XML News from Thursday, December 11, 2003

THe W3C Technical Architecture Working Group has published the last call working draft of Architecture of the World Wide Web, First Edition. This describes how URIs, HTTP, and XML should and should not be used. Extracting just the prinicpples, conmstraints, and good practices,

• Silent recovery from error is harmful.
• The identification mechanism for the Web is the URI.
• A resource owner SHOULD assign a URI to each resource that others will expect to refer to.
• Web architecture does not constrain a Web resource to be identified by a single URI.
• Resource owners should not create arbitrarily different URIs for the same resource.
• If a URI has been assigned to a resource, agents SHOULD refer to the resource using the same URI, character for character.
• Avoid URI ambiguity.
• Authors of specifications SHOULD NOT introduce a new URI scheme when an existing scheme provides the desired properties of identifiers and their relation to resources.
• Agents making use of URIs MUST NOT attempt to infer properties of the referenced resource except as licensed by relevant specifications.
• A resource owner who creates a URI with a fragment identifier and who uses content negotiation to serve multiple representations of the identified resource SHOULD NOT serve representations with inconsistent fragment identifier semantics.
• User agents MUST NOT silently ignore authoritative server metadata.
• Agents do not incur obligations by retrieving a representation.
• Publishers of a URI SHOULD provide representations of the identified resource consistently and predictably.
• Publishers of a URI SHOULD provide representations of the identified resource.
• Format designers SHOULD provide for version information in language instances.
• Format designers SHOULD document change policies for XML namespaces.
• Language designers SHOULD provide mechanisms that allow any party to create extensions that do not interfere with conformance to the original specification.
• Language designers SHOULD specify agent behavior in the face of unrecognized extensions.
• Language designers SHOULD design formats that allow authors to separate content from presentation and interaction concerns.
• Language designers SHOULD provide mechanisms for identifying links to other resources and to portions of representation data (via fragment identifiers).
• Language designers SHOULD provide mechanisms that allow Web-wide linking, not just internal document linking.
• Language designers SHOULD allow authors to use URIs without constraining them to a limited set of URI schemes.
• Language designers SHOULD incorporate hypertext links into a data format if hypertext is the expected user interface paradigm.
• Language designers who create new XML vocabularies SHOULD place all element names and global attribute names in a namespace.
• Resource owners who publish an XML namespace name SHOULD make available material intended for people to read and material optimized for software agents in order to meet the needs of those who will use the namespace vocabulary.
• Specifications that use QNames to represent URI/local-name pairs SHOULD NOT allow both forms in attribute values or element content where they would be indistinguishable from URIs.
• Language designers who use QNames as identifiers of Web resources MUST provide a mapping to URIs.
• In general, server managers SHOULD NOT assign Internet Media Types beginning with "text/" to XML representations.
• In general, server managers SHOULD NOT specify the character encoding for XML data in protocol headers since the data is self-describing.

Comments are due by March 31, 2004.

Daniel Veillard has released version 2.6.3 of libxml2, the open source XML C library for Gnome. This release supports the latest XInclude working draft syntax.

The W3C XML Core Working Group has published a proposed edited recopmmendation of the XML Information Set. The changes are very minor overall. A lot of specific references to XML 1.0 have been deleted, and some very obscure points on what happens when a notation is declared multiple times have been clarified. This shouldn't have much effect on anybody.