Resource Directory Description Language

This version: January 2, 2001

Latest Version: January 2, 2001

Previous Version: January 2, 2001

Editors:

Note: you are looking at the actual XML Resource Directory for the http://www.openhealth.org/RDDL/ namespace.

Introduction

This document defines a Resource Directory Description Language. A Resource Directory serves as a text description of a resource identifier such as an XML Namespace [1] and includes links to resources associated with the namespace such as schemata, stylesheets and/or other resources associated with the namespace URI. A Resource Directory Description is designed to be suitable for service as the body of a resource returned by deferencing a URI serving as an XML Namespace name.

The Resource Directory Description Language is an extension of XHTML Basic 1.0 with a new element named "resource". The resource element serves as an XLink to the referenced resource.

This document defines the syntax and semantics of the Resource Directory Description Language, and also serves as a Resource Directory Description for the namespace http://www.openhealth.org/RDDL/.

The Resource Directory Description 1.0 DTD has been produced as an extension of XHTML Basic 1.0 [5].

Background

The Resource Directory Description Language was initially proposed and specified after discussion on the XML-DEV mailing list.

resource

The resource element is qualified with the namespace URI http://www.openhealth.org/RDDL/

The resource element represents a simple xlink with an additional attribute content-type which provides for an optional content type specifiers. The content-type attribute is not namespace qualified.

The rddl:resource element may be placed within the html body. The %Flow.mix entity has been redefined to contain rddl:resource so it rougly may be placed anywhere a p tag may be placed.

The rddl:resource element itself uses the %Flow.mix content model, and SHOULD have content which describes the associated resource.

<!ELEMENT rddl:resource (#PCDATA | %Flow.mix;)*>
<!ATTLIST rddl:resource
  %Common.attrib;
  xmlns:rddl	CDATA	#FIXED 'http://www.openhealth.org/RDDL/'
  xlink:type	(simple|arc|locator|resource) "simple"
  xlink:role	CDATA		'http://www.openhealth.org/RDDL/'
  xlink:arcrole CDATA		#IMPLIED
  xlink:title	CDATA		#IMPLIED
  xlink:href	CDATA		#IMPLIED
  xlink:label	CDATA		#IMPLIED
  xlink:from	CDATA		#IMPLIED
  xlink:to	CDATA		#IMPLIED
  xlink:show	(none) #FIXED "none"
  xlink:actuate (none) #FIXED "none"
  content-type	CDATA		#IMPLIED
  >

The definition above has been edited for clarity. RDDL has been defined using Modularization for XHTML. Following this recommendation, element prefixing can be overridden using internal subset parsed entities.

Attributes

xlink:arcrole

A URI.

The xlink:arcrole defines the type of the link. Software perfoming resource resolution may dispatch on the xlink:arcrole value.

When the resource is intended to refer to a schema, the arcrole may be used to determine the type of the schema. e.g. A DTD, XSD, or RDF Schema. In this case such schemata are named by a URI. The URI should be well known. For example:

XHTML may be referenced by http://www.openhealth.org/RDDL/arcrole.htm#XHTML
XSD may be referenced by http://www.openhealth.org/RDDL/arcrole.htm#XSD
RDF Schema may be referenced by http://www.openhealth.org/RDDL/arcrole.htm#RDFS

The document http://www.openhealth.org/RDDL/arcrole.htm is itself a RDDL directory.

xlink:role

A URI.

The xlink:role defaults to the RDDL namespace URI: http://www.openhealth.org/RDDL/.

In general it will not be otherwise specified but may be used to distinguish among related schemata such as for HTML strict, transitional and frameset. The xlink:role of a link should be thought of as the type of the resource referenced by the link.

Ed. need to further discuss uses of and compare xmlink:arcrole and xlink:role

xlink:href

The xlink:href known as the Locator attribute contains a mandatory URI referencing the target resource

xlink:title

A human readable short descriptive title. This should be specified but not in lieu of descriptive content.

xlink:show

Not used. The only legal value is "none".

xlink:actuate

Not used. The only legal value is "none".

content-type

An optional attribute defining the media content type

The content-type attribute is not namespace qualified regardless of whether the containing resource element is namespace prefixed or not.

Resources within the body

In another example resources can be placed within the body, allowing intermingling of text descriptions and resource links.

<html>
	<head></head>
	<body>
	 <rddl:resource 
	   xlink:type="simple"
	   xlink:title="XML Schema"
	   xlink:arcrole="http://www.openhealth.org/RDDL/arcroles.htm#XSD"
	   xlink:href="http://www.openhealth.org/XMLCatalog/xcat-xhtml1.xsd" 
	   > <p>Here is the description of the XSD Schema being described 
	   within a <a class="element" href="#resource">resource</a> tag.</p>
	 </rddl:resource>
	</body>
 </html>

Here is the description of the XSD Schema being described within a resource tag.

Resources defined within this document

Below are the resources defined within this document

CSS Stylesheet

A CSS stylesheet used to provide the "look-and-feel" of this document.

DTD

The RDDL DTD is defined using Modularization for XHTML