Learning UML

Interactions and Collaborations

Formally, a collection of classes, their messages, and their associations is known as a collaboration. A collection of specific objects playing the roles of the classes, their stimuli, and their specific links playing the roles of the associations, is known as a collaboration instance. A collection of messages is known as an interaction and a collection of stimuli is known as an interaction instance. An interaction is said to occur within the context of a collaboration because an interaction is a subset of the contents of a collaboration; and an interaction instance is said to occur within the context of a collaboration instance because an interaction instance is a subset of the contents of a collaboration instance.

You may show an interaction using one of two forms:

Generic-form interaction

Shows two or more possible sequences of message or stimuli exchanges using repetition and conditionality.

Repetition

Involves repeating a set of messages or stimuli — for example, repeating the set of messages or stimuli in steps 6a and 6b of the interaction and collaboration description to generate the project-status report.

Conditionality

Involves communicating one set of messages or stimuli rather than another set of messages or stimuli — for example, conditionally performing step 5 or 6 of the interaction and collaboration description to generate the project-status report.

Instance-form interaction

Shows one actual sequence of message or stimuli exchanges without ...