This is the archive of the goodrelations dicussion list

Dear all:

I recently found out that there is a pitfall when dealing with  
xsd:data type data in RDF & SPARQL. While GoodRelations itself does  
not use xsd:date, this may affect product features modeled in domain- 
specific extensions of GoodRelations (as described in [1]).

Assume you define a property

foo:modelYear a owl:DatatypeProperty ;
	rdfs:subPropertyOf gr:datatypProductOrServiceProperty ;
	rdfs:label "The date of introduction of a car make and model "@en ;
	rdfs:range xsd:date ;
	rdfs:domain gr:ProductOrService .


If you do now attach this to a car model

data:myCar a gr:ProductOrServiceModel ;
	rdfs:label "1998 Chevrolet Convertible"@en ;
	foo:modelYear "1998-04-01"^^xsd:date .

then querying for a model with modelYear = "1998-04-01" may not return  
matches, e.g. the following SPARQL query will likely fail:
SELECT ?model
{
     ?model a gr:ProductOrServiceModel .
     ?model rdfs:label ?label .
     ?label bif:contains "Chevrolet" .
     ?model foo:modelYear ?date .
     FILTER(?date = "1998-04-01"^^xsd:date) .
}
Limit 10
The problem is that xsd:date is internally holding hour information  
that may also be modified by time-zone differences when the data is  
being processed by the underlying RDF repository. The following query  
should work:

SELECT ?model
{
     ?model a gr:ProductOrServiceModel .
     ?model rdfs:label ?label .
     ?label bif:contains "Chevrolet" .
     ?model foo:modelYear ?date .
     FILTER(xsd:dateTime(?date) >=  
"1998-04-01T00:00:00Z"^^xsd:dateTime &&
         xsd:dateTime(?date) <= "1998-04-01T23:59:59Z"^^xsd:dateTime) .
}
Limit 10
Source & Acknowledgments:
http://www.semanticoverflow.com/questions/947/dbpedia-sparql-endpoint-xsddate-comparison-weirdness

Best wishes

Martin Hepp

[1] http://www.ebusiness-unibw.org/wiki/Own_GoodRelations_Vocabularies
--------------------------------------------------------
martin hepp
e-business & web science research group
universitaet der bundeswehr muenchen

e-mail:  hepp at ebusiness-unibw.org
phone:   +49-(0)89-6004-4217
fax:     +49-(0)89-6004-4620
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          http://www.heppnetz.de/ (personal)
skype:   mfhepp
twitter: mfhepp

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