Abstract The usage of process choreographies and decentralized Business Process Management Systems has been named as an alternative to centralized business process orchestration. In choreographies, control over a process instance is shared between independent parties, and no party has full control or knowledge during process runtime. Nevertheless, it is necessary to monitor and verify process instances during runtime for purposes of documentation, accounting, or compensation. To achieve business process runtime verification, this work explores the suitability of the Bitcoin blockchain to create a novel solution for choreographies. The resulting approach is realized in a fully-functional software prototype. This software solution is evaluated in a qualitative comparison. Findings show that our blockchain-based approach enables a seamless execution monitoring and verification of choreographies, while at the same time preserving anonymity and independence of the process participants. Furthermore, the prototype is evaluated in a performance analysis.
Web service orchestrations-expressed in the Web service business process execution language (WS-BPEL or BPEL for short)-are a manifestation of the two-level-programming paradigm where services, i.e. the business functions used by the composite application, are composed through BPEL's control flow constructs. BPEL processes Web service orchestrations, business functions therefore can be transparently accessed remotely, allowing to build composite applications that integrate business functions provided by different partners on different locations. As of today, execution of BPEL processes, i.e. the evaluation of the processes' control flow, is performed by a central workflow engine. In certain scenarios, such as complex collaborative cross-partner interactions, this approach of centralized workflow enactment leads to "un-natural" process models; process models that are not driven by the processes' original business goal but by infrastructural or organizational reasons. In this paper, we propose an alternative approach to enacting BPEL process control flow in a distributed, decentralized manner. We present the overall process lifecycle and give a detailed description of the underlying process model. Establishing scalable and cross-enterprise workflow management systems (WfMSs) in the cloud requires the adaptation and extension of existing concepts for process management. This paper proposes a scalable and cross-enterprise WfMS with a multitenancy architecture. Especially, it can activate enactment of workflow processes by cloud collaboration. We do not employ the traditional engine-based WfMSs. The key idea is to have the workflow process instance to be self-protected and does not need a workflow engine to secure the data therein. Thus, the process instance discovery and activity execution can be fully independently and distributed. As a result, we can employ the data storage system, Big Table, to store the process instances, which may form a big data. The applying of element-wise encryption and chained digital signature makes it satisfy major security requirements of authentication, confidentiality, data integrity, and nonrepudiation.