15.3 Natures

     

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	http://www.rddl.org/natures#mailbox
Generic HTML	http://www.isi.edu/in-notes/iana/assignments/media-types/text/html
HTML 4.0	http://www.w3.org/TR/html4/
HTML 4 Strict	http://www.w3.org/TR/html4/strict
HTML 4 Transitional	http://www.w3.org/TR/html4/transitional
HTML 4 Frameset	http://www.w3.org/TR/html4/frameset
XHTML	http://www.w3.org/1999/xhtml
XHTML 1.0 Strict	http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict
XHTML 1.0 Transitional	http://www.w3.org/TR/xhtml/1/DTD/xhtml/1-transitional
RDF schema	http://www.w3.org/2000/01/rdf-schema#
RELAX core grammar	http://www.xml.gr.jp/xmlns/relaxCore
RELAX namespace grammar	http://www.xml.gr.jp/xmlns/relaxNamespace
Schematron schema	http://www.ascc.net/xml/schematron
OASIS Open Catalog	http://www.rddl.org/natures#SOCAT
W3C XML Schema Language schema	http://www.w3.org/2001/XMLSchema
XML character data	http://www.w3.org/TR/REC-xml.html#dt-chardata
XML escaped text	http://www.w3.org/TR/REC-xml.html#dt-escape
XML unparsed entity	http://www.w3.org/TR/REC-xml.html#dt-unparsed
IETF RFC	http://www.ietf.org/rfc/rfc2026.txt
ISO standard	http://www.iso.ch/
Python software	http://www.rddl.org/natures/software#python
Java software	http://www.rddl.org/natures/software#java

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.