从http://schemas.opengis.net上下载了一套schema，然后用xsd工具将其中的schema转换为C#类。
opengis有将近一百多个个schema，而且每个schema之间相互的import和include，并且在其中还应用了iso的相关schema。
出错，看不懂是那里有问题。
提示如下：
Schema validation warning: Undefined complexType 'http://www.opengis.net/gml:AbstractFeatureType' is used as a base for complex type restriction. Line 24, position 5.
..........
Warning: Schema could not be validated. Class generation may fail or may produce incorrect results.
Error: Error generating classes for schema 'sensorML'.- The attribute group SecurityAttributesOptionGroup is missing.
3Q！！！
