Is there a way to draw interaction overview diagram in PlantUML?

Question

This requires combining activity with sequence diagram. I tried several different ways but it gives syntax error. One example below, in which it points error in line 3 at 'Participant':

@startuml

Start

:action1;

Participant alpha

Participant beta

Mainframe sd

alpha --> beta : message

alpha <.. beta : response

@enduml

Answer 1

Hello A.,

• Is that what you want?

With using sub-diagram '{{' and '}}':

@startuml
Start

:action1
{{
Participant alpha
Participant beta

Mainframe sd
alpha -> beta : message
alpha <-- beta : response
}}
;

:action2;

:action3;
@enduml

If that can help,
Regards,
Th.