Bernard Butler

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We study the problem of optimising the provisioning of collections of virtual machines (VMs) having different placement constraints (e.g., security and anti-collocation) and characteristics (e.g., memory and disk capacity), given a set of physical machines (PMs) with known specifications, in order to achieve the objective of maximising an IaaS cloud(More)
The performance and scalability of access control systems is growing more important as organisations deploy ever more complex communications and content management systems. Fine-grained access control is becoming more pervasive, so decisions are more frequent and policy sets are larger. We outline a flexible performance testing framework that accepts XACML(More)
The performance and scalability of access control systems is a growing concern as organisations deploy ever more complex communications and content management systems. This paper describes how an (offline) experimental testbed may be used to address performance concerns. To begin, timing measurements are collected from a server component incorporating the(More)
Resource access control policies for an organization are often derived from best practice standards or from high level business policies. To ensure that access control is enforced effectively, these business policies need to be translated into deployable system configurations or lower level policies for multiple diverse systems. These target policy(More)
As the need for more pervasive and more complex access controls grows, the challenge of ensuring the performance of access control systems is becoming apparent. Researchers have proposed several solutions to mitigate performance problems, including: adjusting the policy set; re-engineering the policy decision point (PDP); and decomposing the policies and(More)
Organisations are deploying ever more complex communications and content management systems to control entitlements to read, write and share protected digital resources. The resulting access control policy infrastructure defines and resolves the complex decision boundary between safety and openness. Moreover, for information security models enabling ethical(More)