Sequence diagrams

Question 1

What are sequence diagrams?

Answer 1

Sequence diagrams visually represent the interactions between objects or components in a system over time in chronological order

Question 2

What are sequence diagrams used for?

Answer 2

• Represent and analyse use cases
• Provide an intuitive way to convey behaviour
• Reflect visually dynamic behaviour

Question 3

What are actors?

Answer 3

A type of role where it interacts with the system and its objects. Always out of scope of the system we aim to model.

Question 4

What are lifelines?

Answer 4

Named element that depicts an individual participants in a sequence diagram. Each instance in a sequence diagram is represented by a lifeline

Question 5

What are messages?

Answer 5

Communication between objects.

Question 6

What are reply messages?

Answer 6

• Reply messages are represented with a dotted line
• Show messages being sent from the receiver to the sender.

Question 7

What are found messages?

Answer 7

Messages sent where we do not know the source of the message. Represented with a dot and and an arrow out of it to the lifeline.

Question 8

What are lost messages?

Answer 8

Lost messages represent messages to where the receiver is not known by the system. Represnted by O—>

Question 9

What are guards?

Answer 9

Guard conditions are used when we need to restrict the flow of messages on the pretext of a condition being met.

Question 10

What is alt?

Answer 10

Alternative operators or alt represents an if-then-else statement in a sequence diagram. Only runs with guard condition tests true.

Question 11

What is opt?

Answer 11

Optional operator or opts, represents the logic of a standard if statement, if the guard conditional is failed then it is ignored.

Question 12

What is a loop?

Answer 12

Loop operator, indicates the section that will run repeatedly the number of times it runs is determined by the minint and maxint params of the operator