Answers inline:
On 17/07/2014 12:01, "David Torres" <[email protected]> wrote:
>Hi Andy,
>
>Thank you very much for your response, it works as a charm!
>
>For the general interest, I put my solution (using "east" function to
>simplify it)
>
>[...]
>
>SpatialQuery.init(); // it registers all the property functions related to
>spatial, you'll need the Jena-Spatial jar in your classpath
>
>// nodes for the literal values (float)
>NodeValue nodeLatitud = NodeValue.makeDecimal(this.position.getLatitude()
>);
>NodeValue nodeLongitud =
>NodeValue.makeDecimal(this.position.getLongitude()
>);
>
>// anonymous variables used as auxiliary
>Var varAnon1 = Var.alloc("anon1");
>Var varAnon2 = Var.alloc("anon2");
>
>// main block is an ElementTriplesBlock created previously
>Triple tripleListLatitude = Triple.create(varAnon1, RDF.first.asNode(),
>nodeLatitud.asNode() );
>mainBlock.addTriple(tripleListLatitude);
>Triple tripleListLatitudeFollows = Triple.create(varAnon1,
>RDF.rest.asNode(), varAnon2);
>mainBlock.addTriple(tripleListLatitudeFollows);
>Triple tripleListLongitude = Triple.create(varAnon2, RDF.first.asNode(),
>nodeLongitud.asNode() );
>mainBlock.addTriple(tripleListLongitude);
>Triple tripleListLongitudeFollows = Triple.create(varAnon2,
>RDF.rest.asNode(), RDF.nil.asNode() );
>mainBlock.addTriple(tripleListLongitudeFollows);
>Triple tripleEast = Triple.create(Var.alloc(varResult),
>NodeFactory.createURI("http://jena.apache.org/spatial#east";), varAnon1);
>mainBlock.addTriple(tripleEast);
>
>[...]
>
>After compiling it...
>Op op = Algebra.compile(query);
>
>I get this Algebra:
>
>(project (?result ?lat ?long)
> (bgp
> (triple ?result <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <
>http://www.w3.org/2003/01/geo/wgs84_pos#SpatialThing>)
> (triple ?result <http://www.w3.org/2003/01/geo/wgs84_pos#lat> ?lat)
> (triple ?result <http://www.w3.org/2003/01/geo/wgs84_pos#long> ?long)
> (triple ?anon1 <http://www.w3.org/1999/02/22-rdf-syntax-ns#first>
>39.2085)
> (triple ?anon1 <http://www.w3.org/1999/02/22-rdf-syntax-ns#rest>
>?anon2)
> (triple ?anon2 <http://www.w3.org/1999/02/22-rdf-syntax-ns#first>
>-2.713)
> (triple ?anon2 <http://www.w3.org/1999/02/22-rdf-syntax-ns#rest> <
>http://www.w3.org/1999/02/22-rdf-syntax-ns#nil>)
> (triple ?result <http://jena.apache.org/spatial#east> ?anon1)
> ))
>
>After optimizing it...
>
>Op op2 = Algebra.optimize(op);
>
>(project (?result ?lat ?long)
> (propfunc <http://jena.apache.org/spatial#east>
> ?result (39.2085 -2.713)
> (bgp
> (triple ?result <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <
>http://www.w3.org/2003/01/geo/wgs84_pos#SpatialThing>)
> (triple ?result <http://www.w3.org/2003/01/geo/wgs84_pos#lat> ?lat)
> (triple ?result <http://www.w3.org/2003/01/geo/wgs84_pos#long>
>?long)
> )))
>
>Therefore, the translation seems to work properly.
>
>I still have two questions:
>
>1) After optimizing the algebra, when I return it to a query using:
>Query queryOptimized = OpAsQuery.asQuery(op2);
>
>If I serialize "queryOptimized" I get the long form (using the RDF list).
>Indeed, in my fuseki service I receive this long query instead of the
>optimized form.
>
>SELECT ?result ?lat ?long
>WHERE
> { _:b0 <http://www.w3.org/1999/02/22-rdf-syntax-ns#rest> _:b1 .
> _:b1 <http://www.w3.org/1999/02/22-rdf-syntax-ns#first> 39.2085 .
> _:b1 <http://www.w3.org/1999/02/22-rdf-syntax-ns#rest> _:b2 .
> _:b2 <http://www.w3.org/1999/02/22-rdf-syntax-ns#first> -2.713 .
> _:b2 <http://www.w3.org/1999/02/22-rdf-syntax-ns#rest> <
>http://www.w3.org/1999/02/22-rdf-syntax-ns#nil> .
> ?result <http://jena.apache.org/spatial#east> _:b0 .
> }
Yes this is normal.
When translating back from a property function ARQ can't tell what was
originally used to represent the intermediate nodes in the list. It
assumes that they were using Blank Nodes like a standard RDF list would be
using. Then it just prints out the triple patterns pretty much as-is.
>
>I suppose there are no differences in performance, but...
There shouldn't be since the shorthand form causes the parser to generate
the equivalent triple patterns
>
>Is it normal? Could I improve my code?
No, you can't do anything to improve your code AFAICT.
Note that in principal ARQ could be made to be smarter and output the
compacted form but that isn't implemented currently
Rob
>2) How do you answer the questions so quickly??? Thank you very much for
>your useful tips ;-)
>
>David
>
>
>2014-07-16 15:16 GMT+02:00 Andy Seaborne <[email protected]>:
>
>> On 16/07/14 09:08, David Torres wrote:
>>
>>> Hello,
>>>
>>> I'm trying to implement this using ARQ API:
>>>
>>> SELECT ?placeName{
>>> ?place spatial:nearby (51.46 2.6 10 'km') .
>>> ?place rdfs:label ?placeName}
>>>
>>> I'm able to create the function as follows:
>>>
>>> ExprList args = new ExprList();
>>>
>>> NodeValue nodeLatitud = NodeValue.makeDecimal(51.46);
>>> NodeValue nodeLongitud = NodeValue.makeDecimal(2.6);
>>> NodeValue nodeRadius = NodeValue.makeDecimal(10);
>>> NodeValue nodeUnit = NodeValue.makeString("km");
>>>
>>> args.add(nodeLatitud);
>>> args.add(nodeLongitud);
>>> args.add(nodeRadius);
>>> args.add(nodeUnit);
>>>
>>> Expr function = new E_Function("http://jena.apache.org/spatial#nearby";,
>>> args);
>>>
>>> But now, I don't know how to insert this function in the main query.
>>>
>>> For example, this would include as filter clause, but of course it
>>>hasn't
>>> the same effects:
>>>
>>> ElementGroup body = new ElementGroup();
>>>
>>> ElementFilter emfilter = new ElementFilter(function);
>>> body.addElement(emfilter) ;
>>>
>>> Any help would be appreciated!
>>>
>>> David
>>>
>>>
>> (brief reply)
>>
>> ElementFilter and E_* are all about FILTER expressions.
>>
>> Property Functions like spatial:nearby are completely different :
>>
>> 1/ Build the query using basic graph patterns - no mention of "property
>> functions"
>>
>> Basic graph pattern of
>>
>> ?place spatial:nearby bnode .
>>
>> and bnode is head of the RDF list (more triples).
>>
>> 2/ register the property function with the property function registry.
>>
>> then when a query is compiled (first stage of execution) the registered
>> property triggers code to convert the triples to the algebra for
>>calling a
>> property function.
>>
>> Try using "arq.qparse" on a query you know works with a property
>>function
>> and a list as object argument. e.g.
>>
>> ---------------
>> prefix list: <http://jena.hpl.hp.com/ARQ/list#>
>>
>> SELECT * {
>> ?x list:index (?idx ?m)
>> }
>> ----------------
>>
>> then try:
>> arq.qparse --print=op (outputs the raw algebra as per the SPARQL spec)
>>
>> arq.qparse --print=opt (outputs the algebra after the optimizer)
>>
>> The optimizer includes the property function translation.
>>
>> Andy
>>
>>
>>
