Sequence diagram: crossed arrows

+5 votes
asked Jun 17, 2013 in To be sorted by anonymous

Is it possible to draw crossed arrows in a sequence diagram? I'm working on workflows involving crossing of messages to express race conditions, something like:

S1 sends a message to S2

At the same time, S2 sends a message to S1


I'm not sure if it follows the UML standards but this is allowed by tools like MS Visio or Rational

Thanks in advance

commented Jul 16, 2018 by albert (3,180 points)
edited Aug 4, 2018 by albert
See also

Interesting especially in the light of e.g. asynchronous communication (MPI).
I doubt that it is possible as it is a SEQUENCE diagram.

1 Answer

0 votes
answered May 23 by The-Lu (46,400 points)

Hello A. and all,

See some new enhancements [on V1.2022.6beta] about this topic, here:

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

!pragma teoz true

S1 ->(30) S2: msg 1\n
& S2 ->(30) S1: msg 2

note left S1: msg\nS2 to S1
& note right S2: msg\nS1 to S2

If that can help,