Emmanuel Pietriga wrote:
> Ryan Lee wrote:
> > Chris Bizer wrote:
> >
> >> Hi Emmanuel,
> >>
> >> I think this is definitively useful behaviour. The question which is
> >> coming
> >> to my mind is, what should be the default behaviour?
> >>
> >> Should the query engine by default use subproperty and subclass
> >> relationships, which I guess will slow it significantly down?
>
> It will slow it down, but I'm not sure to what extent (this will
> partially depend on the complexity of class and property hierarchies).
> But I would say that the language's expressive power and ease of use is
> more important than implementation/performance issues (though these of
> course have to be taken into account).
>
>
>
> >> My understanding is that Fresnel is about visualizing materialized RDF
> >> graphs and inferencing (if needed) is done on a lower layer before
> >> Fresnel
> >> gets involved.
>
> Yes indeed. But if you think about the Fresnel presentation designer, it
> can be very convenient to write a single lens that will apply to a class
> and all its subclasses. If you don't have subclass/subproperty
> inferencing at the FSL level, you have to define as many lens domains as
> there are subclasses. And the lens won't apply to subclasses that the
> stylesheet designer did not know of (or forgot).
>
>
> > This is the same approach SPARQL is also taking.
> >>
> >> Thus I think (if at all) you should tell the engine explicitly to do
> >> inferencing using '!' and the none-inferencing case should be the
> >> default.
> >
> >
> > Agreed.
>
> Ok, so we all seem to agree that this is a useful feature. We only
> disagree on whether this should be the default behaviour and on the syntax.
>
> I'm okay witht the idea of having the subclass/subproperty-unaware
> version the default, but then I'm not sure I like "!" as the notation
> for the subclass/subproperty-aware version. I can live with it, that's
> mostly a question of personal taste, but if anybody has another idea for
> how to convey this, please submit it. Unless everybody's happy with the
> ! notation, in which case we'll leave it as such.
Coming back to this issue after a while, here's what I am about to do:
- default type tests will be subclass/subproperty-unaware
- symbol ^ will be used as a type test prefix to denote a
subclass/subproperty-aware type test.
So:
*/ex:prop1/*
would only select paths that go through ex:prop1 properties, but not
subproperties of ex:prop1,
while:
*/^ex:prop1/*
would select paths that go through ex:prop1 properties or subproperties
of it.
--
Emmanuel Pietriga
INRIA Futurs - Projet In Situ tel : +33 1 69 15 34 66
Bat 490, Université Paris-Sud fax : +33 1 69 15 65 86
91405 ORSAY Cedex FRANCE http://www.lri.fr/~pietriga
Received on Thu Oct 13 2005 - 06:07:13 EDT