Towards Semantic Integration of Plant Behavior Models with AutomationML's Intermediate Modeling Layer

AutomationML is an emerging IEC standard for storing and exchanging engineering data among the heterogeneous software tools involved in the engineering of production systems. One important subset of such engineering data is the plant behavior. To make this data exchangeable, AutomationML uses the existing industry data format PLCopen XML. However, at the development stages of production systems, the plant behavior is usually defined using other representation means, such as Gantt charts, impulse diagrams, and sequential function charts. To make such plant behavior models exchangeable, AutomationML introduces the so-called Intermediate Modeling Layer (IML) with corresponding transformation rules to decouple the employed modeling languages from the target format PLCopen XML. However, IML itself as well as the transformations from and to IML are only semi-formally described. This not only hinders the adoption of IML as a common language for representing plant behavior, but also renders impossible the composition of heterogeneous plant behavior models for carrying out integrated analyses of the global plant behavior. In this work, we aim at clarifying syntactical and semantical aspects of IML by proposing a metamodel and operational semantics for IML. This constitutes the first step towards formalizing and validating transformations between behavioral modeling languages currently employed in the production domain (e.g., Gantt charts), IML, and PLCopen XML. Having this foundation, we aim at utilizing IML as the semantic domain for the composition of heterogeneous plant behavior models.