Hi Jens,
Il giorno 15/lug/09, alle ore 17:04, Jens Lehmann ha scritto:
Hello Piero,
Piero Molino schrieb:
Hello everyone,
Now, i don't know where to start from for doing this (my software is
in java). Wich dump should i use? Anyone knows reliable opensource
libraries for managing owl (i never used it before so i'm really new
to it)?
There are several ways to achieve this depending on how exactly you
measure distance between classes. One way would be to use SPARQL and
query the official endpoint, e.g. using Jena [1]. The second way would
be to use the OWL API [2]. What to do specifically, depends on your
distance metric.
Ok thankyou, the two libraires you're suggesting me are an extremely
good starting point.
For instance, you could ask yourself whether two
classes A1 and A2 are similar in your scenario if A1 is a super
class of
A2.(?) A simple way would be to query parent classes of A1 until a
class
A' is found, which is also parent of A2. You then get a path from A1
to
A2 with A' as middle element and can measure its length. Due to the
existence of owl:Thing such a path always exists.
This remembers me of leacock chodorow measure used in my research lab
for calculating semantic distance in wordnet. The fact that there's a
class wich is a kind of root is a good thing for this. There's
something alse like that i should know? Or can you even suggest me
something like a tool for visualizing the ontology and became aware of
his characteristics? (in a university course we used protege for
building example ontologies, could it be useful?)
Google comes up with a
few papers with more sophisticated approaches related to measuring
distance in ontologies [3,4,5], which might be helpful.
It's really funny that the second paper you're suggesting me has been
done by researchers in the same laboratory of the same university i'm
actually working in :) so i thank you for your suggestion and i will
probably go ask them some suggestion about distance metrics.
Is there some kind of limitation i'm not aware of that can
stop me doing what i described?
In your description, you assume that there is one class for each
object.
In general, an object can be instance of several classes. In
particular,
it can also belong to several "most specific" classes. However, this
does seem to be rare in the DBpedia ontology (and you can generalise
the
above description to this case).
Ok i get it. Now for example let's take:
http://dbpedia.org/page/Bari
(my home town). the rdf:type property (wich i'm assuming is the one
useful for the maping) gives back:
rdf:type
dbpedia-owl:Place
dbpedia-owl:Area
dbpedia-owl:Resource
dbpedia-owl:PopulatedPlace
http://dbpedia.org/class/yago/AncientGreekCities
http://dbpedia.org/class/yago/CitiesAndTownsInApulia
http://dbpedia.org/class/yago/CoastalCitiesAndTownsInItaly
http://dbpedia.org/class/yago/PortCitiesInItaly
Googling yago i've found it's an ontology based on wordnet structer
(more or less). By the way as you told me the classes are one more
specific than another. Is there a way to determinate how "deep" a
class is other than calculating a path to owl:Thing ? I'm asking this
because right now i'm thinking of mapping an instance to one class,
maybe the most specific one, by te way i may find come other ways like
map to every class and than take the deepest... i don't know i will
have to think a bit more about this :)
Kind regards,
Jens
Thank you again.
Regards,
Piero
[1]http://jena.sourceforge.net/
[2]http://owlapi.sourceforge.net/
[3]http://www.aaai.org/Papers/Workshops/2005/WS-05-01/WS05-01-015.pdf
[4]http://www.di.uniba.it/~cdamato/kes2008-AKS_Track.pdf
[5]http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?tp=&arnumber=4444245&isnumber=4444190
--
Dipl. Inf. Jens Lehmann
Department of Computer Science, University of Leipzig
Homepage: http://www.jens-lehmann.org
GPG Key: http://jens-lehmann.org/jens_lehmann.asc
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