The question posed in this thesis is how the use of ontologies by information systems affects their development and their performance. Several aspects about ontologies are presented, namely design and implementation issues, representational languages, and tools for ontology manipulation. The effects of the combination of ontologies and information systems are then investigated. An ontology-based tool to identify email message features is presented, and its implementation and execution details are discussed. The use of ontologies by information systems provides a better understanding about their requirements, reduces their development time, and supports knowledge management during execution time
