Resource Directory Description Language
In computing, Resource Directory Description Language (RDDL) is an extension of XHTML Basic 1.0. An RDDL document, called a Resource Directory, provides a package of information about some target. The targets which RDDL was designed to describe are XML Namespaces.
External links
RDDL is designed to allow both human readers and software robots to find any sort of resource associated with a particular namespace. Instead of putting one thing at the end of a namespace URI, RDDL puts a document there that lists all the machine-processable documents that might be available, including, but not limited to:
DTDs
Schemas in a variety of languages (including RELAX, Schematron, the W3C Schema language, TREX, and others)
CSS, XSLT, and other style sheets
Specification documents