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Re: nonmon mapping and punning

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Wed, 23 Jan 2008 12:59:38 -0500 (EST)
Message-Id: <20080123.125938.88447122.pfps@research.bell-labs.com>
To: jjc@hpl.hp.com
Cc: public-owl-wg@w3.org

From: Jeremy Carroll <jjc@hpl.hp.com>
Subject: Re: nonmon mapping and punning
Date: Wed, 23 Jan 2008 17:44:37 +0000

> Peter F. Patel-Schneider wrote:
> 
> > When would a triple-based implementation have to modify "a triple in
> > response to adding a triple"?  Which design principle does this violate,
> > and where did it come from?
> 
> 
> If I have understood correctly, the following sequence of operations, at 
> an API level, would result in this situation. I'll express it as a merge 
> of two ontologies, in order to answer your second question about design 
> principle.

Throughout I'm putting reasonable [for this example] guesses in [].

> A program manipulates an API, such as the Jena Ontology API
> 
> http://jena.sourceforge.net/ontology/index.html
> 
> It creates an ontology 

At which point it has a Jena [!OWL DL] ontology.

> and adds an object property p to it, 

At which point it has a Jena [!OWL DL] ontology.

> and adds a 
> maxCardinality restriction on p. 

At which point it still has a Jena [!OWL DL] ontology, but not an OWL DL
ontology (as restrictions have to be part of an axiom for the ontology
to be OWL DL [but let's ignore this for now]).

> This ontology is then written out to a 
> file.

How?  

> If I understand correctly the RDF/XML corresponding to the 
> maxCardinality restriction should have type owl:Restriction

[i.e., should have a type triple to owl:Restriction]

Well, if the idea is to write an RDF/XML document that encodes an OWL
1.1 DL ontology then yes, but I don't know whether this is necessary
otherwise.

> It then creates a second ontology and adds a data property, also called 
> p to it, and adds a minCardinality restriction on p. This second 
> ontology is then written out to a second file.

Same issues as before.

> If I understand correctly the RDF/XML corresponding to the 
> minCardinality restriction should have type owl:Restriction

Ditto.

> It then creates a third ontology, being the union of the first two, 
> corresponding to the RDF merge operation.

Now there is no assurance that the ontology is an OWL DL ontology.
Further, I believe that Jena does not have a way of checking that the
ontology is an OWL DL ontology.  Note that this checking is, in itself,
non-monotonic, in that adding information can turn an OWL DL ontology
into a non-OWL DL ontology.

> If this is written out to a third file, in a way that conforms with OWL 
> 1.1 DL, then

This may not be possible.

> If I understand correctly the RDF/XML corresponding to the 
> maxCardinality restriction should have type owl:ObjectRestriction
> 
> and
> the minCardinality restriction should have type owl:DataRestriction.

If the ontology is in OWL DL (which requires a non-monotonic
determination) and one wants to write the ontology as triples in the way
specified right now in the OWL 1.1 documents, yes.

> This has involved the deletion of two triples with predicate rdf:type 
> and object owl:Restriction.

What deletion?  

> Our expectations for merge are found in RDF Semantics, for example,
> 
> http://www.w3.org/TR/rdf-mt/#mergelem
> [[
> Merging lemma. The merge of a set S of RDF graphs is entailed by S, and 
> entails every member of S.
> 
> This means that a set of graphs can be treated as equivalent to its merge
> ]]

Yes, in the RDF semantics, but you are performing operations that are
not related to the RDF semantics, so why should this principle play
here?

> Jeremy

peter
Received on Wednesday, 23 January 2008 18:31:03 GMT

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