An Introduction to the Fuzzy Set and Possibility Theory-Based Treatment of Flexible Queries and Uncertain or Imprecise Databases

The information to be stored in databases is not always precise and certain, and, occasionally, some information might be missing altogether.1 When the available information is imperfect, it is often desirable to try to represent it in the database nonetheless, so that it can be used to answer queries of interest as much as possible. A related issue is the handling of imperfect or flexible queries. For example, a natural query language may use a word or a phrase whose meaning is vague or even entirely unclear. As another example, a query may reflect a user’s uncertainty about what he is looking for. In addition, one may want to use vague predicates in a query to express pbl]References among the admissible answers.