Wayne State University
Industrial Engineering
Reproduced with permission from NeXT Computer, Inc.
A Reference Guide to NeXT in Higher Education, Fall 1992
ยช 1992 NeXT Computer, Inc
Better decision making with custom model building software
Computer modeling software is becoming an increasingly important tool in designing and analyzing various systems-from factories to automobiles to animated films.
Although a number of simulation languages are currently available, including Witness, SIMON, and Automod, according to Olugbenga Mejabi, assistant professor of industrial engineering at Wayne State University, "The current programs deal only in 'flat' abstractions. A machine tool in a factory, for example, is represented simply as a resource that changes from idle to busy and back again, and ignores the fact that it has electric motors, tool changers, and computer controls that contribute to its overall behavior. These programs permit little or no extension of the semantics of the languages. They're also difficult to use and make typical modeling quite unintuitive."
To address these problems, which Mejabi says "contribute to an increased risk of poor decision making and costly mistakes," he and four Ph.D. candidates initiated their own model builder project. They decided to create their model builder on the NeXT platform because of its development capabilities.
"After a detailed investigation of numerous data representation and programming philosophies," Mejabi says, "it became clear to us that object-orientation provided exactly what we needed to develop our simulation framework. Object-oriented concepts such as abstract data types, object identity, data hiding, inheritance, and dynamic binding helped us produce a modeling and simulation architecture that provides multiabstraction modeling, extensibility in the language and architecture, and many elements of intuitive modeling."
As for NeXT technology in particular, he says,"The NeXT environment provides the best mix of object-oriented operating software and development tools around. NeXTSTEP, the Application Kit, and Interface Builder have literally saved us several months of work."
He continues, "We wrote the code for our model builder in fewer than nine months. It would have taken us three to four times that on a Sun SPARCstation, and it would have been even more difficult in a DOS environment. In fact, I doubt we would have even attempted the project in a DOS environment."
To date, Mejabi and his graduate students have constructed prototypes of simple manufacturing systems. They are currently building models of more complicated manufacturing systems with the model builder architecture, investigating the design of computer-integrated manufacturing systems, and planning for information and material flow in highly automated manufacturing systems.
The second and third phases of the project involve extending to the architecture and developing libraries of objects for modeling in domains such as intelligent manufacturing systems, financial system modeling, and decision process modeling. By the end of the third phase, the architecture will be suitable for modeling complex systems as either discrete events or continuous models.
"We consider our NeXT-based model builder an important advance in simulation methodology," Mejabi concludes. "The ultimate result will be our ability to model more complex systems and large-scale operations than before, and to use the same simulation software in a variety of application domains. If used appropriately, the analyst should be able to perform more rapid analyses and therefore investigate more alternatives. This should lead to better planning and better decision making."
For more information, please contact:
Olugbenga Mejabi
Assistant Professor of Industrial Engineering
Wayne State University
5050 Anthony Wayne Drive
Detroit, MI 48202
(313) 577-3134
mejabi@sneezy.eng.wayne.edu