Aspect] is a simple and practical aspect-oriented extension to Java With just a few new constructs, AspectJ provides support for modular implementation of a range of crosscutting concerns. In AspectJ's dynamic join point model, join points are well-defined points in the execution of the program; pointcuts are collections of join points; advice are special method-like constructs that can be attached to pointcuts; and aspects are modular units of crosscutting implementation, comprising pointcuts, advice, and ordinary Java member declarations. AspectJ code is compiled into standard Java bytecode. Simple extensions to existing Java development environments make it possible to browse the crosscutting structure of aspects in the same kind of way as one browses the inheritance structure of classes. Several examples show that AspectJ is powerful, and that programs written using it are easy to understand.

An overview of AspectJ

A prevalent and pervasive view of designing is that it can be modeled using variables and decisions made about what values should be taken by these variables. The activity of designing is carried out with the expectation that the designed artifact will operate in the natural world and the social world. These worlds impose constraints on the variables and their values; so, design could be described as a goal-oriented, constrained, decision- making activity. However, design distinguish- es itself from other similarly described activities not only by its domain but also by additional necessary features. Designing involves exploration, exploring what variables might be appropriate. The process of explo- ration involves both goal variables and deci- sion variables. In addition, designing involves learning: Part of the exploration activity is learning about emerging features as a design proceeds. Finally, design activity occurs within two contexts: the context within which the designer operates and the context produced by the developing design itself. The designer’s perception of what the context is affects the implication of the context on the design. The context shifts as the designer’s perceptions change. Design activity can be now characterized as a goal-oriented, con- strained, decision-making, exploration, and learning activity that operates within a con- text that depends on the designer’s percep- tion of the context.

Design Prototypes: A Knowledge Representation Schema for Design

This lecture maps the concepts and templates explored in this tutorial with well-known architectural prescriptions, including the 4+1 approach of the Rational Unified Process, the Siemens Four Views approach, and the ANSI/IEEE-1471-2000 recommended best practice for documenting architectures for software-intensive systems. The lecture concludes by re-capping the highlights of the tutorial, and asking for feedback.

Documenting Software Architectures: Views and Beyond

As the size of software systems increases, the algorithms and data structures of the computation no longer constitute the major design problems. When systems are constructed from many components, the organization of the overall system -- the software architecture -- presents a new set of design problems. This level of design has been addressed in a number of ways including informal diagrams and descriptive terms, module interconnection languages, templates and frameworks for systems that serve the needs of specific domains, and formal models of component integration mechanisms. In this paper we provide an introduction to the emerging field of software architecture. We begin by considering a number of common architectural styles upon which many systems are currently based and show how different styles can be combined in a single design. Then we present six case studies to illustrate how architectural representations can improve our understanding of complex software systems. Finally, we survey some of the outstanding problems in the field, and consider a few of the promising research directions.

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An Introduction to Software Architecture

Software architectures have high costs for change, are complex, and erode during evolution We believe these problems are partially due to knowledge vaporization Currently, almost all the knowledge and information about the design decisions the architecture is based on are implicitly embedded in the architecture, but lack a first-class representation Consequently, knowledge about these design decisions disappears into the architecture, which leads to the aforementioned problems In this paper, a new perspective on software architecture is presented, which views software architecture as a composition of a set of explicit design decisions This perspective makes architectural design decisions an explicit part of a software architecture Consequently, knowledge vaporization is reduced, thereby alleviating some of the fundamental problems of software architecture

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Software Architecture as a Set of Architectural Design Decisions

"Designing a large software system is an extremely complicated undertaking that requires juggling differing perspectives and differing goals, and evaluating differing options. Applied Software Architecture is the best book yet that gives guidance as to how to sort out and organize the conflicting pressures and produce a successful design." -- Len Bass, author of Software Architecture in Practice. Quality software architecture design has always been important, but in today's fast-paced, rapidly changing, and complex development environment, it is essential. A solid, well-thought-out design helps to manage complexity, to resolve trade-offs among conflicting requirements, and, in general, to bring quality software to market in a more timely fashion. Applied Software Architecture provides practical guidelines and techniques for producing quality software designs. It gives an overview of software architecture basics and a detailed guide to architecture design tasks, focusing on four fundamental views of architecture--conceptual, module, execution, and code. Through four real-life case studies, this book reveals the insights and best practices of the most skilled software architects in designing software architecture. These case studies, written with the masters who created them, demonstrate how the book's concepts and techniques are embodied in state-of-the-art architecture design. You will learn how to: * create designs flexible enough to incorporate tomorrow's technology; * use architecture as the basis for meeting performance, modifiability, reliability, and safety requirements; * determine priorities among conflicting requirements and arrive at a successful solution; and * use software architecture to help integrate system components. Anyone involved in software architecture will find this book a valuable compendium of best practices and an insightful look at the critical role of architecture in software development.

Applied software architecture

http://courses.ece.ubc.ca/417/public/Hofmeister.pdf

A general model of software architecture design derived from five industrial approaches

To help us identify and focus on pragmatic and concrete issues related to the role of software architecture in large systems, we conducted a survey of a variety of software systems used in industrial applications. Our premise, which guided the examination of these systems, was that software architecture is concerned with capturing the structures of a system and the relationships among the elements both within and between structures. The structures we found fell into several broad categories: conceptual architecture, module interconnection architecture, code architecture, and execution architecture. These categories address different engineering concerns. The separation of such concerns, combined with specialized implementation techniques, decreased the complexity of implementation, and improved reuse and reconfiguration.

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Software architecture in industrial applications

We compare five industrial software architecture design methods and we extract from their commonalities a general software architecture design approach. Using this general approach, we compare across the five methods the artifacts and activities they use or recommend, and we pinpoint similarities and differences. Once we get beyond the great variance in terminology and description, we find that the 5 approaches have a lot in common and match more or less the "ideal" pattern we introduced.

/pdf/generalizing-a-model-of-software-architecture-design-from-1eaz44wdh1.pdf

Generalizing a Model of Software Architecture Design from Five Industrial Approaches

The navigation of a web application is the possible sequences of web pages a user can visit. In the simplest case the next page is determined by the current page and the action (e.g. link, button) selected by the user. However, many web applications now incorporate adaptive navigation, where the next page also depends on the user's mode, for example whether they are a customer or an administrator, or depends on what pages the user has visited previously.Navigation models are useful for clarifying requirements and specifying implementation behavior. When a model is formal, it can also be used to generate design or implementation artifacts, and can be verified for properties such as broken links or length of navigation path. These uses are all important for the case of simple navigation, but even more important for adaptive navigation because of the added complexity. However, none of the current formal approaches can support adaptive navigation.In this paper we present an approach that uses Statecharts to formally model adaptive navigation, and show how important properties of a navigation model are verified using existing model-checking tools. We summarize the kinds of properties that can be checked with such a model, and describe how to use the Symbolic Model Verifier (SMV) tool to perform the verification. Finally, we use the Blockbuster® web site as a case study to demonstrate how our approach can uncover navigation problems that arise when new requirements are imposed.

Christine Hofmeister

Papers

Applied software architecture

A general model of software architecture design derived from five industrial approaches

Software architecture in industrial applications

Generalizing a Model of Software Architecture Design from Five Industrial Approaches

Modeling and verification of adaptive navigation in web applications