that acknowledged the existence of URLs and URNs. Most importantly, it defined a formal syntax for Universal Resource Identifiers (i.e. URL-like strings whose precise syntaxes and semantics depended on their schemes). In addition, the attempted to summarize the syntaxes of URL schemes in use at the time. It acknowledged -- but did not standardize -- the existence of relative URLs and fragment identifiers. Refinement In December 1994, formally defined relative and absolute URLs, 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 IETF RFC 2141 in May 1997. The publication of IETF RFC 2396 in August 1998 saw the URI syntax become a separate specification and most of the parts of RFCs 1630 and 1738 relating to URIs and URLs in general were revised and expanded by the IETF. The new RFC changed the meaning of "U" in "URI" to "Uniform" from "Universal". In December 1999, provided a minor update to RFC 2396, allowing URIs to accommodate IPv6 addresses. A number of shortcomings discovered in the two specifications led to a community effort, coordinated by RFC 2396 co-author Roy Fielding, that culminated in the publication of IETF RFC 3986 in January 2005. While obsoleting the prior standard, it did not render the details of existing URL schemes obsolete; RFC 1738 continues to govern such schemes except where otherwise superseded. IETF 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 2001, the W3C's Technical Architecture Group (TAG) published 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. In August 2002, IETF 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. 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