یو آر آی شناختگر یکنواخت منبع شناسگر یکنواخت منبع

یوآرآی (به انگلیسی: URI) مخفف "شناختگر یکنواخت منبع" یا شناسگر یکنواخت منبع (به انگلیسی: Uniform Resource Identifier) است و در علوم رایانه به رشته‌ای از نویسه‌ها گفته می‌شود که برای شناسایی یک نام یا منبع روی اینترنت بکار می‌رود. چنین شناسایی‌ای این امکان را فراهم می‌کند تا منابع مختلف روی یک شبکه (معمولا جهان وب) با یکدیگر به وسیله‌ی قراردادهایی مشخص، تعامل داشته باشند.[۱]

پانویس [ویرایش]

↑ مشارکت‌کنندگان ویکی‌پدیا، «Uniform Resource Identifier»، ویکی‌پدیای انگلیسی، دانشنامهٔ آزاد (بازیابی در ۲۸ اسفند ۱۳۸۹).
رده‌های صفحه: اینترنت

قس عربی

معرف الموارد الموحد (بالإنجلیزیة: Uniform Resource Identifier) ویعرف أیضاً باسم أوری (بالإنجلیزیة: URI) وهو عبارة عن عنوان فرید یستخدم لتحدید المحتوى على الشبکة، مثل صفحة من النص أو الصوت أو الفیدیو کلیب أو صورة ثابتة أو متحرکة أو برنامج. الشکل الأکثر شیوعا لمعرف الموارد هو عنوان صفحة الویب، الذی هو شکل معین أو فرع لعنوان الموقع الموحد URL. معرف الموارد عادة ما یصف کیفیة الوصول إلى الموارد والحاسوب الذی یحتوی على الموارد واسم الموارد (اسم الملف) على الحاسوب مثال هذا ال uri "http:\www.w3.org\Icons\WWW\w3c_main.gif" عبارة عن وصف لملف صورة من النوع gif واسمه w3c_main موجود على حاسوب (Server) اسمه www.w3.org یتم الوصول الیه عن طریق البروتوکول http Protocol.
[عدل]العلاقة بین اسم الموارد الموحد وعنوان الموقع الموحد



مخطط فیین لمعرف الموارد الموحد
أوری یمکن أن یصنف بحسب عنوان إنترنت أو الاسم أو الثنان معاً.
هذه بذرة مقالة عن الحاسوب أو العاملین فی هذا المجال تحتاج للنمو والتحسین، ساهم فی إثرائها بالمشارکة فی تحریرها.
تصنیف: علم الحاسوب

قس انگلیسی

In computing, a uniform resource identifier (URI) is a string of characters used to identify a name or a resource. Such identification enables interaction with representations of the resource over a network (typically the World Wide Web) using specific protocols. Schemes specifying a concrete syntax and associated protocols define each URI.
Contents [show]
[edit]Relationship to URL and URN



Diagram of URI scheme categories. Schemes in the URL (locator) and URN (name) categories form subsets of URI, and also (generally) disjoint sets. Technically URL and URN function as resource IDs; however, one cannot exactly categorize many schemes as one or the other: we can treat all URIs as names, and some schemes embody aspects of both categories.
URIs can be classified as locators (URLs), as names (URNs), or as both. A uniform resource name (URN) functions like a person's name, while a uniform resource locator (URL) resembles that person's street address. In other words: the URN defines an item's identity, while the URL provides a method for finding it.
The ISBN system for uniquely identifying books provides a typical example of the use of URNs. ISBN 0-486-27557-4 (urn:isbn:0-486-27557-4) cites, unambiguously, a specific edition of Shakespeare's play Romeo and Juliet. To gain access to this object and read the book, one needs its location: a URL address. A typical URL for this book on a Unix-like operating system would be a file path such as file:///home/username/RomeoAndJuliet.pdf, identifying the electronic book saved in a file on a local hard disk. So URNs and URLs have complementary purposes.
[edit]Technical view
A URL is a URI that, in addition to identifying a network-homed resource, specifies the means of acting upon or obtaining the representation: either through description of the primary access mechanism, or through network "location". For example, the URL http://en.wikipedia.org/wiki/Main_Page identifies a resource, in this case English Wikipedia's home page, whose representation, in the form of the home page's current HTML and related code, as encoded characters, is obtainable via the HyperText Transfer Protocol from a network host whose domain name is en.wikipedia.org. A uniform resource name (URN) is a URI that identifies a resource by name, in a particular namespace. One can use a URN to talk about a resource without implying its location or how to access it. The resource does not need necessarily to be accessible over a network. For example, the URN urn:isbn:0-395-36341-1 is a URI that specifies the identifier system, i.e. international standard book number (ISBN), as well as the unique reference within that system and allows one to talk about a book, but the URI doesn't suggest where and how to obtain an actual copy of it.
Technical publications, especially standards produced by the IETF and by the W3C, normally reflect a view outlined in a W3C Recommendation of 2001, which acknowledges the precedence of the term URI, rather than endorsing any formal subdivision into URL and URN: "URL is a useful but informal concept: a URL is a type of URI that identifies a resource via a representation of its primary access mechanism (e.g., its network "location"), rather than by some other attributes it may have."[1] A URL is simply a URI that happens to point to a physical resource over a network.[2]
However, in non-technical contexts and in software for the World Wide Web, the term URL remains widely used. Additionally, the term web address (which has no formal definition) often occurs in non-technical publications as a synonym for a URI that uses the 'http' or 'https' scheme; an assumption that can lead to confusion when viewing XML source: the standard means of uniquely identifying an XML language in a document is to declare its XML namespace that begins with 'http' and uses the syntax for a genuine domain name followed by a file hierarchy, but which has no need to point to any specific file location that actually exists.[3]
[edit]Syntax

See also: URI generic syntax
The URI syntax consists of a URI scheme name (such as "http", "ftp", "mailto" or "file") followed by a colon character, and then by a scheme-specific part. The specifications that govern the schemes determine the syntax and semantics of the scheme-specific part. However, URI syntax does require all schemes to adhere to a general syntax that (among other things) reserves certain characters for special purposes (without always identifying those purposes). The URI syntax also enforces restrictions on the scheme-specific part in order to (for example) provide for a degree of consistency when the part has a hierarchical structure.
Percent encoding can add extra information to a URI.
[edit]History

[edit]Naming, addressing, and identifying resources
URIs and URLs have a shared history. In 1994, Tim Berners-Lee’s proposals for HyperText[4] implicitly introduced the idea of a URL as a short string representing a resource that is the target of a hyperlink. At the time, people referred to it as a 'hypertext name'[5] or 'document name'.
Over the next three and a half years, as the World Wide Web's core technologies of HTML (the HyperText Markup Language), HTTP, and web browsers developed, a need to distinguish a string that provided an address for a resource from a string that merely named a resource emerged. Although not yet formally defined, the term Uniform Resource Locator came to represent the former, and the more contentious Uniform Resource Name came to represent the latter.
During the debate over defining URLs and URNs it became evident that the two concepts embodied by the terms were merely aspects of the fundamental, overarching notion of resource identification. In June 1994, the IETF published Berners-Lee's RFC 1630: the first RFC that (in its non-normative text) acknowledged the existence of URLs and URNs, and, more importantly, defined a formal syntax for Universal Resource Identifiers — URL-like strings whose precise syntaxes and semantics depended on their schemes. In addition, this RFC attempted to summarize the syntaxes of URL schemes in use at the time. It also acknowledged, but did not standardize, the existence of relative URLs and fragment identifiers.
[edit]Refinement of specifications
In December 1994, RFC 1738 formally defined relative and absolute URLs[citation needed], refined the general URL syntax, defined how to resolve relative URLs to absolute form, and better enumerated the URL schemes then in use. The agreed definition and syntax of URNs had to wait until the publication of RFC 2141 in May 1997.
The publication of RFC 2396 in August 1998 saw the URI syntax become a separate specification[6] and most of the parts of RFCs 1630 and 1738 relating to URIs and URLs in general were revised and expanded.[by whom?] The new RFC changed the significance of the "U" in "URI": it came to represent "Uniform" rather than "Universal". The sections of RFC 1738 that summarized existing URL schemes migrated into a separate document.[7] IANA keeps a registry of those schemes;[8] RFC 2717 first described the procedure to register them.
In December 1999, RFC 2732 provided a minor update to RFC 2396, allowing URIs to accommodate IPv6 addresses. Some time later, a number of shortcomings discovered in the two specifications led to the development of a number of draft revisions under the title rfc2396bis. This community effort, coordinated by RFC 2396 co-author Roy Fielding, culminated in the publication of RFC 3986 in January 2005. This RFC, as of 2009 the current version of the URI syntax recommended for use on the Internet, renders RFC 2396 obsolete. It does not, however, render the details of existing URL schemes obsolete; RFC 1738 continues to govern such schemes except where otherwise superseded – RFC 2616 for example, refines the 'http' scheme. Simultaneously, the IETF published the content of RFC 3986 as the full standard STD 66, reflecting the establishment of the URI generic syntax as an official Internet protocol.
In August 2002, RFC 3305 pointed out that the term 'URL' has, despite its widespread use in the vernacular of the Internet-aware public at large, faded into near obsolescence. It now serves only as a reminder that some URIs act as addresses because they have schemes that imply some kind of network accessibility, regardless of whether systems actually use them for that purpose. As URI-based standards such as Resource Description Framework make evident, resource identification need not suggest the retrieval of resource representations over the Internet, nor need they imply network-based resources at all.
On November 1, 2006, the W3C Technical Architecture Group published 'On Linking Alternative Representations To Enable Discovery And Publishing',[9] a guide to best practices and canonical URIs for publishing multiple versions of a given resource. For example, content might differ by language or by size to adjust for capacity or settings of the device used to access that content.
The Semantic Web uses the HTTP URI scheme to identify both documents and concepts in the real world: this has caused confusion as to how to distinguish the two. The Technical Architecture Group of W3C (TAG) published an e-mail in June 2005 on how to solve this problem. The e-mail became known as the httpRange-14 resolution.[10] To expand on this (rather brief) email, W3C published in March 2008 the Interest Group Note Cool URIs for the Semantic Web.[11] This explains the use of content negotiation and the 303-redirect code in more detail.
[edit]URI reference

A URI reference may take the form of a full URI, or just the scheme-specific portion of one, or even some trailing component thereof – even the empty string. An optional fragment identifier, preceded by #, may be present at the end of a URI reference. The part of the reference before the # indirectly identifies a resource, and the fragment identifier identifies some portion of that resource.
To derive a URI from a URI reference, software converts the URI reference to 'absolute' form by merging it with an absolute 'base' URI according to a fixed algorithm. The system treats the URI reference as relative to the base URI, although in the case of an absolute reference, the base has no relevance. The base URI typically identifies the document containing the URI reference, although this can be overridden by declarations made within the document or as part of an external data transmission protocol. If the base URI includes a fragment identifier, it is ignored during the merging process. If a fragment identifier is present in the URI reference, it is preserved during the merging process.
Web document markup languages frequently use URI references to point to other resources, such as external documents or specific portions of the same logical document.
[edit]Uses of URI references in markup languages
In HTML, the value of the src attribute of the img element provides a URI reference, as does the value of the href attribute of the a or link element.
In XML, the system identifier appearing after the SYSTEM keyword in a DTD is a fragmentless URI reference.
In XSLT, the value of the href attribute of the xsl:import element/instruction is a URI reference; likewise the first argument to the document() function.
[edit]Examples of absolute URIs
http://example.org/absolute/URI/with/absolute/path/to/resource.txt
ftp://example.org/resource.txt
urn:issn:1535-3613
[edit]Examples of URI references
http://en.wikipedia.org/wiki/URI#Examples_of_URI_references ("http" specifies the 'scheme' name, "en.wikipedia.org" is the 'authority', "/wiki/URI" the 'path' pointing to this article, and "#Examples_of_URI_references" is a 'fragment' pointing to this section.)
http://example.org/absolute/URI/with/absolute/path/to/resource.txt
//example.org/scheme-relative/URI/with/absolute/path/to/resource.txt
/relative/URI/with/absolute/path/to/resource.txt
relative/path/to/resource.txt
../../../resource.txt
./resource.txt#frag01
resource.txt
#frag01
(empty string)
[edit]URI resolution

To resolve a URI means either to convert a relative URI reference to absolute form, or to dereference a URI or URI reference by attempting to obtain a representation of the resource that it identifies. The 'resolver' component in document processing software generally provides both services.
One can regard a URI reference as a same document reference: a reference to the document containing the URI reference itself. Document processing software can efficiently use its current representation of the document to satisfy the resolution of a same document reference without fetching a new representation. This is only a recommendation, and document processing software can alternatively use other mechanisms to determine whether to obtain a new representation.
The current URI specification as of 2009, RFC 3986, defines a URI reference as a same document reference if, when resolved to absolute form, it equates exactly to the base URI in effect for the reference. Typically, the base URI is the URI of the document containing the reference. XSLT 1.0, for example, has a document() function that, in effect, implements this functionality. RFC 3986 also formally defines URI equivalence, which can be used to determine that a URI reference, while not identical to the base URI, still represents the same resource and thus can be considered to be a same document reference.
RFC 2396 prescribed a different method for determining same document references; RFC 3986 made RFC 2396 obsolete, but RFC 2396 still serves as the basis of many specifications and implementations. This specification defines a URI reference as a same document reference if it is an empty string or consists of only the # character followed by an optional fragment.
[edit]Relation to XML namespaces

XML has a concept of a namespace, an abstract domain to which a collection of element and attribute names can be assigned. The namespace name (a character string which must adhere to the generic URI syntax) identifies an XML namespace. However, the namespace name is generally not considered[12] to be a URI because the 'URI-ness' of strings is, according to the URI specification, based on their intended use, not just their lexical components. A namespace name also does not necessarily imply any of the semantics of URI schemes; a namespace name beginning with 'http:', for example, likely has nothing to do with the HTTP protocol. XML professionals have debated this thoroughly on the xml dev electronic mailing list; some feel that a namespace name could be a URI, since the collection of names comprising a particular namespace could be regarded as a resource that is being identified, and since a version of the 'Namespaces in XML' specification says that the namespace name is a URI reference.[13] But the consensus seems to suggest that a namespace name is just a string that happens to look like a URI, nothing more.
Initially, the namespace name could match the syntax of any non-empty URI reference, but an erratum to the 'Namespaces In XML Recommendation' later deprecated the use of relative URI references. A separate specification, issued for namespaces for XML 1.1, allows IRI references, not just URI references, to serve as the basis for namespace names.
To mitigate confusion that began to arise among newcomers to XML from the use of URIs (particularly HTTP URLs) for namespaces, a descriptive language called RDDL (Resource Directory Description Language) developed, though the specification of RDDL[14] has no official standing and no relevant organization (such as W3C) has considered or approved it. An RDDL document can provide machine- and human-readable information about a particular namespace and about the XML documents that use it. Authors of XML documents were encouraged[by whom?] to put RDDL documents in locations such that if a namespace name in their document somehow becomes de-referenced, then an RDDL document would be obtained, thus satisfying the desire among many developers for a namespace name to point to a network-accessible resource.
[edit]See also

For help on using external links on Wikipedia, see Help:URL and Wikipedia:External links
.arpa – uri.arpa is for dynamic discovery
Dan Connolly
CURIE (Compact URI)
Dereferenceable URI (an HTTP URI)
History of the Internet
Internationalized Resource Identifier (IRI)
Namespace (programming)
Percent-encoding
Persistent Uniform Resource Locator (PURL)
Uniform naming convention (UNC)
Uniform Resource Locator (URL)
Uniform Resource Name (URN)
URI scheme
Website
XRI (Extensible Resource Identifier)
[edit]References

^ URI Planning Interest Group, W3C/IETF (21 September 2001). "URIs, URLs, and URNs: Clarifications and Recommendations 1.0". Retrieved 2009-07-27.
^ Much of this discussion comes from RFC3305, titled 'Report from the Joint W3C/IETF URI Planning Interest Group: Uniform Resource Identifiers (URIs), URLs, and Uniform Resource Names (URNs): Clarifications and Recommendations'. This RFC outlines the work of a joint W3C/IETF working group set up specifically to normalize the divergent views held within the IETF and W3C over the relationship between the various 'UR*' terms and standards. While not published as a full standard by either organization, it has become the basis for the above common understanding and has informed many standards since then.
^ Morrison, Michael, 2006. Sams Teach Yourself XML. Sams Publishing. Hour 5: Putting Namespaces to Use, p 91.
^ Palmer, Sean B.. "The Early History of HTML". Retrieved 2009-04-30.
^ "W3 Naming Schemes". W3. Retrieved 2009-07-24. "The format of a hypertext name consists of the name of the naming sub-scheme to be used, then a name in a format particular to that sub-scheme, then an optional anchor identifier within the document. For example, the format is for all internet-based access methods:
scheme : // host.domain:port / path / path # anchor"
^ "FAQS.org". FAQS.org. Retrieved 2012-04-03.
^ This separate document is not explicitly linked[by whom?], RFC 2717 and RFC 4395 point to the IANA registry as the official URI scheme registry.
^ "IANA registry of URI schemes". Iana.org. 2012-03-26. Retrieved 2012-04-03.
^ "w3.org". w3.org. Retrieved 2012-04-03.
^ The httpRange-14 resolution consists of three bullet points: see Fielding, Roy T. (2005-06-18). "[httpRange-14 Resolved"]. Retrieved 2009-07-24., and did not help much to reduce the confusion.
^ "W3.org". W3.org. Retrieved 2012-04-03.
^ Harold, Elliote Rusty (2004). XML 1.1 Bible, Third Edition, Wiley Publishing Inc., p. 291. ISBN 0-7645-4986-3.
^ World Wide Web Consortium (1999-01-14). "Namespaces in XML" (PDF). W3C. Retrieved 2009-09-14. "[Definition:] The attribute's value, a URI reference, is the namespace name identifying the namespace."
^ "rddl.org". rddl.org. Retrieved 2012-04-03.
[edit]External links

RFC 3986 / STD 66 (2005) – the current generic URI syntax specification
RFC 2396 (1998) and RFC 2732 (1999) – obsolete, but widely implemented, version of the generic URI syntax
RFC 1808 (1995) – obsolete companion to RFC 1738 covering relative URL processing
RFC 1738 (1994) – mostly obsolete definition of URL schemes and generic URI syntax
RFC 1630 (1994) – the first generic URI syntax specification; first acknowledgement of URLs in an Internet standard
URI Schemes – IANA-maintained registry of URI Schemes
Architecture of the World Wide Web, Volume One, §2: Identification – by W3C
Example of discussion about names and addresses
The URI is the Thing – by Paul Downey (2008)
W3C materials related to addressing
W3C URI Clarification
The Self-Describing Web (2008) – from W3C
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Categories: URI schemes

قس اردو

یکساں وسیلی شناختگر (Uniform Resource Identifiers) حروف کی ایک خاص ترتیب ، نظم و نسق یا نسقہ کو کہا جاتا ہے جو کہ کسی وسیلہ (resource) کی شناخت یا اسکو نام دینے (اسمیابی) کے لیۓ استعمال کیا جاتا ہے۔
زمرہ جات: تدبیر یوآرآئیمعیار شبکہ شناختگر

قس عبری

Uniform Resource Identifier: ביטוי המזהה נתיב למקור מידע (Resource) באופן חד חד ערכי. URI מהווה למעשה הרחבה של URL כך שניתן לזהות כל מקור מידע בעזרתו ולא רק דפי אינטרנט.
ערך זה הוא קצרמר בנושא מחשבים. אתם מוזמנים לתרום לוויקיפדיה ולהרחיב אותו.
קטגוריות: קצרמר מחשביםתקנים בתקשורת מחשביםכתובות רשת
משובים קודמיםמשוב על הערך


قس چینی

在電腦术语中，统一资源标识符（Uniform Resource Identifier，或URI)是一个用于标识某一互联网资源名称的字符串。 该种标识允许用户对网络中（一般指万维网）的资源通过特定的协议进行交互操作。URI由包括确定语法和相关协议的方案所定义。
目录 [显示]
[编辑]与URL和URN的关系



URL方案分类图。URL(定位符)和URN(名称)方案属于URI的子类，大致上属于不相交集合。技术上讲，URL和URN属于资源ID；但是，人们往往无法将某种方案归类于两者中的某一个：所有的URI都可被作为名称看待，而某些方案同时体现了两者中的不同部分。
URI可被视为定位符（URL），名称（URN）或两者兼备。统一资源名（URN）如同一个人的名称，而统一资源定位符（URL）代表一个人的住址。换言之，URN定义某事物的身份，而URL提供查找该事物的方法。
用于标识唯一书目的ISBN系统是一个典型的URN使用范例。例如，ISBN 0-486-27557-4(urn:isbn:0-486-27557-4)无二义性地标识出莎士比亚的戏剧《罗密欧与朱丽叶》的某一特定版本。为获得该资源并阅读该书，人们需要它的位置，也就是一个URL地址。在类Unix操作系统中，一个典型的URL地址可能是一个文件目录，例如file:///home/username/RomeoAndJuliet.pdf。该URL标识出存储于本地硬盘中的电子书文件。因此，URL和URN有着互补的作用。
[编辑]技术观点
URL是一种URI，它标识一个互联网资源，并指定对其进行操作或取得该资源的方法。可能通过对主要访问手段的描述，也可能通过网络“位置”进行标识。例如，http://www.wikipedia.org/这个URL，标识一个特定资源（首页）并表示该资源的某种形式（例如以编码字符表示的，首页的HTML代码）是可以通过HTTP协议从www.wikipedia.org这个网络主机获得的。URN是基于某命名空间通过名称指定资源的URI。人们可以通过URN来指出某个资源，而无需指出其位置和获得方式。资源无需是基于互联网的。例如，URN urn:isbn:0-395-36341-1 指定标识系统（即国际标准书号ISBN）和某资源在该系统中的唯一表示的URI。它可以允许人们在不指出其位置和获得方式的情况下谈论这本书。
技术刊物，特别是IETF和W3C发布的标准中，通常不再[哪时？]使用“URL”这一术语，因为很少需要区别URL和URI。[1] 但是，在非技术文献和万维网软件中，URL这一术语仍被广泛使用。此外，术语“网址”（没有正式定义）在非技术文献中时常作为URL或URI的同义词出现，虽然往往其指代的只是“http”和“https”协议。
[编辑]RFC 3305
关于URI的讨论多源于题目为《W3C/IETF URI规划联合小组报告：统一标识资源符（URI），URL和统一资源名（URN）：阐明与建议》的 RFC3305 文件。这一RFC文件描述了一个，以统一W3C和IETF内部对于各种“UR*”术语之间关系的不同看法为目的而设立的，W3C/IETF联合工作小组的工作。虽然未作为标准被这两个组织所发布，但该文件确立了上述种种共识，并就此催生了许多标准的诞生。
[编辑]文法

参见：URI通用文法
URI文法由URI协议名（例如“http”，“ftp”，“mailto”或“file”），一个冒号，和协议对应的内容所构成。特定的协议定义了协议内容的语法和语义，而所有的协议都必须遵循一定的URI文法通用规则，亦即为某些专门目的保留部分特殊字符。URI文法同时也就各种原因对协议内容加以其他的限制，例如，保证各种分层协议之间的协同性。百分号编码也为URI提供附加信息。
[编辑]历史

[编辑]命名、定位与标识资源
URI与URL有着共同的历史。在1990年，Tim Berners-Lee的关于超文本的提案[2] 间接地引入了使用URL作为一个表示超链接目标资源的短字符串的概念。当时，人们称之为“超文本名”[3] 或“文档名”。
在之后的三年半中，由于万维网的HTML（超文本标记语言）核心技术、HTTP与浏览器都得到了发展，区别提供资源访问和资源标记的两种字符串的必要性开始显现。虽然其时尚未被正式定义，但“统一资源定位符”这一术语开始被用于代表前者，而后者则由“统一资源名称”所表示。
在关于定义URL和URN的争论中，人们注意到两者事实上基于同一个基础的“资源标识”的概念。在1994年6月，IETF发布了Berners-Lee的RFC 1630，（非正式地）指出了URL和URN的存在，并进一步定义了“通用资源标识符”——语义和语法由具体协议规定的类URL字符串的规范文法。此外，该RFC文档亦尝试定义了其时正被使用着的URL协议的文法，同时指出（但并未标准化）了相对URL和片段标识符的存在。
[编辑]标准改良
1994年12月，RFC 1738 正式定义了绝对和相对URL，改进了URL文法，定义了如何解析URL为绝对形式，并更加完善地列举了其时正处于使用中的URL协议。而URN定义和文法直到1997年5月RFC 2141公布后才正式统一。
1998年8月，随着RFC 2396的发表，URI文法形成了独立的标准[4]，同时RFC 1630和1738中关于URI和URL的许多部分也得到了修订和增补。[谁？]。新RFC修改了“URI”中“U”的含义：它开始代表统一（Uniform）而不再是通用（Universal）。RFC 1738中总结了既存URL协议的部分被移至另外一篇独立文档中。[5]IANA 保留着这些协议的注册信息[6]，而RFC 2717首次描述了注册它们的流程。
在1999年12月，RFC 2732对RFC 2396进行了小幅更新，开始允许URI包括IPv6地址。一段时间以后，在两个标准中暴露出的一些问题促使了一系列的修订草案的发展，这些草案被统称为rfc2396bis。这一由RFC 2396的共同作者Roy Fielding引导协调的集体努力，由2005年1月RFC 3986的发布推至了顶峰。该RFC文档成为了现今（2009年）于互联网上被推荐使用的URI文法版本，并使得RFC 2396成为了历史。然而，它却并未替代现有的URL协议细节；RFC 1738继续管辖着大多数协议，除了某些已被它取而代之的场合——例如被RFC 2616改良的”HTTP”协议等。与此同时，IETF发布了RFC 3986，亦即完整的STD 66标准，标识着URI通用文法正式成官方因特网协议。
在2002年8月，RFC 3305指出，虽然术语“URL”仍被广泛地用于日常用语之中，但其本身已几乎被废弃。其现在的功用，仅是作为对于某些URI因包含某种指示着网络可达性的协议而作为地址存在的提醒而已。基于URI的众多标准，例如资源描述框架等，已经清楚地表明，资源标识本无需指出通过互联网获得资源副本的方法，亦无须指出资源是否基于网络。
在2006年11月1日，W3C技术架构小组公布了《连接替代副本使查找和发布可行化》，一个对于发布给定资源的多个版本的权威URI和其最佳实践的指导。例如，内容可能因用于访问资源的设备的支持性和设定不同，而语言或大小上有所调整已适应这种差异。
语义网使用HTTP URI协议以标识文档和现实世界中的概念：这使得人们就如何区分二者产生了一些困扰。W3C技术架构小组(TAG)在2005年6月发布了一封关于如何解决这一问题的电子邮件，该邮件被称为“http范围-14 决议” 。[7]
为了扩充这个（相当简短的）电子邮件，W3C在2008年3月发布了互联网组注释《用于语义网的酷URI》[8]。这一文档详细阐释了内容协商和303重定向码的使用。
[编辑]URI引用

另一种类型的字符串——“URI引用”——代表一个URI并（相应地）代表被该URI所标识的资源。非正式使用中，URI和URI引用的区别少有被提及，但协议文档自然不应允许歧义的存在。
URI引用可取用的格式包括完整URI，URI中协议特定的部分，或其后附部分——甚至是空字符串。一个可选的片段标识符以#开头，可出现在URI引用的结尾。引用中，#之前的部分间接标识一个资源，而片段标识符则标识资源的某个部分。
为从URI引用获得URI，软件将URI引用与一个绝对“基址”基于一个固定算法合并，并转换为“绝对”形式。系统将URI引用视作相对于基址URI，虽然在绝对引用的情况下基址并无意义。基址URI一般标识包含URI引用的文档，但仍可被文档内包含的声明，或外部数据传输协议所包括的声明改写。若基址URI包括一个片段标识符，则该标识符在合并过程中被忽略。如果在URI引用中出现片段标识符，则在合并过程中被保留。
网络文档标记语言时常使用URI引用指向其它资源，如外部文档或同一逻辑文档的其他部分等。
[编辑]标记语言中URI引用的使用
在HTML中，img元素的src属性值是URI引用，a或link元素的href属性值亦如是。
在XML中，在一个DTD中的SYSTEM关键字之后出现的系统描述符是一个无片段的URI引用。
在XSLT中，xsl:import元素/指令的href属性值是一个URI引用，document()函数的第一个参数与之相仿。
[编辑]绝对URI的例子
http://example.org/absolute/URI/with/absolute/path/to/resource.txt
ftp://example.org/resource.txt
urn:issn:1535-3613
[编辑]URI引用的例子
http://en.wikipedia.org/wiki/URI#Examples_of_URI_references （"http" 指定协议名, "en.wikipedia.org"是“典据”, "/wiki/URI"是指向英文维基页面的“路径”，而"#Examples_of_URI_references"是指向英文维基页面相应片段的“片段”。)
http://example.org/absolute/URI/with/absolute/path/to/resource.txt
//example.org/scheme-relative/URI/with/absolute/path/to/resource.txt
/relative/URI/with/absolute/path/to/resource.txt
relative/path/to/resource.txt
../../../resource.txt
./resource.txt#frag01
resource.txt
#frag01
(空字符串)
[编辑]URI解析

“解析”一个URI意味着将一个相对URI引用转换为绝对形式，或者通过尝试获取一个可解引URI或一个URI引用所代表的资源来解引用这个URI。文档处理软件的“解析”部分通常同时提供这两种功能。
一个URI引用可以是一个同文档引用：一个指向包含URI引用自身的文档的引用。文档处理软件可有效地使用其当前的文档资源来完成对于同文档引用的解析而不需要重新取得一份资源。这只是一个建议——文档处理软件自然可以选用另外的方法来决定是否获取新资源。
当前截至2009 年的URI规范，RFC 3986，将一个同文档引用的URI定义为“当解析为绝对形式时与引用的基文档地址完全一致的文档”。一般来说，基文档URI就是包含引用的文档的URI。例如，XSLT 1.0包括document()函数以实现这一功能。RFC 3986同时也正式定义了URI等效性，一个可以被[谁？]用来判断一个与基URI不同的URI是否表示同一个资源，并因此可以被认为是同文档引用。
RFC 2396给出了一个不同的判断同文档引用的方法；RFC 3986替代了RFC 2396，但RFC 2396仍旧作为许多规范和实现的基础而存在。这一规范将一个空字符串或仅包括#字符和可选的片段标识符组成的URI引用定义为同文档引用。
[编辑]与XML命名空间的关系

XML拥有一个叫命名空间的，一个可包含元素集和属性名称的抽象域的概念。命名空间的名称（一个必须遵守通用URI文法的字符串）用于标识一个XML命名空间。但是，命名空间的名称一般不被[谁？]认为是一个URI，因为URI规范定义了字符串的“URI性”是根据其目的而不是其词法组成决定的。一个命名空间名称同时也并不一定暗示任何URI协议的语义；例如，一个以”http:”开头的命名空间名称很可能与HTTP协议没有任何关系。XML专家们就这一问题在XML开发电子邮件列表上进行了深入的辩论；一部分人认为[谁？]命名空间名称可以是URI，由于包含一个具体命名空间的名称集可以被看作是一个被标识的资源，也由于“XML中的命名空间”规范的一个版本指出过命名空间名称“是”一个URI引用。[9] 但是，集体共识似乎指出一个命名空间名称只是一个凑巧看起来像URI的字符串，仅此而已。
早先，命名空间名称是可以匹配任何非空URI引用的语法的，但后来的一个对于“XML命名空间建议”的订正废弃了相对URI引用的使用。一个独立的、针对XML 1.1的命名空间的规范允许使用IRI引用作为命名空间名称的基准，而不仅是URI引用。
为了消除XML新人中产生的对于URI（尤其是HTTP URL）的使用的困惑，一个被称为RDDL（资源目录描述语言）的描述语言被建立了，虽然RDDL的规范并没有正式地位，也并没有获得任何相关组织（例如W3C）的检查和支持。一个RDDL文档可以提供关于一个特定命名空间和使用它的XML文档的，机器与人类都能读懂的信息。XML文档的作者鼓励使用RDDL文档，这样一旦文档中的命名空间名称被索引，（系统）就会取得一个RDDL文档。这样，许多开发者对于让命名空间名称指向网络可达资源的需求就能得到满足。
[编辑]参考文献

^ URI Planning Interest Group, W3C/IETF. URIs, URLs, and URNs: Clarifications and Recommendations 1.0. 21 September 2001 [2009-07-27].
^ Palmer, Sean B.. The Early History of HTML [2009-04-30].
^ W3 Naming Schemes. W3 [2009-07-24]. "The format of a hypertext name consists of the name of the naming sub-scheme to be used, then a name in a format particular to that sub-scheme, then an optional anchor identifier within the document. For example, the format is for all internet-based access methods:
scheme : // host.domain:port / path / path # anchor"
^ FAQS.org
^ This separate document is not explicitly linked[谁？], RFC 2717 and RFC 4395 point to the IANA registry as the official URI scheme registry.
^ IANA registry of URI schemes
^ The httpRange-14 resolution consists of three bullet points: see Fielding, Roy T.. [httpRange-14 Resolved]. 2005-06-18 [2009-07-24]., and did not help much to reduce the confusion.
^ W3.org
^ World Wide Web Consortium. Namespaces in XML (PDF). W3C. 1999-01-14 [2009-09-14]. "[Definition:] The attribute's value, a URI reference, is the namespace name identifying the namespace."

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