This paper presents a middleware that supports reliable web services built on active replication. The middleware is responsible for maintaining the consistency of the replicas' states. A Java package for handling the interactions with the middleware and the failures of the web services is provided for programmers to use when writing client applications. The package reduces the complexity in developing client applications.

Temporal databases maintain past, present and future data. TSQL2 is a query language designed for temporal databases. In TSQL2, the GROUP BY clause has the temporal grouping property. In temporal grouping, the time line of each attribute value is partitioned into several sections, and aggregate functions are computed for each time partition. This paper describes two approaches to parallelising an algorithm for computing temporal aggregates. The two approaches have been implemented on a n SGl Powerchallenge SIMP parallel system. The experimental results show that the performance of the two approaches depends on data skew ratio and the number of processors used in the computation.

Distributed termination detection concerns deteciing the termination of a distributed computation spread across a set of processors. Most solutions to the problem are not intended for dynamic systems where processes can be created and destroyed during the computation. I n this paper, a termination detection algorzthm which can be applied to both static and dynamic systems is proposed. The scheme can be applied to any kind of connection topology. The number of control messages is lower than some previous approaches.

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