Redmine

Hi,

I would like to add another identification system to Redmine, based on a web service. Basically, I already have a database with a list of users, and I created a PHP Web Service to retrieve data from that database. So, I would like to use this Web Service in Redmine. My question is : should I change the code directly (not really a nice way to do it) or is it possible to write a plug-in for that ?

Thanks.