HACCP is a fundamental tool for food safety system . To determine Critical Control Points (CCPs). Among 12 steps including 7 principles of HACCP Application, question tree is one of important tool as a guidance principle and it falls under principles number 2 of HACCP Program, Determine critical control points. The profound understanding of conception of question tree is very crucial to ensure developing HACCP plant is value added, effective.
A source for HACCP Guideline: http://www.fda.gov/Food/GuidanceRegulation/HACCP/ucm2006801.htm