Expressing XACML policy

Hi All,

I'm looking how to express following "plain" language access rule:

Only policy holders can have access to given policy. Policy and subject
association is kept in the database and resource in XACML request context is
unique policy identifier. Each subject in the database has list of policies
and each policy has association with all "policy holders".

Is there is any way how to reffer to the subject or resource attributes
stored in the database in the XACML policy definition?

Thanks,

Giedrius