Enhancing dependability through flexible adaptation to changing requirements

This paper describes an architectural approach that facilitates the dynamic adaptation of systems to changing domain rules. The approach relies on 'coordination contracts', a modelling and implementation primitive we have developed for run-time reconfiguration. Our framework includes an engine that, whenever a service is called, checks the domain rules that are applicable and configures the response of the service before proceeding with the call. This approach enhances dependability in two essential ways: on the one hand, it guarantees that system execution is always consistent with the domain logic because service response is configured automatically (i.e., without any need for programmer intervention); on the other hand, it makes it possible for changes to be incorporated into existing domain rules, and from new rules to be created, with little effort, because coordination contracts can be superposed dynamically without having to change neither the client nor the service code. Our approach is illustrated through a case study in financial systems, an area in which dependability arises mainly in the guise of business concerns like adherence to agreed policies and conditions negotiated on a case-by-case basis. We report on an information system that ATX Software developed for a company specialised in recovering bad credit. We show in particular how, by using this framework, we have devised a way of generating rule-dependent SQL code for batch-oriented services

Enveloping Sophisticated Tools into Process-Centered Environments

We present a tool integration strategy based on enveloping pre-existing tools without source code modifications or recompilation, and without assuming an extension language, application programming interface, or any other special capabilities on the part of the tool. This Black Box enveloping (or wrapping) idea has existed for a long time, but was previously restricted to relatively simple tools. We describe the design and implementation of, and experimentation with, a new Black Box enveloping facility intended for sophisticated tools --- with particular concern for the emerging class of groupware applications

Computer Science in Japanese Universities

This paper presents some impressions of computer science in Japanese universities based on the authors' sabbatical visits. The focus is primarily on such structural aspects of the discipline as departmental organization, faculty and student populations, funding, research activity, and computing facilities. Perhaps the key observation is that Japanese cultural practices influence the way in which computer science is approached in Japanese universities to a larger degree than might be imagined. Key words: Japanese universities, computer science, cultural influences. 1 Introduction Despite the association of Japan with high technology, most Western scientists know little about computer science in Japan. Many factors contribute to this phenomenon, including language and cultural differences, a shortage of readily available information, and a degree of technical chauvinism. The problem is aggravated by a general lack of the kind of widespread long-term individual contacts between compute..

Realities of calibrating terrorism threats:[Re]Learning from three maritime events

Over the last ten years there has been a major shift in programming language design from procedural languages to object-oriented languages. Most universities have adopted an object-oriented language for their first programming course. However, far less consideration has been given to the program development environment. In this paper we argue that the environment is possibly more important than the language and existing environments fail to fully support the object-oriented paradigm. We describe a new program development environment and show how it has been specifically designed to support object-oriented design and programming

Reasoning About Implicit Invocation

Implicit invocation [SN92, GN91] has become an important architectural style for large-scale system design and evolution. This paper addresses the lack of specification and verification formalisms for such systems. Based on standard notions from process algebra and trace semantics, we define a formal computational model for implicit invocation. A verification methodology is presented that supports linear time temporal logic and compositional reasoning. First, the entire system is partioned into groups of components (methods) that behave independently. Then, local properties are proved for each of the groups. A precise description of the cause and the effect of an event supports this step. Using local correctness, independence of groups, and properties of the delivery of events, we infer the desired property of the overall system. Two detailed examples illustrate the use of our framework. 1 Introduction A critical issue for large-scale systems design and evolution is the choice of an ..

_.I Abstract Reasoning about implicit invocation*

Implicit invocation [SN92, GN91] has become an important architectural style for large-scale system design and evolu-tion. This paper addresses the lack of specification and ver-ification formalisms for such systems. Based on standard notions from process algebra and trace semantics, we define a formal computational model for implicit invocation. A verification methodology is presented that supports linear time temporal logic and compositional reasoning. First, the enbire system is partioned into groups of components (meth-ods) that behave independently. Then, local properties are proved for each of the groups. A precise description of the cause and the effect of an event supports this step. Using local correct,ness, independence of groups, and properties of the delivery of events, we infer the desired property of the overall system. Two detailed examples illustrate the use of our framework.