Close Enough? Criteria for Sufficient Simulations of IEC 61499 Models

The IEC 61499 standard defines a model for distributed control systems based on function blocks (FBs) and event-driven execution. Although interoperability and portability between tools are core goals of the standard, the behavior of an executable model varies significantly between run-time environments (RTEs). This presents challenges for comparing execution traces, e.g., when validating that a simulation of an IEC 61499 model conforms to a specific RTE. In this paper, we propose a methodology for analyzing the behavior of custom IEC 61499 RTEs based on example models that cover specific language features or known semantic variants. These examples are derived from an analysis of the standard and relevant literature on IEC 61499 semantics. We founded a publicly available repository of collected examples that can be used to analyze the RTE behavior in a structured way. Our approach provides a starting point for a future comprehensive set of example models. In this paper, we focus on FB network execution and demonstrate the effectiveness of our approach by comparing the behavior of 4diac FORTE and a model simulator. Our methodology offers a systematic and practical way for identifying implemented semantic variants of IEC 61499.