Transaction Logic with (Complex) Events

ABSTRACT. 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 (TR), a logic precisely designed to model and execute (ACID) transactions in KBs defined in 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 TR is a natural choice to deal with transactions, it remains the question whether if TR 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 TR can express and detect complex events, and in particular, how SNOOP event expressions can be translated in the logic. Afterwards, we show why TR 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 TR, which guarantees that every complex event detected in a transaction is necessarily responded. Along with its syntax, model theory and executional semantics, in this paper we prove the correspondence of Transaction Logic with Events with TR, and that it enjoys from important properties of non-monotonic logics, like support.