UML - Sequence Diagrams

What are the two types of UML diagrams?

• Structural (Static): Emphasizes the system's structure, focusing on objects, attributes, operations, and relationships.
• Behavioral (Dynamic): Emphasizes the system's behavior, showing object collaborations and state changes.

What is a sequence diagram?

A sequence diagram shows the dynamic behavior of elements in a system, illustrating the order in which events occur and the interactions over time.

What are the elements of a sequence diagram?

• Lifeline: Represents actors, classes, or objects
• Entity: System data
• Boundary: System boundaries like user interfaces
• Control: Manages interactions between boundaries and entities

What is a synchronous message in a sequence diagram?

A synchronous message requires a response before the interaction can continue.

What is an asynchronous message in a sequence diagram?

An asynchronous message doesn’t need a reply to continue the interaction, and the reply is indicated with a dotted line.

What is the communication label syntax in a sequence diagram?

The syntax is: [guard]*[iteration] sequence_number : return_variable := operation_name (argument_list).

What are creation and deletion messages in a sequence diagram?

Objects can be created or destroyed during the sequence of events based on messages sent.

What are found and lost messages in a sequence diagram?

• Found: The sender is unknown
• Lost: The receiver is unknown

What is a reflexive message in a sequence diagram?

A reflexive message occurs when an object sends a message to itself or calls itself.

What is an alternative fragment in a sequence diagram?

An alternative fragment is used to show a choice between two or more message sequences.

What is an option combination fragment in a sequence diagram?

An option combination fragment is used to represent a sequence that occurs only under a certain condition.

What is a loop fragment in a sequence diagram?

A loop fragment represents a repetitive sequence of events.

What is a parallel fragment in a sequence diagram?

A parallel fragment represents parallel execution of interactions.

What is an interaction use in a sequence diagram?

An interaction use refers to a fragment that calls or uses another interaction to simplify large and complex diagrams.

What is the purpose of activation in a sequence diagram?

Activation shows when an object is active or executing during an interaction. It’s depicted as a thin rectangle over the lifeline.