- From: <Patrick.Stickler@nokia.com>
- Date: Mon, 5 Nov 2001 11:51:50 +0200
- To: w3c-rdfcore-wg@w3.org
Literals as subjects don't work because they are just ambiguous strings. E.g. consider the following simple example: "fi" <rdf:type> <urn:iso:3166_1> . "fi" <rdf:type> <urn:iso:3166_1> . One defines a language, the other a country. Yet these get merged into ambigous "knowledge" about the subject "fi". What is it? A language or a country? Both? How does one differentiate between where it denotes *only* the country or the language? So, unfortunately, literals as subjects don't work (or at least don't scale reliably, beyond very small closed systems). The problem is that so many folks are used to using strings as values, relying on static, native understanding embodied in the systems they use, that they keep trying to use strings in their knowledge bases, when in fact, in most cases, they should be using resources identified by URIs. Thus rather than <urn:foo> dc:title [ rdf:value "Foo"; dc:language [ rdf:value "fi"; rdf:type <urn:iso:3166_1>; rdf:label [ rdf:value "Finnish"; dc:language [ rdf:value "en"; ... ] ]; rdf:label [ rdf:value "Suomi"; dc:language [ rdf:value "en"; ... ] ]; ... ] ]. (where '...' represents possible infinite recursion of "local" specification of type due to the fact that literals are not resources about which global knowledge can be defined...) We should be doing stuff like <urn:foo> dc:title [ rdf:value "Foo"; dc:language <voc://iso.ch/3166_1/fi> ]. <voc://iso.ch/3166_1/fi> rdf:label [ rdf:value "Finnish"; <voc://iso.ch/3166_1/en> ]. <voc://iso.ch/3166_1/fi> rdf:label [ rdf:value "Suomi"; <voc://iso.ch/3166_1/fi> ]. Representation as resources can be achieved for most, if not all, literals, such that the use of actual RDF literals would remain only for actual strings to which no further interpretation is intended to be applied. Whatever we work out with regards to typed data literals, let's also perhaps try to find a solution that encourages more useful and scalable knowledge representations -- particularly those employing controlled vocabularies, and which will (hopefully) encourage folks to move away from the problemmatic use of ambiguous strings. Cheers, Patrick PS: BTW, the specification of the 'voc:' URI scheme for vocabularies, taxonomies, and codes will be published as an I-D shortly. -- Patrick Stickler Phone: +358 50 483 9453 Senior Research Scientist Fax: +358 7180 35409 Nokia Research Center Email: patrick.stickler@nokia.com
Received on Monday, 5 November 2001 04:52:01 UTC