a URI Reference with a Regular Expression
	As described in Section 4.3, the generic-URI syntax is not sufficient		As described in Section 4.3, the generic URI syntax is not sufficient
	to disambiguate the components of some forms of URI. Since the		to disambiguate the components of some forms of URI. Since the
	"greedy algorithm" described in that section is identical to the		"greedy algorithm" described in that section is identical to the
	disambiguation method used by POSIX regular expressions, it is		disambiguation method used by POSIX regular expressions, it is
	natural and commonplace to use a regular expression for parsing the		natural and commonplace to use a regular expression for parsing the
	potential four components and fragment identifier of a URI reference.		potential four components and fragment identifier of a URI reference.
	The following line is the regular expression for breaking-down a URI		The following line is the regular expression for breaking-down a URI
	reference into its components.		reference into its components.
	^(([^:/?#]+):)?(//([^/?#]*))?([^?#]*)(\?([^#]*))?(#(.*))?		^(([^:/?#]+):)?(//([^/?#]*))?([^?#]*)(\?([^#]*))?(#(.*))?
	skipping to change at line 1286 ¶		skipping to change at line 1324 ¶
	and, going in the opposite direction, we can recreate a URI reference		and, going in the opposite direction, we can recreate a URI reference
	from its components using the algorithm in step 7 of Section 5.2.		from its components using the algorithm in step 7 of Section 5.2.
	C. Examples of Resolving Relative URI References		C. Examples of Resolving Relative URI References
	Within an object with a well-defined base URI of		Within an object with a well-defined base URI of
	http://a/b/c/d;p?q		http://a/b/c/d;p?q
	the relative URIs would be resolved as follows:		the relative URI would be resolved as follows:
	C.1. Normal Examples		C.1. Normal Examples
	g:h = g:h		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/b/c/g
	g/ = http://a/b/c/g/		g/ = http://a/b/c/g/
	/g = http://a/g		/g = http://a/g
	//g = http://g		//g = http://g
	?y = http://a/b/c/?y		?y = http://a/b/c/?y
	skipping to change at line 1358 ¶		skipping to change at line 1396 ¶
	nonsensical forms of the "." and ".." complete path segments.		nonsensical forms of the "." and ".." complete path segments.
	./../g = http://a/b/g		./../g = http://a/b/g
	./g/. = http://a/b/c/g/		./g/. = http://a/b/c/g/
	g/./h = http://a/b/c/g/h		g/./h = http://a/b/c/g/h
	g/../h = http://a/b/c/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/g;x=1/y
	g;x=1/../y = http://a/b/c/y		g;x=1/../y = http://a/b/c/y
	All client applications remove the query component from the base URI		All client applications remove the query component from the base URI
	before resolving relative URIs. However, some applications fail to		before resolving relative URI. However, some applications fail to
	separate the reference's query and/or fragment components from a		separate the reference's query and/or fragment components from a
	relative path before merging it with the base path. This error is		relative path before merging it with the base path. This error is
	rarely noticed, since typical usage of a fragment never includes the		rarely noticed, since typical usage of a fragment never includes the
	hierarchy ("/") character, and the query component is not normally		hierarchy ("/") character, and the query component is not normally
	used within relative references.		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?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
	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 URI		Some parsers allow the scheme name to be present in a relative URI
	if it is the same as the base URI scheme. This is considered to be		if it is the same as the base URI scheme. This is considered to be
	a loophole in prior specifications of partial URIs [RFC1630]. Its		a loophole in prior specifications of partial URI [RFC1630]. Its
	use should be avoided.		use should be avoided.
	http:g = http:g		http:g = http:g ; for validating parsers
	http: = http:		| http://a/b/c/g ; for backwards compatibility
	D. Embedding the Base URI in HTML documents		D. Embedding the Base URI in HTML documents
	It is useful to consider an example of how the base URI of a		It is useful to consider an example of how the base URI of a
	document can be embedded within the document's content. In this		document can be embedded within the document's content. In this
	appendix, we describe how documents written in the Hypertext Markup		appendix, we describe how documents written in the Hypertext Markup
	Language (HTML) [RFC1866] can include an embedded base URI. This		Language (HTML) [RFC1866] can include an embedded base URI. This
	appendix does not form a part of the URI specification and should not		appendix does not form a part of the URI specification and should not
	be considered as anything more than a descriptive example.		be considered as anything more than a descriptive example.
	HTML defines a special element "BASE" which, when present in the		HTML defines a special element "BASE" which, when present in the
	"HEAD" portion of a document, signals that the parser should use		"HEAD" portion of a document, signals that the parser should use
	the BASE element's "HREF" attribute as the base URI for resolving		the BASE element's "HREF" attribute as the base URI for resolving
	any relative URIs. The "HREF" attribute must be an absolute URI.		any relative URI. The "HREF" attribute must be an absolute URI.
	Note that, in HTML, element and attribute names are		Note that, in HTML, element and attribute names are
	case-insensitive. For example:		case-insensitive. For example:
	<!doctype html public "-//IETF//DTD HTML//EN">		<!doctype html public "-//IETF//DTD HTML//EN">
	<HTML><HEAD>		<HTML><HEAD>
	<TITLE>An example HTML document</TITLE>		<TITLE>An example HTML document</TITLE>
	<BASE href="http://www.ics.uci.edu/Test/a/b/c">		<BASE href="http://www.ics.uci.edu/Test/a/b/c">
	</HEAD><BODY>		</HEAD><BODY>
	... <A href="../x">a hypertext anchor</A> ...		... <A href="../x">a hypertext anchor</A> ...
	</BODY></HTML>		</BODY></HTML>
	A parser reading the example document should interpret the given		A parser reading the example document should interpret the given
	relative URI "../x" as representing the absolute URI		relative URI "../x" as representing the absolute URI
	<http://www.ics.uci.edu/Test/a/x>		<http://www.ics.uci.edu/Test/a/x>
	regardless of the context in which the example document was		regardless of the context in which the example document was
	obtained.		obtained.
	E. Recommendations for Delimiting URIs in Context		E. Recommendations for Delimiting URI in Context
	URIs are often transmitted through formats which do not provide a		URI are often transmitted through formats that do not provide a
	clear context for their interpretation. For example, there are		clear context for their interpretation. For example, there are
	many occasions when URIs are included in plain text; examples		many occasions when URI are included in plain text; examples
	include text sent in electronic mail, USENET news messages, and,		include text sent in electronic mail, USENET news messages, and,
	most importantly, printed on paper. In such cases, it is important		most importantly, printed on paper. In such cases, it is important
	to be able to delimit the URI from the rest of the text, and in		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		particular from punctuation marks that might be mistaken for part
	of the URI.		of the URI.
	In practice, URIs are delimited in a variety of ways, but usually		In practice, URI are delimited in a variety of ways, but usually
	within double-quotes "http://test.com/", angle brackets		within double-quotes "http://test.com/", angle brackets
	<http://test.com/>, or just using whitespace		<http://test.com/>, or just using whitespace
	http://test.com/		http://test.com/
	These wrappers do not form part of the URI.		These wrappers do not form part of the URI.
	In the case where a fragment identifier is associated with a URI		In the case where a fragment identifier is associated with a URI
	reference, the fragment would be placed within the brackets as well		reference, the fragment would be placed within the brackets as well
	(separated from the URI with a "#" character).		(separated from the URI with a "#" character).
	In some cases, extra whitespace (spaces, linebreaks, tabs, etc.)		In some cases, extra whitespace (spaces, linebreaks, tabs, etc.)
	may need to be added to break long URIs across lines. The		may need to be added to break long URI across lines. The
	whitespace should be ignored when extracting the URI.		whitespace should be ignored when extracting the URI.
	No whitespace should be introduced after a hyphen ("-") character.		No whitespace should be introduced after a hyphen ("-") character.
	Because some typesetters and printers may (erroneously) introduce a		Because some typesetters and printers may (erroneously) introduce a
	hyphen at the end of line when breaking a line, the interpreter of a		hyphen at the end of line when breaking a line, the interpreter of a
	URI containing a line break immediately after a hyphen should ignore		URI containing a line break immediately after a hyphen should ignore
	all unescaped whitespace around the line break, and should be aware		all unescaped whitespace around the line break, and should be aware
	that the hyphen may or may not actually be part of the URI.		that the hyphen may or may not actually be part of the URI.
	Using <> angle brackets around each URI is especially recommended		Using <> angle brackets around each URI is especially recommended
	as a delimiting style for URIs that contain whitespace.		as a delimiting style for URI that contain whitespace.
	The prefix "URL:" (with or without a trailing space) was		The prefix "URL:" (with or without a trailing space) was
	recommended as a way to used to help distinguish a URL from other		recommended as a way to used to help distinguish a URL from other
	bracketed designators, although this is not common in practice.		bracketed designators, although this is not common in practice.
	For robustness, software that accepts user-typed URIs should		For robustness, software that accepts user-typed URI should
	attempt to recognize and strip both delimiters and embedded		attempt to recognize and strip both delimiters and embedded
	whitespace.		whitespace.
	For example, the text:		For example, the text:
	Yes, Jim, I found it under "http://www.w3.org/Addressing/",		Yes, Jim, I found it under "http://www.w3.org/Addressing/",
	but you can probably pick it up from <ftp://ds.internic.		but you can probably pick it up from <ftp://ds.internic.
	net/rfc/>. Note the warning in <http://www.ics.uci.edu/pub/		net/rfc/>. Note the warning in <http://www.ics.uci.edu/pub/
	ietf/uri/historical.html#WARNING>.		ietf/uri/historical.html#WARNING>.
	skipping to change at line 1505 ¶		skipping to change at line 1543 ¶
	G. Summary of Non-editorial Changes		G. Summary of Non-editorial Changes
	G.1. Additions		G.1. Additions
	Section 4 (URI References) was added to stem the confusion		Section 4 (URI References) was added to stem the confusion
	regarding "what is a URI" and how to describe fragment identifiers		regarding "what is a URI" and how to describe fragment identifiers
	given that they are not part of the URI, but are part of the URI		given that they are not part of the URI, but are part of the URI
	syntax and parsing concerns. In addition, it provides a reference		syntax and parsing concerns. In addition, it provides a reference
	definition for use by other IETF specifications (HTML, HTTP, etc.)		definition for use by other IETF specifications (HTML, HTTP, etc.)
	which have previously attempted to redefine the URI syntax in order		that have previously attempted to redefine the URI syntax in order
	to account for the presence of fragment identifiers in URI		to account for the presence of fragment identifiers in URI
	references.		references.
	Section 2.4 was rewritten to clarify a number of misinterpretations		Section 2.4 was rewritten to clarify a number of misinterpretations
	and to leave room for fully internationalized URIs.		and to leave room for fully internationalized URI.
	Appendix F on abbreviated URLs was added to describe the shortened		Appendix F on abbreviated URLs was added to describe the shortened
	references often seen on television and magazine advertisements and		references often seen on television and magazine advertisements and
	explain why they are not used in other contexts.		explain why they are not used in other contexts.
	G.2. Modifications from both RFC 1738 and RFC 1808		G.2. Modifications from both RFC 1738 and RFC 1808
	Changed to URI syntax instead of just URL.		Changed to URI syntax instead of just URL.
	Confusion regarding the terms "character encoding", the URI		Confusion regarding the terms "character encoding", the URI
	skipping to change at line 1533 ¶		skipping to change at line 1571 ¶
	names regarding the character sets have been changed to more		names regarding the character sets have been changed to more
	accurately describe their purpose and to encompass all "characters"		accurately describe their purpose and to encompass all "characters"
	rather than just US-ASCII octets. Unless otherwise noted here,		rather than just US-ASCII octets. Unless otherwise noted here,
	these modifications do not affect the URI syntax.		these modifications do not affect the URI syntax.
	Both RFC 1738 and RFC 1808 refer to the "reserved" set of		Both RFC 1738 and RFC 1808 refer to the "reserved" set of
	characters as if URI-interpreting software were limited to a single		characters as if URI-interpreting software were limited to a single
	set of characters with a reserved purpose (i.e., as meaning		set of characters with a reserved purpose (i.e., as meaning
	something other than the data to which the characters correspond),		something other than the data to which the characters correspond),
	and that this set was fixed by the URI scheme. However, this has		and that this set was fixed by the URI scheme. However, this has
	not been true in practice; any character which is interpreted		not been true in practice; any character that is interpreted
	differently when it is escaped is, in effect, reserved.		differently when it is escaped is, in effect, reserved.
	Furthermore, the interpreting engine on a HTTP server is often		Furthermore, the interpreting engine on a HTTP server is often
	dependent on the resource, not just the URI scheme. The		dependent on the resource, not just the URI scheme. The
	description of reserved characters has been changed accordingly.		description of reserved characters has been changed accordingly.
	The plus "+", dollar "$", and comma "," characters have been added to		The plus "+", dollar "$", and comma "," characters have been added to
	those in the "reserved" set, since they are treated as reserved		those in the "reserved" set, since they are treated as reserved
	within the query component.		within the query component.
	The tilde "~" character was added to those in the "unreserved" set,		The tilde "~" character was added to those in the "unreserved" set,
	since it is extensively used on the Internet in spite of the		since it is extensively used on the Internet in spite of the
	difficulty to transcribe it with some keyboards.		difficulty to transcribe it with some keyboards.
			The syntax for URI scheme has been changed to require that all
			schemes begin with an alpha character.
	The "user:password" form in the previous BNF was changed to		The "user:password" form in the previous BNF was changed to
	a "userinfo" token, and the possibility that it might be		a "userinfo" token, and the possibility that it might be
	"user:password" made scheme specific. In particular, the use		"user:password" made scheme specific. In particular, the use
	of passwords in the clear is not even suggested by the syntax.		of passwords in the clear is not even suggested by the syntax.
	The question-mark "?" character was removed from the set of allowed		The question-mark "?" character was removed from the set of allowed
	characters for the userinfo in the authority component, since		characters for the userinfo in the authority component, since
	testing showed that many applications treat it as reserved for		testing showed that many applications treat it as reserved for
	separating the query component from the rest of the URI.		separating the query component from the rest of the URI.
	skipping to change at line 1568 ¶		skipping to change at line 1609 ¶
	reserved within the authority component, since several new schemes		reserved within the authority component, since several new schemes
	are using it as a separator within userinfo to indicate the type		are using it as a separator within userinfo to indicate the type
	of user authentication.		of user authentication.
	RFC 1738 specified that the path was separated from the authority		RFC 1738 specified that the path was separated from the authority
	portion of a URI by a slash. RFC 1808 followed suit, but with a		portion of a URI by a slash. RFC 1808 followed suit, but with a
	fudge of carrying around the separator as a "prefix" in order to		fudge of carrying around the separator as a "prefix" in order to
	describe the parsing algorithm. RFC 1630 never had this problem,		describe the parsing algorithm. RFC 1630 never had this problem,
	since it considered the slash to be part of the path. In writing		since it considered the slash to be part of the path. In writing
	this specification, it was found to be impossible to accurately		this specification, it was found to be impossible to accurately
	describe and retain the difference between the two URIs		describe and retain the difference between the two URI
	<foo:/bar> and <foo:bar>		<foo:/bar> and <foo:bar>
	without either considering the slash to be part of the path (as		without either considering the slash to be part of the path (as
	corresponds to actual practice) or creating a separate component just		corresponds to actual practice) or creating a separate component just
	to hold that slash. We chose the former.		to hold that slash. We chose the former.
	G.3. Modifications from RFC 1738		G.3. Modifications from RFC 1738
	The definition of specific URL schemes and their scheme-specific		The definition of specific URL schemes and their scheme-specific
	syntax and semantics has been moved to separate documents.		syntax and semantics has been moved to separate documents.
	The URL host was defined as a fully-qualified domain name. However,		The URL host was defined as a fully-qualified domain name. However,
	many URLs are used without fully-qualified domain names (in contexts		many URLs are used without fully-qualified domain names (in contexts
	for which the full qualification is not necessary), without any host		for which the full qualification is not necessary), without any host
	(as in some file URLs), or with a host of "localhost".		(as in some file URLs), or with a host of "localhost".
	The URL port is now *digit instead of 1*digit, since systems are		The URL port is now *digit instead of 1*digit, since systems are
	expected to handle the case where the ":" separator between host and		expected to handle the case where the ":" separator between host and
	port is supplied without a port.		port is supplied without a port.
	The recommendations for delimiting URIs in context (Appendix E) have		The recommendations for delimiting URI in context (Appendix E) have
	been adjusted to reflect current practice.		been adjusted to reflect current practice.
	G.4. Modifications from RFC 1808		G.4. Modifications from RFC 1808
	RFC 1808 (Section 4) defined an empty URL reference (a reference		RFC 1808 (Section 4) defined an empty URL reference (a reference
	containing nothing aside from the fragment identifier) as being a		containing nothing aside from the fragment identifier) as being a
	reference to the base URL. Unfortunately, that definition could be		reference to the base URL. Unfortunately, that definition could be
	interpreted, upon selection of such a reference, as a new retrieval		interpreted, upon selection of such a reference, as a new retrieval
	action on that resource. Since the normal intent of such references		action on that resource. Since the normal intent of such references
	is for the user agent to change its view of the current document to		is for the user agent to change its view of the current document to
	the beginning of the specified fragment within that document, not to		the beginning of the specified fragment within that document, not to
	make an additional request of the resource, a description of how to		make an additional request of the resource, a description of how to
	correctly interpret an empty reference has been added in Section 4.		correctly interpret an empty reference has been added in Section 4.
	The description of the mythical Base header field has been replaced		The description of the mythical Base header field has been replaced
	with a reference to the Content-Location header field defined by		with a reference to the Content-Location header field defined by
	MHTML [RFC2110].		MHTML [RFC2110].
	RFC 1808 described various schemes as either having or not having the		RFC 1808 described various schemes as either having or not having the
	properties of the generic-URI syntax. However, the only requirement		properties of the generic URI syntax. However, the only requirement
	is that the particular document containing the relative references		is that the particular document containing the relative references
	have a base URI which abides by the generic-URI syntax, regardless of		have a base URI that abides by the generic URI syntax, regardless of
	the URI scheme, so the associated description has been updated to		the URI scheme, so the associated description has been updated to
	reflect that.		reflect that.
	The BNF term <net_loc> has been replaced with <authority>, since the		The BNF term <net_loc> has been replaced with <authority>, since the
	latter more accurately describes its use and purpose. Likewise, the		latter more accurately describes its use and purpose. Likewise, the
	authority is no longer restricted to the IP server syntax.		authority is no longer restricted to the IP server syntax.
	Extensive testing of current client applications demonstrated that		Extensive testing of current client applications demonstrated that
	the majority of deployed systems do not use the ";" character to		the majority of deployed systems do not use the ";" character to
	indicate trailing parameter information, and that the presence of a		indicate trailing parameter information, and that the presence of a
	semicolon in a path segment does not affect the relative parsing of		semicolon in a path segment does not affect the relative parsing of
	that segment. Therefore, parameters have been removed as a separate		that segment. Therefore, parameters have been removed as a separate
	component and may now appear in any path segment. Their influence		component and may now appear in any path segment. Their influence
	has been removed from the algorithm for resolving a relative URI		has been removed from the algorithm for resolving a relative URI
	reference. The resolution examples in Appendix C have been modified		reference. The resolution examples in Appendix C have been modified
	to reflect this change.		to reflect this change.
			Implementations are now allowed to work around misformed relative
			references that are prefixed by the same scheme as the base URI,
			but only for schemes known to use the <hier_part> syntax.
	H. Full Copyright Statement		H. Full Copyright Statement
	Copyright (C) The Internet Society (1998). All Rights Reserved.		Copyright (C) The Internet Society (1998). All Rights Reserved.
	This document and translations of it may be copied and furnished to		This document and translations of it may be copied and furnished to
	others, and derivative works that comment on or otherwise explain it		others, and derivative works that comment on or otherwise explain it
	or assist in its implementation may be prepared, copied, published		or assist in its implementation may be prepared, copied, published
	and distributed, in whole or in part, without restriction of any		and distributed, in whole or in part, without restriction of any
	kind, provided that the above copyright notice and this paragraph are		kind, provided that the above copyright notice and this paragraph are
	included on all such copies and derivative works. However, this		included on all such copies and derivative works. However, this
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