Languageless Typed Literals from Jeremy Carroll on 2003-05-04 (w3c-rdfcore-wg@w3.org from May 2003) (original) (raw)

I offered to propose the removing of language tags from typed literals.

The only difficult bit is rdf:XMLLiteral.

This message is discussion, giving the options, and I will send the proposal in a follow-up.

Option 1: XMLLiteral ceases to be a typed literal but we revert to the old treatment where it was simply a special.

Advantages: It divorces the needs of typing from the needs of XMLLiteral.

Disadvantages: Ugly (we had pre-last call comments asking us to change, which we did). Systems are required to have significant support for XMLLiteral, and cannot combine XMLLiteral support with their datatype support. N-triples for XML literals changes, and the test cases have to change. Significant support for XMLLiteral is required even by systems that do not support RDF/XML.

Option 2: Literals can have both a type and a language tag if and only if the type is rdf:XMLLiteral, otherwise unchanged.

Advantages Least change from the last call while correcting the mistake.

Disadvantages Ugly. XMLLiteral becomes a syntactic exception as well as a semantic exception. (So our response to pfps-08 shifts from reject to reject with menaces)

Option 3: (this is the one I will propose) Change syntactic treatment of rdf:parseType="Literal" to do the wrapping and include the language tag in with the rdf-wrapper element. The datatype rdf:XMLLiteral then does not have a language tag, but is essentially a sub-datatype of xsd:string (i.e. it is the identity mapping on a certain class of canonical XML documents)

Advantages: XMLLiteral ceases to be a special case (except that it is in the RDF namespace, and gets handled in the semantics before any other datatyping)

Disadvantages: Ugly for parser writers. N-triples for XML literals changes, and the test cases have to change.

Option 4: Language tag is simply dropped from all typed literals including rdf:XMLLiteral

Advantages: Simple. rdf:XMLLiteral ceases to be a special case. Parser tests for XMLLiterals do not change

Disadvantages: Entailments concerning XMLLiterals and language tags change. I would prompt the I18N WG to object. (I would see, for example, the ruby tests in http://www.w3.org/2002/03owlt/editors-draft/draft/proposed-misc-200-xmlliteral as overly prejudiced by such a change)

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Option 4 in my mind is simply incorrect - there are XMLLiterals for which the language is semantic meaningful.

Option 3 requires the RDF/XML parser to deal with the problem in its entirety Options 1 and 2 divide the problems amongst other components of a semantic web stack.

Jeremy

Received on Sunday, 4 May 2003 16:02:53 UTC