Form, Fit, Function (FFF) Rule

Form, Fit, Function (FFF) is the change-classification heuristic that drives the most consequential decision in change management: does a change preserve interchangeability with the previous revision, or does it break it? FFF-preserving changes increment the revision; FFF-affecting changes typically force a part-number change to protect the install base.

What it covers

• Form — physical attributes: shape, size, mass, color, material, surface.
• Fit — interfaces: how the part mates and integrates into the next-level assembly.
• Function — the part’s job: what it does in service.
• Decision tree — preserve all three → revise; break any one → likely a new part number.
• Codified in change procedures — most PLM workflows include an FFF-impact question on the ECR/ECO.

Relationships (see sidebar)

• Conforms to ISO 10007 configuration-management practice.
• Supports Change Management (ECO/ECN) and Configuration Management.
• Implemented by virtually every PLM with structured change workflows: Siemens Teamcenter, PTC Windchill, Aras Innovator, PTC Arena, and Oracle Agile.