Exact ranges and using S-B

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...

Sergey