Operator and Operand for a Combined Fragment

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About combined fragment

A combined fragment can consist of one or more interaction operators and one or more interaction operands. Number of interaction operands (just one, or more than one) depends on the last interaction operator of this combined fragment.

Use the Tool Palette, or context menus to create these elements. The operator type shows up in the descriptor in the upper-left corner of the design element. Note that you can define multiple operators in a combined fragment. In this case, the descriptor contains the list of all operators, which is a shorthand for nested operators.

When an operator is created, add the allowed operands, using the combined fragment's context menu.

A combined fragment can be expanded over several lifelines, detached from and reattached to lifelines. In the Object Inspector, use the Operators field to manage operators within the combined fragment.

Each combined fragment is attached to its lifeline with a black dot. This dot is an individual diagram element, which can be selected or deleted. Deleting a dot means detaching a combined fragment from the lifeline. Note that a combined fragment cannot be detached from all lifelines and should have at least one attachment dot.

You can reattach a combined fragment later, using the Tie Frame tool.


When a combined fragment is created, the operator is shown in a descriptor pentagon in the upper left corner of the frame. You can change the operator type, using the Operators field of the Object Inspector, which is immediately reflected in the descriptor.

The descriptor may contain several operators. UML 2.0 specification provides this notation for the nested combined fragments. In Modeling you can use this notation, or create nested combined fragment nodes.


Operands are represented as rectangular areas within a combined fragment, separated by the dashed lines. When a combined fragment is initially created, the number of operands is defined by the pattern defaults. Further, you can create additional operands, or remove the existing ones.

Note that the uppermost area of the operator is empty and does not contain any operands. It is reserved for the descriptor. Clicking on this area selects the entire operator; clicking on one of the dotted rectangles selects the corresponding operand. If a combined fragment contains only one operand, the entire combined fragment and the single existing operand are still separately selectable.

See Also