Behavior : Sequence Diagrams - Lifelines

11 important questions on Behavior : Sequence Diagrams - Lifelines

Besides Connectable Elements, the book also use the term..

Participants in the Interaction.

What is the format of the participants?

The format is  roleName: TypeName,

Where either part of the name may be empty, but not both.

As they are not objects, we do not underline the participant names,

In a Sequence Diagram these connectable elements “head” a  ....?

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What does a lifeline represent?

Each lifeline represents a time- ordered sequence of EVENTS (called OCCURRENCES), from top to bottom , that are SENT from or RECEIVED on the lifeline.

From the perspective of the each timeline, moving from the top of the diagram to the bottom represents the order of time

What is the message sequence in this diagram?

At the Patron, the yesYouMay message is received after the Patron sends the mayIBorrowBooks.

At the CirculationSystem, the mayIBorrowBooks message is received before it sends the yesYouMay message.

At the NOTIONAL level, use of parentheses is rare, but otherwise, it is a place for...

Argument Values

When the arguement values are used at the NOTIONAL level, the notational level indicates, what?

It indicates an attempt to give the model reader a notion of what is going on, without attempting to be formally correct or to specify a detailed implementation.

What kind of shape is the head of a lifeline?

It is usually a rectangle, other shapes can be used to indicate the type of the participating connectable element, depending on the stereotypes used in your methodology (e.g., Active Class, Entity Class, and Control Class

Where are heads of a lifeline located?

The heads of the lifelines that participate in a Sequence Diagram usually all align at the top of the diagram.

However, lifelines can be created during an Interaction, in which case the heads are located at the point of creation.

What are the 9 different lifeline occurences?

1.    Synchronous call             ( Sen)
2.   A Synchronous call         ( Sen )
3.    Synchronous call             ( Received )
4.   A Synchronous call          ( Received)
5.    Synchronous message   ( Return )
6.    Participant Creation
7.    Object Destroyed
8.    Self Message
9.    Execution Specification

What will you see headed as lifeline headed, but is not recommended?

You will probably find many examples in the literature of lifelines headed by Actors.

Unfortunately, Actors cannot be connectable elements and cannot be parts.

On the other hand, all the UML tools will support the use of Actors as lifelines.

This approach is usually explained as reasonable because of changing system perspective.

For example:
if you focus on one subsystem, all the other subsystems will be as an Actor to the subsystem of interest, but all the subsystems are ultimately only parts of the

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