From: Jeremy Carroll <jjc@hplb.hpl.hp.com>

Date: Fri, 22 Nov 2002 20:42:48 +0000

Message-ID: <3DDE96C8.9000901@hpl.hp.com>

To: Dan Connolly <connolly@w3.org>

CC: Brian McBride <bwm@hplb.hpl.hp.com>, RDF Core <w3c-rdfcore-wg@w3.org>

Date: Fri, 22 Nov 2002 20:42:48 +0000

Message-ID: <3DDE96C8.9000901@hpl.hp.com>

To: Dan Connolly <connolly@w3.org>

CC: Brian McBride <bwm@hplb.hpl.hp.com>, RDF Core <w3c-rdfcore-wg@w3.org>

Brian wrote: >This point seems to be > subtle enough to have misled DanC. I am sorry Dan, I've got another one. Dan wrote: > xsd:float rdfs:subClassOf xsd:double. > > That is *not* datatype(xsd:float, xsd:double) entailed > by the empty graph; the value space of float is *not* > specified to be a subset of the value space of double. > So there's no justification ala step 2 above. > > For details, see > Floating-point datatypes are not real datatypes > Mark Reinhold <mr@eng.sun.com> > 5 October 1999 > http://lists.w3.org/Archives/Public/www-xml-schema-comments/2000JanMar/0130.html Unfortunately the details describe descrepancies between the *mappings* of the two datatypes not their *value spaces*. A proof of (with appropriate knowledge of datatypes). xsd:float rdfs:subClassOf xsd:double . xsd:float value space defn: http://www.w3.org/TR/xmlschema-2/#float [[ The basic ˇvalue spaceˇ of float consists of the values m × 2^e, where m is an integer whose absolute value is less than 2^24, and e is an integer between -149 and 104, inclusive. In addition to the basic ˇvalue spaceˇ described above, the ˇvalue spaceˇ of float also contains the following special values: positive and negative zero, positive and negative infinity and not-a-number. ]] xsd:double value space defn: http://www.w3.org/TR/xmlschema-2/#double [[ The basic ˇvalue spaceˇ of double consists of the values m × 2^e, where m is an integer whose absolute value is less than 2^53, and e is an integer between -1075 and 970, inclusive. In addition to the basic ˇvalue spaceˇ described above, the ˇvalue spaceˇ of double also contains the following special values: positive and negative zero, positive and negative infinity and not-a-number. ]] The special values are the same, and each of the basic values of xsd:float is an xsd:double because if |m| < 2^24 then |m|<2^53 and if -149 <= e <= 104 then -1075 <= e <= 970. QED. Moreover we see that xsd:int rdfs:subClassOf xsd:double . but not xsd:int rdfs:subClassOf xsd:float . by similar reading of the recommendation. (I am sorry Brian, I know you hate this. I tend to side with Dan in principle, but also wonder about why we should want to do this. I am not sure anyone would implement this). Frankly worrying about these relationships is implicit in our charter. JeremyReceived on Friday, 22 November 2002 15:43:06 EST

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