Lifelines

A lifeline is a notation that represents the existence of an object or classifier role over a period of time. Lifelines appear only in sequence diagrams, where they show how each instance (object or classifier role) participates in the interaction.

For example, a "Place Online Order" interaction in an e-commerce application includes a number of lifelines in a sequence diagram, including lifelines for a ":Cart" object, ":OnlineOrder" object, and ":CheckoutCart" object. As the interaction is developed, stimuli are added between the lifelines.

Shape

A lifeline appears as a vertical dashed line in a sequence diagram.

Lifeline for an Object

Lifeline for a Classifier Role

Using Lifelines

When a classifier role or object appears in a sequence diagram, it will automatically have a lifeline. Lifelines indicate the following:

Naming Conventions

A lifeline has the name of an object or classifier role. For details, see Objects or Classifier Roles.

Related Topics

Classifier Roles | Model Elements and Relationships in Sequence Diagrams | Messages | Objects | Stimuli