Dissenting Opinion: xml:lang and rdf:parseType="Literal"

@@ draft jjc - for consideration by em, bwm, danbri and WG @@

The internationalization working group has registered a dissenting opinion on the treatment agreed by RDFCore concerning rdf:parseType="Literal". @@ add link to dissent, when it comes @@ This dissent is to changes made by the RDF Core working group in response to comments concerning the last call design, particularly comments concerning the datatype rdf:XMLLiteral.

This feature of RDF is the single feature to have attracted most comments both during and before last call. These included comments from Reagle ( on use of canonicalization and use of an XML wrapper), Prud'hommeaux, the Web Ontology WG, Patel-Schneider, (concerning: language tag in canonical XML; malformed literals of type rdf:XMLLiteral; typed literals and language tags; aliases of rdf:XMLLiteral; language tags in rdf:XMLLiteral in the LBase appendix), Berners-Lee , Marchiori.

Resolving these comments to the WG's (and the commentators') satisfaction involved changes that impacted aspects that were known to be important to the internationalization working group, and they were informed. Dürst then commented further (regarding language tagging and rdf:XMLLiteral, XMLLiteral and octets, using rdf:datatype="&rdf;XMLLiteral"). A detailed analysis was provided by Ishida.

The Working Group gave further consideration to the comments of Dürst and Ishida. Changes were made to avoid the problems with octets, and these were agreed by Dürst. The other arguments were not found to be compelling, for example Carroll's response to Ishida. Most of the substantive arguments had already been made in the WG decision of 9th May.

Before that decision, the WG has considered four different designs, for the result of an rdf:parseType="Literal":

A special sort of (untyped) literal

Such as in the 29th August 2002 Working Draft.

A special sort of typed literal.

Similar to the last call design. This would remain the only datatype that can have a language identifier.

A normal typed literal, with an XML wrapper

The wrapper carries an xml:lang attribute.

A normal typed literal, without an XML wrapper

This follows Exclusive XML Canonicalization, and loses the xml:lang attribute. This is the chosen design, in the current editors drafts.

Members of the WG have argued that:

• The treatment of xml:lang is performed by Exclusive XML Canonicalization (which had been reviewed and accepted by the I18N WG).
• An RDF specific solution to perceived deficiences in exclusive canonicalization would not be interoperable with other ad hoc solutions.
• Long term, a solution based on a generic XML solution, perhaps not dissimilar to XML fragments, would be better.
• The simplicity of the current design will encourage deployment of XMLLiteral, which will aid internationalization concerns.

An important consideration, reflected most in the comments from the Web Ontology WG and Patel-Schneider's concerns, is that unless rdf:XMLLiteral is a normal datatype with no special treatment of language, then OWL Lite and OWL DL do not support it. No version of the OWL Abstract Syntax has permitted literals other than plain literals (with or without language tags) or typed literals (without a language tag). Thus, any solution, other than the last two of the four above, would require substantive changes to OWL DL and OWL Lite.

To summarize:

The Working Group did accept an @@what concession do we make - add 'at risk' part, add exit criteria@@ We ask the Director to confirm the WG decision despite this dissent.