Mohammad Ahmadi Achachlouei: In the last two decades, enterprise architecture (EA) has become a common approach for the management of information systems in organizations. However, the academic development of the field has not paralleled this turn of events. There is considerable divergence among researchers as to the very definition of EA. The present project seeks to clarify the concepts of EA, drawing relevant examples from the academic literature and addressing different perspectives in EA research community. The study aims to reveal the ontological arguments about the nature of EA and the related notions and to take one step towards developing theoretical foundations of the field. The present project first critically reviews the competing, predominant academic definitions of EA and identifies major research circles in the field. Based on an analysis of recent doctoral dissertations and of key academic publications, it then reviews the perspectives of the various research circles regarding different notions related to the concept of EA. Template analysis (thematic coding) of the data (eleven doctoral dissertations, as well as articles and books cited as the principle references in the dissertations) is performed to critically review and analyze the concept of enterprise architecture. A critical review of the previous work examining EA research communities in isolation shows that even articles claiming to provide a big picture of the EA research community are ultimately focused on one narrow research circle. In the current project, a novel categorization of the current EA research circles is presented, and their views on the concept of EA and the related notions are discussed.