Re: The Q model

From: Lars Marius Garshol <larsga@ontopia.net>
Subject: Re: The Q model
Date: Fri, 05 Aug 2005 01:17:56 +0200

> * Lars Marius Garshol
> |
> | Hmmm. I think probably you're reading more into this statement than
> | I intended by it. Clearly, RDF represented in Q is still the same
> | RDF, and so the same OWL/RDFS semantics will apply as when RDF is
> | just triples, but, as you note below, this will be a semantics that
> | ignores the two extra elements.
> 
> * Peter F. Patel-Schneider
> | 
> | This seems to be akin to extending propositional semantics to
> | first-order sentences by ignoring the quantifiers and variables.  I
> | just don't see how it is obvious that it will work.
> 
> Ah, no, this is not what I mean. What I mean is that you can use the
> existing RDFS/OWL semantics on Q instances, provided you ignore two of
> the elements in each quint (specifically, statement-id and context).
> That may sound silly, because it means we're back to RDF, but it does
> mean that the RDFS/OWL semantics can be applied to Topic Maps
> represented in Q, although with the limitation that reification will
> be ignored (as it is in RDF), that variant names will be ignored
> (which is not much of a loss), and that the semantics only apply to
> statements in the unconstrained scope.
> 
> This means that you get RDFS/OWL semantics for Topic Maps provided you
> restrict yourself to an RDF-compatible subset of Topic Maps. That's a
> gain for Topic Maps users, though unlikely to excite RDF users much.
> 
> Of course, some porting work is necessary to describe exactly how this
> would work, but I can't really see how it's possible for this to fail.

Oh, so you are doing something similar to porting propositional semantics to
predicate calculus statements that don't mention quantification or use
variables.  OK, but so what?  You could do this for any injection of any syntax
into any other syntax.

[...]

> | What makes you think that a reasonable combined semantics is even
> | possible?
> 
> Let me be clear here: I think the model is valuable even if no such
> combined semantics is possible, for two reasons:
> 
>  (1) It's useful for implementations, for conversion, and for general
>      understanding of the relationship between the two models.

But without some sort of semantic relationship, what good is it?  For example,
I might combine the relational and OO DB models by mapping them into disjoint
subsets of some larger syntax, perhaps tuples with OIDs added, where relational
tuples map into big tuples with empty OIDs and OO information uses big tuples
with non-empty OIDs.  But what does this get me?  The two input formalisms
don't interact at all.

>  (2) It's useful because it makes it possible to find out if a
>      reasonable combined semantics is possible.

But then the proof of the pudding *is* the semantics.

[...]

> | Note that I'm not saying that this is not possible.  I am instead
> | saying that you, as the proposer, need to show that it is indeed
> | possible.
> 
> I can hardly disagree with that.
> 
> -- 
> Lars Marius Garshol, Ontopian         <URL: http://www.ontopia.net >
> GSM: +47 98 21 55 50                  <URL: http://www.garshol.priv.no >
> 

peter

Received on Friday, 5 August 2005 07:42:25 UTC