Change or Extend System Domain (System.User) model?

Hello, I have a need to extend the various Entities in the System Domain Model. One example is that I want to put a REGEX validation on the Username for a specified pattern and validate the user creation. However, when I try to, it tells me 'Module System is not editable'. If I were to use the Mendix security model and have my validations and extensions at the same time, I was wondering what is the best way to achieve this. Thanks, Shrinivas
1 answers

You can not change the system Domain Model. But you could inherit. Look at the Administration model which inherits from system.user. This way you achieve what you want.

For checking new usernames you should look at how new users are created now. Either adjust it or create you own forms and do there the checks and validation and break the proces off if the username does not validate.