        {C..b0}
  -----> a0 ----> a1 ----> A   .... WD_A
 /      ^         |
C       |         v
 \----> b0 ------> b1 ----> B  .... WD_B
                    {C..a1}




    A_lvl (B) is a1
    A_lvl (b1) is a1
    A_lvl (b0) is < a0

    B_lvl (A) is b0
    B_lvl (a1) is b0
    B_lvl (a0) is b0


delta(a1, B)

        changes from A
                conflict fixes for B from a0 .. a1

        changes from B
                b0 .. B

delta (a1, WD_A)

        changes from A
                a1 .. A

        changes from B
                none

delta (a1, WD_B)

        changes from A
                none

        changes from B
                b0 .. B



delta (a1, A)

        changes from A
                a1 .. A

        changes from B
                none


delta (b0, WD_B)

        changes from A
                C .. a1
        changes from B
                b0..B

# Modifications 2002 Copyright (C) Walter Landry and the Regents of the
#                                        University of California
# tag: Tom Lord Sat Jan  5 13:45:40 2002 (manual/=lemmas)
#
