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the idea of a 'reserved' vocabulary

From: patrick hayes <phayes@ai.uwf.edu>
Date: Thu, 13 Jun 2002 19:08:35 -0500
Message-Id: <p05111a00b92ed72a69ab@[65.217.30.123]>
To: Jonathan Borden <jonathan@openhealth.org>
Cc: w3c-rdfcore-wg@w3.org

Here's a rough draft of what Id like to say in the RDF MT document 
about 'reserved' (we don't say 'dark' these says) vocabulary, to give 
you an idea of what is being proposed here.

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What does it mean to assert an RDF graph? The normal answer is that 
each triple can be read as a simple proposition, and the graph as a 
whole represents the conjunction of all of these propositions, so 
that what is asserted is the content of all the triples in the graph. 
Asserting a triple amounts to saying that it is true, and what that 
means, in turn, depends on what defines the meanings of the terms 
used in the graph. Before discussing that in more detail, we first 
note that it is also possible to use RDF triples simply as a 
data-structuring mechanism for encoding expressions of other 
languages which have a more complex syntax. If those 'encoding' 
triples are regarded as assertions in the same way as other triples, 
complexities can arise because the meaning they would have when seen 
simply as RDF assertions might not correspond to their intended 
interpretation in the other language. To accommodate such encodings 
and avoid these complications, we allow that some urirefs may be 
declared to be 'reserved'. Triples using urirefs from any reserved 
vocabulary can be present in an RDF graph but do not themselves make 
any RDF assertions. They may, however, be part of an encoding of 
expressions in some other language which itself may be asserted by 
the RDF graph in question, according to the semantic rules of that 
other language. We note that an RDF parser or processor is not 
required to treat such triples in any special way, unless it also 
needs to access the content expressed in that other language encoded 
in an RDF graph.

Since reserving a vocabulary effects the meaning of RDF, the 
authority to declare a uriref or urirefs 'reserved' in this sense 
rests with the W3C.  A uriref or set of urirefs is reserved only if 
it is declared to be so by a W3C Recommendation. In particular, 
reserving a vocabulary cannot be done by simply asserting on a 
webpage that it is to be considered reserved. There is no way to 
state in RDF, or any language encoded in RDF, that a uriref is 
reserved, or for any RDF document to entail this as a consequence.

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And then the basic MT rule for I(E) is slightly modified so that it reads:

If E is a triple S P O . then I(E)=true if S, P and O are not reserved and ....

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That is all that is being suggested. And yes, this is the old 
'unasserted triples' idea in a slightly updated form.

Pat


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Received on Thursday, 13 June 2002 20:08:36 EDT

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