ConversionException in TDB-backed OntModel

[Martynas Jusevicius <ma...@gmail.com>]

Hey list,

I switched from in-memory OntModel

  OntModel model = ModelFactory.createOntologyModel();

to TDB-backed persistent OntModel

  OntModel model =
ModelFactory.createOntologyModel(OntModelSpec.OWL_MEM,
TDBFactory.createNamedModel(ONT_MODEL_URI,
getContext().getRealPath("/WEB-INF/tdb/ontologies")));

And I can see that behavior changed, since I get this exception on
model.listIndividuals() which wasn't there before:

  com.hp.hpl.jena.ontology.ConversionException: Cannot convert node
"http://l-userpic.livejournal.com/83083903/3100850"@en to OntResource

Is OntModelSpec.OWL_MEM not the default model spec used in
createOntologyModel()?

More to the point - I can see that my FOAF data is broken - there is a
literal object where foaf:image expects a resource:

  <foaf:image>http://l-userpic.livejournal.com/67781107/4730072</foaf:image>

but I can't do much about it since it is the kind of raw data I want
to accept from users.

I do not need inference right now but might use it in the future - so
how do I deal with ConversionException on broken data like this?

Thanks,

Martynas
semantic-web.dk

Re: ConversionException in TDB-backed OntModel

[Ian Dickinson <ia...@epimorphics.com>]

Hi Martynas,

On 28/04/11 11:08, Martynas Jusevicius wrote:
> I switched from in-memory OntModel
>
>    OntModel model = ModelFactory.createOntologyModel();
>
> to TDB-backed persistent OntModel
>
>    OntModel model =
> ModelFactory.createOntologyModel(OntModelSpec.OWL_MEM,
> TDBFactory.createNamedModel(ONT_MODEL_URI,
> getContext().getRealPath("/WEB-INF/tdb/ontologies")));
>
> And I can see that behavior changed, since I get this exception on
> model.listIndividuals() which wasn't there before:
>
>    com.hp.hpl.jena.ontology.ConversionException: Cannot convert node
> "http://l-userpic.livejournal.com/83083903/3100850"@en to OntResource
>
> Is OntModelSpec.OWL_MEM not the default model spec used in
> createOntologyModel()?
No, it's not. The default is OWL_MEM_RDFS_INF, for backwards 
compatibility with Jena 1. Possibly a mistake in hindsight, but hard to 
change now without breaking user code.

> More to the point - I can see that my FOAF data is broken - there is a
> literal object where foaf:image expects a resource:
>
>    <foaf:image>http://l-userpic.livejournal.com/67781107/4730072</foaf:image>
>
> but I can't do much about it since it is the kind of raw data I want
> to accept from users.
>
> I do not need inference right now but might use it in the future - so
> how do I deal with ConversionException on broken data like this?
If you're anticipating broken data, you could always turn off strict 
mode, so that .as() will always succeed no matter what's in the model:

http://jena.sourceforge.net/javadoc/com/hp/hpl/jena/ontology/OntModel.html#setStrictMode%28boolean%29

Whether this is helpful or not is application defined :)

Ian

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