- From: Johannes Koch <johannes.koch@fit.fraunhofer.de>
- Date: Mon, 17 Nov 2008 15:49:43 +0100
- To: ERT WG <public-wai-ert@w3.org>
Hi Shadi Shadi Abou-Zahra schrieb: > Johannes Koch wrote: >> >> Shadi Abou-Zahra schrieb: >> >>> It is indeed clearer and is simpler for sub-classing. For example, >>> you can create a my:probablyPass class from earl:cannotTell pretty >>> easily because it is defined as a class. This is an essential >>> functionality. >> >> The earl:Outcome http://www.w3.org/ns/earl#cannotTell is not a class, >> it's a resource. > > Do you mean the resource of type class can not be sub-classed (ie to say > "my:probablyPass - rdfs:subclassOf - earl:cannotTell")? In RDF, every class is a resource. But not every resource is a class. earl:Outcome is a class (its rdf:type is rdfs:Class) and so can be sub-classed (e.g. my:CannotTellOutcome rdfs:subClassOf earl:Outcome). earl:cannotTell is a resource, an instance of earl:Outcome, but not a class itself, and so cannot be sub-classed. Someone who wants to extend the outcome vocabulary part, might do the following: <rdf:RDF ... xmlns:my="http://www.example.org/my#"> <!-- define new class CannotTellOutcome as a sub-class of earl:Outcome --> <rdfs:Class rdf:ID="CannotTellOutcome"> <rdfs:subClassOf rdf:resource="http://www.w3.org/ns/earl#Outcome"/> </rdfs:Class> <!-- make http://www.w3.org/ns/earl#cannotTell of type my:CannotTellOutcome --> <rdf:Description rdf:about="http://www.w3.org/ns/earl#cannotTell"> <rdf:type rdf:resource="http://www.example.org/my#CannotTellOutcome"/> </rdf:Description> <!-- define a new value probablyPass which is of type my:CannotTellOutcome --> <my:CannotTellOutcome rdf:ID="probablyPass"> ... </my:CannotTellOutcome> </rdf:RDF> -- Johannes Koch Fraunhofer Institute for Applied Information Technology FIT Web Compliance Center Schloss Birlinghoven, D-53757 Sankt Augustin, Germany Phone: +49-2241-142628 Fax: +49-2241-142065
Received on Monday, 17 November 2008 15:03:31 UTC