Objects provide an abstraction that clients can interact with. The behavior of an object is the collection of provided interactions (called methods or operations and, collectively, an interface) and the response to these method calls (or "messages"). All interactions with an object must be through its interface and all knowledge about an object is from its behavior (returned values or side effects) to the interface interaction.
Monday, June 27, 2005
From an article on object-relational modelling (emphasis mine):