A description of a boundary (typically a subsystem, or the work of a particular team) within which a particular model is defined and applicable.
*Multiple models are in play on any large project.* Yet when code based on distinct models is combined, software becomes buggy, unreliable, and difficult to understand. Communication among team members becomes confused. It is often unclear in what context a model should *not* be applied.
Model expressions, like any other phrase, only have meaning in context.
**Therefore:** Explicitly define the context within which a model applies. Explicitly set boundaries in terms of team organization, usage within specific parts of the application, and physical manifestations such as code bases and database schemas. Keep the model strictly consistent within these bounds, but don't be distracted or confused by issues outside.
See also Continuous Integration. > Apply Continuous Integration to keep model concepts and terms strictly consistent within these bounds, but don’t be distracted or confused by issues outside. Standardize a single development process within the context, which need not be used elsewhere.