Protégé as SKOS editor


Dr Nicolas Figay, HDR shared Combined usage of SKOS and OWL: an experimentation on the Digital Europa Thesaurus, which among others addresses the visualization of semantic graphs. The report includes: Experimentation Step 2: opening a SKOS thesaurus with Protégé with import of SKOS RDF Schema for OWL DL. I had difficulties in obtaining the same outcome as reported and by 24. March 2023 added a comment on this. Dialogue with colleague Volkan Çağdaş, volkan@yildiz.edu.tr, provided a solution. The outcome is presented below.

Use of Protégé as SKOS editor


Start Protégé. Via File / Open open your SKOS file.
    Via the Classes tab you should see among others skos:Concept, and
    Via the Entities tab you should see the many Individuals of skos:Concept

Back to the Active ontology tab.
    The lower third of the window presents a sub-window with title Imported ontologies.
    The relevant ontology is rendered by the file ‘skos-owl1-dl.rdf’ , which may be imported directly from http://www.w3.org/TR/skos-reference/skos-owl1-dl.rdf. Alternatively, the file may be downloaded and stored locally, before it is imported (to reduce transfer time during import).
    The imported file should now be mentioned among Imported ontologies.

Via File/Save save and integrate the files. - Do note that the integration implies that the saved file includes both a link to the imported file/ ontology, but also a re-arrangement of the namespaces above. The original SKOS .rdf files should thus be kept in a different folder, or strict naming rules applied.
    Via the ObjectProperty tab notice the rich hierarchy of semantic relations.
    Via Windows / Views / Individual views / Annotations you get access to the content of the SKOS file and can start editing.

The file you saved includes as mentioned above both the imported file/ ontology, but also a re-arrangement of the namespaces. Most likely it is stored with a .rdf extension. You may change the extension from .rdf to .owl (e.g. when you save the file first time). Then (next day) when you start Protégé and open the .owl file, you should be able to to start editing right away. But do be concerned to navigate between the .owl compliant and the .rdf compliant version of your SKOS file.
 

Visualization of SKOS broader and narrower relations, etc. by means of Protégé and OntoGraf

Start Protégé. Via File / Open open your SKOS file, import ‘skos-owl1-dl.rdf’, and save (if it is not done already).

Via Windows / Tabs / (List of tabs) make sure that OntoGraf is marked

Click the OntoGraf tab. When the window opens, in the Search entry, write the name of an Individual and click the Search button. A number of concept relations should appear in various colors. In the line below the Search entry and button, find and click the ArcTypes button.
    If the number of ArcTypes is only two, go to File / Open . You are asked whether you want to open in the current window. Respond: No, and select the file that you just stored.
    Again find Windows / Tabs / OntoGraf . Click OntoGraf and repeat the search – or search another Individual.
    Now you should be able to edit the depiction of semantic relations among the Individuals.

In the default setting, clicking the Search button presents Individuals which ‘contains’ the searched concept. Additionally, from the field to the right of the Search entry, you may select other options (starts with, ends with, exact match, regexp) to get other related Individuals.

Again, if your SKOS file is saved with .owl extension, you should be able to go directly to OntoGraf and visual editing.


Erik Stubkjær, est@plan.aau.dk, 2023-05-22.