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Diagram Elements and Mapping to Model Elements

The sequence diagram maps onto a single collaboration.

There are 2 required specialist top level diagram elements (Figs) FigClassifierRole and FigMessage

FigClassifierRole represents a classifierrole in the model. It's composite diagram elements will be FigLifeLine and FigHead

FigMessage represents a message between two classifier roles in the model (or a self message back to the same classifier role).

Suggested composite structure of FigClassifierRole

The y co-ordinate a FigHead within FigClassifierRole is zero unless there is an incoming FigMessage[Create]. In this case the FigHead is positioned so that the first incoming FigMessage[Create] is the centre of FigHead (see fig 89 of UML1.4.2 spec).

FigHead will be composed of either FigHeadObject or FigHeadActor. FigHeadActor will only be used if their is a classifier attached of type actor.

FigLifeLine will be a transparent rectangle displayed immediately below FigHead. It will contain a single dashed line down from the top and a variable number of FigActivations. The dashed line ends at the end of the FigLifeLine or at the last outgoing FigMessage[DestroyAction]

FigActivations are created and modified dynamically when the user adds, removes repositions an incoming or outgoing message. An X at the end of a FigActivation respresentats destruction of that instance. The algorithm for creating FigActivations on a FigLifeLine is - TBD

Modes and Selections for user interaction

A specialist Mode is required for drawing a FigMessage. This will not allow the source end to move while drawing. When placing the destination end on another FigClassifierRole the edge should snap to a horizontal line if the height difference is within n pixels. Otherwise the message edge should be placed at the diagonal angle gestured by the user (see fig 88 of UML1.4.2 spec).

It should also be possible to click on the diagram to insert a vertex point before directing the message back to the original FigClassifierRole or to some other.

Dragging FigClassifierRoles should be limited to the horizontal plane.

Resizing the height of one FigClassifierRole should resize the height of all but it should not be possible to resize so that any FigMessage is forced to move.

It should be possible to drag a FigMessages up and down with such a drag forcing reposition or rebuilding of FigActivations.


It is not possible to reassign a different action to an existing message.

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