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[protege-owl] Modeling multiple distinct relations of one instance using GraphWidgets

Paradies, Simon simon.paradies.ext at siemens.com
Wed Oct 29 09:14:47 PDT 2008


Hi all,

I would like to create an OWL-ontology in which instances can be modeled using the GraphWidget form functionality provided by Protégé 3.x. It should be possible to define multiple different relations between one instance and others of several types. Unfortunately, it is not possible to assign multiple connector slots to a single class (is there some reason other than "nobody has programmed it yet" for this?). 
Thus, I tried to use reification to circumvent the issue. First, I worked through the GraphWidget tutorial for OWL ontologies at http://protegewiki.stanford.edu/index.php/Graph_Widget_Tutorial_OWL but I was unable to locate the ClinicalTrialOntologyLite.pprj (where to get it?) and  the interesting part (reification) seems to be still missing. I was, however, able to produce reified properties using the N-ary relation pattern wizard but failed to have them rendered graphically using the GraphWidget.
Second, I followed the graph widget tutorial at http://protege.stanford.edu/doc/tutorial/graph_widget/ and tried to adopt the concepts to Protégé-OWL. To some point, I was successful but more on that below...
Relation reification seems to work a bit different (correct me when I am wrong) using either the N-ary relation pattern wizard or the design pattern described in the graph widget tutorial (non OWL). The difference is that in order to work with the GraphWidget, a reified relation (class) must be a child of protege:DIRECTED-BINARY-RELATION to inherit protege:FROM and protege:TO properties which are used to define valid endpoints of the relation. Using the N-ary relation pattern wizard, arbitrary properties could be defined for that purpose (does not work with GraphWidgets though).

Using protege:DIRECTED-BINARY-RELATION I made the following observations:
* the OWL sublanguage changed form DL to full (due to imported proprietary Protégé classes, i.e., protege:X?)
* it is not possible to control the cardinality, the parent's cardinality is always dominating the child's cardinality. Additionally, once a range is set, it is impossible to remove that range and it is valid for all classes below protege:DIRECTED-BINARY-RELATION. Compared to classical Protégé (slots), it seems that it is not possible to edit the slot at class but just the top level slot (it is no possibility to choose as in Protégé-classic). Is this a bug?

I was unable to fully adopt the modeling concepts for reified relations using GraphWidgets as described in http://protege.stanford.edu/doc/tutorial/graph_widget/ for non-OWL to OWL. Having replicated the Organization class of the newspaper example including all relevant relations and classes (including those in protege:DIRECTED-BINARY-RELATION), the reified relations tab still complains that the "http://www.owl-ontologies.com/ReificationTest#Organization has no slots that contain reified relations (subclasses of :DIRECTED-BINARY-RELATION)". This is true insofar as it just contains a property that relates to a reified relation (which is a class) as it is not possible to put classes in slots. However, it is modeled exactly equivalent (hopefully) to the newspaper example (non OWL). Is this a bug, am I missing something, or it is done differently in Protégé-OWL respectively?

Further questions:
* Supposed it is possible to model and render reified relations using GraphWidgets the same way in Protégé-OWL  as it is possible in Protégé-classic. How can I restrict the cardinality of relations then?
* Is there a way to accomplish instance modeling using GraphWidgets with the requirements described at the top using simple binary or n-ary relations (reifications) and thus keeping the sublanguage in OWL-DL? 

Thanks for attention,
Simon

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