Ontology Maintenance with an Algebraic Methodology: a Case Study *
J. Jannink, Gio C. M. Wiederhold · 2003
There is a growing need to combine information from multiple existing knowledge bases for unanticipated us-es, and to maintain such information when the underly-ing knowledge bases change. The autonomy of diverse knowledge sources is an obstacle to integrating all per-tinent knowledge within a single knowledge base. The cost of maintaining integrated knowledge within a sin-gle knowledge base grows both with the volatility and the number of the sources from which the information originates. Establishing and maintaining application specific portions of knowledge sources are therefore ma-jor challenges to ontology management. Rather than materializing all of the information from the sources into a single knowledge base, we are de-veloping an algebra that enables the construction of virtual knowledge bases geared towards a specific appli-cation. This algebra consists of composable operators that transform contexts into contexts. Operators ex-press the relevant parts of a source and the conditions for combining sources using a rule language. The rules define what is necessary to achieve a valid transfor-mation from the source information to the application context. Rules which expose the relevant parts of a source determine what we call a congruity measure be-tween the source and its target application. The rules which articulate knowledge from diverse sources estab-lish a similarity measure between them. We focus on one example to show how the use of our al-gebra is an important framework for establishing new applications using existing knowledge, and for main-taining up to date knowledge in the face of changes to the underlying sources. We have used an on-line dic-tionary that is autonomously maintained to develop a novel thesaurus application. With over 112,000 entries, two million words in the definitions, and semi-annual updates, this dictionary has provided us with a test bed to examine the issues of creation and maintenance of knowledge contexts using an algebraic methodology.