Service order provisioning is an important telecommunication application that automates the process of providing telephone services in response to the customer requests. It is an example of a multi-system application that requires access to multiple, independently developed application systems and their databases. In this paper, we describe the design and implementation of a prototype system 1 that supports the execution of the Flexible Transactions and its use to develop the service order provisioning application. We argue that such approach may be used to support the development of multi-system, flow-through processing applications in a systematic and organized manner. Its advantages include fast and easy specification of new services, support for testing of the declaratively specified work-flows, and the specification of potential concurrency among the tasks constituting an application.

Orca is a portable, object-based distributed shared memory (DSM) system. This article studies and evaluates the design choices made in the Orca system and compares Orca with other DSMs. The article gives a quantitative analysis of Orca’s coherence protocol (based on write-updates with function shipping), the totally ordered group communication protocol, the strategy for object placement, and the all-software, user-space architecture. Performance measurements for 10 parallel applications illustrate the trade-offs made in the design of Orca and show that essentially the right design decisions have been made. A write-update protocol with function shipping is effective for Orca, especially since it is used in combination with techniques that avoid replicating objects that have a low read/write ratio. The overhead of totally ordered group communication on application performance is low. The Orca system is able to make near-optimal decisions for object placement and replication. In addition, the article compares the performance of Orca with that of a page-based DSM (TreadMarks) and another object-based DSM (CRL). It also analyzes the communication overhead of the DSMs for several applications. All performance measurements are done on a 32-node Pentium Pro cluster with Myrinet and Fast Ethernet networks. The results show that the Orca programs

Following Burstall, a flow diagram can be represented by a pair consisting of a graph and a functor from the free category to the category of sets and relations. A program is verified by incorporating the assertions of the Floyd-Naur proof method into a second functor and exhibiting a natural transformation to the program. A broader range of properties is obtained by substituting spans for relations and introducing oplaxness into both the functors representing programs and the natural transformations in the morphisms between programs. The apparent complexity of this generalization is overcome by the observation that an oplax functor J Sp(C) is essentially the same as a functor e J C where e J is the twisted arrow category of J. Thus, a program is a presheaf F (G) Set as are the properties of the program. By analogy with categorical models of first-order logic, a program and the properties which pertain to it are subobjects of a suitably chosen base object. In this setting safety ...

Introduction. The beginning of modern computer science can be marked by Alan Turings paper, which among other advances, showed that there are unsolvable problems. [1] Within the infinite set of solvable problems there is a set of technically feasible and problems that are not technically feasible to solve (e.g., problems that it would take a supercomputer of today 10,000 years to solve). Thus, from the beginning, computer science has been viewed as the science of problem solving using computers. One category of computer science research is devoted to outwardly encroaching upon the set of infeasible problems. Advances in computer hardware, for example, lead to more powerful computers that execute faster and have larger stores of memory. Advances in hardware are meant to result in improvements in the raw computing power of the devices that can be brought to bear in order to solve more complex problems. Additionally, research efforts focusing on complexity and alg