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From Marco Neumann <>
Subject Re: [GenericRuleReasoner] inner workings
Date Tue, 12 Mar 2019 22:18:17 GMT
so what's your current recommendation for a superior third party rules
reasoner that works efficiently with the jena tooling? free & commercial
option welcome


On Mon 14. Jan 2019 at 19:16, Dave Reynolds <>

> Hi Barry,
> [Agreed that dev is probably the better place to discuss this.]
> The two engines in jena are indeed loosely styled on RETE and on tabled
> datalog. However, I wouldn't claim they were particularly complete or
> good implementations of either. So while looking at some of the source
> literature that inspired them might be helpful don't expect very much of
> what's covered in the literature to be present in the code.
> For RETE then the wikipedia article [1] is a good summary and source of
> starting references. I had a copy of the original Forgy paper [1](ref
> 1), among others,when I was doing the work. There has been a *lot* of
> work on improvements to RETE since the 80s and while there were times
> when we might have done a new forward engine using more modern
> techniques it never happened.
> For the backward engine the approach is a variant of SLG-WAM as used for
> XSB but highly highly simplified since we can't express general tuples
> or recursive data structures within jena's triples. A few google
> searches haven't turned up the exact paper that originally inspired the
> approach. The closest I've found are [2] and [3], which probably cover
> the same ground.
> Let me reinforce that the Jena engines are really simplified. They were
> enough to get the job done at the time (over a decade ago now) and have
> proved useful for some people since but I wouldn't want to defend any of
> the implementation choices.
> Dave
> [1]
> [2]
> [3]
> On 14/01/2019 16:33, ajs6f wrote:
> > I have no useful general information about the reasoning framework, but
> I am copying this over to dev@. Discussions of how to extend Jena
> definitely have a place there.
> >
> > ajs6f
> >
> >> On Jan 14, 2019, at 6:40 AM, Nouwt, B. (Barry)
> <> wrote:
> >>
> >> Hi all, I want to investigate the inner workings of the
> GenericRuleReasoner (with the purpose of extending it in the future). In
> Jena's documentation I read:
> >>
> >> "Jena includes a general purpose rule-based reasoner which is used to
> implement both the RDFS and OWL reasoners but is also available for general
> use. This reasoner supports rule-based inference over RDF graphs and
> provides forward chaining, backward chaining and a hybrid execution model.
> To be more exact, there are two internal rule engines one forward chaining
> RETE engine and one tabled datalog engine - they can be run separately or
> the forward engine can be used to prime the backward engine which in turn
> will be used to answer queries."
> >> source:
> >>
> >> Apart from Jena's documentation, Jena's mailing lists and its source
> code, are there any resources that can better help me grasp what is
> happening inside the generic rule reasoner? For example, the text above
> mentions the forward chaining RETE engine and the tabled datalog engine,
> are there any scientific papers that I might read to better understand
> their inner workings?
> >>
> >> Maybe this question is better suited for the
> <>?
> >>
> >> Regards, Barry
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Marco Neumann

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