- From: Guus Schreiber <schreiber@cs.vu.nl>
- Date: Thu, 09 Oct 2008 16:03:19 +0200
- To: SWD WG <public-swd-wg@w3.org>
- Message-ID: <48EE0F27.6030205@cs.vu.nl>
Alistair, Sean, all, I promised (in our post-telecon discussion) to provide some thoughts on the issues raised by Peter on behalf of the OWL WG [1]. Guus NOTATIONS [[ The OWL WG notes that one portion of SKOS (Notations) uses custom datatypes. Although these seem to be benign, because RDF and OWL allow extra datatypes, the use of these datatypes is not likely to be supported by many tools. The presence of extra datatypes may cause difficulties in some tools, which may just reject SKOS documents that have these datatypes. ]] Sean already pointed out that we can indicate in the document that user-defined datatypes are only explicitly needed when one needs multiple notations (so only in Sec. ). In addition I would like to add the tools should not reject SKOS documents containing user-defined datatypes, see the OWL reference section on datatype reasoning [2], in particular the last sentence: [[ Unrecognized datatypes should be treated in the same way as unsupported datatypes. ]] LEXICAL LABELS [[ objects as values of data property (example) suggestion: don't do this ]] Note sure what this comment refers to. All examples in 5.4 [3] use literals as values of label properties. The skos-xl extension handle object as values of label properties in an OWL-DL consistent manner. DOCUMENTATION PROPERTIES [[ using literal in object property (examples) suggestion: don't do this ]] We define the skos:note and its subproperties currently as owl:ObjectProperty. From an OWL Full perspective this is fine (owl:DatatypeProperty is a subproperty of owl:ObjectProperty in OWL Full [4]), but for OWL DL this is a problem. Part of the problem is that OWL forces you to make a choice between either object or datatype property, and we do not want to force this choice upon SKOS users. My proposal would be to follow a "least-commitment" strategy and change skos:note to be just an rdf:Property. This does not make it OWL-DL compliant yet, but allows people who want to use it within OWL DL to add a triple with the required OWL property type. So instead of being OWL-DL inconsistent it becomes OWL-DL incomplete. [[ use of rdf:value (example) suggestion: don't use rdf:value ]] This refers to example 25 [5]. I note that rdf:value has no particular semantics and is mainly a usage convention (and in practice is actually not used a lot). I suggest to change the example to use a user-defined property to refer to the value. I also suggest (but this is independent of the OWL WG comment), to add another property statement to illustrate why this pattern is used at all. Whether this also implies changes to the Primer I'm not sure. We may have the pattern with the blank node to have two variations: one with a custom value property and one with rdf:value. I also note that we use rdf:value a lot in the namespace file [6] to specify change notes. My proposal is to drop these change notes altogether. [1] http://lists.w3.org/Archives/Public/public-swd-wg/2008Oct/0059.html [2] http://www.w3.org/TR/owl-ref/#DatatypeSupport [3] http://www.w3.org/TR/2008/WD-skos-reference-20080829/#L1409 [4] http://www.w3.org/TR/owl-ref/#OWLFull [5] http://www.w3.org/TR/2008/WD-skos-reference-20080829/#L1812 [6] http://www.w3.org/TR/2008/WD-skos-reference-20080829/skos.rdf
Received on Thursday, 9 October 2008 14:03:54 UTC