Physical AI Reference Framework (PAI-RF) — Definition

Physical AI Reference Framework (PAI-RF) V1.0 — Definition establishes a technology-agnostic reference structure for consistently describing, organizing, and relating engineering facts relevant to systems analyzed as Physical AI. It defines five complementary Reference Domains: Scenario (context), Mechanism (causation), Capability (ability), Behavior (manifestation), and Component (constitution). These domains distinguish different classes of engineering facts and are connected through typed Core relations rather than arranged as system components, implementation layers, or sequential stages. The canonical framework is expressed as D + R + X + Q: five Reference Domains (D), Core typed relations (R), Cross-Cutting Concerns (X), and a Claim/Evidence/Assessment Overlay (Q). The Definition explains common representation semantics, including Conditions and Constraints, Definition and Instance, system boundary distinctions, claim-specific evidence, and the attribution of AI contribution within system capability. It also establishes controlled extensibility through Profiles and Extensions while maintaining the boundaries of the Core. Six SVG figures illustrate the structural concepts. This document serves as the definitional reference for PAI-RF V1.0. Normative implementation, representation, and conformance requirements are specified separately in RF02, which has its own independent Zenodo record and DOI.