The Time/Place/Object model for tracking and history management in manufacturing line control

Tracking and production history management for manufacturing lines requires the ability to retrieve traced-back production performance data from raw materials to final products. Requirements are not so simple. At first, manufactured objects are split into or combined with other objects. Since traditional temporal models concentrate on time-varying or time-series objects, the change of the unit of object management cannot be handled. Secondly, not only object branching and merging but also object dividing and accumulating need to be represented. Conventional workflow models focus on only branching and merging, because of the characteristics of the workflow domain. Thirdly, production histories need to be retrieved in different perspectives according to the purpose of the retrieved data. However, the view of the temporal models is focusing on only the time dimension, while the view of workflow history is only a projection from entire history. We propose the Time/Place/Object model to satisfy the requirements in manufacturing line management and describe the structure and the behavior of a manufacturing line. The model provides the definite categories of five process primitives, three object forms, four invocation logics of ECA rules, and three views of production history. We have developed a family of middleware based on the model and applied it to a tracking system for a steel mill plant