A formal method for software architecture analysis based on aspect orientation

A major cause of many complications in the field of software architectures is the lack of appropriate abstractions for separating, combining and encapsulating concerns of various kinds in architectural descriptions. Architectures of most complex software-intensive systems involve concerns that inherently crosscut the natural boundaries of the elements composing the architecture descriptions. Crosscutting concerns intersect the common modularity of systems as prescribed by their architecture descriptions, by traversing both the components and connectors, i.e., the relationships among the components. Crosscutting concerns are critical aspects of many architectural problems. However, architectural descriptions written in special-purpose languages (ADLs) like Wright, Darwin, Rapide and Acme should support descriptions of multiple structures, which include diagrams, models and views, that intentionally address different kinds of concerns. ADLs should show how various concerns affect each other in architectural designs; they should also allow one to identify, analyze and elaborate architectural concerns that cut across several software components, such as transactions, security, load balancing, synchronization, reuse, customization, scalability, etc.; they should, but they do not. This dissertation presents a new approach to software architecture that is suitable for supporting concern-oriented development and documentation of architectures for software-intensive systems. This approach allows for creating and documenting a multidimensional software structure that is referred to as concern-oriented software architecture; it provides new mechanisms for encapsulating individual concerns into independent architectural constructs. The ultimate goal of this new approach is to provide support for achieving design by concerns all through the development and description of software architectures. Moving towards this goal, we present a particular concern-oriented architectural framework called Perspectival Concern-Spaces (PCS). The PCS Framework offers a flexible and extensible means a) for supporting advanced separation of concerns in architectural design, and in the construction and evolution of software-intensive systems; and b) for filling the gap between architectural descriptions and modern software development artifacts. To show the feasibility of the proposed approach, we provide new modeling techniques that are used to describe and apply an aspect-oriented architectural pattern, called the On-demand Remodularization pattern. We give several examples of how the PCS Framework can be used to integrate concern-oriented architectural documentations with mainstream software development artifacts.

In the past decade, software architecture research has mainly focused on the concept formulation and the development of various architecture description languages. This field has now matured enough and thus requires more emphasis on techniques for developing and analyzing software architecture specifications. SAM is a general software architecture model for developing and analyzing software architectures. In this paper, we show how to integrate high-level Petri nets and first-order temporal logic as the foundation of SAM to establish a unified framework for specifying and analyzing all aspects of a software architecture. We provide a set of heuristics, which are supported by well-defined existing methods and techniques developed by other researchers as well as our own, for software architecture development and analysis. We demonstrate the application of this framework and the heuristics with an example.

The management of software evolution as well as the maintenance of its complexity is of two most important problems to be solved by software engineering. Several solutions have been considered, one of them being the separation of concerns. These concepts have been extended along the life cycle of software development and thus, aspect oriented software development (AOSD) arose and shed new light on software evolution problems. In this paper we focus on the seamless integration of AOSD and software architecture to support dynamic software evolution in architecture level. Thus we propose an incremental aspect-oriented (AO) architecture modeling approach. In the approach we introduce a unified formal model, namely aspect weaving connector (AWC), to formalize the underlying mechanisms of aspect dynamic weaving in architecture level. Meanwhile, we introduce a simple and seamless extension of ACME ADL to support the modular representation of architectural aspects, components, AWC and their composition forms. For the unified connector model has been applied in our implemented framework for dynamic software architecture, a case study on adaptive JPS (Java pet store) is illustrated to show the advantages of this approach and the unified model.

Architecture description languages deal with the description, analysis and reuse of software architectures. This paper describes DAOP-ADL, a component- and aspect-based language to specify the architecture of an application in terms of components, aspects and a set of plug-compatibility rules between them. With the aim of connecting the specification of the application architecture to the implementation, we describe our language using XML and XML Schemas. The DAOP-ADL language was designed to be interpreted by DAOP, our own dynamic component- and aspect-oriented platform. DAOP provides a composition mechanism that plugs aspects into components dynamically at runtime. The software architect will use the DAOP-ADL language at design time to describe the architecture of the application. Later this architectural information is loaded into the DAOP platform, which needs it to establish the dynamic connections between autonomous components and aspects. Therefore, the use of DAOP-ADL closes the gap between design and implementation of component- and aspect-based applications.

Architecture description languages (ADLs) play an important role in specifying the software architectures. While most of these ADLs are unable to deal with the change directly, especially for dynamic evolution of software systems. This paper proposes an XML-based ADL, named Breeze/ADL, which is supported by Breeze Graph Grammar (BGG) - a graph grammar we defined, to describe software architecture and capture the change in the architecture definition. Our approach is explained in two directions. First, we give the basic definitions of Breeze/ADL, and then show how to map the BGG to Breeze/ADL to specify the structural model, style constraints and dynamic evolution. The other direction is that we use a Client/Server application as a running example to demonstrate our approach throughout this paper. In this approach, the software architecture description has both a textual and a graph representations, and the unplanned change can be captured and defined.

Software architecture lies at the backbone of any software system and its choice directly influences important non-functional characteristics such as maintainability, extensibility, etc. Up-to-date software architecture descriptions should be at any time available to support the analysis and evaluation of the current state of the architecture. However the current state of the art lacks both methodologies and tools for ensuring availability of architecture descriptions and fails to offer objective means for evaluating software architectures. Currently, no generally accepted method for comparing software from an architecture point of view exists. In this paper, we present our current results towards creating a so-called architecture quality index that includes a bidirectional architecture quality model as well as a quality benchmark created for the context of the ARAMIS research project. The proposed architecture quality index aims to support the architects to evaluate and compare the architecture of software systems based on information extracted during the considered systems' run-time.

Software architectures, chemical abstract machine, specification, refinement. In this paper we propose an approach to compare descriptions of software architectures based on the CHAM formalism. The need to compare descriptions of the same system at different level of abstraction often arises typically when the software practice uses a stepwise refinement approach. Differently from other approaches presented in the literature our framework allows for expressing correct refinement both of the static structure and of the dynamic behaviour of an architecture. Statically we rely on a suitable definition of partial morphism between the signatures of the two architectures. Dynamically we propose a notion of structure preserving simulation which allows the behaviors of the two CHAM descriptions to be (preorderly) related. In both definitions an important role is played by the membrane construct which allows for expressing non-functional constraints on the architecture to be refined. The main idea is to use the membranes to denote basic software components of the architecture that can be further decomposed during a refinement process but that cannot be destroyed even if the behaviour of the overall system is preserved. One point in favour of our approach is that we do not constrain too much the further development since we only require the membrane structure to be preserved.

Architecture description languages are a sound and convenient approach to software architecture representation. The majority of well-known ADLs provide separation of computation and communication in components and connectors, respectively. However, computation and communication are not the only crosscutting concerns that may appear in a software architecture description. Traditional ADLs do not normally provide appropriate support to separate any kind of crosscutting concerns, which frequently result in poor architectures descriptions with highly coupled components. In this paper we present the AO-ADL language, based on a symmetric decomposition model that considers components and connectors as the basic structural elements (similar to traditional ADLs). We will show how aspects are treated as specific types of components that are composed by means of connectors. In order to cope with the separation of concerns we enrich the semantic and expressivity of traditional connectors to support either aspectual and nonaspectual component interactions.

The focus of this paper is the design and implementation of dependable quality requirements, and their incorporation in the description of software architecture in an explicit and structured manner. More specifically, we propose three architectural styles for developing dependable collaboration-based software designs based on three notions: (i) the idealized fault-tolerant component model, (ii) the collaboration/role interaction model, and (iii) computational reflection together with a set of design patterns that focus on providing design solutions for implementing fault tolerance techniques, namely, error handling, coordinated recovery and software redundancy. Computational reflection defines a meta-level architecture that is composed of a base level where the application’s logic is implemented and a meta level where meta components are responsible for implementing the application’s quality requirements in a way that it is transparent to application designers. Application designers can apply the notion of separation of concerns and concentrate their attention on the functional requirements, abstracting from the quality requirements.

To keep our software products and cross-product software components maintainable, an approach to software architecture management with a long-term perspective is required. One-time modeling of the intended software architecture is not sufficient. Instead, it must be maintained throughout the whole life-cycle of the software system. Tool support is required to monitor the actual physical software architecture. Deviations must be resolved by modifying the software system or the software architecture description. All software architectures are required to follow a consistent architectural style, which is defined in a technology-neutral way and mapped to all technologies we use in development. In order to support this multi-technology landscape, the architectural style, and our use cases, we developed a tool suite, the BTC RevEngTools.

The approach aims at solving the above problems by including the analysis and verification of two different levels of software development process–design level and implementation level-and bridging the gap between software architecture analysis and verification and the software product. In the architecture design level, to make sure the design correctness and attack the large scale of complex systems, the compositional verification is used by dividing and verifying each component individually and synthesizing them based on the driving theory. Then for those properties that cannot be verified on the design level, the design model is translated to implementation and runtime verification technique is adapted to the program. This approach can highly reduce the work on the design verification and avoid the state-explosion problem using model checking. Moreover, this approach can ensure both design and implementation correctness, and can further provide a high confident final software product. This approach is based on Software Architecture Model (SAM) that was proposed by Florida International University in 1999. SAM is a formal specification and built on the pair of component-connector with two formalisms – Petri nets and temporal logic. The ACV approach places strong demands on an organization to articulate those quality attributes of primary importance. It also requires a selection of benchmark combination points with which to verify integrated properties. The purpose of the ACV is not to commend particular architectures, but to provide a method for verification and analysis of large scale software systems in architecture level. The future research works fall in two directions. In the compositional verification of SAM model, it is possible that there is circular waiting of certain data among different component and connectors. This problem was not discussed in the current work. The translation of SAM to implementation is based on the restricted Petri nets due to the undecidable issue of high level Petri nets. In the runtime analysis of implementation, extraction of the execution trace of the program is still needed to get a white box view, and further analysis of execution can provide more information of the product correctness.

With the growing use of UML diagrams for software architecture description and the importance of non-functional requirements evaluation at software architecture level, filling the scientific gap between architect and requirement analyst is considered to be significant. Software architects are not usually familiar with non-functional requirement analysis and are not able to analyze such requirements easily. On the other hand, non-functional requirements cannot be evaluated directly by UML diagrams. Therefore, the architect should annotate additional information of the nonfunctional requirements to software architecture description and then an executable model can be produced. These executable models can be petri nets, queuing networks, stochastic process algebra and etc. One kind of the UML diagrams that can be used to describe software architecture is component diagram. In this paper, we propose a new algorithm that enables an architect to transform a component diagram into an executable model based on different extensions of petri nets. Moreover, we show how to use this petri net model for performance evaluation and simulation and the implications of this transformation are described completely. Finally, to represent the usage of our proposed algorithm, we consider a case study as an example.

We describe ConcernBASE, a UML-based approach that is an instantiation of the IEEE's Conceptual Framework (Std 1471) for describing software architectures. We show how the approach supports advanced separation of concerns in software architecture by allowing one to identify and define multiple viewpoints, concern spaces and views of an architecture. Our work focuses on integrating the ConcernBASE approach with the Structural Architecture Description Language (SADL) in order to make the verification capabilities of SADL available to those who develop in UML. The result is a UML profile for structural description of software architecture. The paper also presents a prototype tool that supports this UML profile.

It is our great pleasure to welcome you to the 8th International ACM Sigsoft Conference on the Quality of Software Architectures -- QoSA'12. For almost a decade, QoSA aims at advancing the state of the art in the quality assessment and management for software architectures. Specific issues of interest are defining quality measures, evaluating and managing architecture quality, linking architecture to requirements and implementation, and preserving architecture quality throughout the lifetime of the system. Past themes for QoSA include Quality throughout the Software Lifecycle (2011), Research into Practice -- Reality and Gaps (2010), Architectures for Adaptive Software Systems (2009), and Models and Architecture (2008). The umbrella theme of QoSA 2012 is Evolving Architectures. The QoSA'12 call for papers attracted 52 abstracts leading to the final number of 44 submissions from Europe, North and South America, Australia, Asia, and Africa. The program committee accepted 11 long papers and 7 short papers that cover a variety of topics related to the quality of software architectures. In addition, the program includes two keynote speeches, first by Alberto Montresor (University of Trento, Italy) on Designing Extreme Distributed Systems: Challenges and Opportunities, and second by Johan Bendz (Convenor of the ISO/IEC-JTC1-SC7 Working Group on Architecture) on International Standards Supporting Quality in Software Architecture. QoSA is part of the federated event CompArch, this year together with "CBSE 2012: 15th International ACM SIGSOFT Symposium on Component Based Software Engineering," "ISARCS 2012: 3rd International ACM SIGSOFT Symposium on Architecting Critical Systems," "WCOP 2012: 17th International Doctoral Symposium on Components and Architecture," and "ROSS 2012: Workshop on Reusing Open-Source Components." We are grateful to the organizers of all these events for making CompArch a successful federated event on Component-based Software Engineering and Software Architecture.

Interest in software architecture as an area of research, education, and practice within software engineering has been growing steadily over the past decade. Software architecture is concerned with the principled study of large-grained software components, including their properties, relationships, and patterns of combination. It is becoming clear that one key to the effective development, operation, and evolution of software systems is the design and evaluation of appropriate architectures.As a complement to the Fourth Symposium on the Foundations of Software Engineering (FSE-4), whose theme was software architecture, the Second International Software Architecture Workshop (ISAW-2) brought together practitioners and researchers for two intense days of discussion and work. The ISAW-2 proceedings [6] were published in the Joint Proceedings of the SIGSOFT '96 Workshops, ACM Press, ISBN 0-89791-867-3.The participants were organized into three parallel working groups each focused on a different topic within software architecture.• Styles and Patterns ---Techniques and models for centering software architecture activities on generally useful design methods, components, and assemblages of components.• Architecture Description ---Languages and methods for the capture of architectural designs.• Tools and Methods ---Automated aids for designing, evaluating, validating, implementing, and evolving software architectures.Tying these work groups together was the use of a common case study derived from a real-world architecture found in industry. Each working group studied this architecture from its particular perspective and, to a greater or lesser extent, used the case study to organize their discussions. It is interesting to note, for example, that the three groups created specialized depictions of the architecture for their discussion (see figures 6, 8, and 10).The case study was the architecture of the Call Center Customer Care (C4) System, which was developed by Andersen Consulting. A description of the architecture and some of its more interesting challenges appears in Section 2. It is reproduced here in the hopes that it might be prove of continued use to the community.Also appearing here are reports from each working group. The Styles and Patterns Working Group was led by Frances Paulisch, of Siemens, and Mary Shaw, of CMU. The group tried to uncover the styles and patterns that underlay various components of the C4 architecture. In the process, they defined a new kind of architectural style that they named the Data Ooze. The Architectural Description Working Group was led by Paul Clements, of the SEI, and Jeff Magee, of Imperial College. The group concentrated on identifying critical aspects of architectures that require description and on identifying important areas where further work in architectural description is needed. The Tools and Methods Working group was led by William Griswold, of UCSD, and Philippe Kruchten, of Rational. The group pretended to go through a development cycle for the C4 system in order to uncover various architectural tool and method needs.At the conclusion of the workshop, the working group chairs held a panel session in which each group asked a "challenge" question of the other two groups. The questions and responses appear in Section 5.2.We hope that these succeedings capture at least some essence of the very fruitful discussion that occurred at the workshop. Of course, this report cannot replace the benefits of actual attendance. The workshop will indeed continue, and we hope that the reader will be interested in attending a future ISAW.