Design Goals

Must “feel like” DocBook

Most existing documents should still be valid or it should be possible to transform them in simple, mechanical ways into valid documents

Must enforce as many constraints as possible in the schema. Some additional constraints are expressed with Schematron rules

Must simplify many content models

Must give users the flexibility to extend or subset the schema in an easy and straightforward way

Must allow the generation of a (non-normative) XML DTD and W3C XML Schema.