- From: Stephane Fellah <stephanef@imagemattersllc.com>
- Date: Wed, 21 Feb 2007 15:13:15 -0500
- To: "'Richard Newman'" <r.newman@reading.ac.uk>
- Cc: <public-rdf-dawg-comments@w3.org>
Richard, Thanks for the clarification. There are still some ambiguities for typed literals I'd like to clarify. I can distinguish two cases: 1) 2 literals with the same value space. If both literals have the same datatype uri, thus they share the same value space. It is also possible that both literals with different datatypes share the same value space (For example: xsd:int,xsd:float,xsd:double datatypes maps to value space of Numbers). If the implementation provides a comparator for the value space, then it should return the result of this comparison, otherwise delegate the comparison to the lexical form if not supported or equals value returned. 2) 2 literals with different value spaces (and by inference different datatypes). An example would be for custom temporal datatypes to be compared with xsd:dateTime or datatypes for unit of measure. If the implementation provides an "adapter" from one value space to another and a comparator for these "compatible" values, then it should return the result of this comparison, otherwise delegate the comparison to the lexical form if not adapter or comparator supported or equals value returned. That means the comparison in value space would be implementation specific. Does the WG agree with this approach? Let me know if I was not clear. Best regards Stephane Fellah KnowledgeSmarts Architect and Product Manager http://www.imagematterllc.com -----Original Message----- From: public-rdf-dawg-comments-request@w3.org [mailto:public-rdf-dawg-comments-request@w3.org] On Behalf Of Richard Newman Sent: Wednesday, February 21, 2007 2:38 PM To: Stephane Fellah Cc: public-rdf-dawg-comments@w3.org Subject: Re: Ambiguity for Literal order in SPARQL Sorry for omitting that; that's already described in the SPARQL operator selection, which defines < for dateTimes, numeric values, booleans, and simple literals (strings). The additional ordering constraints are only necessary when the more specific ordering rules do not kick in. When two xsd:booleans are compared, the comparison never reaches the literal comparison stage, because op:boolean-less-than(A, B) is used instead. SPARQL defines additional ordering constraints for when these do not apply, e.g., for unknown datatypes, or for comparing an xsd:boolean to a URI. See <http://www.w3.org/2001/sw/DataAccess/rq23/rq25.html#modOrderBy> and <http://www.w3.org/2001/sw/DataAccess/rq23/ rq25.html#OperatorMapping> -R On 21 Feb 2007, at 11:26 AM, Stephane Fellah wrote: > > Richard, > > I agree with the order you suggest however I think prior doing the > comparison on the lexical form, we need to do a comparison on the > value > space (date, numbers, boolean). If the value space comparison returns > equality, then a lexical form comparison needs to be done. > In this case we ensure we have a "semantic"/mathematical ordering > of literal > value, not only syntactic. > > Stephane -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.1.412 / Virus Database: 268.18.3/694 - Release Date: 2/20/2007 -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.1.412 / Virus Database: 268.18.3/694 - Release Date: 2/20/2007
Received on Wednesday, 21 February 2007 20:13:26 UTC