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Re: OWL Syntax - complex restrictions

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Wed, 19 Feb 2003 07:44:46 -0500 (EST)
Message-Id: <20030219.074446.26234869.pfps@research.bell-labs.com>
To: jjc@hpl.hp.com
Cc: www-webont-wg@w3.org

From: Jeremy Carroll <jjc@hpl.hp.com>
Subject: OWL Syntax - complex restrictions
Date: Wed, 19 Feb 2003 11:38:25 +0100

> I attached three tests related to the mapping rule:
> restriction(ID component1 … componentn) 
> (With at least two components)
> =>
>  _:x owl:intersectionOf 
>   T(SEQ(restriction(ID component1) …
>     restriction(ID componentn))) .

This rule should be changed to look like the rule for intersection, in
particular, and the other rules for descriptions and restrictions, this was
an oversight on my part when I added the optional type triples.  I have
just now made this change.

However, read on ...

> The first test (101) shows a simple application of this rule.
> According to both the AS&S WD and the S&AS editors draft this is OWL Lite.


> This rule is the only way on OWL Lite of introducing a bNode that looks 
> somewhat like a description.
> Other use of intersectionOf in OWL Lite is on named classes.

This is the ony way in OWL Lite of introducing a bNode that is a
non-restriction description.

> Other class-like bNodes are all of type owl:Restriction.


> This rule is very fragile, when used backwards.

For OWL Lite, agreed.

> The second test 102 shows has changed an rdf:Description in test 101 to an 
> owl:Class. Since this node is the subject of owl:intersectionOf and the 
> object of rdf:type, this should be relatively innocuous - instead it means 
> that the construct now can only correspond to an abstract syntax description 
> and is hence in OWL DL.

The remedy here is to make the rule look like the other rules for
descriptions, i.e., allow for optional owl:Class and rdfs:Class typing.

> The third test 103 again exhinits the fragility of this rule, since the only 
> change is one #p is replaced by a #q. Again this is enough to make the 
> construct a description rather than a multipart restriction - and hence this 
> file too is in OWL DL according to the published docs.

I agree that this is now in OWL DL.

> This is fixed in my work on syntax by simply not allowing multipart 
> restrictions in the abstract syntax.
> http://sealpc09.cnuce.cnr.it/jeremy/owl-syntax/2003-12-Feb/intro.html

Well, forbidding multi-part resrictions would do the trick.  However, I
don't see that there is nearly sufficient reason to change something that
has been in the OWL abstract syntax since the beginning.

> Another possible fix is to:
> - simply delete the mapping rule.
>   Then not all abstract syntaxes can be mapped, which would need editorial 
> comment, but is non-fatal to the overall design.

I don't view this as a desirable change.

> This fix can also be applied to the EquivalentZZZ's rules and the 
> DisjointClasses rules - only have them defined for two elements.
> Some abstract syntaxes then cannot be mapped, but are semantically equivalent 
> to ones that can.

I view this changes as undesirable.

> Jeremy

Received on Wednesday, 19 February 2003 07:45:03 UTC

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