XPath

• A Way to point into an XML document
• /datum/notes/em
• /datum[@useful="no"/notes

<datum useful="no"<
     <when>2003-09-22</when>
     <where>Oxford</where>
     <value>21.6</value>
     <units>cm</units>
     <notes>
         This is the <em>average</em>
         ankle circumference of the researchers.
 </notes>
</datum>