RE: [xml-dev] RNG vs. XSD : is the use of abstract types and polymorphism a good or bad thing for schemas for XML?

James Clark asserts that it is not the role of a schema language to model "conceptual" relationships such as inheritance. Such relationships are best modeled elsewhere.

Let us suppose that James is correct.

Question: Is it best practice to avoid the inheritance machinery provided in XML Schema -- derive-by-extension, derive-by-restriction, and element substitution? What are the practical benefits of doing so?

/Roger