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proposal to close Qu-03

From: pat hayes <phayes@ihmc.us>
Date: Tue, 1 Jul 2003 23:18:25 -0500
Message-Id: <p0600120dbb2808921e3a@[]>
To: w3c-rdfcore-wg@w3.org
Cc: jjc@hplb.hpl.hp.com
Jeremy, can you give us a pointer to your OWL_DL_in_RDF write-up? I 
would like to have it anyway, but if we can include a pointer in this 
message (and also the Pan response) it would help enormously.


Dear Yuzhong

with reference to your comment 
logged as qu-03, the WG has decide not to accept your comment; but read on.

The issue in question was summarized (in my words) as follows:
There is a class of languages called 'ontology languages'.
Considered as an ontology language, RDFS provides too much expressive 
power, and the extra power is inappropriate for an ontology language.
Therefore, it would be desirable if a subset of RDFS could be
identified which conforms to the requirements for an ontology
language (by imposing constraints on the ability to define classes of 
classes, classes of properties and properties of classes, as outlined 
later in your message.)

As we recently explained in response to a related comment from Jeff 
Pan, the relevant subset of RDF is indeed a subset: that is, one can 
as it were consistently adopt an 'ontology language' discipline 
within legal RDF, even though RDF itself allows other disciplines, so 
does not enforce the style of expression that you prefer; and we 
consider that this freedom is an important design feature of RDF. The 
question however arises of how one might state conditions on RDF 
graphs which correspond to being 'legal' when seen as representations 
within an 'ontology language' discipline.

The discussions surrounding the relationship between OWL-DL (which is 
layered) and OWL-Full (which is not) have led to Jeremy Carroll 
formulating a set of detailed conditions on an OWL/RDF graph which 
suffice for it to be a legal OWL-DL document. These involve providing 
a labelling of the non-RDFS vocabulary into individual, class and 
property URIrefs and some conditions on the occurrence of blank nodes 
in various contexts. It has occurred to several of us that these same 
conditions could be applied to arbitrary RDF graphs and might provide 
a useful way to recognize that an RDF graph was 'layered' in the 
sense that you might accept as more "standard". We have not checked 
what relationship, if any , there might be between the Carroll 
algorithm and the design of RDFS(FA), but mention this work only to 
suggest that there might be a useful embedding of your preferred 
architectural style into the RDFS design; for if so, it would seem 
that RDF is able to serve its primary design aim of being a universal 
medium of data interchange even for users who prefer a layered 

The WG has determined that to include these conditions in the RDF 
normative documents is not appropriate at this stage, but their 
existence may be used to provide a basis for the use of 'ontology 
language' techniques within RDF.


Please reply to this message, copying www-rdf-comments@w3.org, 
indicating whether this response adequately addresses your comment.


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Received on Wednesday, 2 July 2003 00:18:28 UTC

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