The world is constantly changing, and so does required and available knowledge, e.g. stored in Digital Libraries. Knowledge workers heavily rely on the availability and accessibility of knowledge contained in such libraries. The sheer mass of knowledge available today, however, requires sophisticated support for searching and, often considered as equally important, personalization.
In SEKT we address these challenges by using ontologies. Ontologies by nature make implicit knowledge explicit, they describe relevant parts of the world and make them machine understandable and processable. To be effective, ontologies need to change possibly as fast as the parts of the world they describe.
Change discovery aims at generating implicit requirements by inducing ontology changes from existing data. In this deliverable we focus on usage-driven change discovery. Usage data is a very valuable source of contextual information, based on which the ontology can be modified in order to reflect changes in the real world,
We describe a framework, in which ontology evolution and discovering potentially useful changes can be formalized as an optimization problem. ... mehrWe introduce the notion of an evaluation function that allows to measure the quality of an ontology with respect to given criteria. We instantiate the framework for the task of ontology pruning based on usage data, and for the task of collaborative evolution in a multi-user scenario, in which users maintain personalized ontologies. A first case study based on the Bibster system shows very promising results.