The role of abduction in database view updating

Abstract

The problem of view updating in databases consists in modifying the extension of view relations (i.e., relations defined in terms of “base” ones) transforming only the content of the extensional database, i.e., the extensional representation of base relations. This task is non-deductive in nature and its relationships with non-monotonic reasoning, and specifically with abduction, have been recently pointed out. In the paper we investigate the role of abduction in view updating, singling out similarities and differences between view updating and abduction. View updating is regarded as a two-step process: first, view definitions (and constraints) are used to reduce a view update into updates on base relations; then, the content of the extensional database is taken into account to determine the actual transformations to be performed. The first step is abductive in nature; we apply to such a step a definition of abduction based on deduction, which characterizes by means of a unique logical formula the conditions on base predicates which accomplish an update request. We then show how, in the second step, the set of transactions to be performed can be obtained from the formula generated in the first step. We provide a formal result showing the correctness of the approach.