Service oriented architectures (SOA) have emerged as an approach to handle the complexity of enterprise interoperability. Recently, multi-agent systems have been promoted as a technique to deal with cooperation issues involved in SOA. This cooperation is particularly important in several application domains, in which different companies are involved in a concrete service deployment. Agents, among other issues, offer the possibility to decide, if more than one option is available, providing flexibility and robustness. In this paper, we describe the agent-based cooperation process we have followed to enable partner's cooperation in an equipment maintenance workflow. The use of ontologies and relationships with standards is highlighted. The approach is illustrated in an hospital scenario considered in the AIMES project. © Springer-Verlag Berlin Heidelberg 2012.