The Gemini Principles are a set of nine high-level commitments developed in 2018 by the Centre for Digital Built Britain, under the UK’s National Infrastructure Commission, to guide the creation of a National Digital Twin. These commitments are organised into three interrelated themes - Purpose, Trust and Function - each defining a different aspect of the digital-twin ecosystem. The Purpose theme requires that digital twins deliver public benefit, generate clear value and support informed decision-making. The Trust theme emphasizes robust security measures, transparent governance and high data quality, while the Function theme addresses the need for a federated architecture, active data curation and ongoing system evolution.

Together, these principles establish a framework for coordinating disparate asset models into a cohesive, interoperable network. By prescribing open standards and semantic interoperability, the Gemini Principles enable multiple domain-specific twins - covering sectors such as transport, water and energy - to exchange data securely and reliably. They further call for lifecycle governance practices that maintain data provenance and manage change over time. Adopted in procurement guidance, technical frameworks and academic curricula, the Gemini Principles form the foundation for national-scale digital-twin initiatives both within the UK and, increasingly, in international infrastructure projects.