Object-level abduction for view updates

Many database systems provide the user with the possibility of defining views, i.e. mechanisms for introducing intensional definitions of relations among objects. The problem of view updat­ing (i.e. of modifying the extension of views) is an important one both in relational and in deductive databases, and consists in characterizing the set of transformations of the database (database state transitions) which accomplish an update request. This problem has interesting relationships with sorne problems studied in the Artificial Intelligence community, in the field of non-monotoning reasoning, and in particular with abduction (reasoning towards explana­ tions). In this paper we consider databases represented with a logical language and we show how abduction can be used to provide a semantics for view updates in such databases, characterizing with a unique formula the set of transactions which accomplish an update request. Such a formula is the result of a process taking into account the definitions in the intensional database, the defined constraints and the content of the extensional database. Toe process is similar to abduction as long as the extensional database is not considered