A comparison of CMB- and HLA-based approaches to type I interoperability reference model problems for COTS-based distributed simulation

Commercial-off-the-shelf (COTS) simulation packages (CSPs) are software used by many simulation modellers to build and experiment with models of various systems in domains such as manufacturing, health, logistics and commerce. COTS distributed simulation deals with the interoperation of CSPs and their models. Such interoperability has been classified into six interoperability reference models. As part of an on-going standardisation effort, this paper introduces the COTS Simulation Package Emulator, a proposed benchmark that can be used to investigate Type I interoperability problems in COTS distributed simulation. To demonstrate its use, two approaches to this form of interoperability are discussed, an implementation of the CMB conservative algorithm, an example of a so-called “light” approach, and an implementation of the HLA TAR algorithm, an example of a so-called “heavy” approach. Results from experimentation over four federation topologies are presented and it is shown the HLA approach out performs the CMB approach in almost all cases. The paper concludes that the CSPE benchmark is a valid basis from which the most efficient approach to Type I interoperability problems for COTS distributed simulation can be discovered

HLA-CSPIF panel on commercial off-the-shelf distributed simulation

Commercial-off-the-shelf (COTS) simulation packages are widely used in many areas of industry. Several research groups are attempting to integrate distributed simulation principles and techniques with these packages to potentially give us COTS distributed simulation. The High Level Architecture-COTS Simulation Package Interoperation Forum (HLA-CSPIF) is a group of researchers and practitioners that are studying methodological and technological issues in this area. This panel paper presents the views of four members of this forum on the technical problems that must be overcome for this emerging field to be realized

Integrating heterogeneous distributed COTS discrete-event simulation packages: An emerging standards-based approach

This paper reports on the progress made toward the emergence of standards to support the integration of heterogeneous discrete-event simulations (DESs) created in specialist support tools called commercial-off-the-shelf (COTS) discrete-event simulation packages (CSPs). The general standard for heterogeneous integration in this area has been developed from research in distributed simulation and is the IEEE 1516 standard The High Level Architecture (HLA). However, the specific needs of heterogeneous CSP integration require that the HLA is augmented by additional complementary standards. These are the suite of CSP interoperability (CSPI) standards being developed under the Simulation Interoperability Standards Organization (SISO-http://www.sisostds.org) by the CSPI Product Development Group (CSPI-PDG). The suite consists of several interoperability reference models (IRMs) that outline different integration needs of CSPI, interoperability frameworks (IFs) that define the HLA-based solution to each IRM, appropriate data exchange representations to specify the data exchanged in an IF, and benchmarks termed CSP emulators (CSPEs). This paper contributes to the development of the Type I IF that is intended to represent the HLA-based solution to the problem outlined by the Type I IRM (asynchronous entity passing) by developing the entity transfer specification (ETS) data exchange representation. The use of the ETS in an illustrative case study implemented using a prototype CSPE is shown. This case study also allows us to highlight the importance of event granularity and lookahead in the performance and development of the Type I IF, and to discuss possible methods to automate the capture of appropriate values of lookahead

Science teachers' transformations of the use of computer modeling in the classroom: using research to inform training

This paper, from the UK group in the STTIS (Science Teacher Training in an Information Society) project, describes research into the nature of teachers' transformations of computer modeling, and the development of related teacher training materials. Eight teacher case studies help to identify factors that favor or hinder the take-up of innovative computer tools in science classes, and to show how teachers incorporate these tools in the curriculum. The training materials use the results to provide activities enabling teachers to learn about the tools and about the outcomes of the research into their implementation, and help them to take account of these ideas in their own implementation of the innovations

Fact, Fiction and Virtual Worlds

This paper considers the medium of videogames from a goodmanian standpoint. After some preliminary clarifications and definitions, I examine the ontological status of videogames. Against several existing accounts, I hold that what grounds their identity qua work types is code. The rest of the paper is dedicated to the epistemology of videogaming. Drawing on Nelson Goodman and Catherine Elgin's works, I suggest that the best model to defend videogame cognitivism appeals to the notion of understanding

Analysis of operational risk of banks – catastrophe modelling

Nowadays financial institutions due to regulation and internal motivations care more intensively on their risks. Besides previously dominating market and credit risk new trend is to handle operational risk systematically. Operational risk is the risk of loss resulting from inadequate or failed internal processes, people and systems or from external events. First we show the basic features of operational risk and its modelling and regulatory approaches, and after we will analyse operational risk in an own developed simulation model framework. Our approach is based on the analysis of latent risk process instead of manifest risk process, which widely popular in risk literature. In our model the latent risk process is a stochastic risk process, so called Ornstein- Uhlenbeck process, which is a mean reversion process. In the model framework we define catastrophe as breach of a critical barrier by the process. We analyse the distributions of catastrophe frequency, severity and first time to hit, not only for single process, but for dual process as well. Based on our first results we could not falsify the Poisson feature of frequency, and long tail feature of severity. Distribution of “first time to hit” requires more sophisticated analysis. At the end of paper we examine advantages of simulation based forecasting, and finally we concluding with the possible, further research directions to be done in the future

Shocks in coupled socio-ecological systems: what are they and how can we model them?

Coupled socio-ecological systems (SES) are complex systems characterized by self-organization, non-linearities, interactions among heterogeneous elements within each subsystem, and feedbacks across scales and among subsystems. When such a system experiences a shock or a crisis, the consequences are difficult to predict. In this paper we first define what a shock or a crisis means for SES. Depending on where the system boundary is drawn, shocks can be seen as exogenous or endogenous. For example, human intervention in environmental systems could be seen as exogenous, but endogenous in a socio-environmental system. This difference in the origin and nature of shocks has certain consequences for coupled SES and for policies to ameliorate negative consequences of shocks. Having defined shocks, the paper then focuses on modelling challenges when studying shocks in coupled SES. If we are to explore, study and predict the responses of coupled SES to shocks, the models used need to be able to accommodate (exogenous) or produce (endogenous) a shock event. Various modelling choices need to be made. Specifically, the ‘sudden’ aspect of a shock suggests the time period over which an event claimed to be a shock occurred might be ‘quick’. What does that mean for a discrete event model? Turning to magnitude, what degree of change (in a variable or set of variables) is required for the event to be considered a shock? The ‘surprising’ nature of a shock means that none of the agents in the model should expect the shock to happen, but may need rules enabling them to generate behaviour in exceptional circumstances. This requires a certain design of the agents’ decision-making algorithms, their perception of a shock, memory of past events and formation of expectations, and the information available to them during the time the shock occurred

Optimal staffing under an annualized hours regime using Cross-Entropy optimization

This paper discusses staffing under annualized hours. Staffing is the selection of the most cost-efficient workforce to cover workforce demand. Annualized hours measure working time per year instead of per week, relaxing the restriction for employees to work the same number of hours every week. To solve the underlying combinatorial optimization problem this paper develops a Cross-Entropy optimization implementation that includes a penalty function and a repair function to guarantee feasible solutions. Our experimental results show Cross-Entropy optimization is efficient across a broad range of instances, where real-life sized instances are solved in seconds, which significantly outperforms an MILP formulation solved with CPLEX. In addition, the solution quality of Cross-Entropy closely approaches the optimal solutions obtained by CPLEX. Our Cross-Entropy implementation offers an outstanding method for real-time decision making, for example in response to unexpected staff illnesses, and scenario analysis