As Sean Mc Grath says, you'd better keep your URLs working, especially when other webapplication depend on your webapplication...
I started to do this quite soon for my bcoWeb website (just a research prototype, mind you). There were some domain name changes (first objects.bcxml.net, then futsweb.org, then bcoweb.org, then nl.bcoweb.org (don't ask)). But, quite early, there was already a small java app of a fellow scientist that used the exported xml data. So I took care to do some URL redirection right from the beginning so that the most important things kept working without him needing to change his code.
It pays off both early on and late in your webapp's life imho.
My name is Reinout van Rees and I work a lot with Python (programming language) and Django (website framework). I live in The Netherlands and I'm happily married to Annie van Rees-Kooiman.
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