Visual Modeling and 3D-Representation with a Complete Visual Programming Language - A Case Study in Manufacturing

Main goal of this contribution is a first approach to evaluate the suitability of visual programming languages, i.e., Pictorial Janus [3], for the modeling of complex systems and their control strategies. These systems can be seen as networks of communicating objects. Objects select strategies for suitable actions based on incoming messages. Our field of investigation is in computer integrated manufacturing considering the example of a car manufacturing cell. This color sorting assembly buffer (CSAB) schedule jobs in queues. The jobs represent car bodies scheduled in feeder lines for the enameling. Feeder lines collect raw bodies to blocks. Blocks are bodies which are to be enameled by the same color. This organization decreases the cost of expensive change-over-times when changing colors at the enameling. Blocks of bodies are dislocated from the queue and enameled successively. Contradictory system goals, such as minimizing color changes and preserving the sequence of incoming jobs, have to be regarded by appropriate control strategies. Due to the complexity of this (NP-complete) problem and to real–time requirements for on-line control there are no optimal strategies on hand. Consequently, suitable heuristics have to be developed. Often they are designed applying a ‘try-and-error’ method. A modeling framework has to support the rapid prototypingof these systems as well as an expressive end user oriented representation. Both are essential requirements since end users need other visualization techniques than experienced designers due to their different knowledge and interests. Considering complex systems in general and our example in particular we can identify the following requirements for modeling system prototypes: Complex systems require structuring concepts like modularity and hierarchy. System elements are usually characterized by dynamic behavior requiring adequate control structures for concurrency. Rapid prototyping additional requires declarative very high-level languages. Design aspects which are currently not in the designer’s scope are to be hidden. Different parts of the system should be viewed at different abstraction levels, e.g., visual and textual notation. Expressive representations for all persons involved (designer, end user) should be provided. The prototyping framework finally has to support the quick generation, analysis, and modification of a model in an open, integration environment for rapid development of heterogeneous subcomponents.