Writing Filter Functions for ARQ

Applications can add SPARQL functions to the query engine. This is done by writing a class implementing the right interface, then either registering it or using the fake java: URI scheme to dynamically call the function.

Writing SPARQL Value Functions

A SPARQL value function is an extension point of the SPARQL query language that allows URI to name a function in the query processor.

In the ARQ engine, code to implement function must implement the interface com.hp.hpl.jena.query.function.Function although it is easier to work with one the abstract classes for specific numbers of arguments like com.hp.hpl.jena.query.function.FunctionBase1 for one argument functions. Function do not have to have a fixed number of arguments.

Registering the Function

Function registry : global and per-query execution.

ARQ Documentation Page