Execution
An execution is a thin white bar on a lifeline, showing where it is active. Write a block after a message to open one. Bars nest and step to the right as calls go deeper.
diagram sequence "Nested executions"
participant App
participant Parser
App -> Parser : parse() {
Parser -> Parser : next token
return ast
}
return sends a reply from inside a block, to the block’s caller, and ends the bar when it is
the last statement.
Syntax
<a> -> <b> : label { ... }
return [text]
A plain synchronous self-call also opens a short nested bar.
Specification
UML 2.5.1, 17.2.4.4 (p. 569).