Simone Röttger

The COMQUAD component model: enabling dynamic selection of implementations by weaving non-functional aspects

The reliability of non-functional contracts is crucial for many software applications. This added to the increasing attention this issue lately received in software engineering. Another development in software engineering is toward component-based systems. The interaction of both, non-functional aspects and components, is a relatively new research area, which the COMQUAD project is focusing on.Our component model, presented in this paper, enables the specification and runtime support of non-functional aspects in component-based systems. At the same time, a clear separation of non-functional properties and functionally motivated issues is provided. We achieve this by extending the concepts of the existing component-based systems Enterprise JavaBeans (EJB) and CORBA Components (CCM). Non-functional aspects are described orthogonally to the application structure using descriptors, and are woven into the running application by the component container acting as a contract manager. The container implicitly instantiates component specifications and connects them according to the current requests. The selection of actual implementations depends on the particular clients non-functional requirements. This technique also enables adaptation based on the specific quantitative capabilities of the running system.In this paper we give a detailed description of the COMQUAD component model and the appropriate container support. We also provide a simple case study of a multimedia application for better understanding.

Model-Driven Development for Non-functional Properties: Refinement Through Model Transformation

Model driven architecture (MDA) views application development as a continuous transformation of models of the target system. We propose a methodology which extends this view to non-functional properties. Our basic idea is the separation of two different roles in the development process: the role of the measurement designer and the role of the application designer. The former provides a library of measurement definitions which is later used by the latter to annotate functional application models with non-functional property specifications. In this paper we define the notion of context models to allow the measurement designer to provide measurement definitions at different levels of abstraction independently of concrete applications.

Enforceable component-based realtime contracts

We present enforceable component-based realtime contracts, the first extension of component-based software engineering technology that comprehensively supports adaptive realtime systems from specification all the way to the running system.To provide this support, we have extended component-based interface definition languages (IDLs) and component representations in repositories to express realtime requirements for components. The final software, which is assembled from the components, is then executed on a realtime operating system (RTOS) with the help of a component runtime system. RTOS resource managers and the IDL-extensions are based on the same mathematical foundation. Thus, the component runtime system can use information expressed in a component-oriented manner in the extended IDL to derive parameters for the task-based admission and scheduling in the RTOS. Once basic realtime properties can thus be guaranteed, runtime support can be extended to more elaborate schemes that also support adaptive applications (container-managed quality assurance).We claim that this study convincingly demonstrates how component-based software engineering can be extended to build systems with non-functional requirements.

Tool Support for Refinement of Non-functional Specifications

Model driven architecture (MDA) views application development as a continuous transformation of models of the target system. We propose a methodology which extends this view to non-functional properties. In previous publications we have shown how we can use so-called context models to make the specification of non-functional measurements independent of their application in concrete system specifications. We have also shown how this allows us to distinguish two roles in the development process: the measurement designer and the application designer.In this paper we use the notion of context models to allow the measurement designer to provide measurement definitions at different levels of abstraction. A measurement in our terminology is a non-functional dimension that can be constrained to describe a non-functional property. Requiring the measurement designer to define transformations between context models, and applying them to measurement definitions, enables us to provide tool support for refinement of non-functional constraints to the application designer. The paper presents the concepts for such tool support as well as a prototype implementation.

The COMQUAD component container architecture

Component-based applications require runtime support to be able to guarantee non-functional properties. This paper proposes an architecture for a real-time-capable, component-based runtime environment, which allows to separate non-functional and functional concerns in component-based software development. The architecture is presented with particular focus on the real-time-non-real-time split of the runtime environment and the communication issues of respective component types and container parts.