Extending the logical update view with transaction support

Since the database update view was standardised in the Prolog ISO standard, the so called logical update view is available in all actively maintained Prolog systems. While this update view provided a well defined update semantics and allows for efficient handling of dynamic code, it does not help in maintaining consistency of the dynamic database. With the introduction of multiple threads and deployment of Prolog in continuously running server applications, consistency of the dynamic database becomes important. In this article, we propose an extension to the generation-based implementation of the logical update view that supports transactions. Generation-based transactions have been implemented according to this description in the SWI-Prolog RDF store. The aim of this paper is to motivate transactions, outline an implementation and generate discussion on the desirable semantics and interface prior to implementation.Comment: Appeared in CICLOPS 2012. 9 Pages, 0 Figure

SICStus MT - A Multithreaded Execution Environment for SICStus Prolog

The development of intelligent software agents and other complex applications which continuously interact with their environments has been one of the reasons why explicit concurrency has become a necessity in a modern Prolog system today. Such applications need to perform several tasks which may be very different with respect to how they are implemented in Prolog. Performing these tasks simultaneously is very tedious without language support. This paper describes the design, implementation and evaluation of a prototype multithreaded execution environment for SICStus Prolog. The threads are dynamically managed using a small and compact set of Prolog primitives implemented in a portable way, requiring almost no support from the underlying operating system