Further Development of the CityGML Energy Application Domain Extension 3.0

The CityGML Energy Application Domain Extension (ADE) is an open and standardised data model to facilitate multi-scale cross-sectoral Urban Energy Modelling applications. It is based on the international standard CityGML (version 2.0), and was first released in 2018. Since 2024, the data model has been undergoing a major revision to align it with recent developments in CityGML, address feedback from its user community, and better support emerging data and interoperability requirements. The Energy ADE 3.0 beta 7 has been released in autumn 2025. Since its release, several ideas and suggestions for improvement have been collected. This paper presents an overview of some of the most relevant change requests that have been evaluated and eventually implemented, leading to the current beta 8, and the rationale behind these changes. Attention is paid to the modules that have been more affected by such changes, namely the Core module, and the new Building module. Finally, the results of tests with synthetic and real data are provided, confirming the soundness of the updated data model and highlighting no major implementation issues. These results reflect the continued development of the Energy ADE towards its future alignment with CityGML 3.0. At the same time, ideas and feedback dealing with the request to add support for scenario management have lead to start and branch off a new and, currently separate research work focusing on a new and domain-agnostic extension, namely the Scenario ADE.