Cross-organizational service-based processes are increasingly adopted by different companies when they can not achieve goals on their own. The dynamic nature of these processes poses various challenges to their successful execution. In order to guarantee that all involved partners are informed about errors that may happen in the collaboration, it is necessary to monitor the execution process by continuously observing and checking message exchanges during runtime. This allows a global process tracking and evaluation of process metrics. Complex event processing can address this concern by analyzing and evaluating message exchange events, to the aim of checking if the actual behavior of the interacting entities effectively adheres to the modeled business constraints. In this thesis, we present an approach for decentralized monitoring of cross-organizational choreographies. We define a hierarchical propagation model for exchanging external notifications between the collaborating parties. We also propose a runtime event-based approach to deal with the problem of monitoring conformance of interaction sequences. Our approach allows for an automatic and optimized generation of rules. After parsing the choreography graph into a hierarchy of canonical blocks, tagging each event by its block ascendancy, an optimized set of monitoring queries is generated. We evaluate the concepts based on a scenario showing how much the number of queries can be significantly reduced.
