Requirements modification after sequences has been added

[cfsottile]

Say I have these requirements

A: 1, 3, 1, 2
B: 2, 4, 3, 4
C: 2, 3, 2

and I'm writing sequences. I'm half the way through:

A requires 2 pages
B requires 1 page
C requires 1 page
B requires 2 pages

As for now, I have covered these requirements:

• A: _1, _3, 1, 2
• B: _2, _4, _3_, 4
• C: _2_, 3, 2

If i want to make a changes:

• If I modify those requirements which have been covered by sequences, it would alter the last ones and introduced changes can be unintuitive. Maybe I shouldn't be able to do it, and be forced to delete a sequence to alter its related requirements.
• If I modify requirements which haven't been covered by sequences, I won't get into troubles so I should be able to.