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Saturday, March 22, 2008

XML Base (Second Edition) Issued as a Proposed Edited Recommendation

Members of the W3C XML Core Working Group have published a Proposed
Edited Recommendation for "XML Base (Second Edition)." The document
describes a facility, similar to that of HTML BASE, for defining base
URIs for parts of XML documents. As a Proposed Edited Recommendation
(PER), this second edition is not a new version of XML Base: its
purpose is to clarify a number of issues that have become apparent
since the first edition was published. Some of these were first published
as separate errata, others were published in a public editor's draft in
November 2006, and in December 2006. BASE allows authors to explicitly
specify a document's base URI for the purpose of resolving relative
URIs in links to external images, applets, form-processing programs,
style sheets, and so on. The document describes a mechanism for
providing base URI services to XLink, but as a modular specification
so that other XML applications benefiting from additional control over
relative URIs but not built upon XLink can also make use of it. The
syntax consists of a single XML attribute named 'xml:base'. The
specification does not give the 'xml:base' attribute any special status
as far as XML validity is concerned. In a valid document the attribute
must be declared in the DTD, and similar considerations apply to other
schema languages. The deployment of XML Base is through normative
reference by new specifications, for example XLink and the XML Infoset.
Applications and specifications built upon these new technologies will
natively support XML Base. The behavior of 'xml:base' attributes in
applications based on specifications that do not have direct or indirect
normative reference to XML Base is undefined. It is expected that a
future RFC for XML Media Types will specify XML Base as the mechanism
for establishing base URIs in the media types it defines. A companion
document "Testing XML Base Conformance" from the W3C XML Core Working
Group is also available. While "XML Base" does not specify an interface
for determining the base URI of a node in an XML document, various other
specifications directly or indirectly refer normatively to XML Base,
and provide mechanisms by which the results of XML Base processing can
be determined. Some of these specifications have test suites that
include XML Base tests.

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