simple foo;
structure { }
participant Bob {
	{{ /*imports go here*/ }}
	expected Fred something; 
	aspectual RV meth(EM e) {{
		return e.invoke();
	}}
}

expected participant Fred {
	// can only contain expected
}

exists abstract participant  EM {
     	abstract RV invoke();
}
exists abstract participant  RV {
}

simple bar;
structure { }
participant X {
}

participant Y extends X {
}

composite both; 
structure {
  A { C c; }
  B extends A { } 
  C { }
}
attach foo, bar {
  A += X, Bob with {
    provide Fred something by C c
  }
  B += Y 
  C == Fred	
}