On the persistence of computer dreams: an application framework for robust adaptive deployment

The anticipated rewards of adaptive approaches will only be fully realised when autonomic algorithms can take configuration and deployment decisions that match and exceed those of human engineers. Such decisions are typically characterised as being based on a foundation of experience and knowledge. In humans, these underpinnings are themselves founded on the ashes of failure, the exuberance of courage and (sometimes) the outrageousness of fortune. In this paper we describe an application framework that will allow the incorporation of similarly risky, error prone and downright dangerous software artefacts into live systems – without undermining the certainty of correctness at application level. We achieve this by introducing the notion of application dreaming.

Advanced evacuation simulation software and its use in warships

The newly formed Escape and Evacuation Naval Authority regulates the provision of abandonment equipment and procedures for all Ministry of Defence Vessels. As such, it assures that access routes on board are evaluated early in the design process to maximize their efficiency and to eliminate, as far as possible, any congestion that might occur during escape. This analysis can be undertaken using a computer-based simulation for given escape scenarios and replicates the layout of the vessel and the interactions between each individual and the ship structure. One such software tool that facilitates this type of analysis is maritimeEXODUS. This tool, through large scale testing and validation, emulates human shipboard behaviour during emergency scenarios; however it is largely based around the behaviour of civilian passengers and fixtures and fittings of merchant vessels. Hence there existed a clear requirement to understand the behaviour of well-trained naval personnel as opposed to civilian passengers and be able to model the fixtures and fittings that are exclusive to warships, thus allowing improvements to both maritimeEXODUS and other software products. Human factor trials using the Royal Navy training facilities at Whale Island, Portsmouth were recently undertaken to collect data that improves our understanding of the aforementioned differences. It is hoped that this data will form the basis of a long-term improvement package that will provide global validation of these simulation tools and assist in the development of specific Escape and Evacuation standards for warships. © 2005: Royal Institution of Naval Architects.

The use of computer simulation for aircraft evacuation certification: a report from the VERRES project

In this paper a methodology for the application of computer simulation to the evacuation certification of aircraft is suggested. The methodology suggested here involves the use of computer simulation, historic certification data, component testing and full-scale certification trials. The proposed methodology sets out a protocol for how computer simulation should be undertaken in a certification environment and draws on experience from both the marine and building industries. Along with the suggested protocol, a phased introduction of computer models to certification is suggested. Given the sceptical nature of the aviation community regarding any certification methodology change in general, this would involve as a first step the use of computer simulation in conjunction with full-scale testing. The computer model would be used to reproduce a probability distribution of likely aircraft performance under current certification conditions and in addition, several other more challenging scenarios could be developed. The combination of full-scale trial, computer simulation (and if necessary component testing) would provide better insight into the actual performance capabilities of the aircraft by generating a performance probability distribution or performance envelope rather than a single datum. Once further confidence in the technique is established, the second step would only involve computer simulation and component testing. This would only be contemplated after sufficient experience and confidence in the use of computer models have been developed. The third step in the adoption of computer simulation for certification would involve the introduction of several scenarios based on for example exit availability instructed by accident analysis. The final step would be the introduction of more realistic accident scenarios into the certification process. This would require the continued development of aircraft evacuation modelling technology to include additional behavioural features common in real accident scenarios.

Computer simulation of VLTA evacuation performance: a report from the VERRES project

This paper reports on research work undertaken for the European Commission funded study GMA2/2000/32039 Very Large Transport Aircraft (VLTA) Emergency Requirements Research Evacuation Study (VERRES). A particular focus was on evacuation issues with a detailed study of evacuation performance using computer models being undertaken as part of Work Package 2. This paper describes this work and investigates the use of internal stairs during evacuation using computer simulation.

Simulating the Swissair flight 111 in-flight fire using the CFD fire simulation software SMARTFIRE

At 8.18pm on 2 September 1998, Swissair Flight 111 (SR 111), took off from New York’s JFK airport bound for Geneva, Switzerland. Tragically, the MD-11 aircraft never arrived. According to the crash investigation report, published on 27 March 2003, electrical arcing in the ceiling void cabling was the most likely cause of the fire that brought down the aircraft. No one on board was aware of the disaster unfolding in the ceiling of the aircraft and, when a strange odour entered the cockpit, the pilots thought it was a problem with the air-conditioning system. Twenty minutes later, Swissair Flight 111 plunged into the Atlantic Ocean five nautical miles southwest of Peggy’s Cove, Nova Scotia, with the loss of all 229 lives on board. In this paper, the Computational Fluid Dynamics (CFD) analysis of the in-flight fire that brought down SR 111 is described. Reconstruction of the wreckage disclosed that the fire pattern was extensive and complex in nature. The fire damage created significant challenges to identify the origin of the fire and to appropriately explain the heat damage observed. The SMARTFIRE CFD software was used to predict the “possible” behaviour of airflow as well as the spread of fire and smoke within SR 111. The main aims of the CFD analysis were to develop a better understanding of the possible effects, or lack thereof, of numerous variables relating to the in-flight fire. Possible fire and smoke spread scenarios were studied to see what the associated outcomes would be. This assisted investigators at Transportation Safety Board (TSB) of Canada, Fire & Explosion Group in assessing fire dynamics for cause and origin determination.

Applying CBR to measure similarity of software design structures

This paper examines different ways for measuring similarity between software design models for the purpose of software reuse. Current approaches to this problem are discussed and a set of suitable similarity metrics are proposed and evaluated. Work on the optimisation of weights to increase the competence of a CBR system is presented. A graph matching algorithm and associated metrics capturing the structural similarity between UML class diagrams is presented and demonstrated through an example case.

A blackboard architecture for a hybrid CBR system for scientific software

This paper describes the use of a blackboard architecture for building a hybrid case based reasoning (CBR) system. The Smartfire fire field modelling package has been built using this architecture and includes a CBR component. It allows the integration into the system of qualitative spatial reasoning knowledge from domain experts. The system can be used for the automatic set-up of fire field models. This enables fire safety practitioners who are not expert in modelling techniques to use a fire modelling tool. The paper discusses the integrating powers of the architecture, which is based on a common knowledge representation comprising a metric diagram and place vocabulary and mechanisms for adaptation and conflict resolution built on the Blackboard.

Investigating the representation of merging behavior at the floor–stair interface in computer simulations of multi-floor building evacuations

In this article, the representation of the merging process at the floor— stair interface is examined within a comprehensive evacuation model and trends found in experimental data are compared with model predictions. The analysis suggests that the representation of floor—stair merging within the comprehensive model appears to be consistent with trends observed within several published experiments of the merging process. In particular: (a) The floor flow rate onto the stairs decreases as the stair population density increases. (b) For a given stair population density, the floor population's flow rate onto the stairs can be maximized by connecting the floor to the landing adjacent to the incoming stair. (c) In situations where the floor is connected adjacent to the incoming stair, the merging process appears to be biased in favor of the floor population. It is further conjectured that when the floor is connected opposite the incoming stair, the merging process between the stair and floor streams is almost in balance for high stair population densities, with a slight bias in favor of the floor stream at low population densities. A key practical finding of this analysis is that the speed at which a floor can be emptied onto a stair can be enhanced simply by connecting the floor to the landing at a location adjacent to the incoming stair rather than opposite the stair. Configuring the stair in this way, while reducing the floor emptying time, results in a corresponding decrease in the descent flow rate of those already on the stairs. While this is expected to have a negligible impact on the overall time to evacuate the building, the evacuation time for those higher up in the building is extended while those on the lower flows is reduced. It is thus suggested that in high-rise buildings, floors should be connected to the landing on the opposite side to the incoming stair. Information of this type will allow engineers to better design stair—floor interfaces to meet specific design objectives.

Measuring similarity of software designs using graph matching for CBR

This paper examines different ways of measuring similarity between software design models for Case Based Reasoning (CBR) to facilitate reuse of software design and code. The paper considers structural and behavioural aspects of similarity between software design models. Similarity metrics for comparing static class structures are defined and discussed. A Graph representation of UML class diagrams and corresponding similarity measures for UML class diagrams are defined. A full search graph matching algorithm for measuring structural similarity diagrams based on the identification of the Maximum Common Sub-graph (MCS) is presented. Finally, a simple evaluation of the approach is presented and discussed.

Embedding dynamic behaviour into a self-configuring software system

This paper describes a methodology for embedding dynamic behaviour into software components. The implications and system architecture requirements to support this adaptivity are discussed. This work is part of a European Commission funded and industry supported project to produce a reconfigurable middleware for use in automotive systems. Such systems must be trustable against illegal internal behaviour and activity with external origins, additional devices for example. Policy-based computing is used here as an example of embedded logic. A key contribution of this work is the way in which static and dynamic aspects of the system are interfaced, such that the behaviour can be changed very flexibly (even during run-time), without modification, recompilation or redeployment of the embedded application code. An implementation of these concepts is presented, focussing on achieving trust in the use of dynamic behaviour.

A run-time configurable software architecture for self-managing systems

This paper describes a highly flexible component architecture, primarily designed for automotive control systems, that supports distributed dynamically- configurable context-aware behaviour. The architecture enforces a separation of design-time and run-time concerns, enabling almost all decisions concerning runtime composition and adaptation to be deferred beyond deployment. Dynamic context management contributes to flexibility. The architecture is extensible, and can embed potentially many different self-management decision technologies simultaneously. The mechanism that implements the run-time configuration has been designed to be very robust, automatically and silently handling problems arising from the evaluation of self- management logic and ensuring that in the worst case the dynamic aspects of the system collapse down to static behavior in totally predictable ways.

Investigating the use of elevators for high-rise building evacuation through computer simulation

This paper presents a description of a new agent based elevator sub-model developed as part of the buildingEXODUS software intended for both evacuation and circulation applications. A description of each component of the newly developed model is presented, including the elevator kinematics and associated pedestrian behaviour. The elevator model is then used to investigate a series of full building evacuation scenarios based on a hypothetical 50 floor building with four staircases and a population of 7,840 agents. The analysis explores the relative merits of using up to 32 elevators (arranged in four banks) and various egress strategies to evacuate the entire building population. Findings from the investigation suggest that the most efficient evacuation strategy utilises a combination of elevators and stairs to empty the building and clear the upper half of the building in minimum time. Combined stair elevator evacuation times have been shown to be as much as 50% faster than stair only evacuation times.

Knowledge networks change during radical and incremental innovation episodes: a case study on software developmen

The role intra-organizational knowledge exchanges play in innovation processes has been widely acknowledged in the organizational literature. This paper contributes to the understanding of which specific configurations knowledge networks assume during different phases of radical and incremental innovation processes. The case study we selected is a FLOSS (Free/Libre Open Source Software) community consisting of 233 developers committed to the development of a web browser application since November 2002. By harvesting the mailing list, official blog and code repository of a FLOSS community, we investigate the patterns of knowledge exchange and individual contributions of its developers. We measure structural cohesion and compare global and local network properties at different points in time. Preliminary results show that phases of radical and incremental innovation are associated with specific configurations of the knowledge network as a whole as well as with different network positions of the core developers of the software.

Investigating the impact of aircraft exit availability on egress time using computer simulation

This paper examines the influence of exit availability on evacuation time for narrow body aircraft under certification trial conditions using computer simulation. A narrow body aircraft which has previously passed the certification trial is used as the test configuration. While maintaining the certification requirement of 50% of the available exits, six different configurations are examined. These include the standard certification and five other exit configurations based on commonly occurring exit combinations found in accidents. These configurations are based on data derived from the AASK database and the evacuation simulations are performed using the airEXODUS evacuation software. The results show that the certification practise of using half of the available exits predominately down one side of the aircraft is neither statistically relevant nor challenging. For the aircraft cabin layout examined, the exit configuration used in certification trial produces the shortest egress times. Furthermore, three of the six exit combinations investigated result in predicted egress times in excess of 90 seconds, suggesting that the aircraft would not satisfy the certification requirement under these conditions.