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Re: RDF and OWL compatibility

From: Bijan Parsia <bparsia@isr.umd.edu>
Date: Mon, 9 Jan 2006 15:54:38 -0500
Message-Id: <0b9f385d2889b86c8962ab9b66633bc5@isr.umd.edu>
Cc: Michael Sintek <sintek@dfki.uni-kl.de>, public-rif-wg-request@w3.org, public-rif-wg@w3.org
To: Christopher Welty <welty@us.ibm.com>

On Jan 9, 2006, at 3:44 PM, Christopher Welty wrote:

> public-rif-wg-request@w3.org wrote on 01/04/2006 02:35:50 PM:
>> Jos de Bruijn wrote:
>>> On Tue, 2006-01-03 at 18:21 +0000, Dave Reynolds wrote:
>>>> Michael Sintek wrote:
>> The query <s,?p,o> was only one example where higher order would be
>> needed for the "straightforward" mapping.
> Correction: This is not higher order, though it appears so.  I made 
> this
> mistake myself many times.  That many rule systems do not support it 
> is a
> seperate matter (and one we shall strive to address).

As it is sometimes said, often syntactic higher orderness (rather than 
semantic higher orderness) suffices.

(I.e., with syntactic higher order formulas, you can have variables in 
e.g., apparently predicate positions; with formulas interpreted as 
semantically higher order, those (or other) variables range over *sets* 
of elements (or sets of sets of elements) of the domian, rather than 
just over elements of the domain; in, e.g., OWL Full (or HiLog), 
predicates (for example) are reified so that they are both elements of 
the domain and sets of sets of elements of the domain, but the way 
expressions involving predicates as instances and predicates as 
predicates interact are strictly limited).

(Yes, I realize that that attempt at clarification was not really 
clarificatory :))

>> The whole problem is somehow related to supporting T-box vs.
>> A-box reasoning: for the straightforward mapping, Horn logic
>> supports A-box reasoning, but not (much of) T-box reasoning.

(See DLP and the reduction of SHIQ to disjunctive datalog as 
implemented in KAON2 for more details.)

> I don't think so.  T-box vs. A-box reasoning is another issue, I'm 
> sure,
> which overlaps a little with these kinds of problems.  This issue is
> accurately described in the RDF Compatibility page as "meta-modelling" 
> -
> the ability to quantify over predicates

In some sense.

> and thus axiomatize them.

Surely you meant "axiomatize certain aspects of them"? After all, 
classes in a description logic are just one place predicates and 
without metamodeling one can certain richly axiomitize them.

Bijan "Procrastination is the mother of nitpicking" Parsia.
Received on Monday, 9 January 2006 20:55:20 UTC

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