Schedule-based service choreographies for real-time control loops

Today's manufacturing industries are undertaking efforts to further increase the flexibility of their facilities. One way to achieve this goal is the development of distributed, service-oriented architectures (SOA). A challenge for SOAs is the continued support of the real-time requirements imposed by industrial control tasks. This paper presents an approach for executing service choreographies with strong real-time guarantees without a central point of control. Engineers can design the automation workflow as a graph of communicating tasks which are then assigned to devices in the network. Our method generates a cyclic, non-preemptive schedule for each device to achieve global cooperation between them. Using an approach that combines several heuristics, a valid solution for over 99% of the 1.2 million test cases was found. On average, this method was over two orders of magnitude faster than an approach based on MIP-solvers.