Project/Task tracking tool with notifications

Question

I am looking for a particular project/task tracking tool with :

1. Ability to define hierarchy of task. Like Project -> Task -> Sub-task etc.
2. Ability to assign owner.
3. Status level like NotStarted, Inprogress, Impeded, Complete
4. Notification based i.e. any change should be notified through an email or RSS feed.
5. Open source

Thanks.

Answer 1

http://www.redmine.org/ is what you're looking for. I have used it extensively and it works well.

"Project -> Task -> Sub-task" is more like "Project -> Sub-Project -> Task"

But this is a good thing.