From W3C CSS1: CSS1 is a simple style sheet mechanism that allows authors and readers to attach style (e.g. fonts, colors and spacing) to HTML documents. The CSS1 language is human readable and writable, and expresses style in common desktop publishing terminology.
The URI http://www.isi.edu/in-notes/iana/assignments/media-types/text/css
is well-known URI for CSS
From XML 1.0: The XML document type declaration contains or points to markup declarations that provide a grammar for a class of documents. This grammar is known as a document type definition, or DTD. The document type declaration can point to an external subset (a special kind of external entity) containing markup declarations, or can contain the markup declarations directly in an internal subset, or can do both. The DTD for a document consists of both subsets taken together. [1]
The URI http://www.rddl.org/roles.htm#DTD
can be used as a well-known URI for DTD
An RDF Schema is a language which describes vocabularies using the Resource Description Framework.
The RDF Schema namespace URI is http://www.w3.org/2000/01/rdf-schema#
.
The RDF Schema namespace URI is http://www.w3.org/2000/01/rdf-schema#
.
RELAX: Regular Language Description for XML, is An XML Structure Validation Language using Patterns in Trees
The well known URI for RELAX is http://www.xml.gr.jp/relax
.
http://www.xml.gr.jp/xmlns/relaxCore
is the namespace of the root element of a RELAX module.
Schematron is An XML Structure Validation Language using Patterns in Trees.
The schematron spec
The well known URI for Schematron is http://www.ascc.net/xml/schematron
.
http://www.ascc.net/xml/schematron
is the namespace of the root
element of a schematron schema.
An OASIS Open Catalog Format document mapps Public Identifiers to System Identifiers.
The URI http://www.rddl.org/arcrole.htm#SOCAT
can be used as a well known URI for an OASIS Open Catalog.
The XML Schema Definition Language is a formal language for which to describe XML grammars.
The well known URI for XSD is: http://www.w3.org/2000/10/XMLSchema
http://www.w3.org/2000/10/XMLSchema
is also the namespace URI of the root element of an XSD schema.
Schema validation is performed on XML or SGML documents.
A module may be included as part of a schema or software program.
A module may be included as part of a schema or software program.