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Since the end of the Cold War, the monopoly of legitimate organized force of many African states has been eroded by a mix of rebel groups, violent extremist organizations, and self-defence militias created in response to the rise in organized violence on the continent. African Border Disorders explores the complex relationships that bind states, transnational rebels and extremist organizations, and borders on the African continent. Combining cutting edge network science with geographical analysis, the first part of the book highlights how the fluid alliances and conflicts between rebels, violent extremist organizations and states shape in large measure regional patterns of violence in Africa. The second part of the book examines the spread of Islamist violence around Lake Chad through the lens of the violent Nigerian Islamist group Boko Haram, which has evolved from a nationally-oriented militia group, to an internationally networked organization. The third part of the book explores how violent extremist organizations conceptualize state boundaries and territory and, reciprocally, how do the civil society and the state respond to the rise of transnational organizations. The book will be essential reading for all students and specialists of African politics and security studies, particularly those specializing on fragile states, sovereignty, new wars, and borders as well as governments and international organizations involved in conflict prevention and early intervention in the region.

Manipulating semistructured data, such as XML, does not fit well within conventional programming languages. A typical manipulation requires finding all occurrences of a structure matching a structured search pattern, whose context may be different in different places, and both aspects cause difficulty. If a special-purpose query language is used to manipulate XML, an interface to a more general programming environment is required, and this interface typically creates runtime overhead for type conversion. However, adding XML manipulation to a general-purpose programming language has proven difficult because of problems associated with expressiveness and typing. We show an alternative approach that handles many kinds of patterns within an existing strongly-typed general-purpose programming language called bondi. The key ideas are to express complex search patterns as structures of simple patterns, pass these complex patterns as parameters to generic data-processing functions and traverse heterogeneous data structures by a generalized form of pattern matching. These ideas are made possible by the language's support for pattern calculus, whose typing on structures and patterns enables path and pattern polymorphism. With this approach, adding a new kind of pattern is just a matter of programming, not language design. Copyright © 2006, Australian Computer Society, Inc.

When data mining and knowledge discovery techniques must be used to analyze large amounts of data, high-performance parallel and distributed computers can help to provide better computational performance and, as a consequence, deeper and more meaningful results. Recently grids, composed of large-scale, geographically distributed platforms working together, have emerged as effective architectures for high-performance decentralized computation. It is natural to consider grids as tools for distributed data-intensive applications such as data mining, but the underlying patterns of computation and data movement in such applications are different from those of more conventional high-performance computation. These differences require a different kind of grid, or at least a grid with significantly different emphases. This paper discusses the main issues, requirements, and design approaches for the implementation of grid-based knowledge discovery systems. Furthermore, some prospects and promising research directions in datacentric and knowledge-discovery oriented grids are outlined.

Existing interfaces to large-scale hypermedia such as the world wide web have poor conceptual models and poor rendering of navigational and contextual information. New technologies that make it cheaper to use three-dimensional representations suggest the use of richer conceptual models. We discuss criteria for assessing more powerful conceptual models and design decisions that have to be made to exploit richer interfaces. The Treeworld model is suggested as one attractive example of such a model.

Document archives contain large amounts of data to which sophisticated queries are applied. The size of archives and the complexity of evaluating queries makes the use of parallelism attractive. The use of semantically-based markup such as SGML makes it possible to represent documents and document archives as data types. We present a theory of trees and tree homomorphisms, modelling structured text archives and operations on them, from which it can be seen that: many apparently unrelated tree operations are homomorphisms, homomorphisms can be described in a simple parameterised way that gives standard sequential and parallel implementations for them, and certain special classes of homomorphisms have parallel implementations of practical importance. In particular, we develop an algorithm for path expression search, a novel powerful query facility for structured text, taking time logarithmic in the text size. This algorithm is the first example of a new algorithm discovered using homomorphic skeletons over data types.