A model is an abstraction that describes one or more aspects of a problem or a potential solution addressing a problem. Traditionally, models are thought of as zero or more diagrams plus any corresponding documentation. However, nonvisual artifacts such as collections of CRC cards, a textual description of one or more business rules, or the structured English description of a business process are also models. An agile model is a model that is just barely good enough. But how do you know when a model is good enough?
Agile models are just barely good enough when they exhibit the following traits:
Agile models fulfill their purpose. If you don't know why you need to create something, don't create it. That wouldn't be agile.
Agile models ...