Ontology-based Similarity Measures andtheir Application in BioinformaticsDISSERTATIONZUR ERLANGUNG DES GRADES DESDOKTORS DER NATURWISSENSCHAFFTEN DERNATURWISSENSCHAFTLICH-TECHNISCHEN FAKULTÄTEN DERUNIVERSITÄT DES SAARLANDESeingereicht vonANDREAS SCHLICKERSaarbruecken, Mai 2010Tag des Kolloquiums: 02.11.2010Dekan der Fakultät: Prof. Dr. Holger HermannsVorsitzender des Prüfungsausschusses: Prof. Dr. Gerhard WeikumGutachter: Prof. Dr. Dr. Thomas LengauerDr. Mario AlbrechtDr. Marie-Dominique DevignesBeisitzer: Dr. Francisco S. DominguesAbstractGenome-wide sequencing projects of many different organisms produce large numbersof sequences that are functionally characterized using experimental and bioinformaticsmethods. Following the development of the first bio-ontologies, knowledge of the func-tions of genes and proteins is increasingly made available in a standardized format. Thisallows for devising approaches that directly exploit functional information using semanticand functional similarity measures. This thesis addresses different aspects of the devel-opment and application of such similarity measures.First, we analyze semantic and functional similarity measures and apply them forinvestigating the functional space in different taxa. Second, a new software program anda new database are described, which overcome limitations of existing tools and simplifythe utilization of similarity measures for different applications.