The problem of linear feedback design for bilinear control systems guaranteeing their conditional closed-loop stability is considered. It is shown that this problem can be reduced to investigating the conditional stability of solutions of quadratic systems of differential equations depending on parameters of the control law. Sufficient conditions for stability in the cone of a homogeneous quadr...

In this paper we define formally a wide variety of separation-of-duty (SoD) properties, which include the best known to date, and establish their relationships within a formal model of role-based access control (RBAC). The formalism helps remove all ambiguities of informal definition, and offers a wide choice of implementation strategies. We also explore the composability of SoD properties and ...

This paper presents an adaptive fuzzy controller for a class of completely pure-feedback nonlinear systems. Takagi-Sugeno type fuzzy logic systems are used to approximate the unknown nonlinear functions. The controller synthesis is developed by the backstepping technique and the small gain approach. The closed-loop control system is proved to be semi-globally uniformly ultimately bounded (SGUUB...

Role-based access control (RBAC) has been acknowledged as an effective mechanism for specifying and enforcing access control policies. However, it is not always clear how an RBAC policy can be systematically integrated into the system design so as to preserve the desired security requirements. In this paper we propose a representation and a process that supports systematic integration of an acc...

The Extensible Markup Language (XML) is utilised in many Internet applications we are using today. However, as with many computing technologies, vulnerabilities exist in XML that can allow for malicious and unauthorised use. Applications that utilise XML are therefore susceptible to security faults if they do not provide their own methods. Our research focuses on developing a formal language wh...

High assurance computer systems are computer systems where convincing evidence is required that the system satis es a collection of critical properties. To operate correctly, these systems must satisfy properties such as safety and security. Examples of high assurance systems include ight control systems, medical systems, and control systems for nuclear plants. In addition, increased reliance o...

With the growing use of wireless networks and mobile devices, we are moving towards an era where location information will be necessary for access control. The use of location information can be used for enhancing the security of an application, and it can also be exploited to launch attacks. For critical applications, such as the military, a formal model for location-based access control is ne...

Second order sufficient optimality conditions for bang-bang control problems in a very general form have been obtained in [15, 21, 13, 12, 1]. These conditions require the positive definiteness (coercivity) of an associated quadratic form on the finite-dimensional critical cone. In the present paper, we investigate similar conditions for optimal control problems with a control variable having t...

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...