Kommentare zu: Class or Property? Objectification in RDF and data modeling http://jakoblog.de/2009/08/14/class-or-property-objectification-in-rdf-and-data-modeling/ Das Weblog von Jakob Voß Mon, 01 Mar 2010 20:21:25 +0100 http://wordpress.org/?v=2.9.2 hourly 1 Von: Michael Panzer http://jakoblog.de/2009/08/14/class-or-property-objectification-in-rdf-and-data-modeling/comment-page-1/#comment-211925 Michael Panzer Wed, 19 Aug 2009 20:16:11 +0000 http://jakoblog.de/?p=745#comment-211925 I would argue that properties and classes are linked by the domain/range of the property. In OWL, of you assign a range of :Creator to the property dc:creator, a reasoner will automatically classify every individual that is the second argument of dc:creator as an instance of :Creator. RDFS gets complicated in this respect because it allows to treat properties as classes (and classes as properties). Also, because everything has to be a triple, "artificial" properties that belong the metalanguage of the model are predicates at the same level as every other predicate, e.g., rdf:type or rdfs:subClassOf. Because of this awkwardness in the RDFS model these properties become elements of the domain to be expressed and can become arguments of other predicates at any time. I would argue that properties and classes are linked by the domain/range of the property. In OWL, of you assign a range of :Creator to the property dc:creator, a reasoner will automatically classify every individual that is the second argument of dc:creator as an instance of :Creator.

RDFS gets complicated in this respect because it allows to treat properties as classes (and classes as properties). Also, because everything has to be a triple, “artificial” properties that belong the metalanguage of the model are predicates at the same level as every other predicate, e.g., rdf:type or rdfs:subClassOf.

Because of this awkwardness in the RDFS model these properties become elements of the domain to be expressed and can become arguments of other predicates at any time.

]]> Von: Jonathan Rochkind http://jakoblog.de/2009/08/14/class-or-property-objectification-in-rdf-and-data-modeling/comment-page-1/#comment-211611 Jonathan Rochkind Tue, 18 Aug 2009 20:15:38 +0000 http://jakoblog.de/?p=745#comment-211611 PS: "What if Ontology A has defined a “Singer” class and Ontology B defined a “sings” property which refer to the same real-world concept?" Well, then we simply need an ontological description language where we can map from the property to the class, right? Property X with value x is equivalent to entity A. Can OWL do that? I have no idea. But it's certainly do-able conceptually. PS:

“What if Ontology A has defined a “Singer” class and Ontology B defined a “sings” property which refer to the same real-world concept?”

Well, then we simply need an ontological description language where we can map from the property to the class, right? Property X with value x is equivalent to entity A. Can OWL do that? I have no idea. But it’s certainly do-able conceptually.

]]> Von: Jonathan Rochkind http://jakoblog.de/2009/08/14/class-or-property-objectification-in-rdf-and-data-modeling/comment-page-1/#comment-211610 Jonathan Rochkind Tue, 18 Aug 2009 20:13:23 +0000 http://jakoblog.de/?p=745#comment-211610 In terms of entities vs attributes, it seems like the obvious answer is that if the Thing is ever going to need to be described itself (have properties itself) then it should be an entity not an attribute. Right? Am I missing something? Does this hold to class vs. property too? Is it any more complicated than this? "Reification" type approaches seem like ways to make something that had been originally modelled as an 'attribute' _into_ an 'entity' of it's own. Does that seem so? In terms of entities vs attributes, it seems like the obvious answer is that if the Thing is ever going to need to be described itself (have properties itself) then it should be an entity not an attribute. Right? Am I missing something? Does this hold to class vs. property too? Is it any more complicated than this?

“Reification” type approaches seem like ways to make something that had been originally modelled as an ‘attribute’ _into_ an ‘entity’ of it’s own. Does that seem so?

]]> Von: robert http://jakoblog.de/2009/08/14/class-or-property-objectification-in-rdf-and-data-modeling/comment-page-1/#comment-210528 robert Fri, 14 Aug 2009 07:34:39 +0000 http://jakoblog.de/?p=745#comment-210528 coming from a python background, i lean towards applying duck-typing here, too: an object is just the set of it's properties. if this makes it a duck in some context, and a non-vegetarian meal in another, fine. sort of "you are what you do". so i guess, i wouldn't go with classes in most cases. coming from a python background, i lean towards applying duck-typing here, too: an object is just the set of it’s properties. if this makes it a duck in some context, and a non-vegetarian meal in another, fine. sort of “you are what you do”.

so i guess, i wouldn’t go with classes in most cases.

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