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List Info
Thread: OWL inference problem with Jena
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| OWL inference problem with Jena |
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2007-12-10 10:45:10 |
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I'm trying to use OWL inferencing with the Jena adapter. However, type, kind_of? and is_a? methods don't work as I expect.
I've written the following code, which uses the pizza ontology:
require 'rubygems'
require 'active_rdf'
this_dir = File.dirname(File.expand_path(__FILE__))
adapter = ConnectionPool.add_data_source(:type => :jena, :ontology => :owl, :reasoner => :owl_micro)
adapter.load("
http://www.co-ode.org/ontologies/pizza/2007/02/12/pizza.owl";, :format => :rdfxml, :into => :default_model )
Namespace.register :pz, '
http://www.co-ode.org/ontologies/pizza/pizza.owl#';
Namespace.register :test, 'http://www.test.com#'
ObjectManager.construct_classes
a = PZ::Meatypizza.new TEST::new_pizza
a.save ; # => NativeException: java.lang.NullPointerException: null from LiteralLabel.java:382:in `com.hp.hpl.jena.graph.impl.LiteralLabel.getDefaultHashcode'
a.type ; # => [PZ::Meatypizza, RDFS::Resource, OWL::Thing, PZ: omainconcept, PZ::Food, PZ::Pizza]
a.is_a? PZ::Meatypizza # => true
a.is_a? PZ::Pizza ; # => false ?????
which is wrong, though PZ::Pizza is inferred and listed with
a.type
When trying the same with a bad URI, no exceptions are thrown when saving, but no inferencing is done.
a = PZ::Meatypizza.new 'bad_uri'
a.save ; # works
a.type ; # => [RDFS::Resource, PZ::Meatypizza]
a.is_a? PZ::Meatypizza # => true
a.is_a? RDFS::Resource # => false
a.is_a? PZ::Pizza ; # => false
Is this normal behaviour? If not, is there a bug in the Jena adapter or ActiveRDF or is there a problem with the ontology?
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| Re: OWL inference problem with Jena |
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2007-12-11 07:26:20 |
Hello Josè!
On 10.12.2007, at 17:45, José Ignacio wrote:
> I'm trying to use OWL inferencing with the Jena
adapter. However,
> type, kind_of? and is_a? methods don't work as I
expect.
Great to hear from somebody who is trying out Jena and OWL
inferencing.
I myself did not try out the Jena inferencing, but I
forwarded your
email to the person who wrote the code for utilising jenas
inferencing.
How urgent is the question? This week is a little
inconvenient, as a
deadline for an important Semantic Web conference is on
Friday :(
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http
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| Re: OWL inference problem with Jena |
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2007-12-11 07:53:24 |
Hi Benjamin!
Thank you for your answer. It's not urgent, and anyway I'll
be happy
to receive some advice/feedback when using OWL with
ActiveRDF (with
Jena preferably or whatever), as I can't find too much info
on this. I
think semantic web is more interesting as long as advanced
inferencing
is possible, so that an added value is obtained when using
ontologies
in comparison to not using them.
2007/12/11, Benjamin Heitmann <benjamin.heitmannderi.org>:
>
> Hello Josè!
>
> On 10.12.2007, at 17:45, José Ignacio wrote:
>
> > I'm trying to use OWL inferencing with the Jena
adapter. However,
> > type, kind_of? and is_a? methods don't work as I
expect.
>
> Great to hear from somebody who is trying out Jena and
OWL inferencing.
>
> I myself did not try out the Jena inferencing, but I
forwarded your
> email to the person who wrote the code for utilising
jenas inferencing.
>
> How urgent is the question? This week is a little
inconvenient, as a
> deadline for an important Semantic Web conference is on
Friday :(
>
>
> _______________________________________________
> ActiveRDF mailing list
> ActiveRDFlists.deri.org
> http
://lists.deri.org/mailman/listinfo/activerdf
>
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http
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| Re: OWL inference problem with Jena |
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2007-12-20 05:21:01 |
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It seems that the problem is solved by changing line 314 of activerdf-jena's objectmanager/resource.rb:
before:
db.add(self, p, o)
after:
db.add(self, p, o) if !o.nil?
I've tried with simpler ontologies, so it might be related with ontology complexity. May it be a problem with a blank node?
Also, I used is_a? instead of instance_of?, which has the behaviour I desired.
2007/12/10, José Ignacio < joseignacio.fernandezgmail.com">joseignacio.fernandezgmail.com
>:I'm trying to use OWL inferencing with the Jena adapter. However, type, kind_of? and is_a? methods don't work as I expect.
I've written the following code, which uses the pizza ontology:
require 'rubygems'
require 'active_rdf'
this_dir = File.dirname(File.expand_path(__FILE__))
adapter = ConnectionPool.add_data_source(:type => :jena, :ontology => :owl, :reasoner => :owl_micro)
adapter.load
(";
http://www.co-ode.org/ontologies/pizza/2007/02/12/pizza.owl";, :format => :rdfxml, :into => :default_model )
Namespace.register :pz, '
http://www.co-ode.org/ontologies/pizza/pizza.owl#';
Namespace.register :test, '
http://www.test.com#'
ObjectManager.construct_classes
a = PZ::Meatypizza.new TEST::new_pizza
a.save ; # => NativeException: java.lang.NullPointerException: null from LiteralLabel.java:382:in `com.hp.hpl.jena.graph.impl.LiteralLabel.getDefaultHashcode'
a.type ; # => [PZ::Meatypizza, RDFS::Resource, OWL::Thing, PZ:omainconcept, PZ::Food, PZ::Pizza]
a.is_a? PZ::Meatypizza # => true
a.is_a? PZ::Pizza ; # => false ?????
which is wrong, though PZ::Pizza is inferred and listed with
a.type
When trying the same with a bad URI, no exceptions are thrown when saving, but no inferencing is done.
a = PZ::Meatypizza.new 'bad_uri'
a.save ; # works
a.type ; # => [RDFS::Resource, PZ::Meatypizza]
a.is_a? PZ::Meatypizza # => true
a.is_a? RDFS::Resource # => false
a.is_a? PZ::Pizza ; # => false
Is this normal behaviour? If not, is there a bug in the Jena adapter or ActiveRDF or is there a problem with the ontology?
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| Re: Re: OWL inference problem with Jena |
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2007-12-20 09:28:35 |
On 20.12.2007, at 12:21, José Ignacio wrote:
> It seems that the problem is solved by changing line
314 of
> activerdf-jena's
> objectmanager/resource.rb:
>
> before:
> db.add(self, p, o)
>
> after:
> db.add(self, p, o) if !o.nil?
>
> I've tried with simpler ontologies, so it might be
related with
> ontology
> complexity. May it be a problem with a blank node?
>
> Also, I used is_a? instead of instance_of?, which has
the behaviour I
> desired.
Thanks for researching this issue, I will take a look at it
as soon
as possible.
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