Non-instantaneous messages in Sequence Diagram

Question

I have a use case to model non-instantaneous messages in the sequence diagram. For example,

@startuml
A -> C: Starts before 'B' sends
B -> C: But B's message arrives before A's
@enduml

In the diagram, I'd like the start-point of A's arrow to be above B's. But B's arrow end-point should reach C before A's. The only way to do this is to have the message arrows be angled. I'm not sure how this would fit with the syntax, but is this feature possible?

Comments

Hello J. and all,

See some new enhancements about this topic, here:

• https://forum.plantuml.net/14145/plantuml-draw-odd-line?show=15981#c15981

Here is a first proposal (Thank to PlantUML team):

@startuml
!pragma teoz true
A ->(50) C: Starts [before]\nwhen 'B' sends
& B ->(25) C: \nBut B's message\n arrives before A's
@enduml

If that can help,
Regards.

Answer 1

I have represented this with an extra participant representing "uncertainty" or "transport" or similar, depending on the mechanism at work.  I then encode it like this:

@startuml
A -> uncertainty : A message
B -> uncertainty : B message
uncertainty -> C : B message
uncertainty -> C : A message
@enduml