Answers question 3:

Here is a systematic approach:

Translate from A through A1 through A2 through A3 ...
to
{A -> A1 to-stop A1 -> A2 to-stop A2 -> A3 ... }

For each leg l[i] compute the propagation graph p[i] and define
a traversal method t[i] for that traversal graph.
When t[i] enters its target at which it stops, switch to t[i+1].


For 1:

The following is NOT correct:

t0:
  A.x
  X.b t1

t1:
  B
  X.b
    c
  C

translation rule:
tt:
  X.y
defines a traversal tt for class X calling tt for part y
  X.y tt2
defines a traversal tt for class X calling tt2 for part y


This hand-generated traversal is NOT equal to "from A via B to C"?

The above is a summary to:

  class A {
    public void t0( ) {
      x.t0();
    }
  }

  class X {
    void t0(){
      System.out.println(" at X t0");
      b.t1();
    }
    void t1(){
      System.out.println(" at X t1");
      b.t1();
      c.t1();
    }
  }

  class B {
    void t1(){
      System.out.println(" at B t1");
    } 
  }

  class C { 
    void t1(){
       System.out.println(" at C t1");
    } 
  }


The correct answer is:
(Note: Demeter/Java does not handle this correctly
but DJ does)

  class A {
    public void t0( ) {
      x.t0();
    }
  }

  class X {
    void t0(){
      super.t0_bef();
      System.out.println(" at X t0");
      super.t0(); // this is essentially what's missing in the
			// Demeter/Java-generated code
    }
    void t1(){
      super.t1_bef();
      System.out.println(" at X t1");
      b.t1(); 
      c.t1();
    }
  }

  class B {
    void t0_bef() {
      System.out.println(" at B t0");
    }
    void t0() {
      this.t1();
    }
    void t1_bef(){
      System.out.println(" at B t1");
    } 
    void t1() {
      // do nothing; premature termination
      // (to catch t1() on an E-object)
    }
  }

  class C { 
    void t1(){
       System.out.println(" at C t1");
    } 
  }

===============

For 2:

t0:
  A.b1
  B1.b t1

t1: 
  B.if b1
  B1.b
     d
  D.f1
  F1.f t2

t2:
  F.if f1
  F1.f
     g
  G

translation rule:
tt:
  X.y
defines a traversal tt for class X calling tt for part y
  X.y tt2
defines a traversal tt for class X calling tt2 for part y
  X.if y
defines a traversal tt for class X calling tt for part y
but only if part y exists.