The boundary is defined by a LineString (i.e., GeoPolyline) and must be overlaid on the domain boundaries. All its points must be points used for the domain definition. Consequently, it is defined by joining at least two sequential points from the domain. If the points are not sequential, the simulation will not be performed correctly. In almost all cases, a context has more than one boundary. The us-er can define several boundaries for a context as long as they do not overlap or share any points. Each boundary has two properties: the type and the data type. Both properties are multiple-choice fields and are defined by the user after defining the boundaries. The type can be either input, output, or input–output. Regarding the data type, the choices are “H” for depth, “Q” for discharge, “Z” for elevation, and “V” for velocity. When converting this geometry to geojson, each geometry is transformed into a feature, and each feature has its LineString geometry and properties with corresponding values.