OASIS eXtensible Access Control Markup Language (XACML) TC

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RE: [xacml] is-present-designators (fwd)

  • 1.  RE: [xacml] is-present-designators (fwd)

    Posted 11-05-2002 18:12
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    Subject: RE: [xacml] is-present-designators (fwd)


    On Tue, 5 Nov 2002, Daniel Engovatov wrote:
    
    > I agree.  They are not critical and the functionality can be temporarily
    > added as an extension function if some policy really needs it.
    
    Not quite. The only extension function, by using the XACML way of defining
    a new FunctionId, can only do what Simon said, take a bag of elements from
    an *AttributeDesignator, of which they have already been retrieved, and
    then just count the elements in the bag.
    
    However, I would like to make statements like:
    
    If attribute XXX is present and it does NOT match George then Deny.
    
    A simple use of a subject-match, e.g.
    
    (not (subject-match "string-equals" <subj-attr-desg "XXX"> "George"))
    
    doesn't cut it.
    
    I definately need
    
    (subject-attr-is-present "XXX") and (not (subject-match ....)))
    
    To get the right semantic.
    
    -Polar
    
    
    > -----Original Message-----
    > From: simon godik [mailto:simon@godik.com]
    > Sent: Tuesday, November 05, 2002 2:49 PM
    > To: XACML
    > Subject: Re: [xacml] is-present-designators (fwd)
    >
    >
    > There is potential optimization with is-present elements,
    > provided that attribute data storage supports is-present query.
    > I propose to defer this optimization to xacml 1.1.
    >
    > Simon
    >
    > ----- Original Message -----
    > From: "Polar Humenn" <polar@syr.edu>
    > To: "XACML" <xacml@lists.oasis-open.org>
    > Sent: Tuesday, November 05, 2002 2:46 PM
    > Subject: Re: [xacml] is-present-designators (fwd)
    >
    >
    > >
    > > On Tue, 5 Nov 2002, Polar Humenn wrote:
    > >
    > > > There is a way to test if attribute is present without using
    > is-present-designator elements:
    > > > It is to compare bag size selected by the designator to 0:
    > > >
    > > > <apply function-id="integer-greater-than">
    > > >     <apply function-id="type-bag-size">
    > > >         <attribute-designator ..../>
    > > >     </apply>
    > > >     <attr-val ...>0</attr-val>
    > > > </apply>
    > >
    > > Well, I do agree that is a way, but still it may not be all that
    > > efficient.
    > >
    > > Let's say you have an attribute named "face-print" that contains 2MB of
    > > image data. You might have 10 of them.  If you just want to know if its
    > > present, using the IsPresent element just may require the request context
    > > builder to just see if its there. The comparing the bag size would require
    > > the AttributeDesignator, which would actually retrieve them for nothing.
    > >
    > > -Polar
    > >
    > >
    > >
    > >
    > >
    > > >
    > > > My proposal is to drop is-present-attribute-designators
    > > >
    > > > Simon
    > > >
    > > >
    > >
    > >
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