Critical Feature Analysis (CFA) is a data analysis solution for understanding the impact and priority of recommended rule compliance issues in a design. CFA is one part of a comprehensive design for manufacturing (DFM) design flow. This five-part paper series examines the conditions that led to the development of recommended rules, and describes the process by which automated design analysis and rule verification can help designers optimize designs to the fullest and most efficient use of area, while still ensuring manufacturability. Part 1 explains the use of recommended rules and introduces the basic concepts of CFA.