What is GML?

GML (Geography Markup Language) is the OGC XML standard for modeling and exchanging geographic features with geometry, attributes, CRS, and relationships. It is the native format of many WFS services and INSPIRE datasets in Europe.

GML is hierarchical and schema-driven: complex objects (cadastre, networks, 3D) can be richly modeled. Multiple CRS are explicitly supported. Drawbacks: large files, heavy XML parsing in browsers — hence conversion to GeoJSON in web GIS.

In the Netherlands BGT, BAG, and BRK via PDOK often deliver GML through WFS. GML is not GeoJSON (lighter, JSON) or shapefile (binary, Esri tradition). For interoperability between government systems and GIS packages GML remains the professional standard.