Jonathan Vincent

A review of particle swarm optimization. Part I: background and development

Particle Swarm Optimization (PSO), in its present form, has been in existence for roughly a decade, with formative research in related domains (such as social modelling, computer graphics, simulation and animation of natural swarms or flocks) for some years before that; a relatively short time compared with some of the other natural computing paradigms such as artificial neural networks and evolutionary computation. However, in that short period, PSO has gained widespread appeal amongst researchers and has been shown to offer good performance in a variety of application domains, with potential for hybridisation and specialisation, and demonstration of some interesting emergent behaviour. This paper aims to offer a compendious and timely review of the field and the challenges and opportunities offered by this welcome addition to the optimization toolbox. Part I discusses the location of PSO within the broader domain of natural computing, considers the development of the algorithm, and refinements introduced to prevent swarm stagnation and tackle dynamic environments. Part II considers current research in hybridisation, combinatorial problems, multicriteria and constrained optimization, and a range of indicative application areas.

A review of particle swarm optimization. Part II: hybridisation, combinatorial, multicriteria and constrained optimization, and indicative applications

Particle Swarm Optimization (PSO), in its present form, has been in existence for roughly a decade, with formative research in related domains (such as social modelling, computer graphics, simulation and animation of natural swarms or flocks) for some years before that; a relatively short time compared with some of the other natural computing paradigms such as artificial neural networks and evolutionary computation. However, in that short period, PSO has gained widespread appeal amongst researchers and has been shown to offer good performance in a variety of application domains, with potential for hybridisation and specialisation, and demonstration of some interesting emergent behaviour. This paper aims to offer a compendious and timely review of the field and the challenges and opportunities offered by this welcome addition to the optimization toolbox. Part I discusses the location of PSO within the broader domain of natural computing, considers the development of the algorithm, and refinements introduced to prevent swarm stagnation and tackle dynamic environments. Part II considers current research in hybridisation, combinatorial problems, multicriteria and constrained optimization, and a range of indicative application areas.

Improving the quality of use case descriptions: empirical assessment of writing guidelines

Use cases are the main requirements vehicle of the UML and are used widely to specify systems. Hence, the need to write clear and accurate use case descriptions has a significant impact for many practitioners. However, many have pointed to weaknesses in the support offered to those writing use cases, and a number of authors advocate the use of rules in the composition and structuring of use case descriptions. These rules constrain the user, by only allowing certain grammatical constructions, typically guiding the structure or the style of the description For example, the CREWS research project pioneered Use Case Authoring Guidelines, suggesting that the adoption of such guidelines improved resulting use case descriptions. Replication of CREWS studies appeared to confirm the view that use case descriptions were improved through the application of guideline sets, but also noted that learning such rules presented a significant overhead. Hence, a leaner set of guidelines (the CP rules) was developed.This paper describes empirical work to assess the utility of these two sets of writing guidelines (CREWS and CP). In particular, descriptions are assessed against a set of established criteria—a use case quality description checklist, which the authors described in a previous paper.Our findings suggest that the leaner set of guidelines performs at least as well in terms of their ability to produce clear and accurate (comprehensible) descriptions. Hence, that a tractable set of rules may prove applicable to the industrial context, which could lead to effective validation of use cases.

Assessing the quality of use case descriptions

Use cases have, for some years, been a popular approach to specification, as part of the Unified Modelling Language (UML). However, a number of authors have pointed to weaknesses with the approach, particularly in terms of the support offered to the writer of the use case description. This paper describes a Use Case Description Quality Checklist that acts as a check on the quality of the written description. The checklist is derived from theories of text comprehension, taken from the Discourse Processing community. The checklist approach has a number of benefits. First, the approach can be used to derive, or examine further, use case guidelines. That is, by considering whether such guidelines are likely to result in desirable qualities within the resulting description, one is able to make an informed judgement about the utility of those guidelines. Second, one can test for the desirable quality features in existing descriptions, thus enabling empirical validation. Third, as a minimum, the quality features can themselves be used as a checklist for the examination, and revision, of use case descriptions. To demonstrate applicability, the paper reports upon the use, and success, of the approach on an industrial case study.

Principles of Built-In-Test for Run-Time-Testability in Component-Based Software Systems

This paper examines the motivations and expectations of Built-In-Test (BIT) techniques for Run-Time-Testability (RTT) in component-based software systems. The difficulties associated with testing and integrating fully encapsulated components lead to a requirement for testing interfaces. The format of these interfaces is explored at a high level of abstraction, and some possibilities for Built-In-Test (BIT) are described. BIT is concerned with the detection of error conditions arising internally to a component, or arising from erroneous component interactions, and the propagation of these error conditions to a system component having responsibility for error handling and/or recovery. The implications for testability, reliability and maintainability are discussed, and it is concluded that BIT offers potential for improved product quality. Whilst the proposed approach is considered appropriate for a wide range of software systems, issues related to real-time systems, such as deadlock and timing constraints are of particular interest.

Natural strategies for search

In recent years a considerable amount of natural computing research has been undertaken to exploit the analogy between, say, searching a given problem space for an optimal solution and the natural process of foraging for food. Such analogies have led to useful solutions in areas such as optimisation, prominent examples being ant colony systems and particle swarm optimisation. However, these solutions often rely on well defined fitness landscapes that are not always be available in more general search scenarios. This paper surveys a wide variety of behaviours observed within the natural world, and aims to highlight general cooperative group behaviours, search strategies and communication methods that might be useful within a wider computing context, beyond optimisation, where information from the fitness landscape may be sparse, but new search paradigms could be developed that capitalise on research into biological systems that have developed over millennia within the natural world.

Particle Swarm Guidance System for Autonomous Unmanned Aerial Vehicles in an Air Defence Role

This work investigates the utilisation of Particle Swarm Optimisation (PSO) for the nondeterministic navigation of Unmanned Aerial Vehicles (UAVs), allowing them to work cooperatively toward the goal of protecting a wide area against airborne attack. To negate the PSOs inherent weakness in dynamic environments, a neighbourhood scheme is proposed that not only enables the efficient interception of targets several times faster than the UAVs but also facilitates the maintenance of effective airspace coverage. Empirical results suggest that these techniques may indeed be of use in autonomous navigation systems for UAVs in air defence roles.

An evaluation of the utility of web development methods

Although many web development methods exist, they are rarely used by practitioners. The work reported here, seeks to explain why this might be so, and suggests that, for many, the perceived benefits may be outweighed by the difficulty or effort required to learn the method. In attempting to gauge the utility of methods the authors undertook a 2-year study of 23 small web development projects, attempting to use a range of published (academic) methods. Of the 23 projects we found only one case where the developer continued to use an academic web development method throughout the lifecycle. The ability to understand a method and/or its techniques was repeatedly cited as the reason for its abandonment. Our findings also indicate a number of key areas, relating to terminology, completeness, and guidance, where existing methods may be failing their intended users. In attempting to further our understanding of web development methods we completed a comprehensive survey of web development methods; covering 52 web development methods, encompassing a range of different research communities, and drawing upon 63 different sources. Our findings here shed some light upon the confusion of methods for the would-be user. In summary, the findings are that, although there is much of value in a variety of methods, method choice is somewhat bewildering for the newcomer to the field, and many methods are incomplete in some dimension. By providing this work we hope to go some way towards supporting the software engineering community, in both academia and industry, in their understanding of the quality issues that exist with the take up and use of web development methods.

A Coarse-Grained Parallel Genetic Algorithm Employing Cluster Analysis for Multi-modal Numerical Optimisation

This paper describes a technique for improving the performance of parallel genetic algorithms on multi-modal numerical optimisation problems. It employs a cluster analysis algorithm to identify regions of the search space in which more than one sub-population is sampling. Overlapping clusters are merged in one sub-population whilst a simple derating function is applied to samples in all other sub-populations to discourage them from further sampling in that region. This approach leads to a better distribution of the search effort across multiple sub-populations and helps to prevent premature convergence. On the test problems used, significant performance improvements over the traditional island model implementation are realised.

Exploring the Performance of Natural Search Strategies for the Control of Unmanned Autonomous Vehicles

This paper builds on prior research into the application of particle swarm optimisation to autonomous vehicle control in search roles. It examines the use of naturally inspired search strategies to enhance the performance of groups of sensor-based vehicles in applications where there is no knowledge a priori regarding target presence, location, distribution or behaviour (movement). This paper first briefly reviews existing ethological research into search strategies in the natural world, identifying three types of random walk, two multi-phase strategies and two species-specific strategies for further investigation. Experiments are then performed within a simulation environment to compare the performance of naturally inspired strategies with deterministic patterns and random movement, when searching for both static and dynamic targets. Results indicate that performance improvements can be realised, provided that critical relationships within the application domain broadly match those existing in the underlying natural metaphor.