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# Searching a traditional OPAC

- Using expert knowledge and expert languages (subject terms vs. title terms; controlled vs. uncontrolled vocabularies)
- Controlled Vocabulary is unknown to a user (what are subject terms?)
- Formulating Boolean queries is still difficult (different semantics of AND and OR in formal and in natural language)
- Example query:
  AUTHOR ="jackson, peter" AND
  DESCRIPTOR =expert system* AND
  PUBLISHER =addison-wesley AND
  PUBLICATION-TIME >=1995

University of Hagen, IICS, Johannes.Leveling@fernuni-hagen.de