OASIS eXtensible Access Control Markup Language (XACML) TC

  • 1.  proposal for WI #27

    Posted 10-16-2003 20:53
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    Subject: proposal for WI #27


    Attached is a proposal for item #27 based on my original mail on this
    topic. It's purposefully thin on detail since there hasn't been much
    discussion and I suspect that others will have some opinions. This is
    not on the list of topics to discuss at the F2F.
    
    
    seth
    
    
    27: Version number element or attribute in an XACML policy.
    
       Some way of indicating the version of a policy having a
       particular XACML policy id, and a way of placing version
       constraints on a policy reference.
    
    MOTIVATING USE-CASE AND REQUIREMENT
    
      A policy is currently referenced with a PolicyIdReference or a
      PolicySetIdReference using only a single URI. There is no ability to
      specify which version of a policy is being referenced. Versioning may
      be implied informally by file names, but that doesn't provide the
      flexibility to ask for eg. "the most recent policy". There is
      also nothing within a policy that supplies the version of that
      policy.
    
      From a management point of view, these features are critical. Between
      different revisions of policies identifiers may change or new features
      may be added (for instance, required support for new datatypes). More
      to the point, the meaning of a given policy may change between
      revisions, making a previously useful reference now unclear. In order
      to make updates to a policy system clear, there must be some kind of
      versioning system in place.
    
      The requirements are twofold: a way to specify the version of a
      policy, and a way to specify (optionally) what versions of a policy
      are acceptable from a reference.
    
      This is a requirement that comes from people using XACML 1.0
      today. They have asked for a clearer way to manage revisions of
      policies and references to policies that may be updated. It also has
      been discussed by many people in the area of tools development. The
      analogy is to shared libraries, which are managable in large part
      because of a good versioning system.
    
    SUMMARY OF OPEN ISSUES
    
      There are no open issues as this topic has not been discussed in much
      detail within the TC. There is the possibility of exporting version
      information into a SAML assertion wrapping an XACML policy, which may
      have some effect on this proposal.
    
    PROPOSED SOLUTION <# if more than one>
    
      At a high level, a Policy or PolicySet needs a new XML attribute or
      top-level element that specifies a version. This should include at
      least a major and minor value. It may be acceptable to provide a
      default value of 1.0 (for example) if no value is provided. This needs
      to be discussed.
    
      The PolicyIdReference and PolicySetIdReference elements also need a
      new XML attribute that specifies an acceptable version. By default,
      these should always refer either to the most recent version of a
      policy or some fixed value (like 1.0). The value is a simple
      expression that lets you request a specific version, or some version
      above or below a given version. This will be defined in detail if
      others approve of this approach.
    
    DETAILED SOLUTION
    
      None until there is some agreement on the right approach to take, if
      any, for this proposal.
    


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