- From: Sean B. Palmer <sean@mysterylights.com>
- Date: Sun, 26 Aug 2001 17:07:37 +0100
- To: "Larry Masinter - LMM@acm.org" <lmnet@attglobal.net>, "Aaron Swartz" <aswartz@upclink.com>, "Al Gilman" <asgilman@iamdigex.net>
- Cc: <uri@w3.org>
> > Note that earl:TestCase is generally an Object/Class, > > not a Predicate/Property value. Properties can be > > Objects too, of course. > > AG:: No. Yes. My terminology was just confusing. In RDF, statements are comprised of subjects, predicates, and objects. RDF introduces three properties for this that can be used to model each of these. The domains of these three properties are, of course, rdf:Statement. The range for "subject" is rdfs:Resource, the range for "predicate" is rdf:Property, and the range for "object" is a conjunction of rdfs:Resource, and rdfs:Literal. Confusingly, because literals are resources. Anyway... *Properties* can, in the RDF model, be used as the value of an object predicate on any generic rdf:Statement. Because Classes and Properties are both sub classes of rdfs:Resource. However, they are both disjoint from each other, so Classes cannot be used as the value of an predicate predicate on any given rdf:Statement. > [...] The object is not the property, it is the 'value' of the property. Yes. What is sometimes annoying is that people confuse:- :name rdfs:range :Name . with simply:- :Name a rdf:Class . RSS, for example, does this. It uses some URI as a property and a class. Yuck. [...] > Properties are memes, patterns, and not objects. They are not classes, but they can be objects. Once again, it was the terminology that was confusing. If properties could not be used as subjects or objects, then it would be impossible to define them! We are, of course talking past each other. I understand that properties are not things which belong to any other class than rdf:Property. In particular, they are certainly not instacnces of rdfs:Class. [...] > > The semantic assumptions for URNs are the same as > > those for any URI. > > AG:: Yes, that's an assumption, but not a fact. I believe it to be a theoretical fact, but not a practical fact. > It fails to be true of the large category of de_facto URIs known > as search URLs. Once again, the persistence of search URLs is given by their context. In particular, if you believe that the URI identifies the representation of its resource, which is simply "a serach result for X", then of course it's not going to be persistent. In the same way that no changed page is "persistent". Persistence is defined by the context in which an identifier is being used. -- Kindest Regards, Sean B. Palmer @prefix : <http://webns.net/roughterms/> . :Sean :hasHomepage <http://purl.org/net/sbp/> .
Received on Sunday, 26 August 2001 12:07:55 UTC