Redmine

Hello!

I've trying to find some documentation about Redmine core (like a programming guide with UML diagramms or something link that, that helps to modify and extend Redmine core).

I've looked in Wiki Development Guide and Development forum. Wiki articles look like plugin developer guide. On the forum I've found this image, with Developer procedures description, but it's only an image.

Is there more detail docs on Redmine codebase somewhere else ?

Thank you