Guidelines on when to specify Target in Policy as opposed to Rule

XACML allows a Target to be specified for a Policy/PolicySet as well as 
a Rule.
I vaguely undertstand that the Target at the Policy element is there to 
allow
more efficient first-level target filtering before the "more expensive" 
processing
of Target within a rule.

Are there any guidelines on when to specify 
SubjectMatch/ResourceMatch/ActionMatch within
the Target at the Policy level rather than the more common practice of 
specifying it at the Rule
level?

Once obvious guideline that come sto mind is that you place any 
Rule-independent SubjectMatch/ResourceMatch/ActionMatch within
the Target at the Policy level.

Are there any other guidelines or considerations?

-- 
Regards,
Farrukh Najmi

Web: http://www.wellfleetsoftware.com