Alexander Verbraeck

D-SOL; a distributed Java based discrete event simulation architecture

Most discrete event simulation environments are based on a process-oriented, and therefore multi-threaded paradigm. This results in simulation environments that are very hard to distribute over more computers, and not easy to integrate with scattered external information sources. The architecture presented is based on the event-based DES paradigm which is implemented by scheduled method invocation. Objects used in the simulation environment interact with remote, asynchronous subscribed clients in order to produce representations of the simulated system. The environment, which is implemented in Java, consists of a simulation and representation library and is integrated with several statistical libraries.

An evaluation and selection methodology for discrete-event simulation software

For large international companies with their own simulation team it is often hard to select new discrete event simulation software. Often, preferences and application areas between countries differ, and simulation software already in use influences the outcome of the selection process. Available selection methods do not suffice in such cases. Therefore, a two-phase evaluation and selection methodology is proposed. Phase one quickly reduces the long-list to a short-list of packages. Phase two matches the requirements of the company with the features of the simulation package in detail. Different methods are used for a detailed evaluation of each package. Simulation software vendors participate in both phases. The approach was tested for the Accenture world-wide simulation team. After the study, we can conclude that the methodology was effective in terms of quality and efficient in terms of time. It can easily be applied for other large organizations with a team of simulation specialists.

Component-based distributed simulations: the way forward?

Parallel simulation and distributed simulation sometimes appear to be two different worlds. Where parallel simulation aims at increasing the speed of a single model by distributing it over more processors, distributed simulation looks at ways to link entire models or federates that run on different computers. In the case of distributed simulation, the models themselves are hard to distribute, and often they each run on one processor as a monolithic model. This paper advocates building the more traditional simulation models in such a way, that they can be easily distributed. As simulationists, we can learn from component-based theory from the software engineering field to prepare our models for distribution, and parts of our models for reuse. The results of several projects show that componentizing simulation models can have many advantages. The results also show that it is not easy to create models in a componentized way, and that current methods for simulation model building should be adapted.

Simulation building blocks for airport terminal modeling

Airports are an ideal application area for simulation. The processes are in a continuous state of change, are complex and stochastic, involve many moving objects, and require a good performance that can be measured in several different performance indicators. Within airports, but also between airports, the same kind of questions are answered over and over again. Often, however, new simulation models are built for each question, if possible copying some parts of previous models. Structured reuse of simulation components is rarely seen. This paper shows an approach for airport terminal modeling that departs from the assumption that reusable simulation building blocks can form the core of a powerful airport modeling tool, which is able to answer different questions at airports better and faster than traditional models. The building blocks have been implemented in the commercially available simulation language eM-Plant. Several studies carried out with this library were very successful.

Using Simulation to Design an Automated Underground System for Transporting Freight Around Schiphol Airport

To avoid road congestion, we are developing a highly automated underground transport system using automatic guided vehicles (AGVs) around Schiphol Airport. It is unique in its scale, incorporating 16 to 25 km tubes connecting five to 20 terminals, and it includes 200 to 400 AGVs to transport an estimated 3.5 million tons of cargo in 2020 with different ordering priorities. According to the current plans, the system will run from 2006 on. Since 1997, we have used object-oriented simulations to plan the dimensions of the system (number of AGVs, terminal sizes) and to design the layout (network, terminals). We showed that an investment reduction of plus or minus 20 percent is feasible using periodically switched one-way tube sections. We developed a variety of logistics optimization algorithms and heuristics, including allocating AGVs between terminals, scheduling terminals, and controlling traffic. We used simulation control structures to test prototype AGVs on a test site. Performing distributed simulations with a mixture of simulated and real objects, we could reduce the risks of the new technology.

Animating organizational processes Insight eases change

Abstract The use of animation as a communication instrument has many advantages in the process of organization (re)design. An analytical definition of animation is used as a basis for describing the development and the use of animation models. The tasks of developing an animation model are linked to a problem solving process which constitutes the core of a simulation based approach for redesigning organizational processes. The use of an animation model is linked to the different types of communication encountered during a simulation study. As will be shown in two real-life case studies, animation models can help to facilitate and enhance the quality of communication processes during organization (re)design efforts.

User requirements modeling and analysis of software-intensive systems

The increasing complexity of software systems makes Requirements Engineering activities both more important and more difficult. This article is about user requirements development, mainly the activities of documenting and analyzing user requirements for software-intensive systems. These are modeling activities that are useful for further Requirements Engineering activities. Current techniques for requirements modeling present a number of problems and limitations. Based on these shortcomings, a list of requirements for requirements modeling languages is proposed. The proposal of this article is to show how some extensions to SysML diagrams and tables can fulfill most of these requirements. The approach is illustrated by a list of user requirements for a Road Traffic Management System.

A survey on distributed simulation in industry

Distributed simulation is used very little in industry, especially when compared with the interest in distributed simulation from research and from the military domain. In order to answer the question why industry lags behind, the authors have carried out an extensive survey, namely a questionnaire targeted at vendors of commercial-off-the-shelf (COTS) simulation packages and a series of open-ended interviews with experts on distributed simulation. Analysis of the answers obtained establish that it is indeed the case that industry is relatively underdeveloped in the area of distributed simulation and also sheds light on the reasons behind this. A categorization of these responses is given using which it is possible to formulate clear guidelines for further developments of standards for distributed simulation.

Metamodeling and model transformations in modeling and simulation

Metamodeling and model transformations are the key concepts in Model Driven Development (MDD) approaches as they provide a mechanism for automated development of well structured and maintainable systems. However, neither defining a metamodel nor developing a model transformation is an easy task. In this paper, we provide an overview of metamodeling and model transformations in MDD and discuss about the use of a MDD approach in Modeling and Simulation (M&S). In order to support the development of successful model transformations, we define the criteria for the evaluation of model transformations.

Distributed simulation in industry -- a survey, part 3 -- the HLA standard in industry

Distributed simulation, more specifically the HLA standard, is hardly applied in industry. We have conducted an extensive survey with COTS (commercial off-the-shelf) simulation package vendors and simulation experts, both from defence and industry, that focuses, amongst others, on the question what the reasons are behind this phenomenon. In this paper we analyze the reactions that we obtained, categorizing them into arguments related to distributed simulation in general, arguments related to HLA and arguments pertaining to the embedding of HLA concepts in COTS packages. These answers will lead us, we believe, to insights that can serve as guidelines to make distributed simulation more attractive for the industrial simulation community.