What is the difference between a methodology deviation and a methodology revision?

Deviations. Based on the specific conditions and circumstances of a project, projects may be permitted to deviate from a methodology's criteria and procedures for measurement or monitoring. Methodology deviations are documented and justified in the project description and validated during the project validation process. The only deviations permitted are deviations from measurement or monitoring criteria and procedures.

Revisions. A methodology revision is a permanent change to the methodology itself due to an advance in knowledge about the conditions, circumstances or nature of projects generally. All revisions must be assessed through the methodology approval process, and all projects must adhere to the revised version of a methodology after a revision takes place. All changes to a methodology, except for deviations from measuring and monitoring criteria and procedures, will require a formal methodology revision.