interface itop
{
  in void e();
  out void f();
  behaviour
  {
    on e: f;
  }
}

interface imiddle
{
  in void e();
  out void f();
  behaviour
  {
    on e: f;
  }
}

interface ibottom
{
  in void e();
  out void f();
  behaviour
  {
    on e: f;
  }
}

interface ilogger
{
  in void log();
  behaviour
  {
    on log:{}
  }
}

component logger
{
  provides ilogger log;
  behaviour
  {
    on log.log(): {}
  }
}

component middle
{
  provides itop t;
  requires ibottom b;
  requires injected ilogger l;

  behaviour
  {
    on t.e(): {l.log(); b.e();}
    on b.f(): {l.log(); t.f();}
  }
}

component bottom
{
  provides ibottom b;
  behaviour
  {
    on b.e(): b.f();
  }
}

component Injected
{
  provides itop t;
  system
  {
    logger l;
    middle m;
    bottom b;

    m.t <=> t;
    m.b <=> b.b;
    l.log <=> *;
  }
}