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Subject: Re: [xacml] [CR] AttributeSelectorIndirect
Michiharu,
Comments inline.
On Fri, 30 Aug 2002, Michiharu Kudoh wrote:
>
> Line 804-810 of draft 0.16e, there is a resource match in Example 2 Rule 1:
>
> <ResourceMatch MatchId="function:node-match">
> <ResourceAttributeDesignator AttributeId="urn:...:xpath"
> DataType="xsi:string"/>
> <AttributeValue DataType="xsi:string">/md:record</AttributeValue>
> </ResourceMatch>
>
> In the above example, the node-match function is defined as
>
> Function: node-match
> input: xs:string, xs:string
> output: xs:boolean
> description: receive two xpath expressions and executes xpath processor on
> both xpaths. It generates two objects (object type is defined in XPath 1.0,
> i.e. node-set, string, numeric, or boolean). When two objects have an
> intersection, then it returns true, otherwise return false.
This function, although a little unwieldy, is fine, provided you can
provide a deterministic definition for a node-match. ("when two object
have an intersection") is somewhat lacking.
> Instead of the above node-match function and the resource match
> specification, I would prefer the definition and resource match
> specification using <AttributeSelectorIndirect> below:
>
> Function: node-match
> input: object, object
> output: xs:boolean
> description: receive two objects. When two node-sets have an intersection,
> then it returns true, otherwise return false.
>
> <ResourceMatch MatchId="function:node-match">
> <AttributeSelectorIndirect>
> <ResourceAttributeDesignator AttributeId="urn:...:xpath"/>
> </AttributeSelectorIndirect>
> <AttributeSelector RequestContextPath="/md:record"/>
> </ResourceMatch>
Why?
Your previous approach is fine, and works within our type system. It takes
two arguments of primitive types ("xs:string") and returns an xs:boolean.
This approach requires "node-match" to be polymorphic and for XACML
processors to understand abstract data types. Our simple type system
cannot support it. We would now have much more than primitive types, and
sequences of primitive types. We would have abstract data types (i.e.
arbitrary XML nodes) introduced into the type system.
Also, in this case, you must note that the selectors must contain the
"DataType" attribute to make type sense out of their results, as these
selectors can end up in other function applications. I think we are
trying to get rid of the DataType attribute, because of the type
inference.
Also, I think you left the "DataType" attribute out in this example, for
obvious reasons. You don't know what legal value to give it.
In both cases, however, you still need to come up with an explicit
specification of for the function "node-match".
If you can come up with a specification of node-match, I would strongly
prefer that it was a function that fit with our type system, i.e. your
first example, which takes two XPATH expressions and returns a boolean.
> Other example (not AttributeSelectorIndirect but AttributeSelector case) is
> line 825-835. The function:string-equal should be the
> function:general-string-equal because <AttributeSelector> returns an object
> data type (maybe node-set) and it is not proper to hand it to string-equal
> function.
I don't even have a specification for "string-equal", let alone
"general-string-equal", so I don't really understand the difference.
Cheers,
-Polar
> <Condition FunctionId="function:string-equal">
> <SubjectAttributeDesignatorWhere
> AttributeId="urn:...:policy-number" DataType="xsi:string"/>
> <AttributeSelector RequestContextPath="/ctx:Request/ ...
> /md:policyNumber"
> DataType="xsi:string"/>
> </Condition>
>
> [should be]
>
> <Condition FunctionId="function:general-string-equal">
> <SubjectAttributeDesignatorWhere
> AttributeId="urn:...:policy-number" DataType="xsi:string"/>
> <AttributeSelector RequestContextPath="/ctx:Request/ ...
> /md:policyNumber"
> DataType="xsi:string"/>
> </Condition>
>
> Michiharu Kudo
>
> IBM Tokyo Research Laboratory, Internet Technology
> Tel. +81 (46) 215-4642 Fax +81 (46) 273-7428
>
>
>
>
>
> Polar Humenn
> <polar@syr.edu> To: Michiharu Kudoh/Japan/IBM@IBMJP
> cc: <xacml@lists.oasis-open.org>
> 2002/08/30 03:27 Subject: Re: [xacml] [CR] AttributeSelectorIndirect
>
>
>
>
>
>
>
>
> Michiharu,
>
> Is there a use case or example for this type of attribute selector?
>
> Cheers,
> -Polar
>
> On Thu, 29 Aug 2002, Michiharu Kudoh wrote:
>
> > Based on the discussion on Monday call, Simon and I agreed to changing
> the
> > schema to support an AttributeSelectorIndirect element to retrieve a
> XPath
> > expression from the context. I wonder whether the name of this element is
> > appropriate or not.
> >
> > <xs:complexType name="AttributeSelectorBaseType">
> > <xs:element ref="xacml:XPathNamespace" minOccurs="0" maxOccurs
> > ="unbounded"/>
> > <xs:attribute name="DataType" type="xs:anyURI" use="optional"/>
> > <xs:attribute name="XPathVersion" type="xs:anyURI" use="optional"
> default
> > ="http://www.w3.org/TR/1999/Rec-xpath-19991116"/>
> > </xs:complexType>
> >
> > <xs:complexType name="AttributeSelectorType">
> > <xs:complexContent>
> > <xs:extension base="AttributeSelectorBaseType">
> > <xs:attribute name="RequestContextPath" type="xs:string" use
> > ="required"/>
> > </xs:extension>
> > </xs:complexContent>
> > </xs:complexType>
> >
> > <xs:complexType name="AttributeSelectorIndirectType">
> > <xs:extension base="AttributeSelectorBaseType">
> > <xs:choice>
> > <xs:element ref="xacml:SubjectAttributeDesignator"/>
> > <xs:element ref="xacml:ResourceAttributeDesignator"/>
> > <xs:element ref="xacml:ActionAttributeDesignator"/>
> > <xs:element ref="xacml:EnvironmentAttributeDesignator"/>
> > </xs:choice>
> > </xs:extension>
> > </xs:complexType>
> >
> > <xs:element name="AttributeSelector" type="AttributeSelectorType"/>
> > <xs:element name="AttributeSelectorIndirect" type
> > ="AttributeSelectorIndirectType"/>
> >
> > <xs:element name="XPathNamespace" type="xacml:XPathNamespaceType"
> > substitutionGroup="xacml:AbstractDefaults"/>
> > <xs:complexType name="XPathNamespaceType">
> > <xs:attribute name="NamespaceURI" type="xs:anyURI"/>
> > <xs:attribute name="Prefix" type="xs:string" use="optional"/>
> > </xs:complexType>
> >
> >
> > Sample text for this element:
> >
> > 5.28. Element <AttributeSelectorIndirect>
> >
> > The <AttributeSelectorIndirect> element is a free-form pointing device
> into
> > the <xacml-context:Request> element using an attribute designator. The
> > actual xpath expression is retrieved from the context pointed by that
> > attribute designator. Other than that, the semantics is the same with
> > <AttributeSelector> element. Support for the <AttributeSelectorIndirect>
> > element is OPTIONAL.
> >
> > The <AttributeSelectorIndirect> element is of
> AttributeSelectorIndirectType
> > complex type.
> > The <AttributeSelectorIndirect> element has either one of the following
> > elements:
> >
> > SubjectAttributeDesignator
> > ResourceAttributeDesignator
> > ActionAttributeDesignator
> > EnvironmentAttributeDesignator
> >
> > Michiharu
> >
> > IBM Tokyo Research Laboratory, Internet Technology
> > Tel. +81 (46) 215-4642 Fax +81 (46) 273-7428
> >
> >
> >
> >
> >
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>
>
>
>
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