We show how to capture informally stated requirements by an ASM (Abstract State Machine) model. The model removes the inconsistencies, ambiguities and incomplete parts in the informal description without adding details which belong to the subsequent software design. Such models are formulated using application-domain-oriented terminology and standard software engineering notation and bridge the gap between the application-domain and the system design views of the underlying problem in a reliable and practical way, avoiding any formal overhead. The basic model architecture reflects the three main system parts, namely for the manual and automatic light control and for handling failures and services. We refine the ground model into a version that is executable by AsmGofer and can be used for high-level simulation, test and debugging purposes.