標準仕様書(TS)                         TS X 0097:2004

統一資源識別子(URI) 共通構文

Uniform Resource Identifiers (URI): Generic Syntax


この標準仕様書(TS)は,1998年8月にInternet Engineering Task Force (IETF)から公表されたRFC 2396 "Uniform Resource Identifiers (URI): Generic Syntax"を翻訳し,技術的内容を変更することなく作成した標準 仕様書(TS)である。

次は,TSでは省略する。 Network Working Group T. Berners-Lee Request for Comments: 2396 MIT/LCS Updates: 1808, 1738 R. Fielding Category: Standards Track U.C. Irvine L. Masinter Xerox Corporation August 1998 Uniform Resource Identifiers (URI): Generic Syntax 次は,前書きに移動する。 Status of this Memo This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited. Copyright Notice Copyright (C) The Internet Society (1998). All Rights Reserved.

0. 適用範囲 Abstract

統一資源識別子(Uniform Resource Identifier,URI)は,抽象的又は物理的な資源を識別するための小さくまとまった文字の列とする。この標準 仕様書(TS)は,URIの共通構文を定義する。これには,絶対形式及び相対形式の両方,並びにそれらの使用についての指針が含まれる。この規定は,RFC 1738及びRFC 1808における共通定義を改訂し置き換える。

A Uniform Resource Identifier (URI) is a compact string of characters for identifying an abstract or physical resource. This document defines the generic syntax of URI, including both absolute and relative forms, and guidelines for their use; it revises and replaces the generic definitions in RFC 1738 and RFC 1808.

この標準仕様書(TS)は,実装が,すべての可能な識別子型の方式(scheme)固有の要件を知らずにURI参照の共通構成要素を構文解析できるように,すべての妥当なURIの上位集合になっている文法を定義する。この標準 仕様書(TS)は,URIについての派生的な(方式固有の)文法は定義しない。その作業は,各々のURI方式の個別の規定によって行われる。

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.

備考  この標準仕様書(TS)は,URIに適用可能な操作の"上位集合"を示す。それは,URIのための文法及び基本的な機能の規定の両方から成る。妥当なURIが何かを理解するためには,文法及びそれに関連する規定の両方を知らなければならない。示される機能の中には,すべてのURI方式に対しては適用可能でないものがあるし,使用される方式に関係なく,あるメディア型をURIを用いて検索する場合だけに可能な操作もある。 IESG Note This paper describes a "superset" of operations that can be applied to URI. It consists of both a grammar and a description of basic functionality for URI. To understand what is a valid URI, both the grammar and the associated description have to be studied. Some of the functionality described is not applicable to all URI schemes, and some operations are only possible when certain media types are retrieved using the URI, regardless of the scheme used.

1. 導入 1. Introduction

統一資源識別子(URI)は,資源を識別するための簡単であって拡張可能な手段を提供する。URI構文及びセマンティクスのこの規定は,World Wide Webの大域的情報処理の先導的活動によって導入された概念から導出されている。そのような概念の使用は,1990年からあり,"WWWにおける普遍資源識別子(Universal Resource Identifiers in WWW)"[RFC1630]に記述されている。URIの規定は,"インターネット資源位置指定子のための機能推奨事項(Functional Recommendations for Internet Resource Locators)"[RFC1736]及び"統一資源名のための機能要件(Functional Requirements for Uniform Resource Names)"[RFC1737]において概要を示された推奨事項に見合うように設計されている。

Uniform Resource Identifiers (URI) provide a simple and extensible means for identifying a resource. This specification of URI syntax and semantics is derived from concepts introduced by the World Wide Web global information initiative, whose use of such objects dates from 1990 and is described in "Universal Resource Identifiers in WWW" [RFC1630]. The specification of URI is designed to meet the recommendations laid out in "Functional Recommendations for Internet Resource Locators" [RFC1736] and "Functional Requirements for Uniform Resource Names" [RFC1737].

この標準仕様書(TS)は,すべてのURIのための単一であって共通的な構文を定義するために,"統一資源位置指定子(Uniform Resource Locators)"[RFC1738]及び"相対統一資源位置指定子(Relative Uniform Resource Locators)"[RFC1808]を更新し併合している。ただし,個々のURI方式の固有構文を定義したRFC 1738の部分は除外する。これらの部分は,新しいURI方式の登録処理とともに,別の文書として更新されることになる。この標準 仕様書(TS)は,US-ASCII文字集合[ASCII]以外の文字の処理についての課題及び推奨は議論しない。これらの推奨事項は,別の文書で議論される。

This document updates and merges "Uniform Resource Locators" [RFC1738] and "Relative Uniform Resource Locators" [RFC1808] in order to define a single, generic syntax for all URI. It excludes those portions of RFC 1738 that defined the specific syntax of individual URL schemes; those portions will be updated as separate documents, as will the process for registration of new URI schemes. This document does not discuss the issues and recommendation for dealing with characters outside of the US-ASCII character set [ASCII]; those recommendations are discussed in a separate document.


All significant changes from the prior RFCs are noted in Appendix G.

1.1 URIの概要 1.1 Overview of URI


URI are characterized by the following definitions:

統一 Uniform
  • 資源識別子の異なる型を,それらの資源にアクセスするために使用される機構が異なっている場合であっても,同じ文脈で使用できる。
  • 共通の構文規約の統一的な意味解釈が,資源識別子の異なる型にわたって可能になる。
  • 既存の識別子を使用する方法と干渉することなく,資源識別子の新しい型を導入できる。
  • 多くの異なる文脈で識別子を再利用できる。これによって,新しい応用又はプロトコルが,既存の多くの広く使用されている資源識別子の集合を,更に利用し発展させることを可能にする。
Uniformity provides several benefits: it allows different types of resource identifiers to be used in the same context, even when the mechanisms used to access those resources may differ; it allows uniform semantic interpretation of common syntactic conventions across different types of resource identifiers; it allows introduction of new types of resource identifiers without interfering with the way that existing identifiers are used; and, it allows the identifiers to be reused in many different contexts, thus permitting new applications or protocols to leverage a pre-existing, large, and widely-used set of resource identifiers.
資源 Resource


A resource can be anything that has identity. Familiar examples include an electronic document, an image, a service (e.g., "today's weather report for Los Angeles"), and a collection of other resources. Not all resources are network "retrievable"; e.g., human beings, corporations, and bound books in a library can also be considered resources.


The resource is the conceptual mapping to an entity or set of entities, not necessarily the entity which corresponds to that mapping at any particular instance in time. Thus, a resource can remain constant even when its content---the entities to which it currently corresponds---changes over time, provided that the conceptual mapping is not changed in the process.

識別子 Identifier
識別子は,識別性をもつものへの参照として振る舞うことが可能なオブジェクトとする。URIの場合には,そのオブジェクトは,制限された構文をもつ文字の列とする。 An identifier is an object that can act as a reference to something that has identity. In the case of URI, the object is a sequence of characters with a restricted syntax.


Having identified a resource, a system may perform a variety of operations on the resource, as might be characterized by such words as `access', `update', `replace', or `find attributes'.

1.2 URI,URL及びURN 1.2. URI, URL, and URN

URIは,更に,位置指定子,名前又はその両方として分類できる。用語"統一資源位置指定子(Uniform Resource Locator,URL)"は,URIの部分集合であって,資源の名前又はそれ以外の属性によってその資源を識別するのではなく,基本的なアクセス機構(例えば,ネットワークの"位置")の表現によって資源を識別するものを参照する。用語"統一資源名(Uniform Resource Name,URN)"は,URIの部分集合であって,資源が存在しなくなる又は利用不可能になる場合であっても,大域的に一意であって永続性を保つことを要求されるものを参照する。

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 that identify resources via a representation of their primary access mechanism (e.g., their network "location"), rather than identifying 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 that are required to remain globally unique and persistent even when the resource ceases to exist or becomes unavailable.


The URI scheme (Section 3.1) defines the namespace of the URI, and thus may further restrict the syntax and semantics of identifiers using that scheme. This specification defines those elements of the 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 are needed to implement a scheme-independent parsing mechanism for URI references, such that the scheme-dependent handling of a URI can be postponed until the scheme-dependent semantics are needed. We use the term URL below when describing syntax or semantics that only apply to locators.


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 protocol. Gateways, proxies, caches, and name resolution services might be used to access some resources, independent of the protocol 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 to access an "http" URL's resource when it can't be found in a local cache).


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 from one of a set of defined namespaces, each of which has its own set name structure and assignment procedures. The "urn" scheme has been reserved to establish the requirements for a standardized URN namespace, as defined in "URN Syntax" [RFC2141] and its related specifications.


Most of the examples in this specification demonstrate URL, since they allow the most varied use of the syntax and often have a hierarchical namespace. A parser of the URI syntax is capable of parsing both URL and URN references as a generic URI; once the scheme is determined, the scheme-specific parsing can be performed on the generic URI components. In other words, the URI syntax is a superset of the syntax of all URI schemes.

1.3 URIの例 1.3. Example URI


The following examples illustrate URI that are in common use.

      -- ファイル転送プロトコル(File Transfer Protocol)サービスのためのftp方式

      -- Gopher及びGopher+プロトコルサービスのためのgopher方式

      -- ハイパテキスト転送方式プロトコル(Hypertext Transfer Protocol)サービスのためのhttp方式

      -- 電子メールアドレスのためのmailto方式

      -- USENETニュースグループ及び記事(articles)のためのnews方式

      -- TELNETプロトコル経由の対話的サービスのためのtelnet方式

1.4 階層的URI形式及び相対形式 1.4. Hierarchical URI and Relative Forms


An absolute identifier refers to a resource independent of the context in which the identifier is used. In contrast, a relative identifier refers to a resource by describing the difference within a hierarchical namespace between the current context and an absolute identifier of the resource.

URI方式の中には,階層的名前付けシステムをサポートするものがある。この場合,名前の階層は,方式における構成要素を分離する"/"区切り子によって表示される。この標準 仕様書(TS)は,他のURIを生成するために(階層的方式の)'基底'URIと連結して使用可能な,方式非依存であるURI参照の'相対'形式を定義する。階層的URIの構文は,3.で示す。相対URIについての計算は,5.で示す。

Some URI schemes support a hierarchical naming system, where the hierarchy of the name is denoted by a "/" delimiter separating the components in the scheme. This document defines a scheme-independent `relative' form of URI reference that can be used in conjunction with a `base' URI (of a hierarchical scheme) to produce another URI. The syntax of hierarchical URI is described in Section 3; the relative URI calculation is described in Section 5.

1.5 URIの転写可能性 1.5. URI Transcribability


The URI syntax was designed with global transcribability as one of 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, and a few special characters. A URI may be represented in a variety of ways: e.g., ink on paper, pixels on a screen, or a sequence of octets in a coded character set. The interpretation of a URI depends only on the characters used and not how those characters are represented in a network protocol.


The goal of transcribability can be described by a simple scenario. Imagine two colleagues, Sam and Kim, sitting in a pub at an international conference and exchanging research ideas. Sam asks Kim for a location to get more information, so Kim writes the URI for the research site on a napkin. Upon returning home, Sam takes out the napkin and types the URI into a computer, which then retrieves the information to which Kim referred.


There are several design concerns revealed by the scenario:

これらの設計の要点は,必ずしも整合しない。例えば,URI構成要素に対して最も意味のある名前は,システムにはタイプ入力できない文字を要求する場合がある。あるメディアから他のメディアへと資源識別子を転写できることが,URIを最も意味のある構成要素から構成することよりも重要と考えられた。局所的であって地域的な文脈では,及び改良された技術を用いれば,利用者は,より広い範囲の文字を使用でき,そこから利益を得るかもしれない。しかし,それらの使用は,この標準 仕様書(TS)では定義しない。

These design concerns are not always in alignment. For example, it is often the case that the most meaningful name for a URI component would require characters that cannot be typed into some systems. The ability to transcribe the resource identifier from one medium to another was considered more important than having its URI consist of the most meaningful of components. In local and regional contexts and with improving technology, users might benefit from being able to use a wider range of characters; such use is not defined in this document.

1.6 構文記法及び共通要素 1.6. Syntax Notation and Common Elements


This document uses two conventions to describe and define the syntax for URI. The first, called the layout form, is a general description of the order of components and component separators, as in



The component names are enclosed in angle-brackets and any characters outside angle-brackets are literal separators. Whitespace should be ignored. These descriptions are used informally and do not define the syntax requirements.


The second convention is a BNF-like grammar, used to define the formal URI syntax. The grammar is that of [RFC822], except that "|" is used to designate alternatives. Briefly, rules are separated from definitions by an equal "=", indentation is used to continue a rule definition over more than one line, literals are quoted with "", parentheses "(" and ")" are used to group elements, optional elements are enclosed in "[" and "]" brackets, and elements may be preceded with <n>* to designate n or more repetitions of the following element; n defaults to 0.


Unlike many specifications that use a BNF-like grammar to define the bytes (octets) allowed by a protocol, the URI grammar is defined in terms of characters. Each literal in the grammar corresponds to the character it represents, rather than to the octet encoding of that character in any particular coded character set. How a URI is 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 charset of the document which contains it.


The following definitions are common to many elements:

      alpha    = lowalpha | upalpha

      lowalpha = "a" | "b" | "c" | "d" | "e" | "f" | "g" | "h" | "i" |
                 "j" | "k" | "l" | "m" | "n" | "o" | "p" | "q" | "r" |
                 "s" | "t" | "u" | "v" | "w" | "x" | "y" | "z"

      upalpha  = "A" | "B" | "C" | "D" | "E" | "F" | "G" | "H" | "I" |
                 "J" | "K" | "L" | "M" | "N" | "O" | "P" | "Q" | "R" |
                 "S" | "T" | "U" | "V" | "W" | "X" | "Y" | "Z"

      digit    = "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" |
                 "8" | "9"

      alphanum = alpha | digit


The complete URI syntax is collected in Appendix A.

2. URI文字及びエスケープシーケンス 2. URI Characters and Escape Sequences


URI consist of a restricted set of characters, primarily chosen to aid transcribability and usability both in computer systems and in non-computer communications. Characters used conventionally as delimiters around URI were excluded. The restricted set of characters consists of digits, letters, and a few graphic symbols were chosen from those common to most of the character encodings and input facilities available to Internet users.

      uric          = reserved | unreserved | escaped


Within a URI, characters are either used as delimiters, or to represent strings of data (octets) within the delimited portions. Octets are either represented directly by a character (using the US- ASCII character for that octet [ASCII]) or by an escape encoding. This representation is elaborated below.

2.1 URI及び非ASCII文字 2.1 URI and non-ASCII characters


The relationship between URI and characters has been a source of confusion for characters that are not part of US-ASCII. To describe the relationship, it is useful to distinguish between a "character" (as a distinguishable semantic entity) and an "octet" (an 8-bit byte). There are two mappings, one from URI characters to octets, and a second from octets to original characters:

   URI文字の列 -> オクテットの列 -> 元の文字の列
URI character sequence->octet sequence->original character sequence


A URI is represented as a sequence of characters, not as a sequence of octets. That is because URI might be "transported" by means that are not through a computer network, e.g., printed on paper, read over the radio, etc.


A URI scheme may define a mapping from URI characters to octets; whether this is done depends on the scheme. Commonly, within a delimited component of a URI, a sequence of characters may be used to represent a sequence of octets. For example, the character "a" represents the octet 97 (decimal), while the character sequence "%", "0", "a" represents the octet 10 (decimal).

幾つかの資源に対しては,2番目の変換(先の2種類の写像の2番目のもの)が存在する。すなわち,URIの構成要素によって定義されたオクテットの列が,その後,文字の列を表現するために使用される。'charset'が,この写像を定義する。インターネットプロトコルで使用されている多くのcharsetが存在する。例えば,UTF-8 [UTF-8]は,オクテットの列からISO 10646のレパートリにおける文字の列への写像を定義する。

There is a second translation for some resources: the sequence of octets defined by a component of the URI is subsequently used to represent a sequence of characters. A 'charset' defines this mapping. There are many charsets in use in Internet protocols. For example, UTF-8 [UTF-8] defines a mapping from sequences of octets to sequences of characters in the repertoire of ISO 10646.


In the simplest case, the original character sequence contains only characters that are defined in US-ASCII, and the two levels of mapping are simple and easily invertible: each 'original character' is represented as the octet for the US-ASCII code for it, which is, in turn, represented as either the US-ASCII character, or else the "%" escape sequence for that octet.


For original character sequences that contain non-ASCII characters, however, the situation is more difficult. Internet protocols that transmit octet sequences intended to represent character sequences are expected to provide some way of identifying the charset used, if there might be more than one [RFC2277]. However, there is currently no provision within the generic URI syntax to accomplish this identification. An individual URI scheme may require a single charset, define a default charset, or provide a way to indicate the charset used.


It is expected that a systematic treatment of character encoding within URI will be developed as a future modification of this specification.

2.2 予約済み文字 2.2. Reserved Characters


Many URI include components consisting of or delimited by, certain special characters. These characters are called "reserved", since their usage within the URI component is limited to their reserved purpose. If the data for a URI component would conflict with the reserved purpose, then the conflicting data must be escaped before forming the URI.

      reserved    = ";" | "/" | "?" | ":" | "@" | "&" | "=" | "+" |
                    "$" | ","


The "reserved" syntax class above refers to those characters that are allowed within a URI, but which may not be allowed within a particular component of the generic URI syntax; they are used as delimiters of the components described in Section 3.


Characters in the "reserved" set are not reserved in all contexts. The set of characters actually reserved within any given URI component is defined by that component. In general, a character is reserved if the semantics of the URI changes if the character is replaced with its escaped US-ASCII encoding.

2.3 予約済みでない文字 2.3. Unreserved Characters

URIで許可されるが予約済みの目的をもたないデータ文字は,"unreserved"(非予約済み,予約済みではない,など)と呼ぶ。これは,大文字・小文字の字,10進数字,及び約物(punctuation mark)の限定された集合を含む。

Data characters that are allowed in a URI but do not have a reserved purpose are called unreserved. These include upper and lower case letters, decimal digits, and a limited set of punctuation marks and symbols.

      unreserved  = alphanum | mark

      mark        = "-" | "_" | "." | "!" | "~" | "*" | "'" | "(" | ")"


Unreserved characters can be escaped without changing the semantics of the URI, but this should not be done unless the URI is being used in a context that does not allow the unescaped character to appear.

2.4 エスケープシーケンス 2.4. Escape Sequences


Data must be escaped if it does not have a representation using an unreserved character; this includes data that does not correspond to a printable character of the US-ASCII coded character set, or that corresponds to any US-ASCII character that is disallowed, as explained below.

2.4.1 エスケープの符号化 2.4.1. Escaped Encoding


An escaped octet is encoded as a character triplet, consisting of the percent character "%" followed by the two hexadecimal digits representing the octet code. For example, "%20" is the escaped encoding for the US-ASCII space character.

      escaped     = "%" hex hex
      hex         = digit | "A" | "B" | "C" | "D" | "E" | "F" |
                            "a" | "b" | "c" | "d" | "e" | "f"

2.4.2 エスケープする場合及びエスケープしない場合 2.4.2. When to Escape and Unescape


A URI is always in an "escaped" form, since escaping or unescaping a completed URI might change its semantics. Normally, the only time escape encodings can safely be made is when the URI is being created from its component parts; each component may have its own set of characters that are reserved, so only the mechanism responsible for generating or interpreting that component can determine whether or not escaping a character will change its semantics. Likewise, a URI must be separated into its components before the escaped characters within those components can be safely decoded.

予約済みではない文字によって表現できるデータが,エスケープされて出現してもよい場合もある。例えば,予約済みではない"記号"文字の中には,幾つかのシステムによって自動的にエスケープされるものがある。与えられたURI方式が正準化アルゴリズムを定義している場合,予約済みではない文字は,そのアルゴリズムによってエスケープされてよい。例えば,"%7e"が,http URLパスの中で"~"の代わりに使用されることがある。しかし,それら二つは,http URLに対して等価になっている。

In some cases, data that could be represented by an unreserved character may appear escaped; for example, some of the unreserved "mark" characters are automatically escaped by some systems. If the given URI scheme defines a canonicalization algorithm, then unreserved characters may be unescaped according to that algorithm. For example, "%7e" is sometimes used instead of "~" in an http URL path, but the two are equivalent for an http URL.


Because the percent "%" character always has the reserved purpose of 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 escape or unescape the same string more than once, since unescaping an already unescaped string might lead to misinterpreting a percent data character as another escaped character, or vice versa in the case of escaping an already escaped string.

2.4.3 排除されるUS-ASCII文字 2.4.3. Excluded US-ASCII Characters


Although they are disallowed within the URI syntax, we include here a description of those US-ASCII characters that have been excluded and the reasons for their exclusion.


The control characters in the US-ASCII coded character set are not used within a URI, both because they are non-printable and because they are likely to be misinterpreted by some control mechanisms.

   control     = <16進数で00〜1F及び7FのUS-ASCII符号化文字>


The space character is excluded because significant spaces may disappear and insignificant spaces may be introduced when URI are transcribed or typeset or subjected to the treatment of word- processing programs. Whitespace is also used to delimit URI in many contexts.

   space       = <16進数で20のUS-ASCII符号化文字>


The angle-bracket "<" and ">" and double-quote (") characters are excluded because they are often used as the delimiters around URI in text documents and protocol fields. The character "#" is excluded because it is used to delimit a URI from a fragment identifier in URI references (Section 4). The percent character "%" is excluded because it is used for the encoding of escaped characters.

   delims      = "<" | ">" | "#" | "%" | <">


Other characters are excluded because gateways and other transport agents are known to sometimes modify such characters, or they are used as delimiters.

   unwise      = "{" | "}" | "|" | "\" | "^" | "[" | "]" | "`"


Data corresponding to excluded characters must be escaped in order to be properly represented within a URI.

3. URI構文の構成要素 3. URI Syntactic Components


The URI syntax is dependent upon the scheme. In general, absolute URI are written as follows:



An absolute URI contains the name of the scheme being used (<scheme>) followed by a colon (":") and then a string (the <scheme-specific- part>) whose interpretation depends on the scheme.


The URI syntax does not require that the scheme-specific-part have any general structure or set of semantics which is common among all URI. However, a subset of URI do share a common syntax for representing hierarchical relationships within the namespace. This "generic URI" syntax consists of a sequence of four main components:



each of which, except <scheme>, may be absent from a particular URI. For example, some URI schemes do not allow an <authority> component, and others do not use a <query> component.

      absoluteURI   = scheme ":" ( hier_part | opaque_part )


URI that are hierarchical in nature use the slash "/" character for separating hierarchical components. For some file systems, a "/" character (used to denote the hierarchical structure of a URI) is the 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 the resource is a file or that the URI maps to an actual filesystem 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 方式構成要素 3.1. Scheme Component


Just as there are many different methods of access to resources, there are a variety of schemes for identifying such resources. The URI syntax consists of a sequence of components separated by reserved characters, with the first component defining the semantics for the remainder of the URI string.


Scheme names consist of a sequence of characters beginning with a lower case letter and followed by any combination of lower case letters, digits, plus ("+"), period ("."), or hyphen ("-"). For resiliency, programs interpreting URI should treat upper case letters as equivalent to lower case in scheme names (e.g., allow "HTTP" as well as "http").

      scheme        = alpha *( alpha | digit | "+" | "-" | "." )


Relative URI references are distinguished from absolute URI in that they do not begin with a scheme name. Instead, the scheme is inherited from the base URI, as described in Section 5.2.

3.2 機関構成要素 3.2. Authority Component


Many URI schemes include a top hierarchical element for a naming authority, such that the namespace defined by the remainder of the URI is governed by that authority. This authority component is typically defined by an Internet-based server or a scheme-specific registry of naming authorities.

      authority     = server | reg_name


The authority component is preceded by a double slash "//" and is terminated by the next slash "/", question-mark "?", or by the end of the URI. Within the authority component, the characters ";", ":", "@", "?", and "/" are reserved.


An authority component is not required for a URI scheme to make use of relative references. A base URI without an authority component implies that any relative reference will also be without an authority component.

3.2.1 登録簿に基づく名前付け機関 3.2.1. Registry-based Naming Authority


The structure of a registry-based naming authority is specific to the URI scheme, but constrained to the allowed characters for an authority component.

      reg_name      = 1*( unreserved | escaped | "$" | "," |
                          ";" | ":" | "@" | "&" | "=" | "+" )

3.2.2 サーバに基づく名前付け機関 3.2.2. Server-based Naming Authority


URL schemes that involve the direct use of an IP-based protocol to a specified server on the Internet use a common syntax for the server component of the URI's scheme-specific data:



where <userinfo> may consist of a user name and, optionally, scheme- specific information about how to gain authorization to access the server. The parts "<userinfo>@" and ":<port>" may be omitted.

      server        = [ [ userinfo "@" ] hostport ]


The user information, if present, is followed by a commercial at-sign "@".

      userinfo      = *( unreserved | escaped |
                         ";" | ":" | "&" | "=" | "+" | "$" | "," )


Some URL schemes use the format "user:password" in the userinfo field. This practice is NOT RECOMMENDED, because the passing of authentication information in clear text (such as URI) has proven to 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 a set of four decimal digit groups separated by ".". Literal IPv6 addresses are not supported.

      hostport      = host [ ":" port ]
      host          = hostname | IPv4address
      hostname      = *( domainlabel "." ) toplabel [ "." ]
      domainlabel   = alphanum | alphanum *( alphanum | "-" ) alphanum
      toplabel      = alpha | alpha *( alphanum | "-" ) alphanum
      IPv4address   = 1*digit "." 1*digit "." 1*digit "." 1*digit
      port          = *digit


Hostnames take the form described in Section 3 of [RFC1034] and Section 2.1 of [RFC1123]: a sequence of domain labels separated by ".", each domain label starting and ending with an alphanumeric character and possibly also containing "-" characters. The rightmost domain label of a fully qualified domain name will never start with a digit, thus syntactically distinguishing domain names from IPv4 addresses, and may be followed by a single "." if it is necessary to distinguish between the complete domain name and any local domain. To actually be "Uniform" as a resource locator, a URL hostname should be a fully qualified domain name. In practice, however, the host component may be a local domain literal.

備考  リテラルとしてのIPv6アドレスをURLの<host>部分として含むために適切な表現が望まれる。しかし,実際には,まだ決定も実装も行われていない。 Note: A suitable representation for including a literal IPv6 address as the host part of a URL is desired, but has not yet been determined or implemented in practice.


The port is the network port number for the server. Most schemes designate protocols that have a default port number. Another port number may optionally be supplied, in decimal, separated from the host by a colon. If the port is omitted, the default port number is assumed.

3.3 パス構成要素 3.3. Path Component


The path component contains data, specific to the authority (or the scheme if there is no authority component), identifying the resource within the scope of that scheme and authority.

      path          = [ abs_path | opaque_part ]

      path_segments = segment *( "/" segment )
      segment       = *pchar *( ";" param )
      param         = *pchar

      pchar         = unreserved | escaped |
                      ":" | "@" | "&" | "=" | "+" | "$" | ","


The path may consist of a sequence of path segments separated by a single slash "/" character. Within a path segment, the characters "/", ";", "=", and "?" are reserved. Each path segment may include a sequence of parameters, indicated by the semicolon ";" character. The parameters are not significant to the parsing of relative references.

3.4 問合せ構成要素 3.4. Query Component


The query component is a string of information to be interpreted by the resource.

      query         = *uric


Within a query component, the characters ";", "/", "?", ":", "@", "&", "=", "+", ",", and "$" are reserved.

4. URI参照 4. URI References


The term "URI-reference" is used here to denote the common usage of a resource identifier. A URI reference may be absolute or relative, and may have additional information attached in the form of a fragment identifier. However, "the URI" that results from such a reference includes only the absolute URI after the fragment identifier (if any) is removed and after any relative URI is resolved to its absolute form. Although it is possible to limit the discussion of URI syntax and semantics to that of the absolute result, most usage of URI is within general URI references, and it is impossible to obtain the URI from such a reference without also parsing the fragment and resolving the relative form.

      URI-reference = [ absoluteURI | relativeURI ] [ "#" fragment ]


The syntax for relative URI is a shortened form of that for absolute URI, where some prefix of the URI is missing and certain path components ("." and "..") have a special meaning when, and only when, interpreting a relative path. The relative URI syntax is defined in Section 5.

4.1 素片識別子 4.1. Fragment Identifier


When a URI reference is used to perform a retrieval action on the identified resource, the optional fragment identifier, separated from the URI by a crosshatch ("#") character, consists of additional reference information to be interpreted by the user agent after the retrieval action has been successfully completed. As such, it is not part of a URI, but is often used in conjunction with a URI.

      fragment      = *uric


The semantics of a fragment identifier is a property of the data resulting from a retrieval action, regardless of the type of URI used in the reference. Therefore, the format and interpretation of fragment identifiers is dependent on the media type [RFC2046] of the retrieval result. The character restrictions described in Section 2 for URI also apply to the fragment in a URI-reference. Individual media types may define additional restrictions or structure within the fragment for specifying different types of "partial views" that can be identified within that media type.


A fragment identifier is only meaningful when a URI reference is intended for retrieval and the result of that retrieval is a document for which the identified fragment is consistently defined.

4.2 同一文書参照 4.2. Same-document References


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 document is interpreted as a reference to the start of that document, and a reference containing only a fragment identifier is a reference to the identified fragment of that document. Traversal of such a reference should not result in an additional retrieval action. 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 element, then an empty URI reference represents the base URI of the current document and should be replaced by that URI when transformed into a request.

4.3 URI参照の構文解析 4.3. Parsing a URI Reference


訳者注: 最後の文は,"and"がないものとして訳した。 A URI reference is typically parsed according to the four main components and fragment identifier in order to determine what components are present and whether the reference is relative or absolute. The individual components are then parsed for their subparts and, if not opaque, to verify their validity.


Although the BNF defines what is allowed in each component, it is ambiguous in terms of differentiating between an authority component and a path component that begins with two slash characters. The 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 matching. In other words, the authority component wins.


訳者注: 少し意訳している。 Readers familiar with regular expressions should see Appendix B for a concrete parsing example and test oracle.

5. 相対URI参照 5. Relative URI References


It is often the case that a group or "tree" of documents has been constructed to serve a common purpose; the vast majority of URI in these documents point to resources within the tree rather than outside of it. Similarly, documents located at a particular site are much more likely to refer to other resources at that site than to resources at remote sites.


Relative addressing of URI allows document trees to be partially independent of their location and access scheme. For instance, it is possible for a single set of hypertext documents to be simultaneously accessible and traversable via each of the "file", "http", and "ftp" schemes if the documents refer to each other using relative URI. Furthermore, such document trees can be moved, as a whole, without changing any of the relative references. Experience within the WWW has demonstrated that the ability to perform relative referencing is necessary for the long-term usability of embedded URI.


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.

      relativeURI   = ( net_path | abs_path | rel_path ) [ "?" query ]


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 termed an absolute-path reference, as defined by <abs_path> in Section 3.


A relative reference that does not begin with a scheme name or a slash character is termed a relative-path reference.

      rel_path      = rel_segment [ abs_path ]

      rel_segment   = 1*( unreserved | escaped |
                          ";" | "@" | "&" | "=" | "+" | "$" | "," )


Within a relative-path reference, the complete path segments "." and ".." have special meanings: "the current hierarchy level" and "the level above this hierarchy level", respectively. Although this is very similar to their use within Unix-based filesystems to indicate directory levels, these path components are only considered special when resolving a relative-path reference to its absolute form (Section 5.2).


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 (e.g., "this:that"), because it would be mistaken for a scheme name.


It is therefore necessary to precede such segments with other segments (e.g., "./this:that") in order for them to be referenced as a relative path.


It is not necessary for all URI within a given scheme to be restricted to the <hier_part> syntax, since the hierarchical properties of that syntax are only necessary when relative URI are used within a particular document. Documents can only make use of relative URI when their base URI fits within the <hier_part> syntax. It is assumed that any document which contains a relative reference will also have a base URI that obeys the syntax. In other words, relative URI cannot be used within a document that has an unsuitable base URI.


Some URI schemes do not allow a hierarchical syntax matching the <hier_part> syntax, and thus cannot use relative references.

5.1 基底URIの確立 5.1. Establishing a Base URI


The term "relative URI" implies that there exists some absolute "base URI" against which the relative reference is applied. Indeed, the base URI is necessary to define the semantics of any relative URI reference; without it, a relative reference is meaningless. In order for relative URI to be usable within a document, the base URI of that document must be known to the parser.


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 thought of in terms of layers, where the innermost defined base URI has the highest precedence. This can be visualized graphically as:

      |  .----------------------------------------------------.  |
      |  |  .----------------------------------------------.  |  |
      |  |  |  .----------------------------------------.  |  |  |
      |  |  |  |  .----------------------------------.  |  |  |  |
      |  |  |  |  |            <相対参照>            |  |  |  |  |
      |  |  |  |  `----------------------------------'  |  |  |  |
      |  |  |  | (5.1.1) 文書内容に埋め込まれた基底URI  |  |  |  |
      |  |  |  `----------------------------------------'  |  |  |
      |  |  |    (5.1.2) カプセル化実体(メッセージ,文書   |  |  |
      |  |  |                又はなし)の基底URI            |  |  |
      |  |  `----------------------------------------------'  |  |
      |  |      (5.1.3) 実体を検索するために使用するURI       |  |
      |  `----------------------------------------------------'  |
      |           (5.1.4) 応用依存のデフォルト基底URI            |

                   図1 基底URIの優先度の図形的な表示

5.1.1 文書内容内部の基底URI 5.1.1. Base URI within Document Content


Within certain document media types, the base URI of the document can be embedded within the content itself such that it can be readily obtained by a parser. This can be useful for descriptive documents, such as tables of content, which may be transmitted to others through protocols other than their usual retrieval context (e.g., E-Mail or USENET news).


It is beyond the scope of this document to specify how, for each media type, the base URI can be embedded. It is assumed that user agents manipulating such media types will be able to obtain the appropriate syntax from that media type's specification. An example of how the base URI can be embedded in the Hypertext Markup Language (HTML) [RFC1866] is provided in Appendix D.

MIMEコンテナ型(例えば,メッセージ型及びマルチパート型)内に基底URIを埋め込むための機構は,MHTML [RFC2110]によって定義される。MIMEメッセージヘッダ構文を使用しないが,タグ付けされたメタ情報の幾つかの形式をメッセージ内に含めることを許可するプロトコルは,メッセージの一部として基底URIを定義するための,それ自体の構文を定義してもよい。

A mechanism for embedding the base URI within MIME container types (e.g., the message and multipart types) is defined by MHTML [RFC2110]. Protocols that do not use the MIME message header syntax, but which do allow some form of tagged metainformation to be included within messages, may define their own syntax for defining the base URI as part of a message.

5.1.2 カプセル化実体からの基底URI 5.1.2. Base URI from the Encapsulating Entity


If no base URI is embedded, the base URI of a document is defined by the document's retrieval context. For a document that is enclosed within another entity (such as a message or another document), the retrieval context is that entity; thus, the default base URI of the document is the base URI of the entity in which the document is encapsulated.

5.1.3 検索URIからの基底URI 5.1.3. Base URI from the Retrieval URI


If no base URI is embedded and the document is not encapsulated within some other entity (e.g., the top level of a composite entity), then, if a URI was used to retrieve the base document, that URI shall be considered the base URI. Note that if the retrieval was the result of a redirected request, the last URI used (i.e., that which resulted in the actual retrieval of the document) is the base URI.

5.1.4 デフォルト基底URI 5.1.4. Default Base URIで示された条件のいずれもが適用されない場合,基底URIは,応用の文脈によって定義される。この定義は必然的に応用依存となるので,他の手法の一つを使用して基底URIを定義することに失敗した場合には,同じ内容が,応用の異なる型によって異なって解釈されるようになってもよい。

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. Since this definition is necessarily application-dependent, failing to define the base URI using one of the other methods may result in the same content being interpreted differently by different types of application.


It is the responsibility of the distributor(s) of a document containing relative URI to ensure that the base URI for that document can be established. It must be emphasized that relative URI cannot be used reliably in situations where the document's base URI is not well-defined.

5.2 相対参照の絶対形式への解決 5.2. Resolving Relative References to Absolute Form


This section describes an example algorithm for resolving 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 parsed into the four main components as described in Section 3. Note that only the scheme component is required to be present in the base URI; the other components may be empty or undefined. A component is undefined if its preceding separator does not appear in 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 resolution algorithm and may be discarded.


For each URI reference, the following steps are performed in order:



1) The URI reference is parsed into the potential four components and fragment identifier, as described in Section 4.3.



2) If the path component is empty and the scheme, authority, and query components are undefined, then it is a reference to the current document and we are done. Otherwise, the reference URI's query and fragment components are defined as found (or not found) within the URI reference and not inherited from the base URI.



3) If the scheme component is defined, indicating that the reference starts with a scheme name, then the reference is interpreted as an absolute URI and we are done. Otherwise, the reference URI's 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 network-path and we skip to step 7. Otherwise, the reference URI's authority is inherited from the base URI's authority component, which will also be undefined if the URI scheme does not use an authority component.



5) If the path component begins with a slash character ("/"), then 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 reference. The relative path needs to be merged with the base URI's path. Although there are many ways to do this, we will describe a simple method using a separate string buffer.



a) All but the last segment of the base URI's path component is copied to the buffer. In other words, any characters after the last (right-most) slash character, if any, are excluded.



b) The reference's path component is appended to the buffer string.



c) All occurrences of "./", where "." is a complete path segment, are removed from the buffer string.



d) If the buffer string ends with "." as a complete path segment, that "." is removed.



e) All occurrences of "<segment>/../", where <segment> is a complete path segment not equal to "..", are removed from the buffer string. Removal of these path segments is performed iteratively, removing the leftmost matching pattern on each iteration, until no matching pattern remains.



f) If the buffer string ends with "<segment>/..", where <segment> is a complete path segment not equal to "..", that "<segment>/.." is removed.



g) If the resulting buffer string still begins with one or more complete path segments of "..", then the reference is considered to be in error. Implementations may handle this error by retaining these components in the resolved path (i.e., treating them as part of the final URI), by removing them from the resolved path (i.e., discarding relative levels above the root), or by avoiding traversal of the reference.



h) The remaining buffer string is the reference URI's new path component.



7) The resulting URI components, including any inherited from the base URI, are recombined to give the absolute form of the URI reference. Using pseudocode, this would be

         result = ""

         if 方式が定義されている

         if 機関が定義されている


         if 問合せが定義されている

         if 素片が定義されている

         return result
result = "" if scheme is defined then append scheme to result append ":" to result if authority is defined then append "//" to result append authority to result append path to result if query is defined then append "?" to result append query to result if fragment is defined then append "#" to result append fragment to result return result
備考 分離子が参照の中に存在していないことを意味する未定義である構成要素と,分離子は存在するが,そのすぐ後に次の構成要素分離子が続くか,又は参照の終了が続くことを意味する空である構成要素との間の違いを保存するように注意しなければならない。 Note that we must be careful to preserve the distinction between a component that is undefined, meaning that its separator was not present in the reference, and a component that is empty, meaning that the separator was present and was immediately followed by the next component separator or the end of the reference.


The above algorithm is intended to provide an example by which the output of implementations can be tested -- implementation of the algorithm itself is not required. For example, some systems may find it more efficient to implement step 6 as a pair of segment stacks being merged, rather than as a series of string pattern replacements.

備考 WWWクライアント応用の中には,ステップf)において基底パス及び参照パスを併合する前に,参照の問合せ構成要素をそのパス構成要素から分離することに失敗するものがある。これは,問合せ構成要素が文字列"/../"又は"/./"を含む場合,情報の損失を生じるかもしれない。 Note: Some WWW client applications will fail to separate the reference's query component from its path component before merging the base and reference paths in step 6 above. This may result in a loss of information if the query component contains the strings "/../" or "/./".


Resolution examples are provided in Appendix C.

6. URIの正規化及び等価性 6. URI Normalization and Equivalence

多くの場合,異なるURI文字列が,実際には同一の資源を識別することがある。例えば,URLで使用されるホスト名は,実際には,大文字・小文字を区別せず,URL <http://www.XEROX.com>は,<http://www.xerox.com>と等価になる。一般に,正規形の等価性及び定義についての規則は,存在する場合には,方式依存になる。方式が共通構文の要素を使用する場合,共通構文の等価性規則も使用する。すなわち,方式及びホスト名は大文字・小文字を区別せず,明示的な":port"をもつURLは,その方式に対してその(明示された)ポートがデフォルトの場合,ポートを省略したものと等価になる。

In many cases, different URI strings may actually identify the identical resource. For example, the host names used in URL are actually case insensitive, and the URL <http://www.XEROX.com> is equivalent to <http://www.xerox.com>. In general, the rules for equivalence and definition of a normal form, if any, are scheme dependent. When a scheme uses elements of the common syntax, it will also use the common syntax equivalence rules, namely that the scheme and hostname are case insensitive and a URL with an explicit ":port", where the port is the default for the scheme, is equivalent to one where the port is elided.

7. セキュリティへの考慮 7. Security Considerations

訳者注:この節は,内容的に難しい気がする。使われている語も,よく知らないものがある。 そのために,かなり意訳(?要するに分かっていない!)している箇所がある。


A URI does not in itself pose a security threat. Users should beware that there is no general guarantee that a URL, which at one time located a given resource, will continue to do so. Nor is there any guarantee that a URL will not locate a different resource at some later point in time, due to the lack of any constraint on how a given authority apportions its namespace. Such a guarantee can only be obtained from the person(s) controlling that namespace and the resource in question. A specific URI scheme may include additional semantics, such as name persistence, if those semantics are required of all naming authorities for that scheme.

資源と関連付けられた実体の検索などの,恐らく無害であって多重呼出し不変な操作を実行しようとすると,実際には,損害を生じる遠隔操作が発生するといった,URLの構成が可能なことがある。安全でないURLは,通常は,問題となっているネットワークプロトコルのために予約済み以外のポート番号を指定することによって構成される。クライアントは,何の準備もなく,実際には異なるプロトコルが動作しているサイトに接触する。URLの内容は,この他のプロトコルに従って解釈される場合には,予期しない操作を引き起こす命令を含むことになる。gopher URLを使用して,SMTPサーバ経由で意図しない又は偽装したメッセージが送信されたという例があった。

It is sometimes possible to construct a URL such that an attempt to perform a seemingly harmless, idempotent operation, such as the retrieval of an entity associated with the resource, will in fact cause a possibly damaging remote operation to occur. The unsafe URL is typically constructed by specifying a port number other than that reserved for the network protocol in question. The client unwittingly contacts a site that is in fact running a different protocol. The content of the URL contains instructions that, when interpreted according to this other protocol, cause an unexpected 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.


Caution should be used when using any URL that specifies a port number other than the default for the protocol, especially when it is a number within the reserved space.


Care should be taken when a URL contains escaped delimiters for a given protocol (for example, CR and LF characters for telnet protocols) that these are not unescaped before transmission. This might violate the protocol, but avoids the potential for such characters to be used to simulate an extra operation or parameter in that protocol, which might lead to an unexpected and possibly harmful remote operation to be performed.


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 the 'userinfo' component of a URL is strongly disrecommended except in those rare cases where the 'password' parameter is intended to be public.

8. 貢献者 8. Acknowledgements

この標準仕様書(TS)の原規定は,RFC 1738 [RFC1738]及びRFC 1808 [RFC1808]から導入された。これらの規定における貢献者は,この標準 仕様書(TS)の原規定の貢献者でもある。さらに,次の人々による寄与に深く感謝する。

This document was derived from RFC 1738 [RFC1738] and RFC 1808 [RFC1808]; the acknowledgements in those specifications still apply. In addition, contributions by Gisle Aas, Martin Beet, Martin Duerst, Jim Gettys, Martijn Koster, Dave Kristol, Daniel LaLiberte, Foteos Macrides, James Marshall, Ryan Moats, Keith Moore, and Lauren Wood are gratefully acknowledged.

9. 引用規定 9. References

[RFC2277] Alvestrand, H., "IETF Policy on Character Sets and Languages", BCP 18, RFC 2277, January 1998.

[RFC1630] Berners-Lee, T., "Universal Resource Identifiers in WWW: A Unifying Syntax for the Expression of Names and Addresses of Objects on the Network as used in the World-Wide Web", RFC 1630, June 1994.

[RFC1738] Berners-Lee, T., Masinter, L., and M. McCahill, Editors, "Uniform Resource Locators (URL)", RFC 1738, December 1994.

[RFC1866] Berners-Lee T., and D. Connolly, "HyperText Markup Language Specification -- 2.0", RFC 1866, November 1995.

[RFC1123] Braden, R., Editor, "Requirements for Internet Hosts -- Application and Support", STD 3, RFC 1123, October 1989.

[RFC822] Crocker, D., "Standard for the Format of ARPA Internet Text Messages", STD 11, RFC 822, August 1982.

[RFC1808] Fielding, R., "Relative Uniform Resource Locators", RFC 1808, June 1995.

[RFC2046] TS X 0070:2004 多目的インターネットメール拡張(MIME) 第2部 メディア型

備考 Freed, N., and N. Borenstein, "Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types", RFC 2046, November 1996 が, この規定に一致している。

[RFC1736] Kunze, J., "Functional Recommendations for Internet Resource Locators", RFC 1736, February 1995.

[RFC2141] Moats, R., "URN Syntax", RFC 2141, May 1997.

[RFC1034] Mockapetris, P., "Domain Names - Concepts and Facilities", STD 13, RFC 1034, November 1987.

[RFC2110] Palme, J., and A. Hopmann, "MIME E-mail Encapsulation of Aggregate Documents, such as HTML (MHTML)", RFC 2110, March 1997.

[RFC1737] Sollins, K., and L. Masinter, "Functional Requirements for Uniform Resource Names", RFC 1737, December 1994.

[ASCII] US-ASCII "Coded Character Set -- 7-bit American Standard Code for Information Interchange", ANSI X3.4-1986.

[UTF-8] Yergeau, F., "UTF-8, a transformation format of ISO 10646", RFC 2279, January 1998.

10. 原規定の著者の連絡先 10. Authors' Addresses

   Tim Berners-Lee
   World Wide Web Consortium
   MIT Laboratory for Computer Science, NE43-356
   545 Technology Square
   Cambridge, MA 02139

   Fax: +1(617)258-8682
   EMail: timbl@w3.org

   Roy T. Fielding
   Department of Information and Computer Science
   University of California, Irvine
   Irvine, CA  92697-3425

   Fax: +1(949)824-1715
   EMail: fielding@ics.uci.edu

   Larry Masinter
   Xerox PARC
   3333 Coyote Hill Road
   Palo Alto, CA 94034

   Fax: +1(415)812-4333
   EMail: masinter@parc.xerox.com