@startuml
skinparam monochrome true
skinparam SequenceBoxBackgroundColor #ffffff
skinparam ParticipantPadding 5
skinparam shadowing false
hide footbox

title generating a recommendation 

box "Client B"
participant "M.Customer B"
end box

box "Client A"
participant "M.Customer A"
end box

box "Server"
participant M.Collab
participant M.Recommend
end box

activate "M.Customer A"
activate "M.Customer B"
activate M.Collab

M.Collab -> M.Recommend : get_recommendation(configuration, preferences)
activate M.Recommend
M.Collab <-- M.Recommend : return recommendedFeatures
deactivate M.Recommend

par
    M.Collab --> "M.Customer A" : broadcast (recommendedFeatures)
    M.Collab --> "M.Customer B" : broadcast (recommendedFeatures)
end
@enduml