Urban vegetation semantics in CityGML: Key stakeholder survey findings and vegetation ADE development

Urban vegetation, providing critical ecosystem services and supporting biodiversity, is essential for sustainable and resilient cities. Yet its semantic representation in urban digital twins and 3D city models remains inadequate for advanced modeling. Open data standards facilitate interoperable urban modeling. However, the CityGML standard, despite its widespread adoption, provides limited semantic depth for vegetation in its current Vegetation module, constraining dynamic and interdisciplinary applications.To address this, we present the international stakeholder survey evaluation alongside the updated version of the conceptual model of the CityGML 3.0 Vegetation Application Domain Extension (Vegetation ADE v1.1). The ADE enhances semantic richness by introducing extended attributes, feature types, enumerations, and code lists for both SolitaryVegetationObject and PlantCover, including structural components (crown, trunk, root) and dynamic properties via the CityGML Dynamizer module. Additionally, a vegetation management class is established.Refined through feedback from an international stakeholder survey, the model reflects practical requirements from domains including urban studies, ecology, and public administration. The core data modeling structure of ADE v1.0, unanimously supported by survey participants, was retained for ADE v1.1. The new version introduces substantial improvements: 15 attributes were modified, 12 added, and one removed. Nine code lists were revised and one added. Two enumerations were updated. These enhancements ensure ADE v1.1 achieves improved semantic clarity and usability, supporting diverse applications such as vegetation monitoring and adaptive green infrastructure management. This work demonstrates a replicable methodology for participatory standard development and advances the integration of vegetation into data-driven urban digital twins and 3D city models.