Canonical Databases and Certain Answers under Key Constraints

摘要: AbstractIt is an important question to ask what can be deduced from agiven view instance and knowledge about the relational schema withits constraints. We present a procedure which computes minimaldatabase that yields given satis es con-straints on schema. It minimal in sense itcontains exactly certain answers queries asking for basic rela-tions. In this paper, we consider only conjunctive de nitions andunique key CR Categories: H.2.7 [Database Administration]: Security, Integrity, Pro-tection; I.2.4 [Knowledge Representation Formalisms Methods] RelationSystemsGeneral Terms: SecurityAdditional Keywords: Data Privacy, Dependecies, Logical Inference 1 Introduction This paper deals with problem of constructing canonical database in-stances computing presence unique con-straints. The research presented here originates whatcan set assuming thatone has constraints nedon it.Key or functional dependencies are fundamental concept thetheory applications databases [2, 13]. Such donot guarantee consistency data stored database. Theyalso provide (meta-)information theconnections between di erent attributes occuring table nitions. Onone hand information explanatory nature user. On the1