27. The policy engine according to claim 16 , where the policy applying module comprises: a document validating unit that validates whether any instance document in the instantiated context model is matched using each of the policies; a validation report generating unit that generates a validation report for the matched policy; an action enforcing unit that enforces an action part of the matched policy according to the validation report.
27. The policy engine according to claim 16 , where the policy applying module comprises: a document validating unit that validates whether any instance document in the instantiated context model is matched using each of the policies; a validation report generating unit that generates a validation report for the matched policy; an action enforcing unit that enforces an action part of the matched policy according to the validation report. 28. The policy engine according to claim 27 , where the document validating unit comprises: a structure validating unit that validates structure of the instance document in the instantiated context model using a schema document in the policy; and a content validating unit that validates content of the instance document in the instantiated context model using a condition part of the policy.