Property references

GML allows features to have composite or integrated non-geometric properties. This raises the question of how to get some of these complex properties? When Features provided by WFS are encoded in XML, and WFS can use XPath expressions to obtain the components of feature attribute values. The attribute value of a feature can be either a string or a simple XLink。 This means that the server needs to resolve the resource reference as it parses the XPath expression. To accommodate this requirement, all WFS implementations should provide a The valueOf () method to get the specific implementation of the XPath access function.