Re: time arithmatic in SPARQL

Thu, 09 Oct 2008 15:58:25 -0700 


Andy,
Thanks so much for trying to elucidate sparql for me. Your response was edifying in many ways: clarifying the use of date vs dateTime (which I knew), making slightly more clear how UNION works and showing how FILTER works with 'rows' (which I didn't know). Unfortunately, your response raised more questions for me than it answered. To help me try and clarify my problem, I created the following test cases in RDF: 

<rdf:RDF  xmlns:ex="http://temp.example.org/terms/";
    xmlns:loc="http://simile.mit.edu/2005/05/ontologies/location#";
    xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#";
    xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#";>

        <ex:Event rdf:about="http://temp.example.org/terms/Event#case0";>
<ex:date rdf:datatype="http://www.w3.org/2001/XMLSchema#date";>2007-12-31</ex:date> <loc:place rdf:resource="http://temp.example.org/terms/Place#case0_place"; /> 
        </ex:Event>
        <ex:Event rdf:about="http://temp.example.org/terms/Event#case1";>
<ex:date rdf:datatype="http://www.w3.org/2001/XMLSchema#date";>2008-01-06</ex:date> <loc:place rdf:resource="http://temp.example.org/terms/Place#case1_place"; /> 
        </ex:Event>
        <ex:Event rdf:about="http://temp.example.org/terms/Event#case2";>
<ex:starts rdf:datatype="http://www.w3.org/2001/XMLSchema#date";>2008-01-04</ex:starts> <ex:finishes rdf:datatype="http://www.w3.org/2001/XMLSchema#date";>2008-01-05</ex:finishes> <loc:place rdf:resource="http://temp.example.org/terms/Place#case2_place"; /> 
        </ex:Event>
        <ex:Event rdf:about="http://temp.example.org/terms/Event#case3";>
<ex:starts rdf:datatype="http://www.w3.org/2001/XMLSchema#date";>2008-01-07</ex:starts> <ex:finishes rdf:datatype="http://www.w3.org/2001/XMLSchema#date";>2008-01-08</ex:finishes> <loc:place rdf:resource="http://temp.example.org/terms/Place#case4_place"; /> 
        </ex:Event>
        <ex:Event rdf:about="http://temp.example.org/terms/Event#case4";>
<ex:starts rdf:datatype="http://www.w3.org/2001/XMLSchema#date";>2008-01-02</ex:starts> <ex:finishes rdf:datatype="http://www.w3.org/2001/XMLSchema#date";>2008-01-03</ex:finishes> <loc:place rdf:resource="http://temp.example.org/terms/Place#case3_place"; /> 
        </ex:Event>
        <ex:Event rdf:about="http://temp.example.org/terms/Event#case5";>
<ex:starts rdf:datatype="http://www.w3.org/2001/XMLSchema#date";>2008-01-09</ex:starts> <ex:finishes rdf:datatype="http://www.w3.org/2001/XMLSchema#date";>2008-01-10</ex:finishes> <loc:place rdf:resource="http://temp.example.org/terms/Place#case5_place"; /> 
        </ex:Event>
        <ex:Event rdf:about="http://temp.example.org/terms/Event#case6";>
<ex:starts rdf:datatype="http://www.w3.org/2001/XMLSchema#date";>2008-01-01</ex:starts> <ex:finishes rdf:datatype="http://www.w3.org/2001/XMLSchema#date";>2008-01-11</ex:finishes> <loc:place rdf:resource="http://temp.example.org/terms/Place#case6_place"; /> 
        </ex:Event>

</rdf:RDF>
With this as the graph, I tried the following query and discovered that the >= and <= operators do not work as I expected they would 

PREFIX ex: <http://temp.example.org/terms/>
PREFIX loc: <http://simile.mit.edu/2005/05/ontologies/location#>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>

SELECT *
WHERE {
        {?event ex:date ?date .
FILTER (xsd:date(?date) >= xsd:date("2008-01-01") && xsd:date(?date) <= xsd:date("2008-01-11"))} 
        UNION {?event ex:starts ?start;
                        ex:finishes ?end.
FILTER (xsd:date(?start) >= xsd:date("2008-01-02") && xsd:date(?end) <= xsd:date("2008-01-10"))} 
}
ORDER BY ?event
This query returned cases 1, 2, and 3 where I expected it to return cases 1-5. 

If I do instead:

SELECT *
WHERE {
        {?event ex:date ?date .
FILTER (xsd:date(?date) >= xsd:date("2008-01-01") && xsd:date(?date) <= xsd:date("2008-01-11"))} 
        UNION {?event ex:starts ?start;
                        ex:finishes ?end.
FILTER (xsd:date(?start) >= xsd:date("2008-01-01") && xsd:date(?end) <= xsd:date("2008-01-11"))} 
}

I get cases 1-5

Similarly I have to modify the first filter clause thus:
FILTER (xsd:date(?date) >= xsd:date("2007-12-30") && xsd:date(?date) <= xsd:date("2008-01-11")) 
in order to include case 0 in the result.

Also, I haven't even touched on the question of how to retrieve case 6.
Idealy, I'm looking for a query that returns cases 1-6.
I thank you again for trying to enlighten the dense, and appeal to you again for further illumination. 

Jon

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