Used in a sequence diagram, a lifeline shows conditionality on an object lifeline.
An object lifeline represents the existence of an object at a particular time. If the object is created or destroyed during the time period the diagram represents, the lifeline stops or starts at the appropriate point. An object's destruction is marked with a large X.
Name a Lifeline shape and add other property values
Open the element's UML Properties dialog box by double-clicking the icon that represents the element in the tree view or the shape that represents the element in a diagram.
Control which property values display on a shape in a diagram by right-clicking the shape, and then clicking Shape Display Options. In the UML Shape Display Options dialog box, select and clear options to display or hide property values.