# Investigation of Microservice-Based Workflow Management Solutions for Industrial Automation
###### Abstract
Such dynamic requirements and demands cannot be addressed during production automation's design time. Thus, runtime reconfiguration and re-organization of, e.g., workflow management and execution, becomes important and achieving this calls for the usage of new technology. This paper investigates microservice-based approaches with respect to their applicability to engineering design workflow management and execution. The workflow management disciplines described in this paper cover the issues of business process engineering, design process management, and manufacturing workflow management and primarily focus on microservice-based architectural solutions. Research surveys from this domain, such as [6; 7], provide a good general overview of the field. However, the current paper is an investigative work in a specific automation engineering area associated with microservice approaches. While the usage of workflows is a mature discipline in the legacy ISA-95 realm, workflow implementation faces a new set of challenges in modern Industry 4.0 environments where distributed architectures, such as the service-oriented architecture (SOA) or the microservice architecture, are predominant. Thus, this work considers how  
Figure 1: Hierarchical vs. meshed communication models in ISA-95 vs. Industry 4.0 architectures. workflow management and execution based on a microservice architecture can meet the requirements of Industry 4.0 and dynamic markets. For this purpose, the challenges and requirements related to industrial workflow technology were compiled from industry research project reports and scientific publications. The requirements aggregate was then used to evaluate the capabilities of a set of actively developed open source microservice-based workflow management and execution technologies. Although this paper compares open source workflow management solutions that use microservice architectures, the approach used to identify the associated challenges and alternatives follows a particular methodology to conduct thorough studies. This methodology is outlined in [8] and follows the well-known PICOC (Population, Intervention, Comparison, Outcome, and Context) criteria for research question formulation. For this approach, and according to PICOC criteria, this study considered microservice architectures as the application area or domain (population), business process as the technology (intervention), workflow management as the specific technology for which the interventions are compared (comparison), and challenges in the industry as the factors of importance (outcome). The main contributions of this paper are as follows:  
1. It identifies the challenges for the industry with regard to choosing workflow management and execution solutions, which are grouped into a workflow lifecycle, and finds that microservice-based approaches address said challenges properly, especially those related to flexibility and dynamic data exchange. 2. It investigates different microservice-based approaches for workflow management and execution. 3. It investigates and compares how the various microservice-based workflow management methods address industrial requirements and challenges. 4. It compares the concrete implementation features of the microservice-based solutions to support decision-making in various scenarios. This paper is structured as follows: Section 2 discusses the background and related work on workflows and microservices. In Section 3, the requirements and challenges compiled from previous research projects and the scientific literature are classified into a workflow lifecycle. Section 4 presents the set of solutions for workflow management, which are compared and matched to the requirements. Section 5 contains a discussion highlighting the differences identified between each approach studied. Finally, Section 6 concludes the paper by describing the main contributions of this research.