Modelling Architecture Styles

Software systems tend to increase over time in size and complexity. Their development usually spans a long period of time and often results in systems that are hard to understand, debug and maintain. Architectures are common means for organising coordination between components in order to build complex systems and make them manageable. They allow thinking on a higher plane and avoiding low-level mistakes. Grouping architectures that share common characteristics into architecture styles assists component re-use and thus, the cost-effective development of systems. Additionally, architecture styles provide means for ensuring correctness-by-construction by enforcing global properties. The main goal of this thesis is to propose and study formalisms for modelling architectures and architecture styles. For the specification of architectures, we study interaction logics, which are Boolean algebras on a set of component actions. We study a modelling methodology based on first-order interaction logic for writing architecture constraints. To validate the applicability of the approach, we developed the JavaBIP framework that integrates architectures into mainstream software development. JavaBIP receives as input architecture specifications, which it then uses to coordinate software components without requiring access to their source code. JavaBIP implements the principles of the BIP component framework. For the specification of architecture styles, we propose configuration logics, which are powerset extensions of interaction logic. Propositional configuration logic formulas are generated from formulas of interaction logic by using the operators union, intersection and complementation, as well as a coalescing operator. We provide a complete axiomatisation of the propositional configuration logic and a decision procedure for checking that an architecture satisfies given logical specifications. To allow genericity of specifications, we study higher-order extensions of the propositional configuration logic. We provide several examples illustrating the application of configuration logics to the characterisation of architecture styles. For the specification of architecture styles, we also propose architecture diagrams, which is a graphical language rooted in rigorous semantics. We provide methods to assist software developers to specify consistent architecture diagrams, generate the conforming architectures of a style and check whether an architecture model meets given style requirements. We present a full encoding of architecture diagrams into configuration logics. Finally, we report on applications of architecture diagrams to modelling architecture styles identified in realistic case studies of on-board satellite software

Bridging the Gap Between Requirements and Simulink Model Analysis

Formal verification and simulation are powerful tools for the verification of requirements against complex systems. Requirements are developed in early stages of the software lifecycle and are typically expressed in natural language. There is a gap between such requirements and their software implementations.We present a framework that bridges this gap by supporting a tight integration and feedback loop between high-level requirements and their analysis against software artifacts. Our framework implements an analysis portal within the fret requirements elicitation tool, thus forming an end-to-end, open-source environment where requirements are written in an intuitive, structured natural language, and are verified automatically against Simulink models

For Coordination, State Component Transitions

Coordinating component behaviour and, in particular, concurrent access to resources is among the key difficulties of building large concurrent systems. To address this, developers must be able to manipulate high-level concepts, such as Finite State Machines and separate functional and coordination aspects of the system behaviour. OSGi associates to each bundle a simple state machine representing the bundle’s lifecycle. However, once the bundle has been started, it remains in the state Active — the functional states are not represented. Therefore, this mechanism is not sufficient for coordination of active components. In this talk, we presented a methodology for functional component coordination in OSGi by using BIP coordination mechanisms. In BIP, systems are constructed by superposing three layers of modelling: Behaviour, Interaction and Priority. This approach allows us to clearly separate the system-wide coordination policies from the component behaviour and the interface that components expose for interaction. By using BIP, we have shown how the allowed global states and state transitions of the modular system can be taken into account in a non-invasive manner and without any impact on the technology stack within an OSGi container. We illustrated our approach on real-life application use-case