SDL (Specification and Description Language)

In PlantUML, this is a variation of the activity.

This is a gallery of most elements from the documentation.

DiagramSource

@startuml
:Ready;
:next(o); <<procedure>>
:Receiving;
split
 :nak(i); <<input>>
 :ack(o); <<output>>
split again
 :ack(i); <<input>>
 :next(o)
 on several lines; <<output>>
 :i := i + 1; <<task>>
 :ack(o); <<output>>
split again
 :err(i); <<input>>
 :nak(o); <<output>>
split again
 :foo; <<load>>
split again
 :bar; <<save>>
split again
 :i > 5; <<continuous>>
stop
end split
:finish;
@enduml