rdflib.plugins.sparql.CUSTOM_EVALS["exampleEval"] = customEval

[rchateauneu]

I would like to know if this is possible to implement this kind of custom evaluation function, such as in this example:
Source code for examples.custom_eval

Also, do you please know if this would work in a federated query from Wikidata or Wikibase ? Thanks.

[vemonet]

Hi @rchateauneu, thanks for the feedback! I think that should be possible relatively easily, and that would be a required to enable full use of RDFLib custom evals

Currently I focused on implementing custom functions because that was my use-case, but enabling it also for BGP would be better
I am already using the custom eval, but in my case I try to make it easier for the users to define and register multiple functions without having to play too much with the RDFLib SPARQL parsing internals

cf. calling the CUSTOM_EVALS: https://github.com/vemonet/rdflib-endpoint/blob/main/rdflib_endpoint/sparql_endpoint.py#L69
And generating the CUSTOM_EVALS from the list of functions registered by the user: https://github.com/vemonet/rdflib-endpoint/blob/main/rdflib_endpoint/sparql_endpoint.py#L272

2 solutions would come to my mind here:

1. Allowing the user to directly provide their own CUSTOM_EVALS which would overwrite the one I generate from the provided custom functions
2. Implementing a custom_bgp argument, similar to the current custom_functions arg to make it easier for the users to register multiple custom BGP (requires more dev an testing)

Solution 1 is a must-have, that would allow to cover all use-cases I don't think of, I guess that's the solution you'll prefer? And we can also have both in the end: user-friendly "just define your functions", and flexible "rewrite everything by yourself"

I will look into it when I have some time, but feel free to send a pull requests if you want to fix it asap!

I tried the SPARQL endpoint federated queries from Virtuoso (Jena based) and Ontotext GraphDB (RDF4J based) and they were working, I don't think I tried Blazegraph (which is the triplestore used by Wikibase). I would expect it to work, but you never know...
I'll try it next time I put up a public rdflib-endpoint, let me know if you are facing a problem in the meantime

[rchateauneu]

Thanks for the answer.

What I wish it to create a Sparql endpoint usable from a Wikidata query such as these ones:
Wikidata:SPARQL query service/Federated queries
https://www.wikidata.org/wiki/Wikidata:SPARQL_query_service/Federated_queries

Any implementation would be OK as long as I can implement the specific feature of accessing the BGP from part.triples, add more triples to ctx.graph and finally call evalBGP(ctx, part.triples).

[vemonet]

Hi @rchateauneu, I added the option to pass directly the custom evaluation, released in 0.1.5

You can find an example to use it there: https://github.com/vemonet/rdflib-endpoint#-or-directly-define-the-custom-evaluation

Let me know if it is working as expected for you!