Handling Bipolar Queries in Fuzzy Information Processing

Flexible queries have aroused an increasing interest for many years in the database literature (Bosc & Pivert, 1992; Christiansen, Larsen, & Andreasen, 1997; Larsen, Kacpryk, Zadrozny, Andreasen, & Christiansen, 2001), and the fuzzy set-based approach to this problem, introduced about 25 years ago, has been developed both at the theoretical and the practical levels through many works (e.g., Bosc & Kacprzyk, 1995; Petry, 1996). For recent references, see De Caluwe and De Tré (2007) and Galindo, Urrutia, and Piattini (2006). See also the overview chapter by Kacprzyk, Zadrozny, De Tré, and De Caluwe in this book. In almost all of these works, flexible queries are generally thought of in terms of conjunctions of constraints restricting possible values of attributes. By flexible queries, we mean that these constraints could be fuzzy or prioritized. Fuzzy constraints were introduced by Zadeh (1978) as fuzzy restrictions, induced by natural language AbstrAct