Comparing Ontologies — Similarity Measures and a Comparison Study

Ontologies serve as a means for communication at a semantic level. However, to be able to effectively communicate it is first necessary to determine agreement about the ontological structures underlying the communication. For this purpose, we consider ontologies as semiotic sign systems that are used to communicate meaning. Then we propose a methodology for measuring the extents to which two ontologies overlap and fit with each other at various semiotic levels. The measures that we propose are substantiated by a comparison study, where five human subjects have constructed ontologies about the same domain, but in isolation from each other. Building on this set of ontologies we have performed a multiple-phase cross-evaluation in order to determine adequacy of the measures proposed and inter-subject agreement about domain ontologies.