Messaging Interaction Patterns for a Service Bus Concept of PLC-Software

The software architecture of PLC-software has a direct influence on its adaptability, modularity, and flexibility. The software component (Program organization unit, POU) is the smallest unit of PLC-software that is responsible for providing certain machine functionality in an overall production system. The way these software components interact with each other has a significant role in the overall PLC-software architecture. To address current market demands, software components need to be atomic, modular, and loosely coupled. PLC-Service bus-based architecture enables such PLC-software. We are using this architecture as a basis. In this paper, we are evaluating available messaging interaction patterns from the enterprise IT domain. Our evaluation is based on requirements defined by the PLC-Service bus architecture. Therewith, we identified a list of interaction patterns that can be used to design interactions between software components in a PLC-Service bus environment. We use a reference production cell as a running example. To evaluate our findings, we first explain what the PLC-Service bus concept would look like for our running example. Later, we used four practical process scenarios from our running example to evaluate the applicability of identified messaging integration patterns for the PLC-Service bus.