W3C home > Mailing lists > Public > w3c-rdfcore-wg@w3.org > April 2003

proposed closure of vass-02 / property instances

From: Dan Brickley <danbri@w3.org>
Date: Fri, 25 Apr 2003 10:19:17 -0400
To: w3c-rdfcore-wg@w3.org
Message-ID: <20030425141917.GG12807@tux.w3.org>



Instantiation of properties

 Furthermore, although the RDF/S specification claims that properties
 are first-class citizens, properties are not treated as equally as
 classes. In RDF/S, both a metaclass of classes and a metaclass of
 properties is a class, in contrast to Telos, where a metaclass of
 individuals is a class, but a metaclass of properties (metaproperty)
 is a property. Hence, while in Telos a metaproperty can have domain
 and range, in the RDF/S model it cannot. Furthermore, at the data
 layer, a property cannot be of type property, as in the case of
 resources and classes. This is attributed to the fact that the
 rdf:type property is applicable only for classes and RDF/S does not
 provide us with an instantiation mechanism for properties at the data
 layer. The current version of the RQL data model preserves this kind
 of asymmetry in the manipulation of properties.

I propose that we acknowledge that RDF puts limits on the treatment
of property-instances (aka statements) as describable things. But that we
do not accept any reason to change the RDF design at this time.

Regarding Property instances as resources:

I propose...
 * the WG discussed this issue at various times in the context of reification
  and revisions/clarifications to RDF's formal model per the original 1999 spec.

 * the mission of RDF Core as a WG is explicitly a clarificatory one; we 
 are not designing a new RDF, but clarifying the existing one.

 * many RDF _implementations_ allow for property instances (statements) to be
  tagged, grouped, labelled etc.

 * there are proposals (eg. N3) which make such facilities explicit within a 
  Semantic Web data language.

 * the WG will note to the Semantic Web Coordination Group that Last Call 
 comments were received on this, and that any (currently hypothetical) 
 RDF 2 charter designs should take this into account.

 * we do not intent to change the RDF formal model. While acknowledging that 
 a variety of alternate designs might have also been deployable, we believe the 
 current design is workable and has been implemented successfully.

The basic situation imho is that there are plenty of design choices we could
have taken; some more Telos-like. But we're at the stage in our process where we 
are fixing bugs, rather than shopping for a complete new design. 

In that context, the proposal is to reject the LC comment on our WDs.

Received on Friday, 25 April 2003 10:19:18 UTC

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