Abstract: Over the past decade there has been considerable experimentation with the design of architecture description languages that can provide a formal basis for description and analysis of the architectures of component-based systems. As the eld has matured there has emerged among the software architecture research community general consensus about many aspects of the foundations for architectural representation and analysis. One result has been the development of a generic architecture description language, called Acme, that can serve as a common representation for software architectures and that permits the integration of diverse collections of independently developed architectural analysis tools. In this paper we describe the Acme language and tools, and our experience in using it to integrate architecture analysis tools and to describe component-based systems.

Abstract: While implicit invocation (publish-subscribe) systems have good engineering properties, they are difficult to reason about and to test. Model checking such systems is an attractive alternative. However, it is not clear what kinds of state models are best suited for this. In this paper we propose a structural approach, which factors the model checking problem into two parts: behavior specific to a particular implicit invocation system, and reusable runtime infrastructure that handles event-based communication and delivery policies. The reusable portion is itself structured so that alternative runtime mechanisms may be experimented with.

Abstract: The use of largely isolated workstations and laptops as the primary carrier of personal computing is giving way to a world of pervasive computing populated by ubiquitous networks of heterogeneous computing and information facilities. In such a world the boundaries between a user’s personal computation space and other people’s is no longer well defined. As a result, collaboration becomes the dominant mode of computing – in essence, all systems become the basis for on-going computer-supported cooperative work.

Abstract: Complex software systems require expressive notations for representing their software architectures. Two competing paths have emerged. One is to use a specialized notation for architecture -- or architecture description language (ADL). The other is to adapt a general-purpose modeling notation, such as UML. The latter has a number of benefits including familiarity to developers, close mapping to implementations, and commercial tool support. However, it remains an open question as to how best to use object-oriented notations for architectural description, and, indeed, whether they are sufficiently expressive, as currently defined. In this paper we take a systematic look at these questions, examining the space of possible mappings from ADLs into object notations. Specifically, we describe (a) the principle strategies for representing architectural structure in UML; (b) the benefits and limitations of each strategy; and (c) aspects of architectural description that are intrinsically difficult to model in UML using the strategies.

Abstract: A heterogeneous persistent object system provides multiple programming language interfaces. This gives rise to the polylingual inter- operability problem, namely, how can an application uniformly process data objects that have been defined, created and persistently stored us- ing distinct programming language type models. At POS-7, we reported on the PolySPIN approach (polylingual support for persistence, interoperability and naming). A prototype based on PolySPIN, which was built as an extension to the TI/Darpa Open Object-Oriented Database, supports transparent polylingual access for persistent C++ and CLOS objects. The approach, however, assumes that objects in the persistent store are monolingual structures. That is, while a C++ application using the PolySPIN approach may access and manipulate a persistent CLOS object as if it were implemented in C++, that CLOS object must be entirely implemented in CLOS. In this paper, we report on our recent efforts toward extending PolySPIN with pure polylingual persistence capabilities. Our new approach supports transparent construction and ma- nipulation of heterolingual persistent data objects. This means that a persistent object may have in its closure objects that are defined using different languages. The pure polylingual persistence mechanism trans- parently manages heterolingual persistent objects. We illustrate the pure polylingual approach by applying it to a Java-C++ realization of the 007 benchmark as implemented using the TI/Darpa Open Object-Oriented Database.

Abstract: Over the past decade software architecture has emerged as an important subfield of software engineering. During that time there has been considerable progress in developing the technological and methodological base for treating architectural design as an engineering discipline, including specialized architectural description languages, tools, analytic techniques, handbooks, and methods. In this paper I survey the main features of the field, and then compare software architecture with object-oriented systems to illustrate some of the important similarities and differences between the two fields.

Abstract: Over the past decade software architecture has received increasing attention as an important subfield of software engineering. During that time there has been considerable progress in developing the technological and methodologi-cal base for treating architectural design as an engineering discipline. However, much remains to be done to achieve that goal. Moreover, the changing face of technology raises a number of new challenges for software architecture. This paper examines some of the important trends of software architecture in research and practice, and speculates on the important emerging trends, challenges, and aspirations.

Abstract: An important issue for software system development is the documentation of architecture designs. In this report, we describe techniques for the architectural documentation of software-based systems in the context of development processes that use UML for software design. The architectural documentation is organized in four kinds of views: problem domain view, code view, run-time view and deployment view. We examine JavaPhoneTM as a case study to illustrate the approach: what kinds of information are provided in each kind of view, what forms of notation should be used, what are their limitations, and what uses can be made of this documentation.

Abstract: We are moving towards a world of pervasive computing in which users can access and manipulate information from anywhere at anytime. Computing devices and networks are becoming ubiquitous. In this new world, computing will no longer be tethered to desktops: users will become increasingly mobile. As users move across environments, they will have access to a dynamic range of computing devices and software services. They will want to use the resources to perform computing tasks. Today's computing infrastructure does not support this model of computing very well because computers interact with users in terms of low level abstractions: applications and individual devices. Today, if a mobile user wants to use the computing resources of a new environment, he has to manually figure out how to perform a computing task using local resources and/or to migrate his computing context from another environment. Such manual operation is unacceptable in a pervasive computing world because it does not scale with the increasing amount of software services, user mobility and resource dynamism. It also demands that users spend too much time on non-task related configuration activities. This technical report describes an approach called task-driven computing that can be used to solve this problem. The approach is based on the insight that with appropriate system support it is possible to let users interact with their computing environments in terms of high level tasks and free them from low level configuration activities.

Abstract: Multiple architectural views of a system are often helpful in describing a system's design. While there are numerous languages for describing the contents of an individual architectural view, to date those languages have not supported the description of relationships between views. In this report we describe an extension to Acme for expressing maps between the structural aspects of architecture and for expressing constraints over those maps.

Abstract: With an eye toward sharing event-based behavior in architectural descriptions, a number of researchers at ISI (Wile), CMU (Garlan & Kompanek) and Stanford (Luckham & Kenney) started a dialogue to converge on an event standard. The results are summarized in this working report. The main idea of the proposal is to adopt an Acme-like approach: a simple base-level event representation would capture the minimal, core aspects of events. Additionally, other more tool-specific information could be added to those event representations in the form of annotations. In this report we outline the proposed scheme. We begin by enumerating some of the requirements that we identified early in our discussions. Next we discuss the basic ontology of events, activities and their types. Then we introduce two proposals for concrete representation: one based on XML, the other on an Acme-like syntax. Finally, we illustrate how collections of events derived from existing ADLs can be mapped into the activity language.