This is a home for user information related to the International Standard for document model validation of instances with multiple namespaces using different document models. NVDL is Part 4 of ISO/IEC 19757 DSDL (Document Schema Definition Languages) http://www.dsdl.org.
Specification document (from the ISO/IEC page of Freely Available Standards):
http://www.jtc1sc34.org/repository/0816.htm - proposed technical corrigenda
Schemas for NVDL scripts
Note: As shown in the proposed technical corrigenda, the xml:lang= attribute of <message> elements is made optional
Tutorials for NVDL
Sourceforge project for the development of tutorials and test suites:
Public demonstrations available on the web:
Candidate use of NVDL in Atom
http://www.asahi-net.or.jp/~eb2m-mrt/atomextensions/atomextensions.html
Candidate use of NVDL in the Universal Business Language (UBL)
http://lists.oasis-open.org/archives/ubl/200602/msg00117.html
Tools
enovdl - Mono (.NET development platform)
JNVDL - open-source NVDL implementation written in Java
oNVDL - open-source NVDL implementation based on Jing
Validator.nu now exposes the NVDL functionality of oNVDL as a Web service:
Specifications utilizing NVDL
Ecma-376 Office Open XML http://www.ecma-international.org/publications/standards/Ecma-376.htm
W3C Internationalization Tag Set http://www.w3.org/TR/its/
W3C SVG Tiny 1.2 http://www.w3.org/TR/SVGMobile12/
NVDL is the successor of NRL. There are some interesting use cases in James Clark's Namespace Routing Language (NRL) introduction at http://www.thaiopensource.com/relaxng/nrl.html.