Embedded systems are microprocessor-based systems that cover a large range of computer systems from ultra small computer-based devices to large systems monitoring and controlling complex processes. The particular constraints that must be met by embedded systems, such as timeliness, resource-use efficiency, short time-to-market and low cost, coupled with the increasing complexity of embedded system software, demand technologies and processes that will tackle these issues. An attractive approach to manage the software complexity, increase productivity, reduce time to market and decrease development costs, lies in the adoption of the component based software engineering (CBSE) paradigm. The specific characteristics of embedded systems lead to important design issues that need to be addressed by a component model. Consequently, a component model for development of embedded systems needs to systematically address extra-functional system properties. The component model should support predictable system development and as such guarantee absence or presence of certain properties. Formal methods can be a suitable solution to guarantee the correctness and reliability of software systems.   Following the CBSE spirit, in this thesis we introduce the ProCom component model for development of distributed embedded systems. ProCom is structured in two layers, in order to support both a high-level view of loosely coupled subsystems encapsulating complex functionality, and a low-level view of control loops with restricted functionality. These layers differ from each other in terms of execution model, communication style, synchronization etc., but also in kind of analysis which are suitable. To describe the internal behavior of a component, in a structured way, in this thesis we propose REsource Model for Embedded Systems (REMES) that describes both functional and extra-functional behavior of interacting embedded components. We also formalize the resource-wise properties of interest and show how to analyze such behavioral models against them. / PROGRESS

Contemporary approaches to cross-platform mobile application development, such as hybrid apps from PhoneGap and generated native apps from Xamarin, show promise in reducing development time towards Android, iOS and other platforms. At the same time, studies show that there are various problems associated with these approaches, including suffering user experiences and codebases that are difficult to maintain and test properly. In this thesis, a novel prototype framework called Building Blocks was developed with the purpose of investigating the feasibility of utilizing component-based software engineering in solving this problem. The prototype was developed towards Android along with a web interface that allowed users to assemble an Android app using software components. The report concludes that component-based software engineering can be – and already is – utilized successfully to improve cross-platform mobile app development with special regards to user experience. Qualitative data indicate that Building Blocks as a concept is flexible and shows promise for mobile app development in which functionality is often reused, such as enterprise apps. Rapid prototyping using the web-based visual editing tool was another promising area. However, future use of Building Blocks would require further work on the prototype to improve its ease of use.

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Web services provide a standardized means of publishing diverse, distributed applications. Increasingly, corporations are providing services or programs within and between organizations either on corporate intranets or on the cloud. Many of these services can be composed together, ideally automatically, to provide value-added service. Automated Web service composition is an example of such automation where given a specification of an objective to be realized and some knowledge of the state of the world, the problem is to automatically select, integrate, and invoke multiple services to achieve the specified objective. A popular approach to the Web service composition problem is to conceive it as an Artificial Intelligence planning task. This enables us to bring to bear many of the theoretical and computational advances in reasoning about actions to the task of Web service composition. However, Web service composition goes far beyond the reaches of classical planning, presenting a number of interesting challenges relevant to a large body of problems related to the composition of actions, programs, and services. Among these, an important challenge is generating not only a composition, but a high-quality composition tailored to user preferences. In this thesis, we present an approach to the Web service composition problem with a particular focus on the customization of compositions. We claim that there is a correspondence between generating a customized composition of Web services and non-classical Artificial Intelligence planning where the objective of the planning problem is specified as a form of control knowledge, such as a workflow or template, together with a set of constraints to be optimized or enforced. We further claim that techniques in (preference-based) planning can provide a computational basis for the development of effective, state-of-the-art techniques for generating customized compositions of Web services. To evaluate our claim, we characterize the Web service composition problem with customization as a non-classical planning problem, exploit and advance preference specification languages and preference-based planning, develop algorithms tailored to the Web service composition problem, prove formal properties of these algorithms, implement proof-of-concept systems, and evaluate these systems experimentally. While our research has been motivated by Web services, the theory and techniques we have developed are amenable to analogous problems in such diverse sectors as multi-agent systems, business process modeling, component software composition, and social and computational behaviour modeling and verification.

Web services provide a standardized means of publishing diverse, distributed applications. Increasingly, corporations are providing services or programs within and between organizations either on corporate intranets or on the cloud. Many of these services can be composed together, ideally automatically, to provide value-added service. Automated Web service composition is an example of such automation where given a specification of an objective to be realized and some knowledge of the state of the world, the problem is to automatically select, integrate, and invoke multiple services to achieve the specified objective. A popular approach to the Web service composition problem is to conceive it as an Artificial Intelligence planning task. This enables us to bring to bear many of the theoretical and computational advances in reasoning about actions to the task of Web service composition. However, Web service composition goes far beyond the reaches of classical planning, presenting a number of interesting challenges relevant to a large body of problems related to the composition of actions, programs, and services. Among these, an important challenge is generating not only a composition, but a high-quality composition tailored to user preferences. In this thesis, we present an approach to the Web service composition problem with a particular focus on the customization of compositions. We claim that there is a correspondence between generating a customized composition of Web services and non-classical Artificial Intelligence planning where the objective of the planning problem is specified as a form of control knowledge, such as a workflow or template, together with a set of constraints to be optimized or enforced. We further claim that techniques in (preference-based) planning can provide a computational basis for the development of effective, state-of-the-art techniques for generating customized compositions of Web services. To evaluate our claim, we characterize the Web service composition problem with customization as a non-classical planning problem, exploit and advance preference specification languages and preference-based planning, develop algorithms tailored to the Web service composition problem, prove formal properties of these algorithms, implement proof-of-concept systems, and evaluate these systems experimentally. While our research has been motivated by Web services, the theory and techniques we have developed are amenable to analogous problems in such diverse sectors as multi-agent systems, business process modeling, component software composition, and social and computational behaviour modeling and verification.

L’accroissement continu de la complexité des systèmes embarqués pose un problème majeur pour leur développement lequel doit aussi prendre en compte les exigences extra-fonctionnelles et les contraintes du domaine telles que la limitation et le partage des ressources, la distribution, et les contraintes temporelles et de fiabilité. De ce fait, les systèmes embarqués requièrent de nouvelles solutions pouvant efficacement et de manière prévisible répondre à l’ensemble de ces besoins. L’ingénierie logicielle basée composants est un paradigme qui a déjà démontré des aptitudes pour appréhender la complexité logicielle. Cependant, pour supporter de manière efficace les propriétés extra-fonctionnelles, un modèle de composants doit posséder des mécanismes spécifiques. L’objectif de cette thèse est de construire un tel support. Pour ce faire, nous avons analysé de manière systématique des modèles de composants existants à ce jour et identifié des challenges relatifs à la réalisation d’une approche basée composants dédiée au développement des systèmes embarqués. S’appuyant sur ces challenges, nous avons avancé l’état de l’art en développant ProCom, un nouveau modèle de composants qui répond aux attentes des systèmes embarqués au travers de sa sémantique d’exécution et de sa structuration en niveaux. Centré autour de ProCom, nous avons aussi développé PRIDE, son environnement de développement intégré. PRIDE couvre le procédé de développement des premières phases de spécification jusqu’à la synthèse et le déploiement et fournit des moyens d’intégrer différents outils d’analyse et de vérification. La contribution principale de cette thèse réside dans la modélisation et la réalisation d’un support pour la gestion des propriétés extra-fonctionnelles pour les systèmes embarqués construits à base de composants logiciels. Ce support facilite la spécification, le management et l’intégration de propriétés multi-valuées tenant compte du contexte dans lequel elles ont été établies. Les propriétés peuvent être attachées aux éléments architecturaux des modèles de composants et leurs valeurs peuvent être comparées et raffinées durant le développement. En particulier, le fait d’avoir des valeurs multiples avec leur contexte d’évaluation permet de comparer des valeurs provenant de différentes sources. Les concepts proposés ont été illustrés au travers d’exemples représentatifs de systèmes. / The continuously increasing complexity of embedded systems is a major issue for their development, which, in addition, must also consider specific extra-functional requirements and constraints, such as limited and shared resources, distribution, timing, and dependability. Thus, embedded systems call for development solutions that can efficiently and predictably cope with these issues. Component-based software engineering is a proven paradigm to handle complexity. Yet, for efficiently managing extra-functional properties, a component model needs to have dedicated mechanisms that provide a suitable support for their management. The objective of this thesis is to build this support. We have performed a systematic analysis of existing component models and identified challenges of applying a component-based approach to embedded system development. Based on these challenges we have advanced the current state-of-the-art by developing a new component model, called ProCom, that accommodates the specifics of embedded systems through its well-defined execution semantics and layered structure. Centered around ProCom, we have also developed PRIDE, the ProCom Integrated Development Environment. PRIDE supports the development from early specification to synthesis and deployment, providing the means to aggregate various analysis and verification tools. The main contribution of the thesis is in the design and implementation of an extra-functional property management framework that enables to seamlessly specify, manage and integrate multi-valued context-aware extra-functional properties of component-based embedded systems. Properties can be attached to architectural elements of component models and their values can be compared and refined during the development process. In particular, having multiple context-aware values allows values from different sources to be compared. The proposed concepts have been demonstrated on several representative example systems.

<p>The increasing complexity in the development of a configurable real-time system has emerged new principles of software techniques, such as aspect-oriented software development and component-based software development. These techniques allow encapsulation of the system's crosscutting concerns and increase the modularity of the software. The properties of a component that influences the systems performance or semantics are specified separately in entities called aspects, while basic functionality of the property still remains in the component. </p><p>When building a real-time system, different sets of configurations of aspects and components can be combined, resulting in different configurations of the system. The temporal behavior of the system changes and a way to ensure the predictability of the system is needed. </p><p>This thesis presents a tool for aspect-level worst-case execution time analysis, which gives a priori information about the temporal behavior of the system, before the process of composing aspects with components.</p>

<p>Rising complexity in the development of real-time systems has made it crucial to have reusable components and a more flexible way of configuring these components into a coherent system. Aspect-oriented system development (AOSD) is a technique that allows one to put a system’s crosscutting concerns into"modules"that are called aspects. Applying AOSD in real-time and embedded system development one can expect reductions in the complexity of the system design and development. </p><p>A problem with AOSD in its current form is that it does not support predictability in the time domain. Hence, in order to use AOSD in real-time system development, we need to provide ways of analyzing temporal behavior of aspects, components and resulting system (made from weaving aspects and components). Aspect analyzer is a tool that computes the worst-case execution time (WCET) for a set of components and aspects, thus, enabling support for predictability in the time domain of aspect-oriented real-time software. </p><p>A limitation of the aspect analyzer, until now, were that no verification had been made whether the aspect analyzer would produce WCET values that were close to the measured or computed (with another WCET analysis technique) WCET of an aspect-oriented real-time system. Therefore, in this thesis we perform a verification of the correctness of the aspect analyzer using a number of different methods for WCET analysis. These investigations of the correctness of the output from the aspect analyzer gave confidence to the automated WCET analysis. In addition, performing this verification led to the identification of the steps necessary to compute the WCETs of a piece of program, when using a third party tool, which gives the ability to write accurate input files for the aspect analyzer.</p>

<p>During the last years the need for real-time database services has increased due to the growing number of data-intensive applications needing to enforce real-time constraints. The COMponent-based Embedded real-Time database (COMET) is a real-time database developed to meet these demands. COMET is developed using the AspeCtual COmponent-based Real-time system Development (ACCORD) design method, and consists of a number of components and aspects, which can be composed into a number of different configurations depending on system demands, e.g., Quality of Service (QoS) management can be used in unpredictable environments. </p><p>In embedded systems with requirementson high up-time it may not be possible to temporarily shut down the system for reconfiguration. Instead it is desirable to enable dynamic reconfiguration of the system, exchanging components during run-time. This in turn sets demands on the feedback control of the system to adjust to these new conditions, since a new time variant system has been created. </p><p>This thesis project implements improvements in COMET to create a more stable database suitable for further development. A mechanism for dynamic reconfiguration of COMET is implemented, thus, enabling components and aspects to be swapped during run-time. Adaptive feedback control algorithms are also implemented in order to better adjust to workload variations and database reconfiguration.</p>

<p>Increasing complexity of real-time systems and demands for enabling their configurability and tailorability are strong motivations for applying new software engineering principles such as aspect-oriented and component-based software development. The integration of these two techniques into real-time systems development would enable: (i) efficient system configuration from the components in the component library based on the system requirements, (ii) easy tailoring of components and/or a system for a specific application by changing the behavior (code) of the component by aspect weaving, and (iii) enhanced flexibility of the real-time and embedded software through the notion of system configurability and component tailorability.</p><p>In this thesis we focus on applying aspect-oriented and component-based software development to real-time system development. We propose a novel concept of aspectual component-based real-time system development (ACCORD). ACCORD introduces the following into real-time system development: (i) a design method that assumes the decomposition of the real-time system into a set of components and a set of aspects, (ii) a real-time component model denoted RTCOM that supports aspect weaving while enforcing information hiding, (iii) a method and a tool for performing worst-case execution time analysis of different configurations of aspects and components, and (iv) a new approach to modelling of real-time policies as aspects.</p><p>We present a case study of the development of a configurable real-time database system, called COMET, using ACCORD principles. In the COMET example we show that applying ACCORD does have an impact on the real-time system development in providing efficient configuration of the real-time system. Thus, it could be a way for improved reusability and flexibility of real-time software, and modularization of crosscutting concerns.</p><p>In connection with development of ACCORD, we identify criteria that a design method for component-based real-time systems needs to address. The criteria include a well-defined component model for real-time systems, aspect separation, support for system configuration, and analysis of the composed real-time system. Using the identified set of criteria we provide an evaluation of ACCORD. In comparison with other approaches, ACCORD provides a distinct classification of crosscutting concerns in the real-time domain into different types of aspects, and provides a real-time component model that supports weaving of aspects into the code of a component, as well as a tool for temporal analysis of the weaved system.</p> / Report code: LiU-TEK-LIC-2003:23.