From the Executive Summary: "The Global Positioning System (GPS) and other Global Navigation Satellite Systems (GNSS) have enabled widespread adoption of Positioning, Navigation, and Timing (PNT) services in many applications across modern society. [...] This Resilient PNT Conformance Framework was sponsored by U.S. Department of Homeland Security Science and Technology Directorate and developed in coordination with industry and federal agency partners. It provides guidance for defining expected behaviors in resilient PNT user equipment (UE), with the goal of facilitating development and adoption of those behaviors through a common framework that enables improved risk management, determination of appropriate mitigations, and decision making by PNT end-users. To encourage industry innovation, this framework is PNT source agnostic and outcome based. It also contains four levels of resilience so that end-users can select a level that is appropriate based on their risk tolerance, budget, and application criticality. Therefore, a lower level receiver is not necessarily better or worse; instead, it simply reflects a level that meets the user's particular needs. This framework focuses on resilience and applies to UE that outputs PNT solutions, including PNT systems of systems, integrated PNT receivers, and PNT source components (such as GNSS chipsets)."
U.S. Department of Homeland Security: https://www.dhs.gov/