[rdf4j-dev] Custom functions

[Håvard Ottestad <hmottestad@xxxxxxxxx>]

Hi,

I got to thinking about a feature I wished had been available when working on my previous project utilizing Stardog. 

In regular SQL databases you can use PL/SQL to add custom functions. One common function that I’ve always needed is support for extracting all data related to some resource based on rules that I’ve come up with. Usually some sort of recursive traversal that halts if it traverses a certain property or some other criteria. 

This is usually not possible with just SPARQL since you can’t do ?a ?b* ?c. 

When running the RDF4J server/workbench, I wonder if anyone has requested something like a class loader approach to side load functions?

A user could easily implement this on their client, but network latency and query parsing will add a decent amount of overhead. 

Håvard