Re: [BLD] RIF-RDF combination

Since I will not be able to make it to the next telecon and in case the
RDF->RIF embedding will be discussed, I wanted to make 3 points.

1. All the issues except for the untyped RDF literals, which are raised
   in Jos' document, have been taken care of. We discussed them with Jos a
   few days ago and the corrections are online.
   The issue of untyped literals has been shelved because it is not on a
   critical path, and we did not have the time. But it is a minor issue.

   One of the more prominent changes that came out of this discussion is
   that what we called "primitive data types" are now called "symbol spaces".
   A primitive data type is now a special case of a symbol space (includes
   xsd data types and rdf:xmlliteral, and whatever data types will add to this).
   Primitive data types are symbol spaces with fixed domain. Examples of
   symbol spaces that are not primitive data types include rif:iri and
   rif:local.

   The other changes are either cosmetic or additions of definitions that
   were missing.

2. I agree with the embedding part of the document (the second part of
   http://www.w3.org/2005/rules/wg/wiki/Core/RIF-RDF_Compatibility)

3. I do not see much value in the first part of the document (the combined
   models of RIF and RDF). As far as I can see, this is yet another formalism
   for the poor reader to suffer through -- I think for no obvious gain.


	--michael  


> Dear all,
> 
> I created a page about the combination of RIF and RDF, and the embedding
> of RDF in RIF:
> http://www.w3.org/2005/rules/wg/wiki/Core/RIF-RDF_Compatibility
> 
> This page covers the technical aspects of the combination and the
> embedding; not the architectural aspects such as the reference to RDF
> graphs from RIF rule sets.
> 
> Unfortunately it is a bit too late for everyone to read the page before
> the telephone conference today, but I will try to give an overview of
> what I've done.
> 
> In an earlier e-mail [1] I sketched an embedding of RDF in RIF. The idea
> behind this embedding was that the interaction between the RIF and RDF
> would be defined in terms of this embedding. After thinking a bit about
> it, and consulting others, I came to the conclusion that using an
> embedding for defining the interaction is probably not the best way to
> go for a normative specification, for the following reasons: an
> embedding redefines the semantics of a language; it can be shown that
> certain properties are retained when an RDF graph is embedded, but it is
> unclear whether an extension of this embedding with a set of rules
> behaves as expected.
> 
> Therefore, I decided to explore the possibility of defining the
> semantics of the combination in terms of combined models. Not
> surprisingly, it turns out that the combination can be
> (straightforwardly) embedded in an RIF rule set, for reasoning. So, any
> translator which can translate RIF rules to the format A of some rule
> engine, can translate an RIF-RDF combination to a set of rules in the
> format A.
> I explored the three normative kinds of entailment defined in
> [RDF-Semantics], as well as embeddings of these three. The fact that
> these embeddings exist means that this approach of combined models is in
> fact equivalent to the earlier approach of embeddings, with the
> difference that we now have a model-theoretic justification for the
> embeddings.
> 
> During the development of the page I ran into a number of issues, both
> regarding the RIF-RDF combinations and the RIF language itself.  You can
> find these issues throughout the page, indented and marked with the text
> "Issue:". One of the main issues is the treatment of literals and
> datatypes in RIF; it is not clear at the moment (at least to me) how
> ill-typed literals and unknown data types are treated in RIF.
> I will extract the issues on the RIF language and send these in a
> separate e-mail.
> 
> Finally, I started with the definition of a subset of RDFS, based on the
> subset considered in [2], which includes the RDFS ontology vocabulary
> (type, subClassOf, domain, range, etc), which does not suffer from the
> complications in RDFS brought about by the use of the language
> constructs in the language itself, the infinite RDF vocabulary, and the
> treatment of literals. This subset can be used for the exchange of data
> models, without having to deal with all the complications of RDFS.
> 
> 
> Best, Jos
> 
> 
> [1] http://lists.w3.org/Archives/Public/public-rif-wg/2007May/0077.html
> [2] http://data.semanticweb.org/conference/eswc/2007/paper-282/html

Received on Sunday, 19 August 2007 14:11:07 UTC