Simon,
1/ SpinRDF provides ways of defining custom functions and property
functions in SPARQL.
http://spinrdf.org/
There'll probably be something in the SHACL-sphere (not in the standard,
but in the same general area/style/framework) soon.
2/ There are methods in ExprUtils to parse expressions in SPARQL syntax.
You could build a general helper.
That does not enable syntax replacement but does cover (?) your MyFunc
example.
Andy
On 24/04/17 01:02, Simon Schäfer wrote:
Hello,
I have complex SPARQL queries, which I would like to divide into several parts
(like function definitions), in order to reuse these parts among different
SPARQL queries and in order to make a single SPARQL query easier to understand.
What are my options to achieve this?
I had a look at Jenas built in functionality to support user defined function
definitions. The problem with them is that it seems that they can be used only
for simple functionality like calculating the max of two integers. But I have
quite complex functionality, which I don't want to rewrite in Java. Example:
------------------------------------------------------------------------------------------------
select * where {
?s a ?tpe .
filter not exists {
?sub rdfs:subClassOf ?tpe .
filter (?sub != ?tpe)
}
}
------------------------------------------------------------------------------------------------
It would be great if that could be separated into:
------------------------------------------------------------------------------------------------
public class MyFunc extends FunctionBase1 {
public NodeValue exec(NodeValue v) {
return NodeValue.fromSparql("filter not exists {"
+ " ?sub rdfs:subClassOf ?tpe ."
+ " filter (?sub != ?tpe)"
+ "}") ;
}
}
// and then later
FunctionRegistry.get().put("http://example.org/function#myFunc";, MyFunc.class) ;
------------------------------------------------------------------------------------------------
and then:
------------------------------------------------------------------------------------------------
prefix fun:<http://example.org/function#>
select * where {
?s a ?tpe .
filter(fun:myFunc(?tpe))
}
------------------------------------------------------------------------------------------------
Basically I'm looking for a way to call a SPARQL query from within a SPARQL
query. Is that possible?
