This is a series of posts that relate to Validation and the use of the Notification Pattern.
This guy is heading in the same direction that we have been using at my work. There are a few details that he has not yet dealt with:
There is more you can do in this manner than validation. You can apply defaults, calculations and more complex business logic. This is the start of a rules engine.
A key point that is lost in an attributes based approach is that only a single question may be asked.
In this case the question is “Is the system valid”? But is could equally be can I add an XYZ here?