Re: [xacml] CR 144: function "present" needs to be fixed.

[Simon Godik <simon@godik.com>]

If we adopt must-be-present it should have additional args:
must-be-present(attr-kind, attr-id, type-uri);

We also need similar function for the attribute-selector.
must-be-present-xpath(xpath-expr, type-uri)

We can not put functions in the target.

I'd prefer to have mustBePresent attribute in the attribute-designator
and attribute-selector elements. When it's value is set to 'true' and
attribute is not found, attribute-designator expression shall evaluate to
indeterminate.

Simon

----- Original Message -----
From: "Polar Humenn" <polar@syr.edu>
To: "XACML" <xacml@lists.oasis-open.org>
Sent: Tuesday, October 22, 2002 9:25 AM
Subject: [xacml] CR 144: function "present" needs to be fixed.


>
> The function "present" as we discussed yesterday in spec 18d is vague in
> whether it returns "false" or raises an "indeterminate" if the attribute
> is not present.
>
> This needs to be cleared up, and we might address some of Simon's concerns
> of which he alluded to yesterday on "indeterminate" for an attribute that
> is not present. I don't like that, but I'm not against it. So, how about
> two functions?
>
> Since we now requiring DataType to be present in both the attribute of the
> context and in the attribute designator of the policy, such that the look
> up for the attribute is comprised of both the id and data type, we need to
> address this lookup requirement in the function "present". It needs to be
> fixed anyway.
>
> I suggest that we have two functions, summary:
>
> is-present
>     returns true if the attribute is there, and false if not.
>
> must-be-present
>     returns true if the attribute is there, and raises
> indeterminate if not. (The PDP can easily carry a "missing-attribute"
> status from this, if it wanted).
>
>
> So, I suggest replacing the last bullet and paragraph in Section A14.5
> Logical Functions, (i.e. "present") with the following:
>
>
> o is-present
>
> This function SHALL take two arguments. The first argument SHALL be an
> attribute value of type "xs:anyURI" as used in the "AttributeId"  XML
> attribute of an <AttributeDesignator> element. The second argument SHALL
> be an attribute value of type "xs:string" containing the identity of the
> data type as used in the "DataType" XML attribute of the
> <AttributeDesignator> element. This expression SHALL result in "true" if
> the named attribute can be located in the request context, which means
> that an <AttributeDesignator> or <AttributeSelector> element for this
> named attribute will return a bag consisting of at least one element. If
> no value can be found for the attribute in the request context, then this
> expression SHALL result in "false", which means that an
> <AttributeDesignator> or <AttributeSelector> element for this named
> attribute will return an empty bag. If it cannot be determined whether the
> attribute is present or not present in the request context, or its value
> is unavailable, the expression SHALL result in "indeterminate".
>
> o must-be-present
>
> This function SHALL take two arguments. The first argument SHALL be an
> attribute value of type "xs:anyURI" as used in the "AttributeId"  XML
> attribute of an <AttributeDesignator> element. The second argument SHALL
> be an attribute value of type "xs:string" containing the identity of the
> data type as used in the "DataType" XML attribute of the
> <AttributeDesignator> element. This expression SHALL result in "true" if
> the named attribute can be located in the request context, which means
> that an <AttributeDesignator> or <AttributeSelector> element for this
> named attribute will return a bag consisting of at least one element. If
> no value can be found for the attribute in the request context, which
> means that an <AttributeDesignator> or <AttributeSelector> element for
> this named attribute will return an empty bag, this expression SHALL
> result in "indeterminate". If it cannot be determined whether the
> attribute is present or not present in the request context, or its value
> is unavailable, the expression SHALL result in "indeterminate".
>
>
>
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