ConCom - Concept Comparer

A tool for comparing instances of ontological concepts to evaluate their similarity measure.

Institution: Slovak University of Technology
Technologies used: Java, Sesame 1.2.7
Inputs: Publication meta-data ontology
Outputs: Similarity measure
Documentation: HTML, doc, JavaDoc

Addressed Problems

Many approaches acquire user characteristics for a user model to be populated or kept up to date and this way provide a basis for successful personalization of visible aspects in adaptive web-based applications. Some information can be acquired directly from the user (e.g., the user is asked a question, fills in a form), observations of user's behavior while working with the application, analysis of logs on the web server or analysis of the presented content. We focus on the analysis of the presented content especially on evaluation of the similarity to find common or different aspects of the content.

The user can express his or her satisfaction with displayed content. Knowing user's rating of displayed content we can acquire some characteristics by analyzing it. Since the rating varies on different contents we need to find out reasons why it is low or high.

To evaluate similarity measure between instances we proposed a method based on recursive evaluation of the properties compared instances consist of. The main idea of the method is aimed at looking for common property pairs present in both instances and their sequential processing. Every instance of the concept can consist of object or datatype properties that need to be treated differently. When a datatype property is evaluated the method ends after using a metric intended for comparing strings. Object properties are processed recursively by using respective metrics until literals are reached or until there are no properties left. When comparing two instances, properties can appear in different cardinalities:

  • single in both instances,
  • multiple in both instances,
  • single/multiple in one instance only.
Principle of method using recursive traversing of an instance

Principle of method using recursive traversing of an instance.

The total similarity of two instances is aggregated as the mean value of the similarities computed between elements connected to particular properties. When using aggregation of partial similarities the computed result is always the same no matter what the context is. Since each user has different preferences related to similarity, we consider this in similarity computation as well.

For personalization purposes, our goal is not only to compute the similarity between instances but also to investigate reasons that "caused" the similarity or difference. User preferences can be deduced from implicit and explicit user feedback (e.g., rating). We assume that if the instance includes a property which value the user likes it will likely influence his or her rating towards higher (or positive) values. On the other hand, properties of the content with the values that the user dislikes will influence rating towards lower (or negative) values.


  1. Andrejko, Anton - Bieliková, Mária. Investigating Similarity of Ontology Instances and Its Causes. In V. Kurkova, R. Neruda, J. Koutnik (eds.): Artificial Neural Networks - ICANN 2008, Prague, Czech Republic, LNCS 5164, Springer, 2008, pp. 1-10.
  2. Andrejko, Anton - Bieliková, Mária. Estimating similarity of the ontological concepts instances for the adaptive applications based on Semantic Web. [in Slovak] In Václav Snášel (ed.): Znalosti 2008: Proceedings of the 7th annual conference, Bratislava, February 13-15, 2008, pp. 30-41.
  3. Andrejko, Anton - Bieliková, Mária. Estimating similarity of the ontological concepts instances for personalization purposes. [in Slovak] In František Babič, Ján Paralič (eds.): 2nd Workshop on Intelligent and Knowledge Oriented Technologies, WIKT 2007 Proceedings, Košice, November 15-16, 2007, pp. 46-49.
  4. Andrejko, Anton - Bieliková, Mária. Comparing Instances of the Ontological Concepts. In: Tools for Acquisition, Organisation and Presenting of Information and Knowledge (2): Research Project Workshop Horský hotel Poľana, Slovakia September 22-23, 2007, pp. 26-35.
  5. Andrejko, Anton - Barla, Michal - Tvarožek, Michal. Comparing Ontological Concepts to Evaluate Similarity. In: Tools for Acguisition, Organisation and Presenting of Information and Knowledge : Research Project Workshop Bystrá dolina, Nízke Tatry, Slovakia, September 29-30, 2006, pp. 71-78.