W3C home > Mailing lists > Public > public-rdf-dawg@w3.org > July to September 2009

Re: Re 2: [TF-ENT] RDFS entailment regime proposal

From: Bijan Parsia <bparsia@cs.man.ac.uk>
Date: Sun, 27 Sep 2009 20:27:46 +0100
To: Ivan Herman <ivan@w3.org>
Message-Id: <B96C995D-F14B-42B8-BBFC-A74A11195C7B@cs.man.ac.uk>
Cc: Birte Glimm <birte.glimm@comlab.ox.ac.uk>, SPARQL Working Group <public-rdf-dawg@w3.org>
Hope y'all don't mind my jumping in.

On 27 Sep 2009, at 19:31, Ivan Herman <ivan@w3.org> wrote:

> Birtet,
>
> I actually have two more technical questions. I may be very well  
> wrong on two accounts, though.
>
> 1. What does it mean, in the case of RDFS, that a graph is  
> inconsistent? I tried to find out how a _valid_ RDFS graph could be  
> inconsistent... and I did not find it. Can you help in giving an  
> example for what you were thinking about?

s p "<<"^^rdf:XMLLiteral.

This is inconsistent and pure RDFS (I believe a similar example is in  
the ^^rdf semantics document). Obviously, additional datatypes can  
introduce more ops for inconsistency, but xmlliteral is built in.

> 2. About those extra conditions that we have already discussed. The  
> second one is taking care of the proliferation of blank nodes. That  
> is clearly necessary and fine. However... for the 1st restriction  
> referring to the subject position: isn't it only the rdf:_i  
> properties that are the possible source of problems?

In general, yes.

> My impression is that only those properties, more exactly the  
> relevant axiomatic triples, that are leading to an infinite number  
> of triples. If so, isn't it simpler to refer, in that first  
> condition, to the rdf:_i properties only, ie, restrict the axiomatic  
> triples only to those rdf:_i-s that are in the graph.

Should work.

> (AFAIK, this is almost what Herman ter Horst does in his well known  
> paper. More exactly, I think he allows for a bit more than what you  
> describe: he takes the maximum 'n' for which an rdf:_n is in the  
> Graph, and restricts the axiomatic triples to the rdf:_i i<=n cases.  
> That could be a reasonable alternative, too, although generating  
> some more triples than your restriction.)

Quite a few more perhaps a bit too easily. It depends on how many  
rouge ^^rdf:_1000 there are.

One could reasonably argue never to return a binding for which the  
only justification is axiomatic. It would be, after all, trivial. Why  
clutter up results that way?

(Does anyone need rdf:type to be returned for ?p rdf:type Property?  
It's just one more thing to filter out.)

> What do I miss?

Malformed literals, basically.

Cheers,
Bijan. 
Received on Sunday, 27 September 2009 19:23:07 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Thursday, 26 April 2012 12:08:28 GMT