SOX - Schema for Object-Oriented XML 2.0
- A schema language for defining the syntactic structure and partial semantics of XML document types; an alternative to XML DTDs. [W3C Note 30 July 1999]
- http://www.w3.org/TR/NOTE-SOX/

XML-Data
- Describes an XML vocabulary for schemas, that is, for defining and documenting object classes. [W3C Note 05 Jan 1998]
- http://www.w3.org/TR/1998/NOTE-XML-data/

DSD - Document Structure Description
- An XML schema language. A DSD document is a specification of a class of XML documents together with a default mechanism and documentation. FAQs, downloads, tutorials provided.
- http://www.brics.dk/DSD/

DCD - Document Content Description for XML
- This document proposes a structural schema facility, Document Content Description (DCD), for specifying rules covering the structure and content of XML documents. [W3C Note 31 July 1998]
- http://www.w3.org/TR/NOTE-dcd