A robust tri-state election algorithm for scalable applications

Existing election algorithms suffer limited scalability. This limit stems from the communication design which in turn stems from their fundamentally two-state behaviour. This paper presents a new election algorithm specifically designed to be highly scalable in broadcast networks whilst allowing any processing node to become coordinator with initially equal probability. To achieve this, careful attention has been paid to the communication design, and an additional state has been introduced. The design of the tri-state election algorithm has been motivated by the requirements analysis of a major research project to deliver robust scalable distributed applications, including load sharing, in hostile computing environments in which it is common for processing nodes to be rebooted frequently without notice. The new election algorithm is based in-part on a simple 'emergent' design. The science of emergence is of great relevance to developers of distributed applications because it describes how higher-level self-regulatory behaviour can arise from many participants following a small set of simple rules. The tri-state election algorithm is shown to have very low communication complexity in which the number of messages generated remains loosely-bounded regardless of scale for large systems; is highly scalable because nodes in the idle state do not transmit any messages; and because of its self-organising characteristics, is very stable.

Distributed belief revision as applied within a descriptive model of jury deliberations

Belief revision is a well-research topic within AI. We argue that the new model of distributed belief revision as discussed here is suitable for general modelling of judicial decision making, along with extant approach as known from jury research. The new approach to belief revision is of general interest, whenever attitudes to information are to be simulated within a multi-agent environment with agents holding local beliefs yet by interaction with, and influencing, other agents who are deliberating collectively. In the approach proposed, it's the entire group of agents, not an external supervisor, who integrate the different opinions. This is achieved through an election mechanism, The principle of "priority to the incoming information" as known from AI models of belief revision are problematic, when applied to factfinding by a jury. The present approach incorporates a computable model for local belief revision, such that a principle of recoverability is adopted. By this principle, any previously held belief must belong to the current cognitive state if consistent with it. For the purposes of jury simulation such a model calls for refinement. Yet we claim, it constitutes a valid basis for an open system where other AI functionalities (or outer stiumuli) could attempt to handle other aspects of the deliberation which are more specifi to legal narrative, to argumentation in court, and then to the debate among the jurors.

Emergence: a paradigm for robust and scalable distributed applications

Natural distributed systems are adaptive, scalable and fault-tolerant. Emergence science describes how higher-level self-regulatory behaviour arises in natural systems from many participants following simple rulesets. Emergence advocates simple communication models, autonomy and independence, enhancing robustness and self-stabilization. High-quality distributed applications such as autonomic systems must satisfy the appropriate nonfunctional requirements which include scalability, efficiency, robustness, low-latency and stability. However the traditional design of distributed applications, especially in terms of the communication strategies employed, can introduce compromises between these characteristics. This paper discusses ways in which emergence science can be applied to distributed computing, avoiding some of the compromises associated with traditionally-designed applications. To demonstrate the effectiveness of this paradigm, an emergent election algorithm is described and its performance evaluated. The design incorporates nondeterministic behaviour. The resulting algorithm has very low communication complexity, and is simultaneously very stable, scalable and robust.

Natural inspiration for self-adaptive systems

The emergent behaviour of autonomic systems, together with the scale of their deployment, impedes prediction of the full range of configuration and failure scenarios; thus it is not possible to devise management and recovery strategies to cover all possible outcomes. One solution to this problem is to embed self-managing and self-healing abilities into such applications. Traditional design approaches favour determinism, even when unnecessary. This can lead to conflicts between the non-functional requirements. Natural systems such as ant colonies have evolved cooperative, finely tuned emergent behaviours which allow the colonies to function at very large scale and to be very robust, although non-deterministic. Simple pheromone-exchange communication systems are highly efficient and are a major contribution to their success. This paper proposes that we look to natural systems for inspiration when designing architecture and communications strategies, and presents an election algorithm which encapsulates non-deterministic behaviour to achieve high scalability, robustness and stability.

Penalties on car rental agreements

Examines the Cambridge County Court ruling in Volkswagen Financial Services (UK) Ltd v Ramage on whether a clause in a car hire contract which allowed the finance company, upon repudiation of the contract after the hirer fell into arrears, to claim compensation equivalent to the lost future rental payments was unenforceable as a penalty clause, rather than being a reasonable pre-estimate of actual loss. Refers to case law including the Court of Appeal ruling in Anglo Auto Finance Co v James in considering the differing losses which would occur during the course of the hire term according to the natural depreciation of the value of the car. Notes the reasoning of the Court on: (1) contracts of hire compared with hire purchase agreements; (2) the comparative position of the parties and the freedom to contract elsewhere; and (3) the reasonable prediction of future losses.

Postcolonial futures: postcolonial literature and the Obama moment

Since the late 1970s the western academy has encouraged the development of postcolonial literary theory and the formulation of a postcolonial literary canon existing outside the prescriptive narratives of the ‘mother’ country and empire. Having lost faith in the binary oppositions underpinning such narratives, we turned to alternative fictions that contested the construction of the ‘other’, the world divided between the ‘West and the Rest’. The publication of Edward Said’s Orientalism in 1978 marked the beginning of the discipline now known as postcolonial studies with its new ways of understanding ‘the west’s’ relationship with ‘the east’ and, by extension, all the former colonies of empire. Despite these radical origins, however, postcolonialism’s more recent emphasis on the psychological and its affirmation of the hybrid text and self has, for many, served to obscure real economic social realities that have very little to do with the magical or wondrous textual expression of a postcolonial identity. This paper considers problems associated with defining the postcolonial and proposes that, in a literary context, we broaden its meaning to include texts traditionally outside the category of postcolonial literature. To extend the meaning of postcolonial is timely as we are now witnessing its relocation from ‘margin’ to ‘centre’ with the election of Barack Obama. This moment may be seen as a disruption of conventional understandings of what constitutes postcolonial literature, essentially as oppositional discourse that could only define itself as peripheral to, or ‘post’, metropolitan and economic concerns. [From the Author]