Which notation best describes an activity parameter that crosses the frame boundary?

Which notation best describes an activity parameter that crosses the frame boundary?

• A. A rectangle that straddles the frame of an activity diagram
• B. A pin attached to the action boundary
• C. A small square at the boundary
• D. A circular node on the boundary

Answer: (A)

When something crosses the boundary of the activity diagram frame, you need a symbol that shows it belongs to both the inside activity and the outside environment. A rectangle that straddles the frame does this clearly: part of the rectangle is inside the frame and part is outside, signaling an external interface or parameter flowing across the boundary. This visual cue communicates that the parameter isn’t purely internal to the activity, but interacts with something outside it. A pin attached to the action boundary suggests data entering or leaving a specific action inside the frame, not crossing the frame boundary itself. A small square at the boundary or a circular node on the boundary doesn’t specifically convey cross-boundary parameter exchange in the same way, so they aren’t the best representations for this scenario.

When something crosses the boundary of the activity diagram frame, you need a symbol that shows it belongs to both the inside activity and the outside environment. A rectangle that straddles the frame does this clearly: part of the rectangle is inside the frame and part is outside, signaling an external interface or parameter flowing across the boundary. This visual cue communicates that the parameter isn’t purely internal to the activity, but interacts with something outside it.

A pin attached to the action boundary suggests data entering or leaving a specific action inside the frame, not crossing the frame boundary itself. A small square at the boundary or a circular node on the boundary doesn’t specifically convey cross-boundary parameter exchange in the same way, so they aren’t the best representations for this scenario.