<!DOCTYPE html public "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML>
<HEAD>
<TITLE>Mapping of Namespace qualified element names (QNames) to URIs</TITLE>
<META NAME="keywords" CONTENT="XML,RDF,XLink,namespace,URI">
<LINK href="../OHCG_Style.css" rel="stylesheet"/>
</HEAD>
<BODY>
<H2>Mapping namespace qualitied element names to URIs</H2>
<H2>a proposal</H2>
<P>It is necessary to map namespace qualified element
names (<A href="http://web3.w3.org/TR/REC-xml-names/#ns-qualnames">QNames</A>) to URIs for a variety of purposes but particularly in RDF. The
RDF Model and Syntax specification directs this <A href="http://web3.w3.org/TR/REC-rdf-syntax/#grammar">mapping</A> to occur via concatenation of the namespace URI
with the local name. This is acceptable when the namespace URI does
not end with a character which cannot be used to begin an element
name (an <A href="http://web3.w3.org/TR/REC-xml-names/#NT-NCName">NCName</A>) i.e. a <A href="http://www.w3.org/TR/REC-xml#NT-Letter">Letter</A> or
'_', because the first non Letter or '_' encountered from the end of the URI can
be used to delimit the namespace URI from the element name. Yet when the URI
ends in a Letter or '_', several URI, NCName pairs may map to the same
concatenated URI.</P>
<P>It is proposed for namespace URIs that when a namespace URI ends in a Letter
or '_' that a '#' be inserted between the namespace URI and the element tag name
to create the resultant URI. When such a URI is resolvable to a resource of
media type text/html or text/xml, the fragment identifier resolves to an
identifier of the element name. When the document is of type text/html, the
identifier might point to a section which describes the element. When the
document is of type text/xml (or application/xml) and the base document contains
an RDF Schema, the identifier is expected to point to the Property or Class
definition for the element name.</P>
<P>This mapping has the additional effect of constraining the vocabulary or
grammar for a given namespace to those specified by the authority which controls
the base URI. In particular when resolution of the URI involves a DNS lookup,
the ultimate authority is the Administrative Contact for the root DNS name,
though this contact may delegate authority for derivatives of this DNS entry as
it sees fit. For example given a root DNS entry:</P>
<P>openhealth.org</P>
<P><A href="ftp://openhealth.org">ftp://openhealth.org</A></P>
<P><A href="http://www.openhealth.org">http://www.openhealth.org</A></P>
<P><A href="http://www.openhealth.org/RDF/">http://www.openhealth.org/RDF/</A></P>
<P>are derivatives which might be administered
independently. If the namespace URI does resolve to a document, the absense of a
particular fragment identifier might indicate that the element name is not part
of the vocabulary associated with the namespace
URI. In any case, given this mapping of a namespace qualified element name to a URI, the ability to create
new element names within a given namespace URI qualified XML namespace is the same as the ability to create new URIs derived from the namespace URI.</P>
<P>Jonathan Borden</P>
<P><a href="http://www.openhealth.org">The Open Healthcare Group</a></P>
<P>September 17, 2000</P>
<P> </P>
<P> </P>
</BODY>
</HTML>