This study explores complexity metrics for business artifact process models described by Case Management Model and Notation (CMMN). Process models are usually described using Business Process Management (BPM), which is a relatively mature discipline with a large number of practitioners. Over the last few decades a new way of describing data intensive business processes has emerged in BPM literature, for which traditional BPM is no longer adequate. This emerging method, used to describe more flexible processes, is called business artifacts with Guard-Stage-Milestone (GSM). The work on GSM influenced CMMN, which was created to fill a market need for more flexible case management processes for knowledge workers. Complexity metrics have been developed for traditional BPM models, such as the Business Process Model and Notation (BPMN). However, traditional BPM is not suitable for describing GSM or CMMN process models. Therefore, complexity metrics developed for traditional process models may not be applicable to business artifact process models such as CMMN. This study addresses this gap by exploring complexity metrics for business artifact process models using CMMN. The findings of this study have practical implications for the CMMN standard and for the commercial products implementing CMMN. This research makes the following contributions: • The development of a formal description of CMMN using first-order logic. • An exploration of the relationship between CMMN and GSM and the development of transformation procedures between them. • A comparison between the method complexity of CMMN and other popular process methods, including BPMN, Unified Modeling Language (UML) Activity diagrams, and Event-driven Process Charts (EPC). • The creation of a systematic literature review of complexity metrics for process models, which was conducted in order to inform the creation of CMMN metrics. • The identification of a set of complexity metrics for the CMMN standard, which underwent theoretical and empirical validation. This research advances literature in the areas of method complexity, complexity metrics for process models, declarative processes, and research on CMMN by characterizing CMMN method complexity, identifying complexity metrics for CMMN, and exploring the relationship between CMMN and GSM. / Ph.D. (Computer Science)