- From: pat hayes <phayes@ai.uwf.edu>
- Date: Sat, 30 Nov 2002 21:57:20 -0600
- To: Jan Grant <Jan.Grant@bristol.ac.uk>
- Cc: w3c-rdfcore-wg@w3.org
>On Tue, 26 Nov 2002, Patrick Stickler wrote: > >> xsd:decimal rdfs:subClassOf xsd:float . > >This isn't true, because 0.1 does NOT occur in the xsd:float value >space. (it's 2^-1 . 5^-1) > >> xsd:float rdfs:subClassOf xsd:decimal . > >This is true if floats and decimal value spaces are just sets of >numbers, as Jeremy described. In mathematics, there is no such thing as a 'float'. The term was invented for use in programming, and refers to a mode of *representation*, not to a kind of number. So to just blandly assume that it is obvious that the sets of 'floats' and 'decimals' are supposed to be subsets of the positive rationals, is being very casual with what might well be a rather delicate distinction, seems to me. Many systems and even quite a few textbooks take it as obvious that floats and integers, for example, are *disjoint* sets of entities; SpecWare, the leading program-property proving logic, assumes strong typing in which for example the real number zero and the integer zero are considered to be distinct numbers. Some set theoretic FOM formalizations make distinctions like this, and category theory would also treat them as distinct entities (in different categories, with morphisms between them.) In all of these cases the subClassOf relationship above would be firmly rejected. I honestly have no idea what XML schema thinks the relationship between floats and decimals is, even after reading the specs. You can understand phrases like 'set of numbers' in more than one way, depending on what you think 'numbers' are. So I think we should be careful, is all, not to jump the gun over issues like this. The answers are NOT obvious from the published specs. At the very least, we should refer such questions to a suitable authority. I really don't think that we should be saying anything that depends on an *interpretation* of the XSD spec. Instead, we should try to be very clear what information we expect a datatype spec to give an RDF engine, and what RDF takes it to mean, and then we should let the authors of the XML Schema spec tell us what that information actually is for the XSD class of datastructures. If that requires them to do some more work, then fine, but let them do that work, not us for them. We might very well get it wrong, and in any case we don't have either the time or the authority to do it for them. Pat > > >-- >jan grant, ILRT, University of Bristol. http://www.ilrt.bris.ac.uk/ >Tel +44(0)117 9287088 Fax +44 (0)117 9287112 http://ioctl.org/jan/ >"My army boots contain everything not in them." - Russell's pair o' Docs. -- --------------------------------------------------------------------- IHMC (850)434 8903 home 40 South Alcaniz St. (850)202 4416 office Pensacola (850)202 4440 fax FL 32501 (850)291 0667 cell phayes@ai.uwf.edu http://www.coginst.uwf.edu/~phayes s.pam@ai.uwf.edu for spam
Received on Saturday, 30 November 2002 23:53:57 UTC