People, Information Systems and Change

Information systems are the glue between people and computers. Both the social and business environments are in a continual, some might say chaotic, state of change while computer hardware continues to double its performance about every 18 months. This presents a major challenge for information system developers.  The term user-friendly is an old one, but one which has come to take on a multitude of meanings. However, in today’s context we might well take a user-friendly system to be one where the technology fits the user’s cognitive models of the activity in hand. This article looks at the relationship between information systems and the changing demands of their users as the underlying theme for the current issue of Cognition, Technology and Work.  People, both as individuals and organisations, change. The functionalist viewpoint, which attempts to freeze and inhibit such change, has failed systems developers on numerous occasions. Responding to, and building on, change in the social environment is still a significant research issue for information systems specialists who need to be able to create living information systems.     

High-automation proofs for properties of requirements models

We describe an approach and experimental results in the application of mechanized theorem proving to software requirements analysis. Serving as the test article was the embedded controller for SAFER, a backpack propulsion system used as a rescue device by NASA astronauts. SAFER requirements were previously formalized using the prototype verification system (PVS) during a NASA pilot project in formal methods, details of which appear in a NASA guidebook. This paper focuses on the formulation and proof of properties for the SAFER requirements model. To test the prospects for deductive requirements analysis, we used the PVS theorem prover to explore the upper limits of proof automation. A set of property classes was identified, with matching proof schemes later devised. After developing several PVS proof strategies (essentially prover macros), we obtained fully automatic proofs of 42 model properties. These results demonstrate how customized prover strategies can be used to automate moderate-complexity theorem proving for state machine models.     

Multiple expert classification: a new methodology for parallel decision fusion

Abstract. A new parallel hybrid decision fusion methodology is proposed. It is demonstrated that existing parallel multiple expert decision combination approaches can be divided into two broad categories based on the implicit decision emphasis implemented. The first category consists of methods implementing computationally intensive decision frameworks incorporating a priori information about the target task domain and the reliability of the participating experts, while the second category encompasses approaches implementing group consensus without assigning any importance to the reliability of the experts and ignoring other contextual information. The methodology proposed in this paper is a hybridisation of these two approaches and has shown significant performance enhancements in terms of higher overall recognition rates along with lower substitution rates. Detailed analysis using two different databases supports this claim. Received January 19, 1999 / Revised March 20, 2000     

Dynamic problems of shape optimal design for shallow curved plates

The problem of optimal structural design of shallow thin-walled elements such as curved rectangular plates are formulated and solved for dynamic conditions. The distribution of the initial curvature of shallow plates in a nonstrained state is taken as the control function. Dynamic compliance is considered as the minimized performance functional. Optimality conditions are derived for the distributed parameter system considered and applied for the construction of the analytical solution. The rigorous analysis of extremum conditions and behavioural equations shows that the initial optimization problem is decomposed into several problems of classical structural analysis, which can be successfully solved analytically. Some optimal designs obtained for rectangular plates under stretching and bending, and a plate lying on an elastic foundation and subjected to lateral forces are presented. Received: November 27, 1998     

Optimal structural topologies with transmissible loads

In optimal topological design of structures one obtains the configuration of optimal structures when the design domain, the displacement boundary conditions and the applied loads are specified. In the optimal structure one often notices a marked difference between the main bearing structure and the load transfer zones. The latter are composed of relatively light elements the exact nature of which is not always very distinct. The main purpose of this paper is to allow the main bearing part of the structure to emerge. Moreover the actual location of the load along its line of action is not always a design requirement. In order to include this relaxed condition regarding the loading position the concept of transmissible or sliding forces is introduced in topological design of structures. A transmissible force is a force of given magnitude and direction which can be applied at any point along the line of action of the force. The optimization formulation is similar to standard topological design procedure in addition to the condition of transmissability of the forces. It is shown that this condition reduces to an equal displacement constraint along the line of action of the forces. The method is illustrated by typical structural examples. It is observed that this numerical method produces indeed crisp images of the main structural components, unblurred by the secondary load transfer elements. It is also indicated that many results are often replicas of Prager structures which were previously obtained by analytical methods. Received March 3, 1999     

Maximization of eigenvalues using topology optimization

Topology optimization is used to optimize the eigenvalues of plates. The results are intended especially for MicroElectroMechanical Systems (MEMS) but can be seen as more general. The problem is not formulated as a case of reinforcement of an existing structure, so there is a problem related to localized modes in low density areas. The topology optimization problem is formulated using the SIMP method. Special attention is paid to a numerical method for removing localized eigenmodes in low density areas. The method is applied to numerical examples of maximizing the first eigenfrequency. One example is a practical MEMS application; a probe used in an Atomic Force Microscope (AFM). For the AFM probe the optimization is complicated by a constraint on the stiffness and constraints on higher order eigenvalues. Received June 10, 1999