2 "sfa-input" specifies the subset of the requestor context that this match needs to see. It is specified as an xpath expression.
3 For this simple match, we just need to look at sfa-input.
5 "rule" specifies an xpath/xquery expression that evaluates the match. In this case, we just check if the requestor's HRN is the same
6 as the one matched by this rule.
10 <match xmlns="http://www.planet-lab.org/sfa/sfatables/match/2009/8">
11 <sfa-input select="//sfa//user/hrn"/>
12 <rule-input select="//request//user/hrn"/>
13 <processor name="hrn.xsl"/>