Change Categories Based on Mutable Artifacts in PLC Control Software Projects

Automated Production Systems are highly complex mechatronic systems. The increasing complexity of automation software is a main challenge for companies to remain competitive. Added functionality entails software changes, which may cause side effects. Static code analysis and change impact analysis are key methods in computer science for assessing software regarding side effects. However, the requirements of real-time capability, reliability, and mixing different Programmable Logic Controller programming languages in the automation software lead to new requirements for code analysis and change management. This paper introduces a set of change categories designed to provide understandable and comprehensive classifications of changes in automation software. Mutable (i.e., changed or modified between versions) software artifacts serve to differentiate change categories. Aiming for unambiguousness and completeness, this set of categories supports the further work of the change analysis, such as automatic change detection and visualization. The change categories are evaluated through an industrial software project programmed in Siemens TIA Portal comprising 262 program organization units in the health sector.