A Framework for Structured Distributed Object Computing

This paper presents a four-faceted framework for distributed applications that use worldwide networks connecting large numbers of people, software tools, monitoring instruments, and control devices. We describe a class of applications, identify requirements for a framework that supports these applications, and propose a design fulfilling those requirements. We discuss some initial experiences using the framework, and compare our design with other approaches

Dynamic UNITY

Dynamic distributed systems, where a changing set of communicating processes must interoperate to accomplish particular computational tasks, are becoming extremely important. Designing and implementing these systems, and verifying the correctness of the designs and implementations, are difficult tasks. The goal of this thesis is to make these tasks easier. This thesis presents a specification language for dynamic distributed systems, based on Chandy and Misra's UNITY language. It extends the UNITY language to enable process creation, process deletion, and dynamic communication patterns. The thesis defines an execution model for systems specified in this language, which leads to a proof logic similar to that of UNITY. While extending UNITY logic to correctly handle systems with dynamic behavior, this logic retains the familiar UNITY operators and most of the proof rules associated with them. The thesis presents specifications for three example dynamic distributed systems to demonstrate the use of the specification language, and full correctness proofs for two of these systems and a partial correctness proof for the third to demonstrate the use of the proof logic. The thesis details a method for determining whether a system in the specification language can be transformed into an implementation in a standard programming language, as well as a method for performing this transformation on those specifications that can. This guarantees a correct implementation for any specification that can be so transformed

Migração de sistemas legados para ambiente de suporte a projetos e operação

Orientador : Geovane Cayres MagalhãesDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de ComputaçãoResumo: Sistemas de Informação são imprescindíveis nas grandes corporações. Particularmente nas áreas de suporte a projeto e operações de empresas de telecomunicações, os sistemas de informação são a grande vantagem competitiva. Estes sistemas devem ser :flexíveis, estáveis e confiáveis para suportar grandes volumes de transações em um cenário de missão crítica. Este, porém, não é o ambiente mais comum nas grandes empresas. A quantidade de sistemas in:flexíveis, sem documentação, com dados pouco confiáveis e com alto custo de evolução e manutenção é grande. A saída para este impasse está na migração destes sistemas legados para um ambiente de sistemas de informação com arquitetura aberta, ambiente distribuído e que possam ser utilizados por todas as áreas, estando integrados com os demais sistemas da empresa. A migração destes grandes sistemas legados de uma forma abrupta seria um fracasso principalmente em virtude do desconhecimento dos sistemas legados. A migração incremental destes sistemas é a mais apropriada nestes casos. Esta dissertação apresenta uma metodologia para migração de sistemas legados para ambientes de suporte a projetos e operação em etapas. A metodologia desenvolvida foi validada num caso prático no contexto do SAGRE - um sistema de suporte a operações, projetos e informações geográficas desenvolvido pelo CPqDAbstract: Information Systems are essential for corporations. Particularly at design and operational support areas of telecommunications companies, information systems are the competitive advantage. These systems must be :flexible, stable and reliable in order to support a great volume of transactions in a mission critical scenarÍo. This is not the common environment within corporations. There is an expressive amount of inflexible, nondocumented, unreliable systems which bear costly maintenance and evolution. The solution for this situation is the migration of these legacy systems into a new integrated and distributed environment that can also be used by other corporate systems. The abrupt migration ofthese systems could not be successful due to a lack ofknowledge about them. The incremental approach is more appropriate in these cases. This dissertation shows a methodology for migrating legacy systems that support design and operational environments in an incremental mode. The methodology is validated by a case study within the context of SAGRE - a system which support geographic operations, projects and information, developed by CPqDMestradoMestre em Ciência da Computaçã

Bayesian decision support in complex modular systems : an algebraic and graphical approach

Nowadays decision centres are required to make choices in complex and evolving environments, described through multiple and interdependent processes with many associated measurements. The objective of a real time decision making centre is to agree to a sequence of efficacious countermeasures. To achieve this it is usually necessary to integrate opinions and information from an often diverse set of stakeholders, articulating several competing objectives and knowledge over different domains of expertise. A collection of decision support systems can enhance such an integration, not only ensuring that all relevant evidence systematically informs policy making, but also encouraging the decision centre to exhibit an underlying consistency across all its components and to address the problem as a whole. In this thesis we develop a formal framework, extending standard Bayesian methodology, enabling the judgements and the models of groups of experts to be coherently aggregated in a unique entity. We discuss when and how it is possible to do so and the conditions the group needs to agree upon. We call this framework integrating decision support system. We then develop a variety of methodologies to enhance such an integration, enabling integrating decision support systems to be feasibly used in practice

A Framework for Structured Distributed Object Computing

This paper presents a four-faceted framework for distributed applications that use worldwide net-works connecting large numbers of people, software tools, monitoring instruments, and control devices. We describe a class of applications, identify requirements for a framework that supports these applications, and propose a design fulfilling those requirements. We discuss some initial experiences using the framework, and compare our design with other approaches