The nature of a related resource says what the resource is. For example, the nature of a web page might be HTML, and the nature of an image might be JPEG. The nature is indicated by a URL. Normally, this nature URL is a namespace URL for XML applications and a MIME media type URL for everything else. For instance, the XSLT nature is written as http://www.w3.org/1999/XSL/Transform. The JPEG nature is written as http://www.isi.edu/in-notes/iana/assignments/media-types/image/jpeg.
The RDDL specification specifies 24 natures that can be used in
xlink:role attributes. In addition, you are welcome to define your
own, but, when possible, you should use the standard natures so that
automated software can understand your documents and locate the
necessary related resources. These are the standard natures and their
URLs:
CSS stylesheet | http://www.isi.edu/in-notes/iana/assignments/media-types/text/css |
DTD | http://www.isi.edu/in-notes/iana/assignments/media-types/application/xml-dtd |
A mailbox | |
Generic HTML | http://www.isi.edu/in-notes/iana/assignments/media-types/text/html |
HTML 4.0 | |
HTML 4 Strict | |
HTML 4 Transitional | |
HTML 4 Frameset | |
XHTML | |
XHTML 1.0 Strict | |
XHTML 1.0 Transitional | |
RDF schema | |
RELAX core grammar | |
RELAX namespace grammar | |
Schematron schema | |
OASIS Open Catalog | |
W3C XML Schema Language schema | |
XML character data | |
XML escaped text | |
XML unparsed entity | |
IETF RFC | |
ISO standard | |
Python software | |
Java software |
Many other natures can be reasonably derived by following these
examples. For instance, a PNG image could be given the nature http://www.isi.edu/in-notes/iana/assignments/media-types/image/png
because PNG documents have the MIME media type image/png. Software written in Ruby could be
given the nature http://www.rddl.org/natures/software#ruby. An RDF
document can have the nature http://www.w3.org/1999/02/22-rdf-syntax-ns# taken from
its namespace, and so forth.