Many thanks for taking the time to provide such a precise answer. Meanwhile, I’m afraid i would require some clarification.
1- Could you explain the different between 1 and 2. To me the solution are exactly the same. With my current knowledge of Jena. I don’t see 2 different code coming out of "Construct an Infmodel over a TDB" and “Load The TDB model into memory”. In both case i would go with dataset.getNamedModel or getdefaultmodel, which to me would result in an in-memory model, that will be a parameter of a createInfModel….. 2-In (3) I’m not familiar with the term "inference closure”. My guess would be that you mean ontology schema… is there another term for that, could you please clarify in easier jargon. Moreover, I’m not sure to understand the full logic here. Why would i store the result of some query and then query them again. Is this the way to store all the inferredTriple back in the store? Do you mean that you take every triple that is returned and assert them back in the Infmodel or the base model ? By the way does that mean that in general, in jena, there is noway, to generate a model that is the combination of the asserted and all the inferred triple (or a selected set of inferred triple, e.g. all class axioms). As you can see i’m quite confuse ;) . I would much appreciate if you could clarified and detailed a bit further (3) Also if u have good pointers for me to read, please do not hesitate ;) Many thanks, -M- -- Daniel Maatari Okouya Sent with Airmail From: Dave Reynolds Dave Reynolds Reply: [email protected] [email protected] Date: December 11, 2013 at 9:47:51 AM To: [email protected] [email protected] Subject: Re: Jena TDB and Jena Inference cooperation underlying mechanics There's no specific integration of TDB and inference. The rule-based inference engines themselves run in memory but can operate over any model, however it is stored. So there are several options. 1. Construct an InfModel over a TDB based model. When you query the InfModel you will see both the TDB model and any inferences. 2. Load the TDB model into memory then construct an InfModel over that. Then query the InfModel. 3. Prepare an inference closure and store that. Load the data, e.g. into memory, construct the InfModel, query the InfModel for the patterns you are interested in (which might be every triple) store all those results in a TDB model. Then at run time open the closure TDB as a plain model and query it. 4. As 3 but use TDB's high performance RDFS-subset closure. #1 is easy to do but the inference results are stored in memory so it doesn't enable you to scale to models that wouldn't fit in memory anyway. #2 can be faster. Inference involves a lot of queries and query to an in memory model is naturally faster than querying TDB. Whether the cost of the initial load outweighs the speed of inference depends on how caching works out, your data and your queries. #3 gives you good query performance at the cost of an expensive slow cycle to prepare the data. It's not suited to mutating data and requires the preparation phase to be run on a machine with enough memory to compute the closure, or closure subset, that you want. #4 can cope with much larger data sets than #3 at the expense of a more limited range of inference. Dave On 10/12/13 21:58, Daniel Maatari Okouya wrote: > Dear All, > > If they can work together, I would like to understand a bit better the > underlying mechanics of making Jena TDB and the Jena Inference infrastructure > work together. > > > Hence, I have the following question: > > > 1-Can someone have the Jena TDB act like Stardog, in the sense that if one > make a query that would include inferred triple as well ? > > If that is possible, can someone explain to me the underlying mechanics that > it would imply, knowing that i understood the following from the > documentation. > > Inferred triples are situated in an InfGraph/InfModel(warper), which is > obtained by binding a reasoner to a base Graph/Model (understood as the one > containing the asserted triples). One can query that infGraph using the > Querry engine ( However this is happening on an InMemory models). > > My guess here is that if a model is in the TDB, then for our query to include > the inferred triple, this would requires that, the querry to the model is > actually run against the InfModel/Infgraph. However i don’t know if that is > possible and how exactly TDB would do that? Indeed, that would mean choosing > a reasoner, creating the infmodel, and exposing it in lieu of the base model. > > > Can someone explain a bit that mechanics, that is how it works with Jena TDB, > if one wants some inference. For instance, if the actual model is RDFS or OWL > ? how to query it and obtain answer that include the inferred knowledge. Many > thanks > > Best, > > -M- > > > > -- > Daniel Maatari Okouya > Sent with Airmail >
