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Re: [xacml] re: Attribute Selector example

  • 1.  Re: [xacml] re: Attribute Selector example

    Posted 08-26-2002 04:09
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    Subject: Re: [xacml] re: Attribute Selector example


    
    Yes, my impression is, once you agree to using general-string-equal (or
    something similar),  I think every rule that specifies AttributeSelector or
    xpath-expr function must deal with object data type (or something similar).
    Based on this observation, I don't think my original rule example using
    node-match function has unnecessary complexity. Anyway, I agree that the
    following syntax as you suggested is more consistent with the current
    schema than the syntax I first proposed.
    
    <ResourceMatch MatchId="function:node-match">
      <AttributeSelectorIndirect>
        <ResourceAttributeDesignator AttributeId="urn:...:resource:xpath"/>
      </AttributeSelectorIndirect>
      <AttributeSelector RequestContextPath="//md:record"/>
    </ResourceMatch>
    
    I changed the name to AttributeSelectorIndirect because I want
    AttributeSelector at the head. I would prefer the above syntax to the
    syntax below because I don't like to have many XPath expression parsing
    functions (i.e. node-match-1 etc.) other than xpath-expr.
    
    <ResourceMatch MatchId="function:node-match-1">
      <ResourceAttributeDesignator AttributeId="urn:...:xpath"
                                   DataType="xsi:string"/>
      <AttributeValue DataType="xsi:string">//md:record</AttributeValue>
    </ResourceMatch>
    
    Michiharu
    
    IBM Tokyo Research Laboratory, Internet Technology
    Tel. +81 (46) 215-4642   Fax +81 (46) 273-7428
    
    
    
    
                                                                                                                                                        
                          Simon Godik                                                                                                                   
                          <simon@godik.com>        To:       xacml@lists.oasis-open.org                                                                 
                                                   cc:                                                                                                  
                          2002/08/26 16:15         Subject:  Re: [xacml] re: Attribute Selector example                                                 
                                                                                                                                                        
                                                                                                                                                        
                                                                                                                                                        
    
    
    
    Michiharu,
    You are correct, xpath-expr return type is the same as attribute-selector,
    which is a node-set. I was under impression that we have this function
    defined.
    I'm not sure what to do with string-equal receiving output of
    attribute-selector.
    May be the right thing to do is to use general-string-equal(object a,
    object
    b)
    function that you proposed some time ago.
    
    Simon
    
    ----- Original Message -----
    From: "Michiharu Kudoh" <KUDO@jp.ibm.com>
    To: <xacml@lists.oasis-open.org>
    Sent: Sunday, August 25, 2002 12:50 AM
    Subject: Re: [xacml] re: Attribute Selector example
    
    
    >
    > Simon
    >
    > I see that you meant function:node-match-1 in the example. I agree that
    it
    > is another way to specify the same policy. The difference in our opinions
    > would be relevant to how to handle XPath related function and data types
    in
    > XACML. In your example, you said that <AttributeSelector> can be
    translated
    > into 'function:xpath-expr' in Condition. If that is the case, what is the
    > return type of the xpath-expr function? It must be the same with the
    return
    > type of <AttributeSelector>, right? Besides, In line 821-830,
    string-equal
    > function receives a return value of the <AttributeSelector>. What data is
    > handed to the string-equal function?
    >
    > Michiharu
    >
    > IBM Tokyo Research Laboratory, Internet Technology
    > Tel. +81 (46) 215-4642   Fax +81 (46) 273-7428
    >
    >
    >
    >
    >
    >                       Simon Godik
    >                       <simon@godik.com>        To:
    xacml@lists.oasis-open.org
    >                                                cc:
    >                       2002/08/25 13:43         Subject:  [xacml] re:
    Attribute Selector example
    >
    >
    >
    >
    >
    >
    > Michiharu,
    >
    > I see that you want to compute the node-set of xpath expression specified
    > in
    > the request-context before passing it to the node-match function.
    >
    > Of course, something like that could be accomplished in the condition
    > with 'xpath-expr' function:
    > <Apply FunctionId="function:node-match">
    >     <Apply FunctionId="function:xpath-expr">
    >         <ResourceAttributeDesignator
    >             AttributeId="urn:oasis:names:tc:xacml:1.0:resource:xpath"
    >             DataType="xs:string"/>
    >     </Apply>
    >     <AttributeSelector RequestContextPath="..."/>
    > </Apply>
    >
    > You want to do the same thing in the target.
    >
    > I'm not completely sold on your syntax for AttributeSelector. I'd prefer
    > this extension:
    > <AttributeSelector indirect="true"> (or IndirectAttributeSelector)
    >     <ResourceAttributeDesignator AttributeId
    > ="urn:oasis:names:tc:xacml:1.0:resource:xpath"
    >         DataType="xsi:string"/>
    > </AttributeSelector>
    >
    > Better yet to relax 'match' element to allow 'apply' children.
    >
    > Another approach:
    > I think that complication is in 'node-match' function definition that
    takes
    > --results--
    > of xpath expression. That forces you to produce this result, so you
    > need additional semantics in attribute-selector.
    >
    > Consider different function that takes --xpath-expressions-- as arguments
    > (as in examples in section 3). Than you do not have to produce node sets
    > before calling this function and no change in schema is needed.
    >
    > Suppose that node-match-1 has exact same semantics as node-match but
    > take 2 xpath expressions: xpath-expr-request and xpath-expr-rule:
    > node-match-1(xpath-expr-req, xpath-expr-rule).
    >
    > You can use it in the target:
    > <ResourceMatch MatchId="function:node-match-1">
    >     <ResourceAttributeDesignator
    >         AttributeId="urn:oasis:names:tc:xacml:1.0:resource:xpath"
    >         DataType="xsi:string"/>
    >     <AttributeValue DataType="xsi:string">//md:record</AttributeValue>
    > </ResourceMatch>
    >
    > Simon
    >
    >
    >
    >
    >
    >
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