Reconciling operational and declarative specifications

There arc two broad approaches to the specification of the dynamics of information systems, namely the operational and the declarative one. The declarative approach has advantages in terms of abstractness and of locality of infonnation. Its main drawback is the so called frame problem, i.e. the need to explicitly forbid unwanted changes. We propose an extension of the declarative approach which incorporates some aspects of the operational one, thereby eliminating the frame problem. The technique is illustrated on an example, and the resulting specification is compared with the corresponding operational and declarative ones.