On Composing Separated Concerns, Composability and Composition Anomalies

It is generally acknowledged that separation of concerns is a key requirement for effective software engineering: it helps in managing the complexity of software and supports the maintainability of a software system. Separation of concerns makes only sense if the realizations in software of these concerns can be composed together effectively into a working program. The ability to compose systems from independently developed components that can be adapted and extended easily is a long-standing goal in the software engineering discipline. However, both research and practice have shown that composability of software is far from trivial and fails repeatedly. Typically this occurs when components exhibit complex behavior, in particular when multiple concerns are involved in a single component. We believe that, to address the composability problems, we need a better understanding of the requirements involved in successful composition, and in addition define the situations where composition fails. To this aim, in this paper we introduce a number of requirements for designlevel composability and define a category of composition problems that are inherent for given composition models, which we term as composition anomalies

Reconfiguration Service for Publish/Subscribe Middleware

Mission-critical, distributed systems are often designed as a set of distributed, components that interact using publish/subscribe middleware. Currently, in these systems, software components are usually statically allocated to the nodes to fulfil predictability, reliability requirements. However, a static allocation of components has major drawbacks, e.g. the need for quantification of the expenditure of resources to prevent a lack of resources during runtime. A dynamic allocation diminishes the drawbacks of a static allocation by reallocating components during system run-time. The process of dynamic reallocation is considered as a reconfiguration of the system, which can be implemented as an additional functionality of the middleware. In this paper, we propose a new dynamic reconfiguration service for a publish/subscribe middleware that enables dynamic reallocation of components in order to achieve predictable and reliable system behaviour and fulfil deployment requirements. We have built a prototype that validates our research

Optimising software development policies for evolutionary system requirements

Anticipating future software requirements might support the evolution of software systems and as such reduce the cost of development and maintenance in due time. Unfortunately identifying the right set of evolution scenarios is difficult due to the uncertainty of occurrence of future requirements. In this paper we propose the Software Evolution Analysis Model (SEAM) that provides a probabilistic model for evolution requirements, which can more precisely anticipate future requirements and as such reduce the chance on unanticipated requirements. In SEAM the cost of each individual evolution requirement is defined and an optimal set of evolution scenarios is calculated using dynamic programming techniques

Composing Software from Multiple Concerns: Composability and Composition Anomalies

It is generally acknowledged that separation of concerns is a key requirement for effective software engineering: it helps in managing the complexity of software and supports the maintainability of a software system. Separation of concerns makes only sense if the realizations in software of these concerns can be composed together effectively into a working program. The ability to compose systems from independently developed components that can be adapted and extended easily is a long-standing goal in the software engineering discipline. However, both research and practice have shown that composability of software is far from trivial and fails repeatedly. Typically this occurs when components exhibit complex behavior, in particular when multiple concerns are involved in a single component. We believe that, to address the composability problems, we need a better understanding of the requirements involved in successful composition, and in addition define the situations where composition fails. To this aim, in this paper we (a) introduce a general model of composing systems from multiple concerns, (b) introduce a number of requirements for design-level composability and (c) define a category of composability problems that are inherent for given composition models, which we term as composition anomalies

Effect of ovariectomy on magnetic resonance T2* in rat femur

This document describes the results of the two-day workshop on Advanced Separation of Concerns at ECOOP 2001. The workshop combined presentations with tigthly focused work in small groups on these predefined topics: requirements and challenges for ASoC technologies, conventional solutions for ASoC problems, feature interaction, design support for ASoC and design decisions for ASoC models