Descriptions of Entities and Objects
4. A behavior is an action executed by an identifiable entity of the system.
A behavior may be an action of the entire system or an action by one of
the identifiable entities of the system.
Examples of behaviors are, dogs bark, wheels roll, people answer the
telephone, a salesperson makes a sale, a user clicks a button
on a display presented by a web browser.
Behaviors of one object usually either change the state in that object or
are intended to invoke some behavior in another object.
Behaviors are implemented in classes as methods or operations.