- From: Michael Schneider <schneid@fzi.de>
- Date: Tue, 6 Jul 2010 17:55:00 +0200
- To: "Dan Brickley" <danbri@danbri.org>
- Cc: "Toby Inkster" <tai@g5n.co.uk>, "Linked Data community" <public-lod@w3.org>, "Semantic Web" <semantic-web@w3.org>, "Pat Hayes" <phayes@ihmc.us>, Jiří Procházka <ojirio@gmail.com>
Dan Brickley wrote: >2010/7/6 Jiří Procházka <ojirio@gmail.com>: >> On 07/06/2010 03:35 PM, Toby Inkster wrote: >>> It would have a meaning. It would just be a false statement. The >>> same as the following is a false statement: >>> >>> foaf:Person a rdf:Property . >> >> Why do you think so? >> I believe it is valid RDF and even valid under RDFS semantic >extension. >> Maybe OWL says something about disjointness of RDF properties and >classes >> URI can be many things. > >It just so happens as a fact in the world, that the thing called >foaf:Person isn't a property. It's a class. The semantics of RDFS allows to use the same name for both a class and a property. What you call a "fact in the world" is, from a semantics point of view, just one particular interpretation that you have in mind. Other interpretations than yours are possible (I hope :)). And the (model-theoretic) semantics of RDFS is of a form that a given RDF statement is false, only if /all/ possible interpretations are false. (This is not specific to the RDF semantics, btw.) >Some might argue that there are no things that are simultaneously RDF >classes and properties, but that doesn't matter for the FOAF case. Let's not forget that we are here discussing a suggested change of the syntax and (possibly) semantics of the RDF specification, and the FOAF case doesn't matter for this, I would say. FOAF refers to RDFS (and OWL), not the other way round (except, perhaps, as a usecase). Of course, one could define an extension of the RDFS semantics specifically for FOAF that better reflects the intended situation (either formally or informally, or implicitly by a reference implementation of a specific FOAF reasoner). But that's a different discussion. >The >RSS1 vocabulary btw tried to define something that was both, >rss1:image I think; but this was a backwards-compatibility hack. You might find more of these "hacks" elsewhere, and more to come in the future. Interestingly, the idea of using the same name for both a class and a property is somewhat that has been introduced in OWL DL just in OWL 2, so it exists in OWL DL for less than a year now (officially). In RDFS and (therefore) in OWL Full, it has always been allowed, though. >cheers, > >Dan Best, Michael -- Dipl.-Inform. Michael Schneider Research Scientist, Information Process Engineering (IPE) Tel : +49-721-9654-726 Fax : +49-721-9654-727 Email: michael.schneider@fzi.de WWW : http://www.fzi.de/michael.schneider ======================================================================= FZI Forschungszentrum Informatik an der Universität Karlsruhe Haid-und-Neu-Str. 10-14, D-76131 Karlsruhe Tel.: +49-721-9654-0, Fax: +49-721-9654-959 Stiftung des bürgerlichen Rechts, Az 14-0563.1, RP Karlsruhe Vorstand: Prof. Dr.-Ing. Rüdiger Dillmann, Dipl. Wi.-Ing. Michael Flor, Prof. Dr. Dr. h.c. Wolffried Stucky, Prof. Dr. Rudi Studer Vorsitzender des Kuratoriums: Ministerialdirigent Günther Leßnerkraus =======================================================================
Received on Tuesday, 6 July 2010 15:55:34 UTC