   After class generation, add the following two lines after  "public partial class gear_data_exchange_format {":

        [XmlAttributeAttribute("schemaLocation", Namespace="http://www.w3.org/2001/XMLSchema-instance")]
        public string xsiSchemaLocation = "https://www.vdi.de/fileadmin/xml/2610 https://www.vdi.de/fileadmin/xml/2610/GDE_3_3.xsd";