[TBC SE v4.2.1] Sesame connector and RDF data store size

[Tomas.V]

Hello,

I have loaded the full geonames RDF dump (http://www.geonames.org/ontology/documentation.html) into a sesame powered RDF store (Owlim).
As a result, the store currently holds 123M+ triples. Unfortunately, I have noticed that TBC doesn't seem to work with such amount of triples
when connected to the store though sesame connector. The Classes and Properties views get populated, however no instance data is being
retrieved in the Instances view. A-box related SPARQL queries (through the Query Editor) bring zero results as well. There are no problems executing
queries and working with the store in general through Sesame workbench, Jena API + ARQ, so this leads me to think that the issue is TBC related.

Please note, that such behavior is present only when data store size increases significantly. TBC sesame connector works well with smaller data dumps.
I have tested this separately with 4.7M triples from a partial geonames RDF dump.

Any ideas on what might be the problem here?

Regards,
Tomas

[Holger Knublauch]

Hi Tomas,

could you send us some example SPARQL queries that no longer work? Could it be that the instances don't show up because you are looking at a superclass of the actual rdf:type?

Also note that TBC is doing some caching, so whenever you upload new data into a remote store, the local system may need to be refreshed (ideally restart).

Thanks

Holger

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[Tomas.V]

Hi Holger,

Basically none of the SPARQL queries work, only those related to the ontology schema (T-box) concepts. For example:
 
SELECT *
WHERE {
    ?subject rdfs:subClassOf ?object .
} LIMIT 100

works, while:

SELECT *
WHERE {
    ?subject rdf:type geo-ont:Feature .
} LIMIT 100

SELECT *
WHERE {
    ?subject geo-ont:countryCode ?object .
} LIMIT 100

and similar queries don't. Also what I have noticed is that the class geo-ont:Code shows some of its instances (473) in the "Classes view", when there's actually 692 instances in the repository.
However, the classes geo-ont:Class and geo-ont:Feature don't show any instances. Keep in mind that the instances do show up when working with a smaller geonames data repository.
This leads me to think, that perhaps something goes wrong when TBC tries to build an initial cache? I've tried clearing caches, restarting both TBC and sesame server numerous times, but to no avail.


Regards,
Tomas

[Holger Knublauch]

Hi Tomas,

we are having trouble reproducing this. We do not have OWLIM (licenses) and are not aware of general issues with the Sesame bridge. In general, I am afraid this problem may be too far off our current radar that we cannot invest the proper time needed to drill down. Sesame is only a "level 2" database in our support portfolio, as it is not central to our other products. Other databases on our "level 1" including SDB are OK with data of that size. Furthermore, with very large databases, a fat client such as TBC is likely to be inferior to our web based tools such as TopBraid EVN.

Holger