This work proposes a technique for requirements validation and logical structure discovery, compatible with evolutionary process models. The technique is based on a conservation law, called business value invariant, which quantifies the exchange of business objects between a system and its environment. With the invariant, the logical class structure of the designed system is algorithmically derived from its use case model. To validate that the modeled requirements and derived structure faithfully reflect the user requirements, the behavior of the constructed prototype is projected on the business objects exchanged on the system’s boundary, and the projected behavior is animated with a labeled transition system analyzer. The model animation approach explicitly describes the interface between the system and its environment, and through OCL pre- and post-conditions, it distinguishes between system and environment responsibilities. The animated prototype links the outwardly visible “interobject” behavior to the information structures and the behaviors of the comprising parts, or “intraobject” behavior. Unlike formal notations based on logic, the proposed approach does not preclude the owners of the problem from taking part in the problem-solving process, that is, the knowledge locked in the prototype can be validated. The proposed prototyping technique acts as a discursive communication instrument, bringing the worlds of clients and developers a step closer.