This thesis proposes a new concept, the User Use Case (UUC), to explain at the requirements level, how, under the command of the user, an application is really used, as opposed to how the application is actually implemented at the code level. The aim is to compare the UUC diagrams to what an application must do using law-based ontology. The thesis implements a process, Relational to User Use Case (RUC), to build a backward traceability, using the end product, the accomplished application, and works towards constructing the UML documentation.