Handling Bipolar Queries in Fuzzy Information Processing

The chapter advocates the interest of distinguishing between negative and positive preferences in the processing of flexible queries. Negative preferences express what is (more or less, or completely) impossible or undesirable, and by complementation, they specify flexible constraints restricting feasible or tolerated values. Positive preferences are less compulsory, and rather express wishes; they specify attribute values that would be really satisfactory. Because they are often expressed independently, negative and positive preferences may be inconsistent. Consistency is then restored by giving priority to negative preferences, since they express genuine constraints. The chapter discusses the handling of bipolar queries, that is, queries involving negative and positive preferences, in the framework of possibility theory. Both ordinary queries expressed in terms of flexible requirements and case-based queries referring to examples and counterexamples are considered in this perspective.