- From: Gary Ng <Gary.Ng@networkinference.com>
- Date: Wed, 16 Jul 2003 15:28:57 +0100
- To: "Jim Hendler" <hendler@cs.umd.edu>, "Ian Horrocks" <horrocks@cs.man.ac.uk>
- Cc: <public-webont-comments@w3.org>
Yes, of course. Cheers, G > -----Original Message----- > From: Jim Hendler [mailto:hendler@cs.umd.edu] > Sent: 16 July 2003 14:42 > To: Gary Ng; Ian Horrocks > Cc: public-webont-comments@w3.org > Subject: [moved] RE: unsupported datatypes > > 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 10:29:08 UTC