From: pat hayes ([email protected])
Date: 05/29/01
>Hi,
>
>some additions to Pats suggestion:
>
>1) In many applications it is important to distinguish between
>different kind of RDF data, eg.
> the easiest example or different sources of RDF data, one is
>trustworthy, the other one
> not.
That seems to me to be an assertion about the source rather than the
data (?) But in any case it goes well beyond the RDF or DAML
semantics.
>This needs to be reflected in the rule language - it is not
>sufficient to just query if a certain
> fact is present. To distinguish between different sources would
>be enabled by model identifiers
>
> subject[predicate->object]@model
I have no idea what you are talking about. What is a 'model' in this sense?
>It is also possible to allow operations on models, e.g.
>intersection, union and setdifference.
They sound like classes to me.
>1) subject[predicate->object]@(mod1 intersect mod2)
>2) subject[predicate->object]@(mod1 union mod2)
>3) subject[predicate->object]@(mod1 \ mod2)
>
>1+2+3 are allowed in a rule body, only 1 is allowed in a conclusion
>(this still allow to have a horn clause interpretation).
>
>Finally, for most applications it is also useful to allow skolem functions
>as model identifiers, e.g.
>
>subject[predicate->object]@model(X)
>
>This allows parameterized models
>
>Furthermore: Full first order language bodies can be achieved by the
>Lloyd-Topor Transformation,
Can you give a pointer? I havnt heard of this.
>provided
>e.g. semantics for negation. Well-founded semantics is usually
>regarded as the most suitable one -
>especially in the case of RDF (just one predicate symbol).
This idea of there being only one predicate symbol is a joke, right?
Pat
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