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Re: [rdf4j-dev] Custom functions

More along the lines of a stored procedure than an extension to SPARQL. And more advanced than a simple stored query. More like a stored procedure backed by java code. 

Functions look neat, but it doesn’t look like they get access to the underlying connection. 

Håvard

On 13 Jan 2020, at 23:51, Jeen Broekstra <jeen.broekstra@xxxxxxxxx> wrote:


Don't we already have this?  See https://rdf4j.org/documentation/custom-sparql-functions/ .  Or are you thinking of something else, more like 'magic' properties? See https://github.com/eclipse/rdf4j/issues/92 .

Cheers,

Jeen

On Tue, 14 Jan 2020, 03:44 Håvard Ottestad, <hmottestad@xxxxxxxxx> wrote:
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
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