Assuming that sequence-diagram alternatives should be somewhat interchangeable, how does one deal in PlantUML with an alternative leaving lifelines with a different number of nested activations than it encountered at the beginning? For example, here are two sequence diagrams for a "ready" case and a "not-ready" case.
@startuml
title ready case
activate A
A->>B: run
activate B
A->>B: ready
activate B
deactivate B
A->>C: run
activate C
C->>B: connect
activate B
B->B: is ready?
activate B
B-->B: yes
deactivate B
|||
@enduml
@startuml
title not-ready case
activate A
A->>B: run
activate B
A->>C: run
activate C
C->>B: connect
activate B
B->B: is ready?
activate B
B-->B: no
deactivate B
B->>C: terminate
deactivate B
destroy C
... long delay ...
A->>B: ready
activate B
deactivate B
@enduml
And here is a failed attempt to combine those cases in a single sequence diagram using "alt":
@startuml
title combined cases
activate A
A->>B: run
activate B
alt ready case
A->>B: ready
activate B
deactivate B
A->>C: run
activate C
C->>B: connect
activate B
B->B: is ready?
activate B
B-->B: yes
deactivate B
|||
else not-ready case
A->>C: run
activate C
C->>B: connect
activate B
B->B: is ready?
activate B
B-->B: no
deactivate B
B->>C: terminate
deactivate B
destroy C
... long delay ...
A->>B: ready
activate B
deactivate B
end
@enduml
Notice that the first, "ready case" alternative is presented with one activation each of A and B and none for C. However, because this alternative creates new activations for B and C, the second, "not-ready case" alternative is presented with a different set of activations. I could add various messages at the end of "ready case" to arbitrarilly leave it with the same activations it originally encountered, but is there a better way? Or am I missing something fundamental about UML sequence diagrams?
