Although the matrix is used for other purposes, the Known-Unknown matrix in this article from Intelligent Enterprise has been useful to me for many purposes.
Most recently, I'm trying to see what fits in which quadrants as we try to migrate from a third-party mission-critical application to a custom-developer in-house application on a widely-adopted and open platform.
The next step I'd like information on is "How do move forward when you know that you don't know all the issues?"
