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We present a programmatic approach to the optimisation of XACML policies that specifies how a set of access control rules should be best represented for optimised evaluation. The work assumes no changes to the current XACML specification and methods of interpretation shall be made, so that those who consume XACML are unaffected structurally, and those that generate XACML can provide optimised output. Discussion regarding the flexibility of the XACML specification to describe the same access rules with different policy configurations is presented, and is used to formulate a comprehensive analysis of the evaluation costs the possible policy configurations will produce. This leads to the specification of methods that can be employed to produce optimal forms of policy description. These are implemented and evaluated to show the benefits of the approach proposed.

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This paper is concerned with the problem of intrinsically assigning meaning to the signals responsible for autonomic responses in a system. Without an associated cognitive system, the Symbol Grounding Problem would constitute a major barrier in system adaptation and evolution. Based on an ongoing effort towards a formal and pragmatic development of self-regenerative software systems, this paper adopts concepts from Artificial Immune Systems (AIS) engineering, Information Theory and the Situation Calculus dialect of predicate logic. These are used to formalise the monitoring and control of system autonomic functions. In this way danger signals as an immune (self-healing/protecting) response and evolutionary (self-adapting) responses can be formalised into autonomic conditional and anticipatory reaction triggers. Thus any threat or potential enhancement to the system can be monitored for and the appropriate action taken to facilitate system dependability and safety.

This paper presents an ontology-driven secure XML content distribution scheme. This scheme first relies on a semantic access control model for XML documents that achieves three objectives: (1) representing flexible and evolvable policies, (2) providing a high-level mapping and interoperable interface to documents, and (3) automating the granting of fine-grained access rights by inferring on content semantics. A novel XML document parsing mechanism is defined to delegate document access control enforcement to a third party without leaking the document XML schema to it. The Encrypted Breadth First Order Labels (EBOL) encoding is used to bind semantic concepts with XML document nodes and to check the integrity of a document.