This hierarchical model may include more than the two levels shown. Note that a logical hierarchical arrangement does not imply a similar physical arrangement. A flat physical configuration may be organized into a logical lighting control system. The growth of the home automation market requires a variety of products that can work together. Designing to a common model is necessary for interoperability without limiting product differentiation.
Interoperability assures the consumer a choice of control methods with fixtures already installed.
This promotes market growth for add-on features. The consumer might initially wire the house for a lighting control system using simple fixtures and control devices. Later, as needs and budgets allow, the system could be upgraded for extra features. Thus, both consumers and manufacturers win by supporting interoperability derived from a common application model.