Class-Responsibility-Collaborator (CRC) Modeling

 Class-Responsibility-Collaborator (CRC) Modeling

Class-responsibility-collaborator (CRC) modeling [Wir90] provides a simple means for identifying and organizing the classes that are relevant to system or product requirements. Ambler [Amb95] describes CRC modeling in the following way: 

"A CRC model is really a collection of standard index cards that represent classes. The cards are divided into three sections. Along the top of the card you write the name of the class. In the body of the card you list the class responsibilities on the left and the collaborators on the right."

In reality, the CRC model may make use of actual or virtual index cards. The intent is to develop an organized representation of classes. 

Responsibilities are the attributes and operations that are relevant for the class. Stated simply, a responsibility is “anything the class knows or does” [Amb95].

 Collaborators are those classes that are required to provide a class with the information needed to complete a responsibility. In general, a collaboration implies either a request for information or a request for some action.

A simple CRC index card for the FloorPlan class is illustrated in Figure 6.11. The list of responsibilities shown on the CRC card is preliminary and subject to additions or modification. The classes Wall and Camera are noted next to the responsibility that will require their collaboration.

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