Summary
This paper briefly discusses how simulation software can be applied within the field of logistics and manufacturing modeling to diagnose problems and evaluate possible solutions, optimize operations, and mitigate risk factors. The paper also provides a methodology for building models and identifies the criteria for selecting appropriate simulation software. This paper will demonstrate the process of build-ing, analyzing and presenting models of real world systems. Finally, a simple exam-ple of manufacturing model using ShowFlow simulation software is described. Keywords: Business Process Modeling, Simulation Software
1. Introduction
Business Process Modeling (BPM) is becoming increasingly important to organizations in all sectors who are faced with competitive pressure and who strive for increased effectiveness. Only by adopting a business process orientated view can the organization hope to gain the necessary vision, control, and flexibility required to compete effectively in cutthroat markets. Companies are realizing that they must focus on their business from the horizontal perspective of process rather than a vertical departmental driven view.
BPM is seen as a tool for defining, optimizing and extending the enterprise processes. The role of BPM is to deliver operational processes that can be used on an everyday basis by business users. Managing these processes within a company, across a supply chain, for CRM or Internet B2B becomes fundamental to an organization’s success. A process change can impact multiple functions within a business, through a top-down view that sees individuals, enterprise applications and databases connected through enterprise processes.
Enterprise modeling tools support the company in better understanding its goals, its operating context and in designing processes to effectively meet these goals. There is also support for de-signing software and data requirements in many of these tools. A process engine executes the workflow and guides business users in operating the real time processes.
Companies spend a lot of time and money to obtain highest performance from business proc-esses. Besides expensive and complicated techniques, there are catchwords like flexibility, just-in-time, lean production, etc. All these terms are based on the optimization of delivery, reliability, throughput times, stocks, utilization: i.e. costs. The problem is often it is nearly impossible to make a quantitative approach to these characteristics. Two factors are responsible: complexity and uncertainty. With an increasing number of components being in relationship to each other, it be-comes more and more difficult to describe the system mathematically. When the second factor, uncertainty, is involved, even analytical methods fail. Uncertainties include: machine breakdowns, varying cycle times and batch sizes, waste and reject, etc. Throughput times, buffer sizes, the ef-fects of resources influencing each other cannot be determined with conventional methods. Here,
at least, have to resort to assumptions, experience and intuition; although a better insight would be desirable. At least both possibilities of a bad system dimension, too high and too low, cause much costs. For above mentioned problems, simulation can be a powerful tool to justify decisions or even prevent from making wrong decisions.
2. Business Process Simulation Software
Simulation as an engineering and management technique has developed into an established continuous improvement and change management tool. The role of simulation has developed from a one-time single point use, to a strategic top-down view with the power to evaluate across the enterprise those processes that require analysis and optimization for improvement. Simulation usage can now be extended further into the realms of simulating executable business processes, inter-operating with Business Process Management Systems or Business Activity Monitoring Systems.
Simulation provides a unique business insight by adding to the process design and manage-ment by predicting the behavior of the entire process. It provides a unique business foresight in enabling simulation of the future state, based on optimization and analysis of the “Real state”.
By providing true rigor to the design and optimization of business processes, unguided busi-ness agility can be better controlled and renewed confidence delivered into the decisioning around dynamic business process change.
Simulation enables identification of increased value creation opportunities within the busi-ness. It provides the ability to test a process design, investigate tradeoffs in terms of operating rules, resource levels through a ‘virtual pilot’. This type of simulation has been used successfully over a number of years in many manufacturing and service applications. Simulation models have usually been built specifically to help decision making on investments and major change.
Much process design has been static and guided by good commonsense rules, such as the re-duction of handoffs, and rere-duction of non-value added time. This type of process design activity does not predict the performance the company can expect when that process is interlinked with other processes under expected loads and faced with resource or other constraints. Simulation provides this additional insight and can therefore support or be integral to a successful BPM strat-egy, both in initial design and ongoing improvement and monitoring of the live process driven system.
Most business modeling being carried out today relies on the use of spreadsheets and/or pro-ject management software to create propro-ject schedules, do simplified risk analysis calculations, carry out cost and revenue projections and other simple financial analyses. Although such tools are useful and applicable in many cases, they generally do not have the ability to represent the com-plex dynamics and uncertainties present in real world business systems. As such, the projections produced by these tools often do not provide a realistic representation of the future. This can lead to poor decisions.
Discrete event simulation (DES) is the type of simulation most appropriate in this field. It models the movement of entities (‘things’) through a system over time, according to the particular process definition, operating rules, constraints and resource levels. DES takes into account random events and factors which vary over time so providing the most realistic method of testing the likely performance of a process without doing it for real. Fully testing a process for real is often prohibi-tive due to cost, time and the disruption it would cause.
Table 1. A collection of discrete event simulation tools
Simulation tools Description
Arena
Flow oriented visual modeling software based on SIMAN modeling language, drag and drop module -the ability to be tailored to any appli-cation area.
Automod
Flow oriented AutoMod suite provides simulation software that gives a 3D visual image of a facility as well as statistics of how the facility will perform. Complete visual modeling, drag and drop module.
Dymola
An object oriented tool for modeling and simulation of continuous systems Dymola (Dynamic Modeling Laboratory) is a complete tool for modeling and simulation of integrated and complex systems for use within automotive, aerospace, robotics, process and other applications. The modeling environment Dymola, by Dynasim,. Focus on robotics and mechanical systems. Now integrated with Modelica modeling language. Modelica allows integration and reuse of code developed in different modeling and simulation environments.
Enterprise Dynamics
Enterprise Dynamics (formerly known as Taylor ED) is an object-oriented software application used to model, simulate, visualize and control business processes. Most notably, a complete simulation model can be built and simulated in a full VR environment. The software can be used not only for industrial applications but is also a visual simula-tion tool where the user can use the 4D-script programming language to create his own models
Flexsim
Flexsim is a simulation software application used to model, simulate, and visualize business process. Flexsim can help determine plant ca-pacity, balance manufacturing lines, manage bottlenecks, solve inven-tory and WIP problems, test new scheduling practices, optimize pro-duction rates, and justify capital expenditures. Every model in Flexsim can be viewed in 3D virtual reality animation. Besides all of this, Flex-sim provides the modeller with the ability to program models and sub-models directly in C++, leaning on the powerful simulation and graphic libraries of Flexsim.
Goldsim GoldSim Simulation Software provides the ability to simulate discrete event and continuous processes simultaneously, address uncertainty in models. GoldSim is a general purpose simulator for nearly any kind of physical, financial or organizational system. Models are built graphi-cally drawing an influence diagram of system. Goldsim Academic is offered free for students, professors and teachers. Goldsim also pro-vides a player that enables anyone to view your model, without requir-ing the installation of the full package.
Promodel
ProModel Optimization Suite is a simulation-based software tool for evaluating, planning or re-designing manufacturing, warehousing and logistics systems.
Simulation tools Description
items (documents, patients, mechanical parts) and compete for re-sources. It handles N batches (or classes) of homogeneous items, M activities, carried out by workstations, and K types of shared resources. Compared to other commercial simulation packages, Schedula is a lean or "bare bones" product. It entails no simulation language, no pro-gramming, no visual programming of graphical objects, no animation. ShowFlow ShowFlow Simulation is designed to model, simulate, animate and
analyse processes in logistics, manufacturing and material handling. It provides powerful visualisation and reporting tools, in particular for simulation animation. The modeller is facilitated by the availability of many simulation components ready to run.
SIMPLE++/eM-Plant
Object oriented. Partly visual modeling, drag and drop objects and typing code. eM-Plant is a simulator for various fields: logistics, engi-neering, production. It provides a hierarchical library of simulation modules and it is object-oriented.
Simprocess Simprocess is an object-oriented, process modeling and analysis tool. It combines the simplicity of flowcharting with the power of simulation, statistical analysis, Activity-Based Costing (ABC), and animation. SIMUL8 SIMUL8 by Visual Thinking Intl. It allows the user to pick from a
predefined set of simulation objects and statistical distributions to cre-ate the model. It also allows hierarchical modeling. Main focus on discrete event simulation
Taylor II Flow oriented, partly visual modeling, drag and drop objects and typ-ing additional code TLI.
Taylor Enterprise Dynamics
Flow oriented. partly visual modeling, drag and drop objects and typ-ing additional code
Witness
Flow oriented Business Simulation Software WITNESS, by Lanner Group, provides a graphical environment to design discrete event simu-lation models. It allows to automate simusimu-lation experiments, optimize material flow across the facility, and generate animated 3D virtual reality models. Partly visual modeling, drag and drop objects and typ-ing additional code.
VisSim VisSim is for the modeling and simulation of complex dynamic sys-tems, and combines an intuitive drag-and-drop block diagram interface with a powerful simulation engine. The visual block diagram interface offers a simple method for constructing, modifying and maintaining complex system models. The simulation engine provides fast and accu-rate solutions for linear, nonlinear, continuous time, discrete time, time varying and hybrid system designs. VisSim provides a fully integrated control system design environment where all design and simulation tasks can be completed without writing a line of code. VisSim (Visual Solutions), a visual block diagram language for nonlinear dynamic simulation. A block API allows users to create their own blocks in
Simulation tools Description C/C++, FORTRAN, ADA, or Pascal.
SimPy SimPy (= Simulation in Python) is an object-oriented, process-based discrete-event simulation language based on standard Python and re-leased under the GNU GPL. It provides the modeler with components of a simulation model including processes, for active components like customers, messages, and vehicles, and resources, for passive compo-nents that form limited capacity congestion points like servers, check-out counters, and tunnels. It also provides monitor variables to aid in gathering statistics. Random variates are provided by the standard Python random module.
JiST JiST is a high-performance discrete event simulation engine that runs over a standard Java virtual machine. It is a prototype of a new general-purpose approach to building discrete event simulators, called virtual machine-based simulation, that unifies the traditional systems and language-based simulator designs. JiST is developed by Cornell Re-search Foundation, Inc. and it is free for non commercial use.
MathCore MathCore AB offers two main products: MathCore C++, an add-on to the well known Mathematica environment that compiles a subset of Mathematica into highly efficient C++ code. MathCode C++ provides a platform for rapid development of simulations and other expensive computations. MathModelica is is an implementation of Modelica in Mathematica. MathModelica permits object oriented design of physical systems for simulation and visual programming using a graphic editor. MathModelica integrates documentation, runnable code, graphic con-nection diagrams and mathematical formulae in Mathematica note-books.
Pasion Pasion is an object-oriented simulation language. The language has a process/event structure. Pasion source code is translated in Pascal, compatible with Delphi v3 or later. It can be used to model Queuing models. Continuous processes and allows the use of the Bond graphs paradigm.
Simulation Software will show users the throughput of a production system, identify bottle-necks, measure lead times and report utilization of resources. Attributes can be assigned to prod-ucts for routing dependencies. Some of Simulation Software key features that make this feasible include the ability to:
• Incorporate variability and uncertainty - Uncertainty exists in all businesses and organizations. Simulation Software makes it easy to explicitly and quantitatively in-corporate variability and uncertainty into models.
• Represent random discrete events - In many systems, certain events or develop-ments can completely change the behavior of a system and influence the outcome of decisions. Simulation Software has the capability to represent random discrete events,
such as new technological advances, lawsuits, or natural disasters, that can play a critical role in determining which strategic approach is most effective.
• Build top-down hierarchical models - Simulation Software allows you to construct hierarchical multi-layer models that represent greater detail at lower levels in the model structure. As a result, you can build, explore, and explain highly complex busi-ness models without losing sight of the big picture.
• Represent interdependencies and feedback loops - Most real-world business sys-tems have interdependencies and feedback loops connecting variables in space and time. Simulation Software makes it easy to represent these in your models.
• Dynamically link to external data repositories - Business modeling should be based on current information. For large models with large amounts of input data, it can be labor-intensive and burdensome to enter data manually each time you want to update the model. Simulation Software offers the ability to link to ERP and other database systems that represent the most recent information.
• Dynamically link to existing spreadsheets - If currently have valuable data and/or calcuations withing Excel spreadsheets, Simulation Software can seamlessly integrate these into your model.
• Create easy-to-understand presentations that effectively communicate the struc-ture of your model and the results - The best designed business model probably won’t be believe or used if your audience doesn’t understand it. Simulation Software user-friendly graphical interface provides you with the tools to communicate with and convince your audience.
These features and capabilities allow Simulation Software to be used for a variety of business and economic modeling applications, including:
• Strategic Planning - Evaluate alternative strategies and policies and identify those that offer the greatest potential for success.
• Portfolio Management - Determine the optimal portfolio of projects, resources, and/or investments.
• Cost Modeling and Program Planning - Develop program plans that provide the highest likelihood of meeting your objectives on time and under budget.
• Risk Management - Evaluate risks, and then identify cost-effective pre-emptive measures and contingency plans that minimize adverse impacts in an uncertain world. • Supply Chain Management - Evaluate the performance of supply chains in order to optimize your systems to provide the efficiency and flexibility you need to thrive in a competitive marketplace.
• Business Process Modeling and Six Sigma - Model business processes in your or-ganization in order to find the best ways to increase efficiency and minimize defects. • Financial Engineering - Design and/or evaluate new or existing financial
3. Building a Model with Showflow Simulation Software
ShowFlow Simulation Software is rapidly becoming an industry leading product designed to model, simulate, animate and analyze processes in logistics, manufacturing and material handling. ShowFlow is developed from the renowned ShowFlow system.
For simulation to be truly useful, usability and availability are as important as any other con-sideration when choosing software. ShowFlow's price, combined with it's player version and its ability to link with your existing office applications make ShowFlow a logical choice. This "us-ability" and "avail"us-ability" make ShowFlow the software of choice for many colleges, universities and Fortune 500 companies.
Working with ShowFlow usually starts with building a model. All model building is menu driven. A model represents a real world system which is to be studied. In practice, this representa-tion is often simplified. The most important aspect when doing this is to build a model as exactly as necessary and not as detailed as possible. What is the reason for this? The reason is not the least performance of simulation packages, ShowFlow or others, but an efficient, economical and objec-tive-oriented way of working.
A model in ShowFlow consists of four fundamental entities being related to each other: ele-ments, jobs, routings and products. On each element, one or more operations can take place. The three basic operations are processing, transporting and storing; in ShowFlow they are called jobs. Jobs are characterized by a cycle time (cycle times for storage are naturally 0), which can be ran-dom. The entities using the jobs are called products. Products can be defined freely and represent parts, tools, people, etc. They take place on an element and are sent to another element when the operation is finished. Therefore, you need a description of how the products flow through a model. This description is stored in routings. Routings consist of a number of stages (routing records). At each stage it is defined which job-element is used and what the next stage is.
3.1. Layout and Routings
Defining a layout is the first step when building a model. A layout contains a number of dif-ferent element types that you can position in difdif-ferent sizes and in any place on your screen. The following element types are available in ShowFlow: Inout, Machine, Buffer, Conveyor, Transport, Path, Aid (operator), Warehouse and Reservoir. Choosing a type depends on the function in the real world system. A machine is the general purpose representation for any kind of operation so that a machine could be a robot, a mill, a counter, etc. Inout elements represent entries and exits (sink/sources) in a model. They can generate and ‘eat’ products freely. A buffer is for storage. Transports and conveyors represent continuous and discontinuous transportation. Aid elements are generally assigned to other elements. An aid could be an operator. Warehouses and reservoirs are buffers with some special functions. In a warehouse you can place products at a specific location, which is described by a number of cells horizontally and vertically. In a reservoir there is the pos-sibility to define open/close control levels. Each element placed in the layout gets one job auto-matically.
Besides the cycle time, a job also describes how an operation is done concerning input batch, additional resources, etc.
Now one or more routings are to be defined. By selecting the elements one after another you describe the path the products follow in the model. In most models the routing roughly reflect the
flow of products because there are a number of product types taking (nearly) the same path and you can specify differences later. In some applications you have to handle a large number of prod-uct types all using different routings, i.e. in a job shop. In this case, ShowFlow offers the modeler to import process routing descriptions from external files.
3.2. Detailing the Model
The second step is to detail the model. This means entering parameters describing the behav-ior of the model that differ from the default settings. Usually only some of the parameters are needed, so it is not necessary to fill a lot of masks before starting the model for the first time. Most of the parameters are related to the fundamental entities discussed above. Element parameters describe the behavior of the elements: what kind of element it is, stochastic (breakdowns) and deterministic (shifts, pauses), availability, how many products it can store, fixed and variable costs, how it selects its next task, etc. The job parameters are similar.
Many systems seem to be quite simple. When looking at details, one often finds different kinds of rules and strategies to make decisions. That is the reason why implementing these deci-sion points takes most of the modeling time. An important aspect in this phase is the way a simula-tion tool supports the user. Two items have to be discussed: high flexibility for implementing con-trol logic and easy to test right working of the model (verification). Besides special functions for verification the on-line animation in ShowFlow plays a large part. When the layout and the rout-ings are finished, animation is available immediately. All changes in the model can be seen on the screen at once. The user is able to detail and to test the model step-by-step until the model runs according to his wish.
Every company producing simulation software is in a dilemma when developing a concept for control logic. The software should be easy to use but, the system should also allow all possible constructions. These two aspects are hard to combine. Distributors go different ways from fixed implemented strategies or decision tables to interfaces for programming languages or combina-tions of them. Besides a number of default strategies, ShowFlow uses a macro language called TLI (Taylor Language Interface). TLI is an easy to use programming language that allows for modifying the model’s behavior powerfully in combination with simulation-specific predefined and user-definable variables. TLI is used at element, job and routing level. There is also the possi-bility to use TLI interactively during a simulation run to make queries and updates. An interface to own routines written in C, Basic, Pascal, etc. is also available. Typical situations in which the routines have to be modified are loops (i.e. rework), selecting elements as a result of a certain status, assembly, disassembly, etc. ShowFlow can send products from each stage in the model to each other in each quantity. For this purpose the user has direct access to all addresses in a routing and replaces the (in most cases) fixed values by expressions of the following form:
select number with condition from list order expression quantity list location list
These so called ‘select’ statement are used for sending and receiving products. The italic parts in this structure can be values or other expressions. Selections can also be nested. This offers many possibilities for order picking, assembly and complex guiding and receiving strategies. Some ex-amples:
select 1 from 3,4,5
One product will be sent to machine 3, 4 or 5. select 1 from 3,4,5 order - utilization [L]
The same as above, but the machine with the lowest utilization has the highest priority. select maximum[1,F] with elqueue[L]<5 from 3,4,5 quantity 4-elqueue[L]
An (express) order uses the maximum number of machines. Only machines with a stock less than 5 are taken into consideration. Elements are described by fixed acceptance rules for picking products or other TLI-user-definable rules and strategies for entry and exit of products. Examples are:
Entry condition: plan from file
The element chooses the next order from a list stored in a disk file. TLI-entry condition: time|600<120
A conveyor accepts products only for the first 120 seconds in a 600 second interval, (| stands for modulo). The expression is true for 120 seconds.
Product types are described by a code (in combination with an icon) and by size (important for conveyors). Sometimes it is necessary that products get individual information or signs. Informa-tion could be a delivery date, priority, state of work, etc. For this purpose, products are coupled with attributes. Attributes can also work as a pointer to a matrix in which i.e., cycletimes are stored. This enlarges the amount of possible information enormously. Querying and updating of the attributes are done at the jobs by evaluating triggers. A trigger is one (or more) simple lines of text with a TLI-expression. Triggers can be evaluated nearly every time an event is scheduled. They can influence products (with their attributes) or the model status itself. An example is:
Trigger on Entry: curcycle[J]:=att2[C]
The cycle time of the order is stored in the second attribute and is assigned when the product enters the job. Assume that a model is built with ShowFlow. Now starts the actual simulation, apart from the (little) simulation when testing the model.
4. Simulation
In stochastic processes random numbers play an important part. ShowFlow comes with differ-ent random number generators which normally work independdiffer-ently from each other. In some ex-periments you may want to study alternatives of a system. Then the models should run with identi-cal conditions and for this purpose it could be necessary that all generators generate the same se-quence of random numbers.
ShowFlow is fully event-oriented. this means that the time between two events (i.e., beginning and ending of an operation ) needs no CPU time. An internal event list makes sure that all changes in status are evaluated.
For every simulation run, the start situation is free to define. Products can be stored in any quantity at any place in the model. To reduce the warm-up period (moment of time that a model
runs with stable status) you can make a warmstart. For a number of various runs you can define a batch run.
During simulation you can zoom, pan and rotate freely, stop, make modifications and then continue. A model can be simulated during a certain period of time or until a special (user-defined) condition is met. The time representation is fully user-definable (i.e. week 8; tue; 8:30,2) and is displayed by an analog and digital clock. With the single-step-mode you can trace your model in detail or you use the conditional single-step for watching a part of the model only.
While simulating, the screen output can be interactively changed, ranging from no information (as fast as possible), via statistics and simple animation to full animation. With full animation you see each product moving from stage to stage or queuing in the system.
ShowFlow automatically keeps track of a large number of common statistics like utilization, waiting times, etc. Default and user-defined statistics can be displayed as numbers or as dynami-cally changing graphs. Especially determining the end of the warm-up period. ShowFlow can also keep track of any kind of variables you want and display them after the simulation run.
5. Analysis
For a correct description of a model, a number of input data is required like arrival times, cy-cletimes, breakdown failures, etc. Often these data exist in protocols, databases, etc. But the ques-tion is: is there enough data to characterize a process well or are they only a part of reality? That means a detailed analysis with statistical methods should be done first. Taylor can read in datasets and analyze them. Two important parameters are the average value and the standard deviation. another point is the statistical distribution which fits best. A built in routine automatically makes a distribution suggestion for the dataset and displays this distribution depending on the type, in con-tinuous or discrete form on the screen.
Typical information users get from a simulation study is utilizations, throughput times, pro-duction per period and costs. The results are available in different tabular reports (contents and form are predefined, but may be changed by the user), TLI reports (containing a mixture of expla-nation, results and illustration or giving specific results); queries (all results can be queried with TLI interactively including minimum, maximum, average and standard deviation); predefined graphs (wait time histogram, queue graph, status diagram, utilization pie, etc.); user-defined graphs (representation of any kind of data like throughput times, costs, etc.).
Graphs can be displayed in over 10 types of general purpose representation: histograms, bar graphs, x-y plots, pie charts, etc. including averages (whole and cumulative), standard deviation and so on. All reports and graphs can be sent to screen, disk file and printer or you can export these data for use in other programs.
6. Additional Features
In the past animation has been treated as a nice but more or less unnecessary extra. ShowFlow has an extensive built-in animation module. There are several reasons. First, similar to the discus-sion in Section 2.2, the animation can be very useful (but generally not replace) for verifying a model. For this purpose the 2-D animation is available as soon as routing is created. With little additional work, 3-D animation is available too. They are useful when giving presentations to management or customers (often more convincing than rough numbers or in the educational sec-tor. A number of ready-to-use 2-D and 3-D libraries come with the package.
With the built-in paintbox you can define your own icon-sets or draw background illustra-tions. The 3-D paint module allows you to change exiting or to add 3-D element icons. Back-ground drawings are automatically translated into vector files for sealing and rotating. Existing drawings can be imported into the HPGL format.
In addition to the points above there are some special functions useful (not essentially neces-sary) for the daily work. When simulating a lot of alternative models with different parameters and settings you could lose your overview. For this purpose, ShowFlow generates a model documenta-tion (text file) describing the whole model. another important aid is the context-sensitive online help with index and page search facility.
Besides stochastic arrival patterns, ShowFlow can process external files (ASCII-file) with an unlimited number of deterministic product arrivals including arrival time, quantities and product attributes. This offers the possibility to simulate with real data. Special arrival patterns, think of season influences of daily peaks, can be generated with genlink. Genlink generates an external file by taking samples from different distributions.
External files can also be used to define deterministic machine planning or routing specifica-tion (see Secspecifica-tion 2.1). The handling with ASCII-files becomes easier with the integrated text edi-tor. DDE (Dynamic Data Exchange) links exist for windows base products that allow such links.
The ability to created self-running presentations allows you to build models which explain themselves. With a runtime module you can give all models to other people that are participating in a simulation study.
These are Advanced Statistics (with an autofit module which tests distributions to fit data and an experiment module), runtime Development Kit (allowing you to create customized applica-tions), and the Animator (special 3-D animation module with shaded animation).
8. Summary
Enterprise modeling tools support the company in better understanding its goals, its operating context and in designing processes to effectively meet these goals. There is also support for de-signing software and data requirements in many of these tools. A process engine executes the workflow and guides business users in operating the real time processes.
Simulation enables identification of increased value creation opportunities within the business. It provides the ability to test a process design, investigate tradeoffs in terms of operating rules, resource levels through a ‘virtual pilot’. This type of simulation has been used successfully over a number of years in many manufacturing and service applications. Simulation models have usually been built specifically to help decision making on investments and major change.
ShowFlow Simulation Software integrates all functions necessary for a simulation study and combines in a simple manner high flexibility with ease-of-use without making concessions to functionality. many applications in different industries; manufacturing, transportation, distribution, material handling, show this. Fast modeling and online animation are the concept for the use not only by simulation experts. ShowFlow is used more and more in education institutes for their prac-tical courses in engineering.
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CZESŁAW CEGŁOWSKI e-mail: cceglowski@e-ar.pl Akademia Rolnicza w Szczecinie Department of Computer Science Monte Cassino st. 16, 70-466 Szczecin
