Abstract not found

Software architectures shift the focus of developers from lines-of-code to coarser-grained architectural elements and their overall interconnection structure. Architecture description languages (ADLs) have been proposed as modeling notations to support architecture-based development. There is, however, little consensus in the research community on what is an ADL, what aspects of an architecture should be modeled in an ADL, and which of several possible ADLs is best suited for a particular problem. Furthermore, the distinction is rarely made between ADLs on one hand and formal specification, module interconnection, simulation, and programming languages on the other. This paper attempts to provide an answer to these questions. It motivates and presents a definition and a classification framework for ADLs. The utility of the definition is demonstrated by using it to differentiate ADLs from other modeling notations. The framework is used to classify and compare several existing ADLs, enabling us in the process to identify key properties of ADLs. The comparison highlights areas where existing ADLs provide extensive support and those in which they are deficient, suggesting a research agenda for the future.

Abstract not found

In this paper, we propose a means to enhance an architecture description language with a description of component behavior. A notation used for this purpose should be able to express the "interplay" on the component's interfaces and reflect step-by-step refinement of the component's specification during its design. In addition, the notation should be easy to comprehend and allow for formal reasoning about the correctness of the specification refinement and also about the correctness of an implementation in terms of whether it adheres to the specification. Targeting all these requirements together, the paper proposes to employ behaviorprotocols which are based on a notation similar to regular expressions.

As the design of software architectures emerges as a discipline within software engineering, it will become increasingly important to support architectural description and analysis with tools and environments. In this paper we describe a system for developing architectural design environments that exploit architectural styles to guide software architects in producing specific systems. The primary contributions of this research are: (a) a generic object model for representing architectural designs; (b) the characterization of architectural styles as specializations of this object model; and (c) a toolkit for creating an open architectural design environment from a description of a specific architectural style. We use our experience in implementing these concepts to illustrate how style-oriented architectural design raises new challenges for software support environments.

In this paper, the authors address some of the challenges of the current technologies in the area of component-based programming and automated software downloading. These challenges include: component updating at runtime of affected applications, adopting the "true-push" model in order to allow for silent software modification (e.g. for removing minor implementation errors), and finding a way to integrate these technologies and electronic commerce in software components. To respond to these challenges, the SOFA (SOFtware Appliances) architecture, the SOFA component model and its extension, DCUP (Dynamic Component UPdating), are introduced. SOFA and DCUP provide a small set of well scaling orthogonal abstractions which address three areas: the background for electronic commerce, the component model, and support for dynamic component updating in running applications. The updating granularity can scale anything from minor implementation changes to a major reconfiguration. In contrast with the usual belief that it is difficult to map abstractions supporting component based programming to concrete computer systems, the abstractions proposed by DCUP are very easy to map to the Java and CORBA programming environments.

Partial specifications written in many different specification languages can be composed if they are all given semantm in the same domain, or alternatively, all translated into a common style of predicate logic The common semantic domain must be very general, the particular semantics assigned to each specification language must be conducive to composition, and there must be some means of communication that enables specifications to build on one another. The criteria for success are that a wide variety of specification languages should be accommodated, there should be no restrictions on where boundaries between languages can be placed, and intuitive expectations of the specifier should be met.

We are exploring an approach to formally specifying and analyzing software architectures that is based on viewing software systems as chemicals whose reactions are controlled by explicitly stated rules. This powerful metaphor was devised in the domain of theoretical computer science by Banatre and Le M'etayer and then reformulated as the Chemical Abstract Machine, or CHAM, by Berry and Boudol. The CHAM formalism provides a framework for developing operational specifications that does not bias the described system toward any particular computational model. It also encourages the construction and use of modular specifications at different levels of detail. We illustrate the use of the CHAM for architectural description and analysis by applying it to two different architectures for a simple, but familiar, software system, the multiphase compiler.

The software architecture of most systems is described informally and diagrammatically. In order for these descriptions to be meaningful at all, figures are understood by interpreting the boxes and lines in specific, conventionalized ways [5]. The imprecision of these interpretations has a number of limitations. In this paper we consider these conventionalized interpretations as architectural styles and provide a formal framework for their uniform definition. In addition to providing a template for precisely defining new architectural styles, this framework allows for the proof that the notational constraints on a style are sufficient to guarantee the meanings of all described systems and provides a unified semantic base through which different stylistic interpretations can be compared.

A critical issue for complex component-based systems design is the modeling and analysis of architecture. One of the complicating factors in developing architectural models is accounting for systems whose architecture changes dynamically (during run time). This is because dynamic changes to architectural structure may interact in subtle ways with on-going computations of the system. In this paper we argue that it is possible and valuable to provide a modeling approach that accounts for the interactions between architectural reconfiguration and non-reconfiguration system functionality, while maintaining a separation of concerns between these two aspects of a system. The key to the approach is to use a uniform notation and semantic base for both reconfiguration and steady-state behavior, while at the same time providing syntactic separation between the two. As we will show, this permits us to view the architecture in terms of a set of possible architectural snapshots, each with its own s...