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VisOn Documentation

 

VisOn (for Visualisation of Ontologies) is the tool initially developed to represent ontologies as graphs. It quickly evolved to embed the alignment functions and offers different functionalities. We hope this document will be helpful to anyone using VisOn, as it presents the several features available.

 

 

1. Getting the files and running the application

The last version of the OL-Graph implementation and the VisOn tool, as well as the alignment program, can be found on our CVS server by logging anonymously.

$ cvs -d :pserver:cvs@cvs-sop.inria.fr:/CVS/exmosoft login
- ENTER return when asked for the password -
$ cvs -d :pserver:cvs@cvs-sop.inria.fr:/CVS/exmosoft checkout ontoalign

The required packages are located in the lib/ directory of the archive. For example, you will find there the OWL API package and the modified JGraph JAR file. To run the application, just run the 'VisOn' target in ant after compiling.

$ ant compile
$ ant run VisOn

 

2. Building an OL-Graph from an ontology file

The VisOn tool is based upon the construction of graphs named OL-Graph from the OWL structure of the ontology. This work is done underneath each time the user loads an ontology. More details on the structure of OL-Graph coming soon. If you have any question, feel free to contact us.

 

3. Visualization of an ontology as an OL-Graph

The main window of VisOn allows to perform different operations, the different tabs corresponding to these functionalities.

The "Visualization" tab allows to visualize an ontology. To do so, you can load it from the local file system or typing its URI in the popup window appearing when choosing "File/Load...". You can also enter its URI directly in the address bar then pressing the "Visualize" button.

When the ontology is correctly loaded, its URI is displayed in the bar and the panel displays in as an OL-Graph.

 

4. Aligning two ontologies

The "Alignment" tab allows to perform an alignment between two ontologies, specifying their URI or using the "Load" button. You also have to define some important parameters for the alignment process, like the different weights of the entities and their properties. You must also choose the algorithm which will be used to align the ontologies, and the lexical function : right now, you can either use lexical similarity with WordNet or simply use a StringDistance function. These functions are listed in another file, similarityFunctions.xml.

The algorithms you wanna be able to use have to be described in the algorithms directory of the application. They are defined in XML files and contain different informations.

Click here to see a sample algorithm file.

Each 'param' item describes a parameter required for this algorithm. The sample file shows that this algorithm needs : the two OL-Graph objects built from the ontologies, the two OWLOntology objects, an existing alignment et a threshold.

This same algorithms directory must also contain a file named nodeWeights.xml, which describes the different weights for the entities, as well as their default values. The similarity computation uses these weights during the process, and you will have to set them by accessing the "Edit/Set Alignment Parameters" menu item. If they are not defined when you try to align two ontologies, you will be prompted to do so.

Once the alignment is performed, a table displays the aligned entities with the similarity measure between them, and you can save the alignment result in an XML file like this one.

Example of displayed results for the alignment of classes :

 

5. Visualizing two ontologies in a parallel way

The "Aliggnment Visualization" tab allows to visualize two ontologies side by side in order to compare their structure. In the future, once these ontologies are aligned it will be possible to see which entities go together : by clicking on an entity from the graph of first ontology, the second graph will focus on the aligned entity.

 

6. Alignment Evaluation

It is possible to compare two alignments performed between the same two ontologies, for example if you want to compare two different algorithms. To do so, you must select the "Alignments Comparison" tab, then load the two aligments from the local file system or by typing their URIs. You can then launch the comparison process, which will display the results that you can saved in an XML file.

<?xml version='1.0' encoding='utf-8' standalone='yes'?>
    <rdf:RDF xmlns:rdf='http://www.w3.org/1999/02/22-rdf-syntax-ns#'
xmlns:map='http://www.atl.external.lmco.com/projects/ontology/ResultsOntology.n3#'>
    <map:output rdf:about=''>
        <map:precision>1.0</map:precision>
        <map:recall>0.610738255033557</map:recall>
        <fallout>0.0</fallout>
        <map:fMeasure>0.7583333333333334</map:fMeasure>
        <map:oMeasure>0.610738255033557</map:oMeasure>
        <result>0.610738255033557</result>
    </map:output>
</rdf:RDF>

 

7. Alignment Production

It is possible to produce manually an alignment in the "Alignment Production" tab, choosing one by one the different entities you want to align and the value of the similarity.

8. Work in progress and improvements

Better errors management : Right now, some errors still cause the Java Exceptions to display in the console instead of displaying a popup message. It would be nice to centralize the error management to avoid this kind of behaviour.

Graph Layout : The layout problem has been put aside for now, but with big ontologies the displayed graph is not very clear. It depends from the JGraph community, who is working on the problem right now, but we could develop a specific algorithm for our application.

Graph look : It would be interesting for the user to be able to change the looks and the colors used to represent the entities.

 

 

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