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Re: REQDOC: reification

From: Pat Hayes <phayes@ai.uwf.edu>
Date: Fri, 15 Feb 2002 01:11:08 -0500
Message-Id: <p05101433b892543e9e53@[192.168.0.6]>
To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
Cc: webont <www-webont-wg@w3.org>
>One of the requirements in the requirements document is the ability to
>associate properties with statements.  This would require, at least,
>some version of reification of statements, and to work right would require
>a way of referring to statings.
>
>RDF has made a total hash of reification.

I don't agree. RDF certainly screwed up in some ways. It is 
incomplete, and the M&S is confused and ambivalent between divergent 
readings, but the general idea is sound, if rather simple, and the 
use cases that we have been able to discover all pretty much converge 
on one of the two plausible readings of the M&S wording, so the WG 
will probably give a reasonably clear ruling on this soon. So its not 
a total hash. It is pretty useless, in my view, but some people can 
use it coherently and seem happy with it.

>The RDF Core WG is trying to fix
>this a bit, but it is probably out of their scope to make any significant
>improvment (as opposed to significant fix).
>
>I think that adding reification to OWL would be, at best, a significant
>research project and, at worst, a black hole.

I think that what might be called simple object reification - the 
ability to describe syntactic object tokens, including those of the 
language itself, and some kind of external referential linking 
mechanism analogous to ostensive pointing to an expression token - is 
quite do-able, raises no deep black-hole issues (notice I carefully 
did not say 'tr*th pre*d*c*te' ) and provides about 90% of the 
practical functionality needed by enthusiasts of reification. So I 
think that something useful can be done pretty easily. It will be 
moderately trivial from a FOM perspective, for which we should all 
breath sighs of relief.

>In any case, I don't see the motivation for the ability to associate
>properties with statements (in the OWL logic, at least) from the shared
>ontologies goal.  Surely it is possible to share ontologies without
>associating properties with statements.

The real use case is associating them with statings, ie *tokens* of 
expressions in ontology documents. And that is needed in for example 
date-stamping, tracking provenances, that kind of thing.

Pat Hayes
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Received on Friday, 15 February 2002 01:11:07 GMT

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