- From: Benja Fallenstein <b.fallenstein@gmx.de>
- Date: Tue, 04 May 2004 21:18:35 +0200
- To: "Rhoads, Stephen" <SRhoads@ThruPoint.net>
- Cc: "'www-rdf-interest@w3.org'" <www-rdf-interest@w3.org>
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Rhoads, Stephen wrote: | <slightlyOffTopic> | |>>I understand what you mean: intuitively, "the" right |>>range of pet:owner might be foaf:Person. | | Until someone comes along and wants to say: | | Benji rdf:type ex:Dog | Benji pet:owner ex:AtlantaPoliceDepartment I was assuming that pet:owner is defined so that it does have rdfs:range foaf:Person, in a similar way that foaf:mbox is defined to be an inverse functional property. (I'm aware that pets may be 'owned' by something else than a person, although I was more thinking of e.g. families. Restricting pet:owner to people makes sense when you're specifically interested in pets owned by individual persons.) What I think you're ignoring above is that text in URIs and the qnames that abbreviate them is only mnemonic -- it does not *define* what the URI means, it's only a hint. I think that's an important point. You say, | What to do? Range is something broad like "Entity"? And when someone finds | a valid use for pet:owner with a "non-Entity"? but if the precise meaning of pet:owner does *not* include general "entities," much less "non-entities," such a use would not be 'valid' and would not make sense. If I see a use for ~ Annie foaf:mbox <mailto:AandEMiller@example.com> ~ Elin foaf:mbox <mailto:AandEMiller@example.com> then that doesn't change the fact that it's not a *valid* use -- even though the address was obviously specifically created to be used by Annie and Elin together, so if you look only at the qname, 'foaf:mbox,' the above makes perfect sense. The problem is that it defies one of the very purposes of foaf:mbox, namely identifying people (well, entities ;-) ) uniquely. If I want to express the above semantics, I should make up my own property that is defined with the semantics I intend. And the very same thing applies to "global domain and range constraints within the context of the Web." Their point is being able to infer something -- in our example, that the object of pet:owner is a person. There are other uses, too, but this is the most fundamental one. If you don't like that from a pet:owner triple you can infer that the object is a foaf:Person, you can make up your own property. So my point in this e-mail is: You seem to be saying that global domain and range constraints should not be used -- or maybe even ignored when they are used -- because they prohibit valid uses of certain properties. But if the owner of the property gives it a range constraint that says that object X is not in its range, than using it with an object X *cannot* be a valid use of the property. You could say that prohibiting these uses is pointless nitpicking, but it's not, because it is what allows us to make useful inferences! And nothing gets less expressive, because you can make your own URI that expresses the semantics you want. You could say that it's better to use standard terms, but it is NOT better to use standard terms for something else than what they were defined for -- and that is what you do if you violate the owner's domain or range constraints. So it's not domain and range constraints that are the problem, it's ignoring the URI owner's definition of a term, including those constraints, that is the problem. Looking at the name of a property doesn't suffice to use it correctly. (I think that's an important point, which is why I reply so elaborately. Sorry for the long mail.) Cheers, - - Benja -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.4 (GNU/Linux) Comment: Using GnuPG with Thunderbird - http://enigmail.mozdev.org iD8DBQFAl+v9UvR5J6wSKPMRAke3AJ9sg5N1V/UBlpFMVGBR6xw40EetFwCg0eHr EjNYD3nBrPwDsAHqV0Wg1Hw= =q70u -----END PGP SIGNATURE-----
Received on Tuesday, 4 May 2004 15:19:48 UTC