Because you can extend the NDS schema, it's easy to allow an application to store customized data in the NDS database. For example, you could write an application that provides fax service functions simply by adding a fax server object class definition into the NDS tree. There are some trade-offs to extending the schema, so when you consider extending the schema, keep in mind the following advantages and disadvantages. Users can build database search queries to easily locate objects of a custom class. You can match the categories of information an object stores to the needs of a custom resource.
Root can extend the schema.
Since schema definitions are global to the entire tree, someone with Supervisor rights at the Root must run the installation utility that extends the schema. For this reason, Novell recommends that the portion of the installation utility that extends the schema be separate from the main installation utility. This allows users with Supervisor rights at the Root to run a very simple installation utility to extend the schema and a user with Supervisor rights to the appropriate container to run the main installation utility. You cannot remove extensions made to the base schema without reinstalling the NDS tree. The following general design principles will guide you in creating efficient schema extensions.