Transaction Logic with (Complex) Events

Sem PDF.This work deals with the problem of combining reactive features, such as the ability to respond to events and define complex events, with the execution of ACID transactions over general Knowledge Bases (KBs). With this as goal, we build on Transaction Logic (T R), a logic precisely designed to model and execute (ACID) transactions in KBs defined by arbitrary logic theories. In it, transactions are written in a logic- programming style, by combining primitive update operations over a general KB, with the usual logic programming connectives and some additional connectives e.g. to express sequence of actions. While T R is a natural choice to deal with transactions, it remains the question whether T R can be used to express complex events, but also to deal simultaneously with the detection of complex events and the execution of transactions. In this paper we show that the former is possible while the latter is not. For that, we start by illustrating how T R can express complex events, and in particular, how SNOOP event expressions can be translated in the logic. Afterwards, we show why T R fails to deal with the two issues together, and propose Transaction Logic with Events to solve the intended problem. The achieved solution is a non-monotonic conservative extension of T R, which guarantees that every complex event detected in a transaction is necessarily responded. Along with its syntax, model theory and executional semantics, we prove some properties, including that it is indeed a conservative extension, and that it enjoys from important properties of non-monotonic logics, like support.publishe

Active Database Rules with Transaction-Conscious Stable-Model Semantics

Semantics represents a major problem area for active databases inasmuch as (i) there is no formal framework for defining an implementationindependent semantics of active rules, and (ii) the various systems developed so far have ad-hoc operational semantics that are widely different from each other. This situation contributes to the difficulty of predicting the run-time behavior of sets of rules: thus, ensuring the termination of a given set of rules is currently viewed as a major research issue. In this paper, we introduce a durable change semantics for active database rules; this semantics improves Starburst's deferred activation notion with concepts taken from Postgres and Heraclitus and the semantic foundations of deductive databases. We provide a formal logic-based model for this transaction-oriented semantics, show that it is amenable to efficient implementation, and prove that it solves the non-termination problem. 1 Introduction Several active database languages and systems hav..