Non-Deterministic Use Case Map Traversal Algorithm for Scenario Simulation and Debugging

The User Requirements Notation (URN) is a Requirements Engineering modeling language published by the International Telecommunication Union (ITU) to formally specify and analyze what a user would expect from a system. In particular, URN allows the modeling of use cases and scenarios of a system with Use Case Maps (UCM). A key benefit of formalizing these models is the added ability to better analyze them; thus gaining insight to improve quality and understanding of the requirements of the system and its capabilities. Existing traversal mechanisms which analyze UCM do not well reflect the inherent stochasticity of system or user interactions, because they are typically designed for visualization purposes rather than simulation and debugging. We propose a novel traversal mechanism that (i) better reflects real systems by incorporating non-determinism, (ii) considers multiple independent scenarios running concurrently, (iii) implements the UCM concept of map instances, and (iv) consequently enables automated simulation and execution as well as user-driven forward and backward debugging of UCM. We validate the novel traversal mechanism by applying it to a crisis response mobile app that allows a first responder to step forwards and backwards through crisis response actions.