# Re: rule proto-proposal

From: Stefan Decker (stefan@db.stanford.edu)
Date: 05/31/01

Pat,

>Im afraid I disagree. In fact, this remark sounds to me to simply be
>nonsensical. What do you mean by 'treating a tuple in a logical way' if
>the tuple has no known relationship to any kind of logical meaning?

Only taking herbrand models into account an atom triple(s,p,o) (syntax)
corresponds to
tuple  <s',p',o'> \in triple'  (semantics). Thats enough of logical meaning
necessary
to do something useful with rules on triples. Do you disagree?
If yes, please specify what else you need.

>I meant musical key shifts, as for example when transposing from C to B
>flat. I think you would have trouble doing that in Prolog with the musical
>notation I sketched above.

I would have trouble doing that in any programming language since I don't know

>I don't think that makes sense, but in any case that is not what I am
>trying to do, or think that DAML should be trying to do.
>
>>However, can be go back to the topic of designing a useful rule language?
>>It seems to me that the difference between:
>>  1) "RDF is a datastructuing language and tripels should not be
>> interpreted as facts" and
>>  2) "RDF tripels are facts"
>>is more than esoteric. It seems obvious that triples can be regarded as
>>atoms in a logical language,
>>at least if I not misunderstood your proposal (see
>>http://www.daml.org/listarchive/joint-committee/0436.html)
>
>They can be, indeed, and I would like to continue to so regard them.
>However, to my mind that it is incompatible with denying that they have a
>semantics, or trying to write rules that ignore the semantics. I still
>cannot understand quite how you manage to reconcile these positions.
>
>>Can we please focus more on designing a useful rule language?
>
>We got into this discussion because with our different notions of what a
>rule language is, we seem to have different notions of what 'useful'
>means. I emphatically do not see DAML rules as intended to provide
>arbitrary open-ended programming functionality.

Me neither.
We can discuss what features we see essential for a rule language, and probably
will come up with a classification of different languages, each one with a
different
purpose.

My minimal requirements for a horn logic based language:
1) The rule language should to able to XXXX RDF
( choose XXXX from { process, transform, reason with, .... )

2) The rule language should support different RDF vocabularies
(this will get more concrete once we reach agreement that we want to
have more than just a fixed vocabulary ).

3) The rule language should be able to distinguish between different RDF
data sources
(data is distributed and has different properties).

More requirements I would argue for
-------------------------------------------------------------------------------------

4) Closed World Reasoning  (test if a triple is in a given RDF model or not)
(requires a suitable semantics for negation - well founded semantics
is suggested for
various reasons).

5) At least syntactically as expressive and convenient as possible (e.g.
FOL-bodies
in rules)

All the best,

Stefan

>Pat
>
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