Stability of book URLs

[Ben Collins-Sussman]

On Apr 21, 2005, at 10:54 AM, Max Bowsher wrote:
>
> Basically, I'm thinking that section numbers absolutely *are* going to 
> change, and chapters might too, so we had must adopt a scheme that 
> doesn't break when that happens.
>

I'm getting smacked by this problem right now.  I try to add a new 
section, and then have to renumber all the subsequent sibling sections. 
  And then I worry about xref's that are now pointing to valid -- but 
incorrect -- section numbers.

We really should give our sections id's that are descriptive, like 
"ch-4-using-branches", rather than "ch-4-sect-2.3", so that we have 
some freedom to rearrange sections, insert new ones, etc.