The concept of logic databases can serve as a clear and expressive foundation of various kinds of information systems. However, classical logic languages refer to a single database state, whereas in modern information systems it is necessary to take dynamic behaviour into account. For this purpose, several update languages have been proposed, among them [AHV95,BK94,BK96,C97,LHL95,MW88,MBM97,WF97a], which allow to specify complex transitions from one database state to another. From the evaluation point of view, a complex state transition can and should be considered as a transaction. Up to now, the isolation property of transactions has been poorly addressed in the context of logic update languages, although it is an important problem even for classical, sequential transactions (see [BHG87] for instance). In this paper we present the ULTRA approach and describe how isolation of independent transactions can be supported. We illustrate the results using an extended example.
Erika Cetindag, Martin Griebl