The document provides an overview of the changes between the third and fourth editions of PMI's Guide to the Project Management Body of Knowledge (PMBOK Guide). Some of the key changes include combining or renaming processes, expanding the triple constraints to include quality, resources and risk, adding new appendices, and aligning the PMBOK Guide with other PMI standards. The fourth edition will replace the third edition as the reference for PMI credential exams, though only a small percentage of exam questions are expected to need updates. The credential exams will be updated on a rolling schedule between June and August 2009.