The Analytical Hierarchy Process (AHP) is a method often applied in Six Sigma or Design for Six Sigma projects in order to prioritise the client needs ascertained before, for example, by pairwise comparison.
BPMN (=Business Process Model and Notation) is a method to model processes graphically in a standardized way. The standard includes a guideline that regulates the look of components of the process illustration (notation). Furthermore, possible connections between those components are standardized (syntax) as well as their meaning (semantics).
A measurement system analysis verifies that the measured data corresponds with the actual reality. Consequently, this tool is used when it is suspected that the measured data does not reflect the actual reality.