- From: Jim Hendler <hendler@cs.umd.edu>
- Date: Wed, 16 Jul 2003 09:41:44 -0400
- To: "Gary Ng" <Gary.Ng@networkinference.com>, "Ian Horrocks" <horrocks@cs.man.ac.uk>
- Cc: <public-webont-comments@w3.org>
Gary- Ian has suggested that he is happy to continue this discussion on www-rdf-logic, is that okay? thanks Jim Hendler At 6:26 PM +0100 7/15/03, Gary Ng wrote: >> -----Original Message----- >> From: Ian Horrocks >> Sent: 15 July 2003 18:02 >> To: Gary Ng >> Cc: public-webont-comments@w3.org >> Subject: Re: unsupported datatypes >> >> On July 15, Gary Ng writes: >> > >> > >> > Another question, this time about unsupported datatypes. >> > >> > In the reference doc, it says: >> > >> > "For unsupported datatypes, lexically identical literals should be >> > considered equal, whereas lexically different literals would not be >> > known to be either equal or unequal. Unrecognized datatypes should >be >> > treated in the same way as unsupported datatypes." >> > >> > The first half of the sentence would suggest to treat a literal of >> > unknown type as just a string. However, I am not entirely sure what >is >> > expected from a reasoner with respect to the behaviour of "would not >be >> > known to be either equal or unequal". >> >> Unknown or unrecognised datatypes are treated as being the lexical >> form (a string) of some unknown datatype. It is obviously the case >> that, whatever the datatype, identical lexical forms map to the same >> element of the value space, and can thus be considered equal. For >> non-identical lexical forms, however, it *cannot* be assumed that they >> do not map to the same element of the value space and are thus >> unequal. >> >> E.g., the lexical forms "1.0" and "01.00" would map to the same value >> (and thus be considered equal) in some datatypes (e.g., decimal), but >> not in others (e.g., string). >> >Yes, I got that. > >But from a practical point of view of handling values from an >unsupported datatype within a reasoning tool, this sounds like I can't >even implement them as strings because since two different strings would >be considered unequal. So the question is, how should I implement them? > >Consider the following: > ><Measurement rdf:ID="a_measurement"> > <hasAValueOf >rdf:datatype="someUnsupportedType">XYZ</hasAValueOf> ></Measurement> > ><Measurement rdf:ID="b_measurement"> > <hasAValueOf >rdf:datatype="someUnsupportedType">ABC</hasAValueOf> ></Measurement> > >by the definition, "XYZ" and "ABC" are neither equal nor unequal. >So what should be the answer to the following question? > >Retrieve all instances of (complementOf(exists hasAValueOf XYZ)) > >Because we cannot *prove* that XYZ = or != to ABC, thus >The answer would be empty. Am I correct? > >If I am correct, then this behaviour is the same as if XYZ and ABC are >classes/instances. So really we can't implement values from unsupported >datatypes as strings. > >Correct? > >G -- Professor James Hendler hendler@cs.umd.edu Director, Semantic Web and Agent Technologies 301-405-2696 Maryland Information and Network Dynamics Lab. 301-405-6707 (Fax) Univ of Maryland, College Park, MD 20742 *** 240-277-3388 (Cell) http://www.cs.umd.edu/users/hendler *** NOTE CHANGED CELL NUMBER ***
Received on Wednesday, 16 July 2003 09:42:15 UTC