The abbreviation F-REX stands for FOI Reconstruction and Exploration, which is a combination of processes, methods and tools for the reconstruction and exploration of data derived from exercises and operations. Exploration of the data generated during these exercises, is done with the tool F-REX Studio, which can display data from many different sources and present them in views, specialized in showing the dataset from a particular perspective. F-REX Studio is the core of the framework, F-REX Framework, whose architecture this document summarizes. The development of F-REX is a constant work in progress, which means that this document is constantly changing, to keep it in sync with the code-base that represents the system.