The model, of course, is inoperable. It offers a guideline or valuation structure that may be applied in as subjective a fashion, or conceptually elastic a framework, as one would wish for. Reality, however defies an open-ended structure even as nature abhors a vacuum. Thus, a compromise is reached by using an explicative model that does allow for conceptual flexibility, yet also shows progression through stages of the process, as in the Broehl model.