Improving software development efficiency and reusability of existing programs is an important topic for industrial automation. Recently, modern software paradigms have been introduced into the automation domain such as object-oriented programming using the IEC 61131-3 standard and component-based design based on the IEC 61499 standard. In this paper, another software paradigm – service-oriented architecture is applied to the software design for automation programs. The proposed SOA pattern is based on a multi-layered structure with enhanced reusability and flexibility. A case study of water heating system is implemented to prove the concept of SOA paradigm.