SPARQL Extensions in Corese

Olivier Corby, INRIA, Novembre 2008.
See also: Corese

Select

Select the result of an expression

select fun(?x) as ?y
where {
  ?x ex:prop ?z
}

Select distinct results of an expression

select distinct fun(?x) as ?y
where {
  ?x ex:prop ?z
}

Group by

Group results according to variable values, count occurrences of other values

select * count(?z) as ?count
where {
  ?x ex:prop ?z
}
group by ?x

Group results according to expression values

select fun(?x) as ?y
where {
  ?x ex:prop ?z
}
group by ?y

Group results according to any argument (January 2009)

select *
where {
  ?x ex:prop ?z
}
group by any

Group by can have more than one argument, it be used with construct.

Construct

Construct with Graph Graph Pattern

construct {
  graph ?g { ?x ex:prop ?y }
}
where {
  graph ?g { ?y ex:prop ?x }
}

Construct with Select expression

construct {
   ?x ex:relat ?z 
}
select fun(?y) as ?z
where {
   ?x ex:prop ?y
}

Construct with aggregate

construct {
   ?x ex:total ?sum 
}
select sum(?y) as ?sum
where {
   ?x ex:prop ?y
}
group by ?x

Construct/Add within the source graph (Update)

add {
   ?x ex:total ?sum 
}
select sum(?y) as ?sum
where {
   ?x ex:prop ?y
}
group by ?x

Result post process

It is possible to post process results of a SPARQL query using an external function. The external function is executed after the completion of SPARQL processing, just before returning the results. It is possible to process such treatment as ordering the results or eliminating results according to new criteria. The principle consists in using an external user defined function within the postProcess() pseudo function. The result of the query is given to the postProcess function by means of a pseudo function results().

prefix my: <function://my.cool.package>
select * where {
?x ?p ?y
filter(postProcess(my:process(results()))
}

The external user defined function retrieves the results by means of a getObject() accessor.

package my.cool.package;

public IDatatype process(IDatatype dt){
   IResults res = (IResults) dt.getObject();
   for (IResult rr : res){
      rr.getResultValue("?x");   
   }
   return dt;
}

It is possible to add or remove a result from IResults result list.

interface IResults {

public int size();
	
public IResult get(int i);
	
public void remove(IResult r);
	
public void add(IResult r);
	
public void add(int n, IResult r);

}