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DIP is a DLQueryTab-style plugin for the Protégé Desktop Ontology Editor (version 5.0 and higher) allowing users to specify which SubClass axioms in their ontologies should hold "in general" but permit exceptions. For example: Student SubClassOf not (pays some Tax) does not permit exceptions like EmployedStudent SubClassOf Student and (pays some Tax) because EmployedStudent would be unsatisfiable. However, in DIP one is able to "flag" the former axiom to be defeasible (susceptible to overruling).
DIP is then able to provide reasoning services that derive sensible conclusions with these statements. In particular, DIP allows the user to:
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Toggle SubClass axioms in the ontology to be treated as defeasible.
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Identify class expressions violating defeasible SubClass axioms (i.e. the exceptions).
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Find all named SuperClasses of a user-specified class expression.
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Find all instances of a user-specified class expression.
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View all defeasible SubClass axioms separately from the rest of the ontology.
The plugin can be enabled in Protégé via the Window->Tabs menu item. The component views of the plugin are also accessible via the Window->Views->DIP views menu item.
Option 1: (Manual method)
Step 1. Click on the annotations button for the selected SubClass axiom in Protégé.
Step 2. Click on the (+) button to add an annotation.
Step 3. If there is an existing "defeasible" annotation property with IRI "http://cair.za.net/defeasible", skip to Step 5. If not, create it.
Step 4. Ensure that the created property has the same settings as pictured below by clicking on "New entity options...".
Step 5. Set the type of the defeasible annotation property to "xsd:boolean" and the value to "true".
Step 6. Click OK to add this annotation to the selected SubClass axiom. The axiom will now be considered as defeasible by the DIP Plugin.
Step 7. Once your ontology contains the defeasible annotation property, you can repeat Steps 1, 2, 5 and 6 for each axiom that you would like to make defeasible.
Note: to make an axiom non-defeasible again, click on the (x) button to remove its defeasible annotation as shown below
Option 2: (Installing an extension to Protégé's editor plugin)
Step 1. If Protégé is open, close it.
Step 2. Replace protege-editor-owl.jar in the bundles/ directory of your Protégé Desktop installation with the downloaded file. Backup the original protege-editor-owl.jar so you can revert back to it if the downloaded file does not function correctly.
Step 3. Fire up Protégé again. If the plugin is correctly recognised you will see an additional button labeled "d" on each SubClass axiom in Protégé. Clicking this button will toggle the defeasibility of the axiom (it provides an automated way to add/remove the annotation described in Option 1 of this guide).
