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Re: firts and rdf:rest as functional property

From: Reto Bachmann-Gmür <reto.bachmann@trialox.org>
Date: Fri, 20 Mar 2009 15:22:21 +0100
Message-ID: <49C3A69D.4010101@trialox.org>
To: Bijan Parsia <bparsia@cs.man.ac.uk>
CC: Michael Schneider <schneid@fzi.de>, Semantic Web <semantic-web@w3.org>
Bijan Parsia said the following on 03/20/2009 03:14 PM:
> On 20 Mar 2009, at 14:02, Reto Bachmann-Gmür wrote:
>
>> Hi Bijan
>>> ...
>>>> If rdf:rest
>>>> and rdf:first are not functional a list could typically not be be
>>>> splitted into different rdf molecules[1]. Splitting graphs into small
>>>> components is essential for applications like diff, sync[2] and
>>>> versioning[3].
>>>
>>> If you are doing to decompose *semantically*, then functionality will
>>> be too weak to do the job anyway.
>> Not sure if I understand you, if a do decomposition of a graph into RDF
>> molecules[1] (as this is done in the Graph Versioning System GVS [2]) if
>> the base ontology contains the fact that rdf:rest and rdf:firts are
>> owl:functionalProperty a list will typically (i.e. if some of the
>> objects of the rdf:first statements are grounded or if the first
>> rdf:List resource is grounded) be split into many small components while
>> otherwise it is (assuming the rdf:List resources are anonymous) all
>> contained in one molecule. Isn't the decomposition into a semantical
>> decomposition?
>
> Sorry, don't have time to peek at that at the moment.
>
> By semantic decomposition, I mean that there will be certain
> properties preserved in the decomposition. See the slides for:
>     http://owl.cs.manchester.ac.uk/2008/iswc-modtut/
Indeed it seems we are not talking about the same, I'm talking about
lossless decomposition of graphs, i.e. a decomposition that has the
property that the union of the components expresses the same meaning as
the original graph.
> Functionality isn't necessarily the problem, but I presume you want
> first to be min1 as well (for a well formed list...having holes is as
> bad as having tentacles).
That's not an issue for decomposition.
> Functionality might have the surprising effect of entailing that two
> things are the same. Which might not be how you want to "repair" the
> tentacled list.
It's not about repairing list, but its exactly about having means of
knowing that "two" things are the same
> So, it's not clear to me that this is the right tool for the job.
> Perhaps I'm wrong about what job you're trying to do?
If you have some time at some point I invite you check out the Graph
Versioning System and see the effect of not asserting that the list
properties are functional of the size of the components containing large
lists.
> rdf:Lists were not introduced for modeling, but for encoding the
> syntax of OWL (taken from DAML+OIL). They have been pressed into
> service for modeling, but the built-in semantics (IMHO) as well as
> other aspects of them aren't really suited for modeling. But we model
> with what's at hand.
Don't see why we should have other list structure to describe lists
outside the owl ontology specification.

Cheers,
reto
Received on Friday, 20 March 2009 14:23:15 GMT

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