Related projects

Encoding Source in XML
http://www.treelight.com/software/encodingSource.html

Literate programming
http://www.literateprogramming.com/
Leo
http://webpages.charter.net/edreamleo/front.html
XML based SRS (Software Requirements Specification)
http://eclipsesrs.sourceforge.net/
Jezix
http://www.tel.fer.hr/users/mtopol/jezix/
JavaML
http://www.badros.com/greg/JavaML/
RML
http://reqs.tigris.org/rml/index.html
XES - XML Encoded Source
http://xes.sourceforge.net/

Reference link
XML 1.1
http://www.w3.org/TR/2004/REC-xml11-20040204/

Useful link
XML 1.1 in French
http://www.yoyodesign.org/doc/w3c/xml11/