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Re: reviewing RDF Semantics

From: pat hayes <phayes@ai.uwf.edu>
Date: Thu, 19 Dec 2002 17:25:24 -0600
Message-Id: <p05111b0bba2802acfc8b@[10.0.100.86]>
To: "Jos De_Roo" <jos.deroo.jd@belgium.agfa.com>
Cc: w3c-rdfcore-wg@w3.org

>Reviewing http://www.w3.org/2001/sw/RDFCore/TR/WD-rdf-mt-20030117/
>I can support approval for this great document!
>In what follows, I only make non-prohibitive remarks...
>
>
>| RDF Semantics
>| W3C Working Draft 12 December 2002
>
>should actally be
>   W3C Working Draft 17 December 2002
>but should later maybe
>   W3C Working Draft 17 January 2003
>
>
>| This Version:
>|   http://www.w3.org/TR/2002/WD-rdf-mt-20021112/
>
>should actually be
>   http://www.w3.org/2001/sw/RDFCore/TR/WD-rdf-mt-20030117/
>but should later maybe
>   http://www.w3.org/TR/2002/WD-rdf-mt-20030117/
>

Yes, both the above noted. I assume that dates and this-version 
things have to be only finally finalized when the thing is finally 
published, if you see what I mean...

>
>very nice Figure 2!

Omnigraffle and BBEdit are two really good reasons to use a Mac.

>
>
>| 3.2.4 rdf:value
>| [...]
>|
>| Since the range of possible uses for rdf:value is so wide,
>| it is impossible to give a precise model-theoretic statement
>| which covers all the intended meanings or use cases. Users
>| are cautioned, therefore, that the use of rdf:value is
>| somewhat risky, and that it should be treated as a 'blank'
>| piece of RDF syntax whose meaning in any particular case
>| should be defined by the user, and may vary from application
>| to application. In practice, the intended meaning is often
>| clear from the context, but may be lost when graphs are
>| merged or when conclusions are inferred.
>
>maybe say that they never contribute to any entailments
>or some such

Good idea.

>
>
>| 3.3.1 A note on rdfs:Literal
>| The semantic conditions on rdfs-interpretations do not include
>| the condition that ICEXT(I(rdfs:Literal)) must be a subset of LV.
>| While this would seem to be required for conformance with [RDFMS],
>| there is no way to impose this condition by any RDF assertion or
>| syntactic closure rule. This limitation is due to the fact that
>| RDF does not allow literals to occur in the subject position of a
>| triple, so there are severe restrictions on what can be said about
>| literals in RDF. Similarly, while properties may be asserted of
>| the the class rdfs:Literal, none of these can be validly

Whoops

>       ^^^
>| transferred to literals themselves.
>
>as you know, it seems to me that (at least) typed literals can be
>perfect subjects (I really don't see why not)

I presume the XML-syntax problems still apply there also (??) If not, 
I agree. But I also no longer really care.... ;-)

>
>
>| 4. Vocabulary entailment and closure rules
>| [...]
>|
>| 4.2 RDFS-entailment and RDFS closures (informative)
>| [...]
>|
>| rdfs 4a' | xxx aaa yyy . | aaa rdfs:domain rdfs:Resource .
>|
>| rdfs 4b' | xxx aaa yyy . | aaa rdfs:domain rdfs:Resource .
>
>(as I did remark before) those seem to be the same,
>but I guess you meant rdfs:range in rdfs4b'

Whoops. Yes.

>
>| 4.3 Datatype entailments (Informative)
>| [...]
>|
>| rdfD 1 | ddd rdf:type rdfs:Datatype . | aaa ppp _:xxx .
>|        | aaa ppp "sss"^^ddd .         | _:xxx rdf:type ddd .
>
>additionally to that we have also been (succesfully) testing
>
>   rdfD 1b | ddd rdf:type rdfs:Datatype . | ddd rdfs:domain ddd .
>
>   rdfD 1c | ddd rdf:type rdfs:Datatype . | aaa ppp _:xxx .
>           | aaa ppp "sss"^^ddd .         | _:xxx ddd "sss" .

Right, but I think we've WG-decided not to include those, regrettably.

>
>| Appendix B: Proofs of lemmas.
>| [...]
>|
>| RDF closure lemma. The Herbrand interpretation of the rdf-closure
>|   of E is an rdf-interpretation of E.
>| [...]
>|
>| so HP contains rdf:type, which is H(rdf:type),
>
>I suppose (that) HP (wasn't defined so far) is defined to be the
>set of urirefs which occur either as arc labels in the graph,
>or as subjects of triples of the form s rdf:type rdf:Property
>no?

Right. What I meant that to be was like the IP of H, if you see what 
I mean. I ought to make that clearer.

Another way to go would be to use suffices throughout and write IP, 
IS etc as P<sub>I</sub>, S<sub>I</sub> , then this would be 
P<sub>H</sub>.  Peter P-S did that in the OWL documents, and it is in 
fact more correct. But this would make it all look a lot more 
'mathematical'.

>
>| Appendix C: Glossary of terms
>| [...]
>|
>| Use (v.) contrasted with mention; to use a piece of syntax
>|   to denote or refer to something else. The normal way that
>|   language is used.
>
>i.e.
>   whenever, in a sentence, we wish to say something
>   about a certain thing, we have to use, in this
>   sentence, not the thing itself but its name or
>   designation -- Alfred Tarski

Nice quote, I'll try to work it in. I bet it sounds even better in German.

>
>maybe also mention "mention"
>
>maybe also "paradox"

Hard to know where to stop, is the problem. I did have 'mention'  in 
there at one point but I realized that I hadn't used it in the text 
anywhere, so it seemed kind of daft to put it into the glossary.

Pat

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Received on Thursday, 19 December 2002 18:25:27 EST

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