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I don't see anywhere that mentions datalog in relationship to Stardog. I see OWL2 and SparQL, which as far as I can tell do not support recursion other than in experimental prototypes. If there is no recursion, it is just conjunctive queries and not datalog.

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> If there is no recursion, it is just conjunctive queries and not datalog.

SPARQL has negation (FILTER NOT EXISTS), though, making query answering PSpace-hard, whereas conjunctive query answering is NP-complete, so the two are very much not the same, although still less expressive then Datalog (which is ExpTime-complete). CQ answering for the Horn fragment of OWL2 is already 2ExpTime-complete, however, making it vastly more expressive than pure Datalog.

It supports SWRL, a LP rule language that has a well-studied relationship with Datalog. FWIW.

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