Handling Emergency Management in [an] Object Oriented Modeling Environment

It has been understood that protection of a nation from extreme disasters is a challenging task. Impacts of extreme disasters on a nation's critical infrastructures, economy and society could be devastating. A protection plan itself would not be sufficient when a disaster strikes. Hence, there is a need for a holistic approach to establish more resilient infrastructures to withstand extreme disasters. A resilient infrastructure can be defined as a system or facility that is able to withstand damage, but if affected, can be readily and cost-effectively restored. The key issue to establish resilient infrastructures is to incorporate existing protection plans with comprehensive preparedness actions to respond, recover and restore as quickly as possible, and to minimize extreme disaster impacts. Although national organizations will respond to a disaster, extreme disasters need to be handled mostly by local emergency management departments. Since emergency management departments have to deal with complex systems, they have to have a manageable plan and efficient organizational structures to coordinate all these systems. A strong organizational structure is the key in responding fast before and during disasters, and recovering quickly after disasters. In this study, the entire emergency management is viewed as an enterprise and modelled through enterprise management approach. Managing an enterprise or a large complex system is a very challenging task. It is critical for an enterprise to respond to challenges in a timely manner with quick decision making. This study addresses the problem of handling emergency management at regional level in an object oriented modelling environment developed by use of TopEase software. Emergency Operation Plan of the City of Hampton, Virginia, has been incorporated into TopEase for analysis. The methodology used in this study has been supported by a case study on critical infrastructure resiliency in Hampton Roads

State space exploration in Markov Models

Performance and dependability analysis is usually based on Markov models. One of the main problems faced by the analyst is the large state space cardinality of the Markov chain associated with the model, which precludes not only the model solution, but also the generation of the transition rate matrix. However, in many real system models, most of the probability mass is concentred in a small number of states in comparison with the whole state space. Therefore, performability measures may be accurately evaluated from these "high probable" states. In this paper, we present as algorithm to generate the most probable state the is more efficient than previous algorithms in the literature. We also address the problem of calculating measures of interest and show how bounds on some measures can b efficiently calculated.Análise de desempenho e dependabilidade baseia-se usualmente em modelos Markovianos. Um dos principais problemas que o analista encontra é a grande cardinalidade do espaço de estados da cadeias de Markov associada ao modelo, o que impede não somente a solução do modelo, mas também a geração da matriz de transição de estados. Entretanto, em muitos modelos de sistemas reais, a maioria da massa de probabilidade está concentrada em um pequeno número de estados em comparação com a totalidade do espaço dos estados. Por conseguinte, medidas de desempenhabilidade ('performability') podem ser avaliadas com precisão a partir desses estados mais prováveis. Neste artigo, apresentamos um algoritmo de geração dos estados mais prováveis que é mais eficiente que algoritmos anteriormente propostos na literatura. Abordaremos também o problema de cálculo das medidas de interesse e mostraremos como limites para algumas medidas podem ser eficientemente calculados

Bolshoi - A Modeling Spreadsheet (Improving Usability of Complex Analytical Modeling Tools)

Spreadsheet programs are very popular financial modeling tools because they allow users to juggle numbers and formulas with a powerful yet intuitive and easy to understand user interface; also, they often are equipped with sophisticated numerical analysis packages for data analysis and powerful presentation utilities for visualizing results. Computer systems performance and reliability modeling tools of today, on the other hand, have un-intuitive user interfaces and are difficult to learn and use. In this work, we propose to design, build, and evaluate Bolshoi, a modeling spreadsheet, with the goal of putting modeling tools comfortably in the hands of non-expert users. In this proposal, we address management of complexity that exists in performance and reliability analysis of real computer and communication systems. Specifically, we propose to do so through the design and development of an advanced modeling tool. Our tool will provide two important functions: (1) a proper interface for building models that will allow system designers not just to define their models, but visualize them in various ways and (2) easy plug-in of existing and future advanced solution techniques. We call this tool Bolshoi, a Modeling Spreadsheet, because it has a spreadsheet-type interface as detailed below. Performance evaluation of real systems is complex, suffers from scalability problems (or the so-called ``state explosion'' problem) and in many cases requires advanced computational techniques. Often, advanced computational techniques are based on exploitation of ``special structure'' in the models (the primary way to deal with state explosion besides getting a bigger machine). With large and complex models, these special structures are very expensive to expose automatically as it involves searching through a combinatorial number of permutations. Proper visualization of models can greatly assist in the discovery of these special structures so that state space reduction techniques can be applied. Discovery of special structure regularly contributes to many orders of magnitude in computational efficiency. Furthermore, models are often defined over infinite state spaces. We believe that a spreadsheet paradigm is ideal for visualizing such models. Without proper modeling tools, much effort and money is wasted by the computer industry, and moreover, the probability of a successful outcome is low. Thus, a good tool is crucial to advances in the state of the art in performance modeling as well as to successful design of systems in the industry. Every system designer should be able to integrate the use of a performance modeling tool into his/her design process. He/she should be able to easily ask ``what-if'' type questions, explore possible design choices, and make decisions based on quantitative results rather than ``gut feeling''. We believe that a modeling spreadsheet is the right abstraction for such tasks, and furthermore, to the best of our knowledge this abstraction has not been exploited for performance evaluation tool purposes. We believe that the approach proposed here will have a significant impact on future performance tool designs as well as make significant strides in wide-spread use of performance evaluation techniques among computer and communication system designers. Furthermore, a modeling tool that does not require expert-level methodology knowledge is also an excellent undergraduate-level and graduate-level educational tool. Opportunities for hands-on experience with modeling and performance evaluation as well as the ability to add new techniques to the tool greatly improve the educational experience of students and their future ability to apply what they have learned in class to design of real computer and communication systems. (Also cross-referenced as UMIACS-TR-2000-10

SIMLIB : a class library for object-oriented simulation

Ankara : The Department of Computer Engineering and Information Science and Institute of Engineering and Science of Bilkent University, 1993.Thesis (Master's) -- Bilkent University, 1993.Includes bibliographical references leaves 83-85.Simulation is one of the most widely used techniques in decision making. Mathematical modeling of a real world system is a major task of the simulation analyst. The selection of a computer language for implementing the model is also important. Recent research in this area has focused on the compatibility between simulation implementations and the object-oriented paradigm. It is the purpose of this thesis to explore the use of an object-oriented approach for the implementation of discrete event simulation applications. We present a class library which provides the skeletal elements of a simulation. The advantages and the disadvantages of the approach are discussed with the help of three prototype implementations: the single-queue/single-server system, the production-line system, and the elevator system.Işıklı, OğuzM.S

Application of Parallel Processing for Object Oriented Discrete Event Simulation of Manufacturing Systems

Industrial Engineering and Managemen