The base schemas (Geometry, Feature, XLink) can be viewed as the components of an application framework for developing schemas or sets of schemas that pertain to a particular domain (e.g. Forestry), jurisdiction (e.g. France), or information community. Furthermore, such application schemas may be developed in a more horizontal fashion to support many information communities.
There are some basic conformance requirements that every application schema must satisfy. Specifically, a conforming GML application schema must heed the following general requirements:
an application schema must adhere to the detailed schema development rules described in Section 5.2
an application schema must not change the name, ...