W3C home > Mailing lists > Public > public-rif-wg@w3.org > May 2008

Re: question about frames

From: Dave Reynolds <der@hplb.hpl.hp.com>
Date: Fri, 09 May 2008 15:30:39 +0100
Message-ID: <4824600F.70200@hplb.hpl.hp.com>
To: Jos de Bruijn <debruijn@inf.unibz.it>
CC: Gary Hallmark <gary.hallmark@oracle.com>, RIF WG <public-rif-wg@w3.org>

Jos de Bruijn wrote:
> 
> 
>> Thanks for clear answers to a not-so-clear question.  Let me expand 
>> just a bit.  In my PR system (OBR), the action that corresponds most
>> closely to a rule "head" or conclusion is the so-called "assert new" 
>> action.  This action creates a new java object (a frame instance of a 
>> given class) , initializes its javabean properties (slots) with given 
>> values, and asserts it to Jess.
>>
>> I want to translate some subset of my rules to BLD, namely rules 
>> without negation, aggregation, or actions other than assert new.
>>
>> Here is a simple rule (fusing OBR and BLD syntax):
>>
>> IF and(?p#P ?p[x->?x]) THEN assert new Q[x->?x]
>>
>> Do I translate to this:
>>
>> forall ?x ?p (Q(?x) :- and(?p#P ?p[x->?x]))
>>
>> That seems a little wrong.  OBR doesn't support relations, only 
>> frames, but it lets one use frames instead of relations. But BLD 
>> doesn't really let one dispense with relations and use only frames.  
>> Is this also an issue for RDF + RIF?
> 
> This is not an issue for RIF-RDF.  If people want to use relations in 
> their rules about RDF data they can do so.  However, they need to keep 
> in mind that there is no connection between frames and relations, other 
> than the connections made in the rules.

True but several uses of RDF rules involve asserting RDF relations 
involving bNodes which is essentially what Gary needs.

A correct modelling of bNodes as existential vars goes beyond Horn of 
course but existing rule language which support bNode introduction are 
typically treating bNodes as skolem constants. We did talk at one point 
about having some distinguished function symbol for building such skolem 
approximations to bNodes. Wouldn't that would give Gary a standardized 
"f" he could use?

Dave
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Received on Friday, 9 May 2008 14:32:19 GMT

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