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
