Abstract. A mathematical semantics is proposed for the notion of architectural connector, in the style defined by Allen and Garlan, that builds on Goguen’s categorical approach to General Systems Theory and other algebraic approaches to specification, concurrency, and parallel program design. This semantics is, essentially, ADL-independent, setting up criteria against which formalisms can be evaluated according to the support that they provide for architectural design. In particular, it clarifies the role that the separation between computation and coordination plays in supporting architecture-driven approaches to software construction and evolution. It also leads to useful generalisations of the notion of connector, namely through the use of multiple formalisms in the definition of the glue and the roles, and their instantiations with programs or system components that can be implemented in different languages or correspond to "real-world" components. 1

Information System Engineering has become under increasing pressure to come up with software solutions that endow systems with the agility that is required to evolve in a continually changing business and technological environment. In this paper, we suggest that Software Engineering has a contribution to make in terms of concepts and techniques that have been recently developed for Parallel Program Design and Software Architectures, which we have named Coordination Technologies. We show how such mechanisms can be encapsulated in a new modelling primitive --- coordination contract --- that can be used for extending Component Based Development approaches in order to manage such levels of change.

Machine", um formalismo de reescrita de multiconjuntos de termos, para uma descric ao uniforme de arquitecturas, computac oes e reconfigurac oes. A ultima abordagem usa uma linguagem de desenho de programas paralelos similar ao UNITY para descrever computac oes, representa as arquitecturas por diagramas no sentido da Teoria das Categorias, e especifica a reconfigurac ao por regras de transformac ao de grafos.

. The evolution of today's markets and the high volatility of business requirements put an increasing emphasis on the flexibility of systems, i.e. on the ability for systems to accommodate the changes required by new or different organisational needs with a minimum impact on the implemented services. In this paper, we put forward an extension of UML with a semantic primitive -- contract -- for representing explicitly the rules that determine the way object interaction needs to be coordinated to satisfy business requirements, as well as the mechanisms that make it possible to reflect changes of the business requirements without having to modify the basic objects that compose the system. Contracts are proposed as extended forms of association classes whose semantics rely on principles that have been used in Software Architectures and Distributed System Design for supporting dynamic reconfiguration. 1 Introduction Market evolution, and the consequent evolution of business requ...

We develop a notion of higher-order connector towards supporting the systematic construction of architectural connectors for software design. A higherorder connector takes connectors as parameters and allows for services such as security protocols and fault-tolerance mechanisms to be superposed over the interactions that are handled by the connectors passed as actual arguments. The notion is first illustrated over a Unity-like parallel program design language that we have been using for formalising aspects of architectural design. A formal, algebraic semantics is then presented which is independent of any Architectural Description Language. Finally, we show how higher-order connectors can be composed. 1

The ability to construct architectural connectors in a systematic and controlled way has been argued to promote reuse and incremental development, e.g., as a way of superposing, a la carte, services like security over a given communication protocol. Towards this goal, we present a notion of high-order connector, i.e., a connector that takes connectors as parameters, for superposing coordination mechanisms over the interactions that are handled by the connectors that are passed as actual arguments. The notion is developed over the language COMMUNITY that we have been using for formalising aspects of architectural design, and illustrated with examples inspired by the case study.

Research in Software Architectures has put forward the concept of connector to express complex relationships between system components, thus facilitating the separation of coordination from computation. A system can then be understood, at a given level of abstraction, in terms of its components and the connectors that establish how they interact. However, for systems in which many interconnections exist between their components, the architectures themselves may become very complex due to the high number of connectors in place. This is especially true in the context of mobile systems in which the interconnections are, by nature, transient in the sense that, at a given instant of time, only a subset of the potential connectors are actually effective. In this paper, we formalise a notion of transient connector that allows, at any given moment, for the architecture to depict only the connectors that are active and, in this way, capture the dynamics of architectures themselves. ...

Many of today's software systems must cope with changing configurations, and my PhD work (among other current research) seeks to provide ways to specify and analyse the dynamics of such architectures. I am looking at work done in Software Architecture, Distributed Systems, Mobile Computing, and Theoretical Computer Science in order to develop a formal framework at a sufficiently abstract level to investigate the fundamental similarities of architectural evolution, dynamic reconfiguration, and mobility and to serve as a high-level Architecture Description Language able to encompass other authors' proposals. The envisaged approach will use rewriting, logical, and categorical techniques. 1 MOTIVATION AND RELATED WORK Software Architecture (SA) is a discipline that addresses the design of the high-level structure of complex systems. According to several researchers [10, 13], two of the most important future directions are high-level Architecture Description Languages (ADLs) and architect...

Data Type Specification, in combination with modal logics for formalizing the process of building systems from interconnected components. This combination of logical and categorical techniques has also been applied to parallel program design languages in the style of UNITY [14] and IP [41], providing semantics for modularization techniques based on the notion of superposition. This has resulted in the development of a programming design language called Community [33]. Two formalisms that provide explicit support for object systems and can reason about their rewriting logic specifications have been recently developed. One is a version of the modal -calculus proposed by Lechner [48, 49] for reasoning about object-oriented Maude specifications. Another is Denker's objectoriented distributed temporal logic DTL + [24, 22], that extends the DTL and D 1 distributed object temporal logics of Ehrich and Denker [30, 23, 29]. Lechner [48, 49] uses her version of the modal -calculus to identif...

Introduction The engineering of Business Systems is under the increasing pressure to come up with software solutions that allow companies to face very volatile and turbulent environments. On the one hand, in order to remain competitive, companies need to be very agile in reacting to changes occurring in the business domain. As the world of business in general becomes more and more aggressive and competitive, and in particular as a consequence of the impact of the Internet and Wireless Technologies, companies require their information systems to be easily adaptable to changes in the business rules with which they operate, most of the time in a way that does not imply interruptions to the services that they provide. Quoting directly from [16], " the ability to change is now more important than the ability to create e-commerce systems in the first place. Change becomes a first-class design goal and requires business and technology architecture whose components can be added, modif