Thesauri and ontologies in digital libraries

This introductory tutorial is intended for anyone concerned with subject access to digital libraries. It provides a bridge by presenting methods of subject access as treated in an information studies program for those coming to digital libraries from other fields. It elucidates through examples the conceptual and vocabulary problems users face when searching digital libraries. It then shows how a well-structured thesaurus/ontology can be used as the knowledge base for an interface that can assist users with search topic clarification (for example through browsing well-structured hierarchies and guided facet analysis) and with finding good search terms (through query term mapping and query term expansion - synonyms and hierarchic inclusion). It touches on cross-database and cross-language searching as natural extensions of these functions. It also mentions the use of more richly structured ontologies, including semantic Web applications. The tutorial covers the thesaurus structure needed to support these functions: concept-term relationships for vocabulary control and synonym expansion, conceptual structure (semantic analysis, facets, and hierarchy) for topic clarification and hierarchic query term expansion). It introduces a few sample thesauri and some thesaurus-supported digital libraries and Web sites to illustrate these principles