[xacml] Proposed resolution from PM-8-01 to PM-8-07

[Michiharu Kudoh <KUDO@jp.ibm.com>]

I believe the following issues from Issues Version 05 for which I am listed
as the champion can be closed based on our latest
Face-to-Face agreements:

- ISSUE: PM-8-01: Internal v.s. External post conditions
XACML does not support any distinction between internal obligation and
external obligation. It depends on the configuration of PEP and/or PDP.

- ISSUE: PM-8-02: Mandatory v.s. advisory post conditions
XACML does not support any distinction between mandatory obligation and
advisory obligation. The meaning of the obligation is determined in each
application.

- ISSUE: PM-8-03: Inapplicable
The obligation is not returned to PEP when the authorization decision is
determined as inapplicable or indeterminate.

-ISSUE: PM-8-04: Base policy v.s. policy reference
The obligation is specified in both policyStatement and
policyCombinationStatement. The scope of the obligation is defined in
ISSUE: PM-1-02 as "The set of obligations returned by each level of
evaluation includes only those obligations associated with the effect
element being returned by the given level of evaluation.  For example, a
policy set may include some policies that return Permit and other policies
that return Deny for a given request evaluation. If the policy combiner
returns a result of Permit, then only those obligations associated with the
policies that returned Permit are returned to the next higher level of
evaluation.  If the PDP's evaluation is viewed as a tree of
policyCombinationStatements, policyStatements, and rules, each of which
returns "Permit" or "Deny", then the set of obligations returned by the PDP
will include only the obligations associated paths where the effect at each
level of evaluation is the same as the effect being returned by the PDP."

-ISSUE: PM-8-05: How to return post-condition via SAML
(I will post the resolution for this issue later)

-ISSUE: PM-8-06: When to execute post condition
When and how PEP executes obligation depends on each application. XACML (as
PDP) does not assume any specific semantics. While obligation implies that
specified operation must be dealt with prior to the requested access, it
does not necessarily mean that the specified operations must be executed
synchronously. Taking the obligatory operation usage scenario like
"customers can register themselves with their private information provided
that such information is deleted in 90 days--- obligation is
delete-in-90days", it is impossible to execute "delete-in-90days"
obligation prior to the requested access. It would be reasonable if such
operation is queued in the application and guaranteed to be executed later.

-ISSUE: PM-8-07: Extension point (line 1315 is typo, the issue number
should be PM-8-07)
Extension point of obligation is 1. obligationId in policyStatement or
policyCombinationStatement and 2. ruleSet combiner or policySet combiner.
This allows policy writers to specify arbitrary identifier of the
user-defined obligation and to specify the semantics of how obligation is
computed in response to the access request.

Michiharu Kudo

IBM Tokyo Research Laboratory, Internet Technology
Tel. +81 (46) 215-4642   Fax +81 (46) 273-7428