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One Model, Many Interests, Many Views
Mapping for the Activity Diagram
Control classically flows from left to right (when drawn horizontally) or top down (when drawn
vertically). Rounded rectangles on branches represent activities or functions. Where an activity
has a decomposition specifying greater detail, a “pitchfork” in the corner of the node indicates the
decomposition is present.
As noted in the “Representing Behavior – Control Constructs” section, diamonds (decision nodes) and
bars (fork and join nodes) represent control constructs upon which behavior is built. As each activity is
completed, control flows along the branch lines to the next activity or control construct. Every construct
has a precise definition that prescribes how control will be passed within the construct and when the
construct itself will end. This structure results in a complete specification of control flow which itself is
fully executable.