Abstract: Software architecture allows us to make many decisions about a software system and analyze it even before it exists in order to make systematic and planned development possible. Similarly, architecture-based software evolution planning makes planned evolution possible by allowing us to make many decisions about evolution of a software system and analyze its evolution at the level of architecture design before software evolution is realized. In this paper, we develop a framework for architecture-based software evolution planning for the class of deterministic evolution plans by defining and relating various essential concepts and developing its valuation mechanism so that a plan with the greatest value among candidate plans can be selected as the optimal plan. A case study is conducted for explicating the framework and exemplifying its usage.

Abstract: This paper presents an extension of existing software architecture tools to model physical systems, their interconnections, and the interactions between physical and cyber components. A new CPS architectural style is introduced to support the principled design and evaluation of alternative architectures for cyber-physical systems (CPSs). The implementation of the CPS architectural style in AcmeStudio includes behavioral annotations on components and connectors using either finite state processes (FSP) or linear hybrid automata (LHA) with plug-ins to perform behavior analysis using the Labeled Transition System Analyzer (LTSA) or Polyhedral Hybrid Automata Verifier (PHAVer), respectively. The CPS architectural style and analysis plug-ins are illustrated with an example.

Abstract: Increasingly, systems must have the ability to self-adapt to meet changes in their execution environment. Unfortunately, existing solutions require human oversight, or are limited in the kinds of systems and the set of quality-of-service concerns they address. Our approach, embodied in a system called Rainbow, uses software architecture models and architectural styles to overcome existing limitations. It provides an engineering approach and a framework of mechanisms to monitor a target system and its environment, reflect observations into a system's architecture model, detect opportunities for improvements, select a course of action, and effect changes in a closed loop. The framework provides general and reusable infrastructures with well-defined customization points, allowing engineers to systematically customize Rainbow to particular systems and concerns.

Abstract: This paper presents a framework for engineering resource-adaptive software targeted at small mobile devices. Rather than building a solution from scratch, we extend and integrate existing work on software infrastructures for ubiquitous computing, and on resource-adaptive applications. This paper addresses two research questions: first, is it feasibility to coordinate resource allocation and adaptation policies among several applications in a way that is both effective and efficient. And second, can end-users understand and control such adaptive behaviors dynamically, depending on user-defined goals for each activity. The evaluation covered both the systems and the usability perspectives, the latter by means of a user study. The contributions of this work are: first, a set of design guidelines, including APIs for integrating new applications; second, a concrete infrastructure that implements the guidelines. And third, a way to model quality of service tradeoffs based on utility theory, which our research indicates end-users with diverse backgrounds are able to leverage for guiding the adaptive behaviors towards activity-specific quality goals.

Abstract: As new market opportunities, technologies, platforms, and frameworks become available, systems require large-scale and systematic architectural restructuring to accommodate them. Today’s architects have few tools and techniques to help them plan this architecture evolution. In particular, they have little assistance in planning alternative evolution paths, trading-off various aspects of the different paths, or knowing best practices for particular domains. In this paper we describe an approach for assisting architects in developing and reasoning about architectural evolution paths. The key in-sight of our approach is that, architecturally, many system evolutions follow certain common patterns – or evolution styles. We define what we mean by an evolution style, and show how it can be used to provide automated assistance for expressing architectural evolution, and for reasoning about both the correctness and quality of evolution paths.

Abstract: One common approach to self-adaptive systems is to incorporate a control layer that monitors a system, supervisorily detects problems, and applies adaptation strategies to fix problems or improve system behavior. While such approaches have been found to be quite effective, they are typically limited to carrying out a single adaptation at a time, delaying other adaptations until the current one finishes. This in turn leads to a problem in which a time-critical adaptation may have to wait for an existing long-running adaptation to complete, thereby missing a window of opportunity for that adaptation. In this paper we improve on existing practice through an approach in which adaptations can be preempted to allow for other time-critical adaptations to be scheduled. Scheduling is based on an algorithm that maximizes time-related utility for a set of concurrently executing adaptations.

Abstract: An emergent domain that raises some unique engineering challenges is that of software architectures to convert large bodies of unstructured data to human-usable knowledge, such as in the domain of socio-cultural information analysis. We report on an architecture based on Service-Oriented Architectures that we are applying in this domain. We list the requirements that such an architecture must support, describe our architecture for addressing them, and outline what we believe are the important engineering and research issues that must still be overcome.

Abstract: Architecture evolution is a key feature of most software systems. There are few tools that help architects plan and execute these evolutionary paths. We demonstrate a tool to enable architects to describe evolution paths, associate properties with elements of the paths, and perform trade-off analysis over these paths.

Abstract: Architecture evolution, a key aspect of software evolution, is typically done in an ad hoc manner, guided only by the competence of the architect performing it. This process lacks the rigor of an engineering discipline. In this paper, we argue that architecture evolution must be engineered — based on rational decisions that are supported by formal models and objective analyses. We believe that evolutions of a restricted form — close-ended evolution, where the starting and ending design points are known a priori — are amenable to being engineered. We discuss some of the key challenges in engineering close-ended evolution. We present a conceptual framework in which an architecture evolutionary trajectory is modeled as a sequence of steps, each captured by an operator. The goal of our framework is to support exploration and objective evaluation of different evolutionary trajectories. We conclude with open research questions in developing this framework.

Abstract: Rainbow is an approach for engineering self-adaptive systems, with run-time, closed-loop control over target systems to monitor, detect, decide, and act on opportunities for system improvement. RAIDE enables adaptation engineers to customize the Rainbow framework, simulate adaptation behavior, and deploy Rainbow run-time components.

Abstract: Analysis at the level of a runtime architecture matches the way experts reason about security or privacy better than a purely code-based strategy. However, the architecture must still be correctly realized in the implementation.

We previously developed Scholia to analyze, at compile time, communication integrity between arbitrary object-oriented code, and a rich, hierarchical intended runtime architecture, using typecheckable annotations. This paper applies Scholia to security runtime architectures. Having established traceability between the target architecture and the code, we extend Scholia to enforce structural architectural constraints. At the code level, annotations enforce local, modular constraints. At the architectural level, predicates enforce global constraints. We validate the end-to-end approach in practice using a real 3,000-line Java implementation, and enforce its conformance to a security architecture designed by an expert.