Task Scheduling with RT Constraints

This paper addresses the problem of scheduling reactive realtime transactions (task groups) implementing a network of extended Finite State Machines communicating asynchronously. Task instances are..

Symbolic Implementation of Connectors in BIP

BIP is a component framework for constructing systems by superposing three layers of modeling: Behavior, Interaction, and Priority. Behavior is represented by labeled transition systems communicating through ports. Interactions are sets of ports. A synchronization between components is possible through the interactions specified by a set of connectors. When several interactions are possible, priorities allow to restrict the non-determinism by choosing an interaction, which is maximal according to some given strict partial order. The BIP component framework has been implemented in a language and a tool-set. The execution of a BIP program is driven by a dedicated engine, which has access to the set of connectors and priority model of the program. A key performance issue is the computation of the set of possible interactions of the BIP program from a given state. Currently, the choice of the interaction to be executed involves a costly exploration of enumerative representations for connectors. This leads to a considerable overhead in execution times. In this paper, we propose a symbolic implementation of the execution model of BIP, which drastically reduces this overhead. The symbolic implementation is based on computing boolean representation for components, connectors, and priorities with an existing BDD package

Let’s Get Physical: Computer Science Meets Systems

In cyber-physical systems (CPS) computing, networking and control (typically regarded as the "cyber" part of the system) are tightly intertwined with mechanical, electrical, thermal, chemical or biological processes (the "physical" part). The increasing sophistication and heterogeneity of these systems requires radical changes in the way sense-and-control platforms are designed to regulate them. In this paper, we highlight some of the design challenges due to the complexity and heterogeneity of CPS. We argue that such challenges can be addressed by leveraging concepts that have been instrumental in fostering electronic design automation while dealing with complexity in VLSI system design. Based on these concepts, we introduce a design methodology whereby platform-based design is combined with assume-guarantee contracts to formalize the design process and enable realization of CPS architectures and control software in a hierarchical and compositional manner. We demonstrate our approach on a prototype design of an aircraft electric power system. © 2014 Springer-Verlag Berlin Heidelberg

A General Framework for Architecture Composability

Architectures depict design principles: paradigms that can be understood by all, allow thinking on a higher plane and avoiding low-level mistakes. They provide means for ensuring correctness by construction by enforcing global properties characterizing the coordination between components. An architecture can be considered as an operator A that, applied to a set of components B, builds a composite component A(B) meeting a characteristic property Φ. Architecture composability is a basic and common problem faced by system designers. In this paper, we propose a formal and general framework for architecture composability based on an associative, commutative and idempotent architecture composition operator ⊕. The main result is that if two architectures A1 and A2 enforce respectively safety properties Φ1 and Φ2 , the architecture A1 ⊕ A2 enforces the property Φ1 ∧ Φ2 , that is both properties are preserved by architecture composition. We also establish preservation of liveness properties by architecture composition. The presented results are illustrated by a running example and a case study

Professionalizing school governance: the disciplinary effects of school autonomy and inspection on the changing role of school governors

Since the 1980s, state schools in England have been required to ensure transparency and accountability through the use of indicators and templates derived from the private sector and, more recently, globally circulating discourses of ‘good governance’ (an appeal to professional standards, technical expertise, and performance evaluation as mechanisms for improving public service delivery). The rise of academies and free schools (‘state-funded independent schools’) has increased demand for good governance, notably as a means by which to discipline schools, in particular school governors – those tasked with the legal responsibility of holding senior leadership to account for the financial and educational performance of schools. A condition and effect of school autonomy, therefore, is increased monitoring and surveillance of all school governing bodies. In this paper, I demonstrate how these twin processes combine to produce a new modality of state power and intervention; a dominant or organizing principle by which government steer the performance of governors through disciplinary tools of professionalization and inspection, with the aim of achieving the ‘control of control’. To explain these trends, I explore how various established and emerging school governing bodies are (re)constituting themselves to meet demands for good governance