We previously learnt to measure the use of SERVICE syntax in queries running on Wikidata Query Service, but we don't have a way to recognize when it is used to federate to an endpoint vs. invoke a helper service.
Examples of federating to an endpoint:
- wdsubgraph:scholarly (resolved via prefix to a concrete URL - see T399805),
- dbpedia:sparql (resolved via prefix to a concrete URL)
- https://query.mimotext.uni-trier.de/proxy/wdqs/bigdata/namespace/wdq/sparql
Examples of helper services:
- wikibase:label
- wikibase:sitelinks
- urn:service:search
This task is to find a way to recognize one from the other (for example, by combining the list of helpers, or looking at how Query Service/Blazegraph differentiates between them). Keep in mind that first prefixes need to be resolved to full URLs - T399805).
The logic doesn't have to be perfect, but helpful enough.