- From: Denny Vrandečić <dvr@aifb.uni-karlsruhe.de>
- Date: Tue, 30 Sep 2008 15:53:43 +0200
- To: Owl Dev <public-owl-dev@w3.org>
Hi, just a thought, and I guess it has a number of problems: Assume an object property O and a property assertion a O lt with lt being a literal and a an individual. Now this would yield an inconsistency since O is an object property, and lt a literal. But if instead in OWL2 a O lt would semantically mean a O x . x rdfs:label lt with x being a new individual, this would not be an inconsistency anymore and it would capture the meaning of most cases this occurs. To give an example, assume some Semantic Web beginner claiming in his FOAF-file the following: my:me foaf:knows "Dan Brickley". it is obviously a mistake, since foaf:knows is an object property connecting two persons, and not a person with a literal (the same happens with DC-Vocabularies and other widely used vocabularies). The actual reading would be my:me foaf:knows _someone . _someone rdfs:label "Dan Brickley" . that our beginner knows someone with the name Dan Brickley (which is indeed a literal). There are a number of problematic technicalities this leads to: 1. the triple my:me foaf:knows "Dan Brickley" does not disappear, and due to the downward-compatibility to RDF it still exists, which means that asking for my:me foaf:knows ?x gives different answers depending if you had an OWL2 aware SPARQL-engine instead of one that only does RDF. And they do not grow monotonically by adding OWL2 -- I am afraid this is a problem. (but then again, the relationship of OWL2 and SPARQL is not very well defined yet, but I assume that such a form of monotonicity would be highly desirable) 2. this introduces new individuals, and I am not sure if this has some theoretical implications. The positive aspect is that it would increase the percentage of valid triples. The above stated error appears quite frequently. Then again, it could also be just best practice to "repair" an OWL- or RDF-document in such a way before actual processing, just as HTML-documents are usually repaired before a DOM is being created or before the document is being rendered. But then again, repair best practices seem to become standardized for HTML5, and thus it may be an idea to pursue this for OWL2 as well (probably as a separate document). Best, denny
Received on Tuesday, 30 September 2008 13:54:18 UTC