Clarifying the project complexity construct: Past, present and future

• Providing a clarification to the ontology/epistemology of project complexity (subjective & objective)
• Exploring historical development of project complexity with considering dominant schools of thought
• Identifying core complexity factors (CCF) required for project managers to manage complex projects

The research explores the historical development of project complexity. Projects are becoming more complex due to unexpected emergent behaviour and characteristics. Complexity has become an inseparable aspect of systems and also one of the important factors in the failure of projects. While much has been written about project complexity, there is still a lack of understanding of what constitutes project complexity. This research includes a systematic literature review to demonstrate the current understanding of commonalities and differences in the existing research. This was achieved by examining more than 420 published research papers, drawn from an original group of approximately 10,000, based on citations during the period of 1990–2015. As a result of this exploration, an integrative systemic framework is presented to demonstrate understanding of project complexity.It was found that there are three primary and distinctive models of project complexity, the Project Management Institute view, the System of Systems view and the view developed from the analysis of citations of research papers, which is called the Complexity Theories view. Further testing is required on a range of complex projects in order to attempt to reconcile these views.