CODEWITHSUNDEEP
conditional-statementsumlspecificationssequence-diagram
user2019510
user2019510

Reputation: 1470

Reading Sequence Diagram with some conditions

I have the following sequence diagram that consists of four lifelines exchanging a set of messages.

My question is:

How can i read the stuffs surrounded by red rectangle in this diagram?

enter image description here

This is My try:

The first one is: "t=0"

as i understood it is a Time observation but i really not sure because as i read through UML reference manual(2004) that the semantic of a time observation is get the current time and has a syntax "t=now" and here t assigned to zero?

the second is a condition "t<=500 ms"

Does this mean that this condition should be true to be able to invoke write(record) message? and what about the condition above this message(t<=50 ms) what this means?

could you please clarify each one of them?

Upvotes: 2

Views: 284

Answers (1)

Red Beard
Red Beard

Reputation: 3506

first of all I am not sure that UML specification defines how to "read" your diagram. Now the following is how I read it. The first one "t=0" for me it specifies the time origin i.e. from this point the time starts. Concerning the second ("t <= 500 ms") it is a constraint which represent the fact that write(record) message must be invoked at most 500 ms after the instant "t=0". It is a constraint of your modeled system and you do not know what happen if it is or is not invoked after this 500 ms deadline because it must not be the case. Hoping it helps.

Upvotes: 2

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