We propose a formal account of XACML, an OASIS standard adhering to the Policy Based Access Control model for the specification and enforcement of access control policies. To clarify all ambiguous and intricate aspects of XACML, we provide it with a more manageable alternative syntax and with a solid semantic ground. This lays the basis for developing tools and methodologies which allow softwar...

Just as organisations have goals describing their primary business objectives, they also have goals with respect to controlling how these objectives are met. These are the control goals of an organisation which are enforced through a system of internal control. Such a system enables them to adhere to external laws and internal regulations, prevent and detect fraud and continuously enhance the o...

Two basic paradigms towards speciication of information security requirements can be taken: continuous speciication and early speciication of requirements. In models supporting continuous specii-cation and reenement of information security requirements, the development organization is more vulnerable to the tampering with partially speciied requirement primitives. This paper proposes a formal m...

Event-B is a refinement-based formal method that has been shown to be useful in developing concurrent and distributed programs. Large models can be decomposed into sub-models that can be refined semi-independently and executed in parallel. In this paper, we show how to introduce explicit control flow for the concurrent sub-models in the form of event schedules. We explore how schedules can be d...

We present a model for an SIR epidemic in a population consisting of two components—locals and migrants. We identify three equilibrium points and we analyse the stability of the disease free equilibrium. Then we apply optimal control theory to find an optimal vaccination strategy for this 2-group population in a very simple form. Finally we support our analysis by numerical simulation using the...

This paper discusses the use of formal methods in the development of the control system for the Maeslant Kering. The Maeslant Kering is the movable dam which has to protect Rotterdam from floodings while, at (almost) the same time, not restricting ship traffic to the port of Rotterdam. The control system, called Bos, completely autonomously decides about closing and opening of the barrier and, ...

A number of timed-trace formalisms, where systems are modelled by time-varying functions, have been proposed for the formal development of real-time systems. In this paper, we illustrate one such approach via the speciication and reenement of the well-known Steam Boiler Control Problem. The case study illustrates the use of a timed-trace formalism to specify deadlines and other timing constrain...

It is well-known that a fundamental problem in embedded control systems is the veriication of the safety requirements. Formal methods and related support tools can successfully be applied in the formal proof that a system is safe. However, the complexity of real systems is such that automated tools often fail to formally validate such systems. A typical case is when \state explosion" problems a...

Recently a set of guidelines, or cookbook, has been developed for modelling and refinement of control problems in Event-B. The Event-B formal method is used for system-level modelling by defining states of a system and events which act on these states. It also supports refinement of models. This cookbook is intended to systematise the process of modelling and refining a control problem system b...

The paper deals with practical aspects of developing control systems. We briefly discuss safety-critical systems, we examine the use of formal methods as a possible technique for increasing safety and reliability (by allowing a formal specification of the initial requirements of the system and by avoiding design errors) and we propose a design methodology for such systems based on data-flow net...