Let you mix and match different XML vocabularies
URIs identify elements and attributes that belong to different XML applications
Prefixes can change if the URI stay the same
<SONG xmlns="http://www.cafeconleche.org/namespace/song"
xmlns:xlink="http://www.w3.org/1999/xlink">
<TITLE>Hot Cop</TITLE>
<PHOTO
xlink:type="simple" xlink:show="onLoad" xlink:href="hotcop.jpg"
ALT="Victor Willis in Cop Outfit" WIDTH="100" HEIGHT="200"/>
<COMPOSER>Jacques Morali</COMPOSER>
<PUBLISHER xlink:type="simple" xlink:href="http://www.amrecords.com/">
A & M Records
</PUBLISHER>
<ARTIST>Village People</ARTIST>
</SONG>