Nested Transactions in a Logical Language for Active Rules

We present a hierarchically structured transaction oriented concept for a rule based active database system In LL LHL we have proposed Statelog as a uni ed framework for active and deductive rules Following the need for better structuring capabilities we intro duce procedures as a means to group semantically related rules and to encapsulate their behavior In addition to executing elementary updates procedures can be called thereby de ning sub transactions which may perform complex computations A Statelog procedure is a set of ECA style Datalog rules together with an import export interface System immanent frame and procedure rules ensure both propagation of facts and processing of results of committed subtransactions Thus Statelog programs specify a nested transaction model which allows a much more structured and natural modeling of complex transactions than previ ous approaches Two equivalent semantics for a Statelog program P are given i a logic programming style semantics by a compilation into a logic program and ii a model theoretic Kripke style semantics While ii serves as a conceptual model of active rule behavior and allows to reason about properties of the speci ed transactions i together with the appropriate execution model yields an operational semantics and can be used as an implementation of P