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Exact ranges and using S-B

From: Sergey Melnik <melnik@db.stanford.edu>
Date: Fri, 15 Feb 2002 09:35:18 -0800
Message-ID: <3C6D46D6.411D30FD@db.stanford.edu>
To: Pat Hayes <phayes@ai.uwf.edu>, Dan Connolly <connolly@w3.org>
CC: RDFCore WG <w3c-rdfcore-wg@w3.org>, Dan Brickley <danbri@w3.org>
After the main telecon DanC raised the point of how S-B can still be
used and how the lexical spaces of datatypes can be referred to.

Pat suggested that writing 

  xsd:date rdfs:range _:1
  dc:Date  rdfs:range _:1

could do the job of making the range of dc:Date to be the lexical space
of xsd:date. I'm contesting this point and making a suggestion.

As currently defined by the MT, the first statement asserts that

  image(IEXT(I(xsd:date))) is subset of CEXT(I(_:1))

That is, CEXT(I(_:1)) may contain many other things besides the lexical
tokens for dates. What we would need, however, is

  CEXT(I(_:1)) is subset of image(IEXT(I(xsd:date)))

i.e. a tighter restriction on the interpretation of _:1.

Of course, we could define a new property like rdfs:restrictsByImage
that has this effect. However, I think the most elegant way of handling
this issue would be to introduce properties like rdfs:exactRange and
rdfs:exactDomain with the "equals" semantics. For example, the
interpretation for

  xsd:date rdfs:exactRange _:1

would be

  image(IEXT(I(xsd:date))) = CEXT(I(_:1))

In fact, these two properties are more powerful than rdfs:range and
rdfs:domain or rdfs:restrictByImage altogether. For example,

my:prop rdfs:exactRange _:1
_:1 rdfs:subClassOf my:Vehicle
_:1 rdfs:subClassOf my:Boat

achieves the same effect as

my:prop rdfs:range my:Vehicle
my:prop rdfs:range my:Boat

I believe this is could be an issue for the schema subgroup (DanB?) to
think about...

Received on Friday, 15 February 2002 12:04:51 UTC

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