pointcut X1(S s1) : 
  this(s1);
pointcut X2(S s2, T t2) : 
  (call(void crossing_x(..)) 
      && this(s2) 
      && target(t2)
  );
pointcut X3(A a1, B b2, C c3) : 
  cflow( * visiting_A1(a1));
pointcut Y4(Source s):
  ! cflow(this(s));

before(S s1) : this(s1) {  };
after(S s2, T t2) :
  (call(void crossing_x(..)) 
      && this(s2) 
      && target(t2)
  ) { } ;