There are more detailed generic processes. The high levels steps are certainly most appropriate, but I have found that even experienced practitioners require a more detailed framework. Modern sourcing is a world appart from setting up buying processes and constitute highly complex projects. For that you need a detailed Work Breakdown Structure (WBS) that is tried and tested, or you might be swollowed whole by your environment!

May I be so forward as to suggest that where the sourcing process lacks credibility, it was brought on by weak project work structures? When it comes to success factors of sourcing projects, I personnally rate a solid WBS second only to the establishment of proper collaboration.