What's a good algorithm for editing a “schedule” most efficiently?

|---------------- A -------------------|
    |--- B ----|      |--- B ---|

|---------------- A -------------------|
    |--- B ----|      |--- B ---|

|---------------- A -------------------|
|--- B ----|                        |--- B ---|

* A removed A-timespan removes all the linked timespans from B
* An added A-timespan, what about this?
* A shortened A-timespan removes all the linked timespans from B that now falls outside A
* A lenghtened A-timespan, will this include all matching B-timespans now inside?

|-------------- A1 --------------|    |-------- A2 --------------|
  |---- B1 ----|  |----- B2 ---|       |---- B3 ----|  |-- B4 --|

|-------------- A1 ---------------------------------|  |--- A2 --|
  |---- B1 ----|  |----- B2 ---|       |---- B3 ----|  |-- B4 --|

1. Lengthen (update) A1
2. Shorten and move (update) A2
3. Re-link (update) B3 from A2 to A1 instead

|-------------- A1 -----------------------------|      |--- A2 --|
  |---- B1 ----|  |----- B2 ---|       |---- B3 ----|  |-- B4 --|

|------------------ A -----------------------|
  |------- B1 -------|  |------- B2 ------|
                           |---|                   <-- I want to remove this from A

|------------------ A1 ----|   |---- A2 -----|
  |------- B1 -------|  |B3|   |--- B2 ---|

|------------------ A1 ----|   |---- A2 -----|
  |------- B1 -------|