Visualization of PLC programs using XML

Due to the growing complexity of PLC programs there is an increasing interest in the application of formal methods in this area. Formal methods allow rigid proving of system properties in verification and validation. One way to apply formal methods is to utilize a formal design approach in PLC programming. However, for existing software that has to be optimized, changed, or ported to new systems there is the need for an approach that can start from a given PLC program. Therefore, formalization of PLC programs is a topic of current research. This paper outlines a re-engineering approach based on the formalization of PLC programs. The transformation into a vendor independent format and the visualization of the structure of PLC programs are identified as an important intermediate step in this process. It is shown how XML and corresponding technologies can be used for the formalization and visualization of an existing PLC program.