Abstract: Designing software in a way that guarantees run-time behavior while achieving an acceptable balance among multiple quality attributes is an open problem. Providing guarantees about the satisfaction of the same requirements under uncertain environments is even more challenging. Tools and techniques to inform engineers about poorly-understood design spaces in the presence of uncertainty are needed, so that engineers can explore the design space, especially when tradeoffs are crucial. To tackle this problem, we describe an approach that combines synthesis of spaces of system design alternatives from formal specifications of architectural styles with probabilistic formal verification. The main contribution of this paper is a formal framework for specification-driven synthesis and analysis of design spaces that provides formal guarantees about the correctness of system behaviors and satisfies quantitative properties (e.g., defined over system qualities) subject to uncertainty, which is treated as a first-class entity. We illustrate our approach in two case studies: a service-based adaptive system and a mobile robotics architecture. Our results show how the framework can provide useful insights into how average case probabilistic guarantees can differ from worst case guarantees, emphasizing the relevance of combining quantitative formal verification methods with structural synthesis, in contrast with techniques based on simulation and dynamic analysis that can only provide estimates about average case probabilistic properties.

Abstract: The backbone of most software architectures and component integration frameworks is one or more architectural styles that provide a domain-speci?c design vocabulary and a set of constraints on how that vocabulary is used. Today's architectural styles are increasingly complex, involving rich vocabularies and numerous constraints. Hence, designing a sound and appropriate style becomes an intellectually challenging activity. Unfortunately, although there are numerous tools to help in the analysis of architectures for individual systems, relatively less work has been done on tools to help in the design of architectural styles. In this paper we address this gap by showing how to map an architectural style, expressed formally in an architectural description language, into a relational model that can then be checked for properties, such as whether a style is consistent, whether a style satis?es some predicates over its architectural structure, and whether two styles are compatible for composition.

Abstract: Software system builders are increasingly recognizing the importance of exploiting design knowledge in the engineering of new systems. One way to do this is to define an architectural style for a collection of related systems. The style determines a coherent vocabulary of system design elements and rules for their composition. By structuring the design space for a family of related systems a style can, in principle, drastically simplify the process of building a system, reduce costs of implementation through reusable infrastructure, and improve system integrity through style-specific analyses and checks. Like architectural style, object-oriented design patterns attempt to capture and exploit design knowledge to ease the process of designing software systems and reusing proven designs. There are, however, significant differences in the roles and capabilities of architectural styles and object-oriented design patterns, as there are between architectural design and object-oriented design. In this paper we illustrate the relationship between software architecture and object-oriented design, as well as the relationship between architectural styles and design patterns. We begin by defining our terms and then proceed to compare and contrast the various approaches with examples.

Abstract: The software architecture of most systems is usually described informally and diagrammatically by means of boxes and lines. In order for these descriptions to be meaningful, the diagrams are understood by interpreting the boxes and lines in specic, conventionalized ways. The informal, imprecise nature 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 denition. In addition to providing a template for precisely dening new architectural styles, this framework allows for analysis within and between dierent architectural styles.

Abstract: 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.

Abstract: Software architecture modeling is important for analyzing system quality attributes, particularly security. However, such analyses often assume that the architecture is completely known in advance. In many modern domains, especially those that use plugin-based frameworks, it is not possible to have such a complete model because the software system continuously changes. The Android mobile operating system is one such framework, where users can install and uninstall apps at run time. We need ways to model and analyze such architectures that strike a balance between supporting the dynamism of the underlying platforms and enabling analysis, particularly throughout a system�s lifetime. In this paper, we describe a formal architecture style that captures the modifiable architectures of Android systems, and that supports security analysis as a system evolves. We illustrate the use of the style with two security analyses: a predicatebased approach defined over architectural structure that can detect some common security vulnerabilities, and inter-app permission leakage determined by model checking. We also show how the evolving architecture of an Android device can be obtained by analysis of the apps on a device, and provide some performance evaluation that indicates that the architecture can be amenable for use throughout the system�s lifetime.

Abstract: Computations are pervasive across many domains, where end users have to compose various heterogeneous computational entities to perform professional activities. Service-Oriented Architecture (SOA) is a widely used mechanism that can support such forms of compositions as it allows heterogeneous systems to be wrapped as services that can then be combined with each other. However, current SOA orchestration languages require writing scripts that are typically too low-level for end users to write, being targeted at professional programmers and business analysts. To address this problem, this paper proposes an approach based on an architectural-style for service orchestration using an end user specification style called SCORE. SCORE uses high-level constructs that can be tailored for different domains and automatically translated into executable constructs by tool support. We demonstrate the usefulness of SCORE across two domains – dynamic network analysis and neuroscience, where users are intelligence analysts and scientists respectively. They can use an architectural style based vocabulary as a basis of their domain-specific

Abstract: An increasingly important class of software-based systems is plat-forms that permit integration of third-party components, services, and tools. Service-Oriented Architecture (SOA) is one such plat-form that has been successful in providing integration and distri-bution in the business domain, and could be effective in other domains (e.g., scientific computing, healthcare, and complex deci-sion making). In this paper, we discuss our application of SOA to provide an integration platform for socio-cultural analysis, a domain that, through models, tries to understand, analyze and predict relationships in large complex social systems. In developing this platform, called SORASCS, we had to overcome issues we believe are generally applicable to any application of SOA within a domain that involves technically naïve users and seeks to establish a sustainable software ecosystem based on a common integration platform. We discuss those issues and the lessons learned about the kinds of problems that occur, and pathways toward a solution.

Abstract: Designing cyber-physical systems(CPSs)increasingly requires the use of multi-domain models throughout the development process. Ensuring consistent relationships between various system models is an important part of an integrated design methodology. This paper describes an architectural approach to reasoning about relations between heterogeneous system models. The runtime base architecture of the system is used as a unifying representation to compare the structure and semantics of the associated models. Each model is related to the base architecture through the abstraction of an architectural view, which captures structural and semantic correspondences between model elements and system entities. The use of the architectural view framework to relate system models from different domains is illustrated in the context of a quadrotor air vehicle.

Abstract: This paper introduces an architectural style for enabling end-users to quickly design and deploy software systems in domains characterized by highly personalized and dynamic requirements.

The style offers an intuitive metaphor based on boxes, pipes, and wires, but retains enough preciseness that systems can be automatically assembled and dynamically reconfigured based on uDesign descriptions. uDesign was primarily motivated and validated within monitoring and control applications for smart spaces, but we envision possible extensions to other domains.

Our contribution differs from early attempts at end-user programming in the level of abstraction, software architecture rather than programming, and in the subject of description: run-time rather than code structures. To validate the approach, the paper presents (a) two case studies, one in health care and one in home security, (b) the formal semantics of uDesign’s primitives, and (c) a mapping of those primitives to an existing software infrastructure: the Aura infrastructure.

Abstract: Over the past 15 years there has been increasing recognition that careful attention to the design of a system�s software architecture is critical to satisfying its requirements for quality attributes such as performance, security, and dependability. As a consequence, during this period the field of software architecture has matured significantly. However, current practices of software architecture rely on relatively informal methods, limiting the potential for fully exploiting architectural designs to gain insight and improve the quality of the resulting system. In this paper we draw from a variety of research results to illustrate how formal approaches to software architecture can lead to enhancements in software quality, including improved clarity of design, support for analysis, and assurance that implementations conform to their intended architecture.

Abstract: Although numerous mechanisms for promoting software reuse have been proposed and implemented over the years, most have focused on the reuse of implementation code. There is much conjecture and some empirical evidence, however, that the most effective forms of reuse are generally found at more abstract levels of software design. In this paper we discuss software reuse at the architectural level of design. Specifically, we argue that the concept of 'architectural style' is useful for supporting the classification, storage, and retrieval of reusable architectural design elements. We briefly describe the Aesop system's Software Shelf, a tool that assists designers in selecting appropriate design elements and patterns based on stylistic information and design constraints.

Abstract: Increasingly, developers look to software architecture to help them control the complexity of their systems. When developing a particular system, designers tend not to explore all possible alternatives for its architecture. Instead, they use specific patterns and idioms that are effective for the domain in which they are working. We term such a collection of patterns and idioms an architectural style.

Unfortunately, with few exceptions current exploitation of architectural style is informal and ad hoc. In this paper we consider an alternative to the ad hoc description of architectural styles, a formal description based on the inherent structure of software architectures. We explore this solution by describing Justo and Cunha's message passing style in Wright, an architecture description language based on CSP.

Abstract: A central aspect of architectural design is the use of recurring organizational patterns and idioms- or architectural styles. Examples include generic system organizations such as those based on dataflow or layers, as well as specific organizational structures such as the classical decomposition of a compiler, the OSI communication stack, and the MVC user interface paradigm.

The principled use of architectural styles has a number of practical benefits. First, it promotes design reuse: routine solutions with well-understood properties can be reapplied to new problems with confidence. Second, it can lead to significant code reuse: often the invariant aspects of an architectural style lend themselves to shared implementations. Third, it is easier for others to understand a system's organization if conventionalized structures are used. For example, even without giving details, characterization of a system as a 'client-server' organization immediately conveys a strong image of the kinds of pieces and how they fit together. Fourth,use of standardized styles supports interoperability. Examples include CORBA object-oriented architecture, and event-based tool integration. Fifth, by constraining the design space, an architectural style often permits specialized,style-specific analyses. For example, it is possible to analyze pipe-filter systems for schedulability, throughput, latency, and deadlock-freedom. Such analyses might not be meaningful for an arbitrary, ad hoc architecture - or even one constructed in a different style. Sixth, it is usually possible to provide style-specific visualizations: this makes it possible to provide graphical and textual renderings that match engineers' domain-specific intuitions about how their designs should be depicted.

Abstract: 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 generic object model for representing architectural designs;
- The characterization of architectural styles as speculations of this object model;
- 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-oriened architectural design raises new challenges for software support environments.

Abstract: 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. The imprecision of these interpretations has a number of limitations. In this paper we consider these convetionalized 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.

Abstract: Architecture evolution is a central feature of virtually all software systems. As new market opportuni-ties, technologies, platforms, and frameworks become available systems must change their organiza-tional structures to accommodate them, requiring large-scale and systematic restructuring. Today arc-hitects have few tools to help them plan and execute such evolutionary paths. In particular, they have almost no assistance in reasoning about questions such as: How should we stage the evolution to achieve business goals in the presence of limited development resources? How can we reduce risk in incorporating new technologies and infrastructure required by the target architecture? How can we make principled tradeoffs between time and development effort? What kinds of changes can be made independently, and which require coordinated system-wide modifications? How can an evolution plan be represented and communicated within an organization? In this report we outline first steps towards a formal basis for assisting architects in developing and reasoning about architectural evolution paths. The key insight behind the approach is that at an architectural level of abstraction many system evolutions follow certain common patterns – or evolution styles. By taking advantage of regularity in the space of common architectural evolutions, and by making the notion of evolutions styles a first-class entity that can be formally defined, we can provide automated assistance for expressing architecture evolution, and for reasoning about both the correctness and quality of evolution paths.

Abstract: Architectural analysis is key to producing high quality architectures. In this demonstration we present two extensions to AcmeStudio, and domain-neutral Architecture Development Environment, to add Performance and Security Simulation. Using AcmeStudio as the integration platform for these analyses allows comparisons and trade-offs between these different quality attributes.