We provide a model-theoretic semantics based on deferred updates, which means that update requests are determined and collected in an evaluation phase without changing the database state and the corresponding updates are performed in a subsequent materialization phase. From a practical point of view, however, a straightforward implementation of the logical semantics is not satisfactory. In this paper we describe some of the arising problems and outline a flexible system architecture, which can serve as a framework for the implementation.
Recovery is done by issuing compensating operations in case of failure.
Although the architecture appears to be rather different from the logical concepts at a first glance, we actually stay close to the logical semantics and can exploit a significant amount of the evaluation flexibility provided by the LOLA system. In particular, we are not tied to a pure top-down evaluation with backtracking.