This Version:January 1, 2010
Latest Version: http://www.rddl.org/2
Previous Version: February 18, 2002
Editors:
This document describes the 2nd version of RDDL (Resource Directory Description Language) and contains substantial input from the W3C Technical Architecture Group. The first and second versions of RDDL are described in the TAG Finding: "Associating Resources with Namespaces" regarding the appropriate representation of an XML Namespace Name relating to the TAG issue: namespaceDocument-8. .
RDDL Version 2 is intended to be backward compatible with RDDL Version 1
This document describes the Resource Directory Description Language (RDDL). A RDDL document, called a Resource Directory, provides a package of information about some target, including:
The Resource Directory Description Language is an extension of XHTML Basic 1.0 with two added
attributes of the a element namedrddl:nature and rddl:purpose.
The Resource Directory Description Language was initially proposed and specified after discussion on the xml-dev mailing list. RDDL reflects contributions from many participants in the xml-dev mailing list
This document has no official standing and has not been considered nor approved by any organization.
a ElementA Resource Directory implements links to related resources using the XHTML
a element, enriched by two attributes in the namespace identified by
the URI http://www.rddl.org/ (identified in this discussion by the
prefix rddl). The attributes are named rddl:nature and
rddl:purpose, and an XHTML a element is considered to be
an entry in the resource directory if either or both of these attributes are present.
Note that there is a rich assortment of other attributes defined by HTML for the
a element, to provide information about its title, language, traversal
and so on; their use is encouraged in Resource Directories.
Related resources have a nature, a machine-readable label
provided by the value of the rddl:nature attribute. For example,
the nature of an XML Schema designed for use with a namespace would be given asrddl:nature="http://www.w3.org/2001/XMLSchema".
In cases where there is only one resource with a particular nature, the purpose of the linked resource may be inferred from this nature. For example, if there is only one related resource for a particular namespace whose nature indicates that it is a schema, processing software might infer that its purpose is to validate elements in that namespace.
The value of this attribute must be a URI reference, which must be converted to absolute form before being used. It provides a machine-readable identifier for the nature of the related resource. Software may dispatch on this value.
When the related resource is an XML language for which a namespace name has been defined, and for which the namespace name adequately distinguishes the nature of the resource, the namespace name should be used as its nature.
When the related resource is not an XML document but is adequately distinguished
by a MIME type, the value of therddl:nature attribute may reflect
this MIME type with values formed by the concatenation of the
prefixhttp://www.isi.edu/in-notes/iana/assignments/media-types/
with a MIME type e.g.http://www.isi.edu/in-notes/iana/assignments/media-types/text/css.
It is anticipated that many related-resource natures will be well known. A list of well-known natures may be found in the Resource Directoryhttp://www.rddl.org/natures.
If a purpose but no nature is provided for a related resource, the default value
ishttp://www.rddl.org/#resource.
Related resources may have a purpose, a machine-readable label
provided by the value of the rddl:purpose attribute. The purpose is
designed to convey the intended usage of the related resource. For example, two
related resources might have natures that indicate they are both schemas, but
the purposes might indicate that one is designed to validate the "strict"
version of the language, the other the "forgiving" form.
The value of this attribute must be a URI reference, which must be converted to absolute form before being used. It provides a machine-readable identifier for the purpose of the link to the related resource. Software may dispatch on this value.
It is anticipated that the purposes of many related resources will be well known. A list of well-known purposes may be found in the Resource Directoryhttp://www.rddl.org/purposes.