Editing Uniform Resource Identifier (section)

=== URI references ===

A ''URI reference'' is either a URI or a ''relative reference'' when it does not begin with a scheme component followed by a colon (<code>:</code>).{{Ref RFC|3986|rsection=4.1}} A path segment that contains a colon character (e.g., <code>foo:bar</code>) cannot be used as the first path segment of a relative reference if its path component does not begin with a slash (<code>/</code>), as it would be mistaken for a scheme component. Such a path segment must be preceded by a dot path segment (e.g., <code>./foo:bar</code>).{{Ref RFC|3986|rsection=4.2}}

Web document [[markup language]]s frequently use URI references to point to other resources, such as external documents or specific portions of the same logical document:{{Ref RFC|3986|rsection=4.4}}
* in [[HTML]], the value of the <code>src</code> attribute of the <code>img</code> element provides a URI reference, as does the value of the <code>href</code> attribute of the <code>a</code> or <code>link</code> element;
* in [[XML]], the [[system identifier]] appearing after the <code>SYSTEM</code> keyword in a [[Document Type Definition|DTD]] is a fragmentless URI reference;
* in [[XSLT]], the value of the <code>href</code> attribute of the <code>xsl:import</code> element/instruction is a URI reference; likewise the first argument to the <code>document()</code> function.

<pre>
https://example.com/path/resource.txt#fragment
//example.com/path/resource.txt
/path/resource.txt
path/resource.txt
../resource.txt
./resource.txt
resource.txt
#fragment
</pre>