- From: Graham Klyne <Graham.Klyne@MIMEsweeper.com>
- Date: Wed, 30 Jan 2002 17:30:30 +0000
- To: Patrick Stickler <patrick.stickler@nokia.com>
- Cc: Jeremy Carroll <jjc@hplb.hpl.hp.com>, Brian McBride <bwm@hplb.hpl.hp.com>, <www-archive@w3.org>
At 06:54 PM 1/30/02 +0200, Patrick Stickler wrote: > >> Though I'd very much like your comments to my question in > >> my MT commments to Pat, that insofar as the actual denoted > >> values are concerned, I wonder if either TDL or S can > >> ensure entailment, since RDF is stuck with non-canonical > >> lexical forms. C.f. the last comment in > >> > >> http://lists.w3.org/Archives/Public/w3c-rdfcore-wg/2002Jan/0400.html > > > > Unfortunately the question doesn't make sense to me -- entailment is a > > relationship between graphs, not something that happens to the values in > > (or denoted by) a graph. > >Then I guess I really don't grok the problem. > >It seemed to me that Dan's expectations of tidy literals was >that he was treating node equality with value equality, rather >than just string equality. I guess it's my turn to try and be clearer. The strict treatment of literals advocated by DanC, and embodied in scheme S, is one way to ensure that literals don't break self-entailment of documents. I don't believe it's the only way, so in my arguments I've not tried to rely on a graph being tidy over literals. Self-entailment means: there is no interpretation that satisfies one instance of a graph but does not satisfy another instance of the same graph (with the same labels and structure). If the denotation of every node in a graph is fully defined by any interpretation together with the syntactic elements to which the interpretation is applied, then self-entailment must follow. Jeremy's original theory for TDL did not provide a specific denotation for each literal in a graph, so a given interpretation could yield different denotations (or no denotation) for different instances of a graph. And the truth-value of graph arcs (triples) depends on the denotations of nodes. So it would be possible for a given graph to evaluate to true OR false under a given interpretation, and this is what breaks self-entailment. Sergey has said he needs tidiness on literals to overcome this. I don't agree: that is a sufficient condition for self entailment, but I don't think it's necessary. E.g. Pat uses a different approach in his MT for blank nodes, which also don't have a fixed denotation under a given interpretation... [Enter my MT notes to Jeremy: (http://lists.w3.org/Archives/Public/www-archive/2002Jan/0147.html).] >Insofar as the graph itself is concerned, literals are just >strings. They don't become values without interpretation >based on a datatype context. > >So all you could entail between two literal nodes is string >equality. Now your language has departed from anything I can understand in terms of the words you use. "entail between two literal nodes" just doesn't mean anything to me: entailment is a relationship between expressions that evaluate to True or False. >But I'll just but out of this particular discussion and let >you more capable and learned folks hash it out. > >(I knew I should have slept less in math class... ;-) Me too... I've spent much of the past year learning something of what I should have learned in class. (Though I must say, I think Pat's an excellent teacher.) #g ------------------------------------------------------------ Graham Klyne MIMEsweeper Group Strategic Research <http://www.mimesweeper.com> <Graham.Klyne@MIMEsweeper.com> __ /\ \ / \ \ / /\ \ \ / / /\ \ \ / / /__\_\ \ / / /________\ \/___________/
Received on Wednesday, 30 January 2002 13:27:33 UTC