Uniform Resource Identifier
In 1990, Tim Berners-Lee's proposals for hypertext implicitly introduced the idea of a URL as a short string representing a resource that is the target of a hyperlink.In July 1992 Berners-Lee's report on the Internet Engineering Task Force (IETF) "UDI (Universal Document Identifiers) BOF" mentions URLs (as Uniform Resource Locators), URNs (originally, as Unique Resource Numbers), and the need to charter a new working group.[7] During the debate over defining URLs and URNs, it became evident that the concepts embodied by the two terms were merely aspects of the fundamental, overarching, notion of resource identification.In June 1994, the IETF published Berners-Lee's first Request for Comments that acknowledged the existence of URLs and URNs.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, IETF RFC 3305[16] pointed out that the term "URL" had, despite widespread public use, faded into near obsolescence, and serves only as a reminder that some URIs act as addresses by having schemes implying network accessibility, regardless of any such actual use.The Semantic Web uses the HTTP URI scheme to identify both documents and concepts for practical uses, a distinction which has caused confusion as to how to distinguish the two.[17] The W3C subsequently published an Interest Group Note titled Cool URIs for the Semantic Web, which explained the use of content negotiation and the HTTP 303 response code for redirections in more detail.Technical publications, especially standards produced by the IETF and by the W3C, normally reflect a view outlined in a W3C Recommendation of 30 July 2001, which acknowledges the precedence of the term URI rather than endorsing any formal subdivision into URL and URN.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 schemes.Such assumptions can lead to confusion, for example, in the case of XML namespaces that have a visual similarity to resolvable URIs.[13]: §3 The authority component consists of subcomponents: This is represented in a syntax diagram as: The URI comprises: The scheme- or implementation-specific reserved character + may be used in the scheme, userinfo, host, path, query, and fragment, and the scheme- or implementation-specific reserved characters !, $, &, ', (, ), *, ,, ;, and = may be used in the userinfo, host, path, query, and fragment.It has the advantage of both being easy for CGI parsers and also acts as an intermediary between HTTP and underlying resource, in this case.