Change Proposal for ISSUE-120

Summary

Simplify the specification by removing features that are documented to be confusing to users.

Rationale

The premise of this rationale, which is argued in detail below, is that mechanisms that bind arbitrary strings ("prefixes") to other arbitrary strings ("bases"), which can then be used in conjunction with a third set of arbitrary strings ("values") to form identifiers ("terms") that are never explicitly stated in the source, are a language design anti-pattern in the context of technology intended for broad Web deployment (e.g. in text/html).

In the context of RDFa, there are a number of mechanisms to define the mappings of "prefixes" and "bases": the prefix="" attribute, the profile="" attribute (which has an additional layer of indirection), and for legacy reasons the xmlns="" attribute. This change proposal proposes to remove all three of these features based on the same rationale. (At a high level, these features are essentially equivalent, being little more than syntactic sugar for each other.) As a result, the places where RDFa accepts a "value" that could have used one of these arbitrary "prefixes" to create a "term" can no longer do so, and is limited to either giving the "term", or using a predefined syntax with known prefixes (specifically, the empty prefix ":foo" which is short for "http://www.w3.org/1999/xhtml/vocab#foo", and the bnode syntax "_:foo").

Details

This change proposal describes changes to this draft, relative to the specification as it stood on January 11th 2011: http://dev.w3.org/html5/rdfa/

• In "2.2 RDFa Processor Conformance", add to the first bullet point an exception for features overridden by the Extensions section.

• In the "3. Extensions to RDFa Core 1.1" section, add a section requiring that when processing CURIEs in attributes on elements is the HTML namespace, the set of mappings from prefixes to URIs must always be treated as empty.

• In the "3. Extensions to RDFa Core 1.1" section, add a section requiring that the "prefix" attribute not be used in conforming documents and add a section requiring that user agents ignore prefix="" attributes on elements in the HTML namespace.

• In the "3. Extensions to RDFa Core 1.1" section, add a section requiring that the "profile" attribute not be used in conforming documents and add a section requiring that user agents ignore profile="" attributes on elements in the HTML namespace.

• In the "3. Extensions to RDFa Core 1.1" section, remove all the sections that refer to the "xmlns:" attributes and replace them with a single section saying that HTML+RDFa does not use the "xmlns:" attributes and that user agents must not let their processing model be affected by "xmlns:" attributes in no namespace (such as those found in text/html).

• Updates examples and other text accordingly, at the editor's discretion.