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Subject: Re: [xacml-comment] 5.31 Element <AttributeSelector>
1. I agree. We should use "context node". So the first sentence should be "The AttributeSelector element's RequestContextPath XML attribute SHALL contain a legal XPath expression. XPath evaluation occurs with respect to a context node that is <xacml-context:Request> element." 2. "... it must also match the attribute's data-type ..." I think 'it' means the value(s) selected by XPath. For example, <Request> <Subject> <Attribute AttributeId="...subject-id" DataType="...XMLSchema#integer"> <AttributeValue>123</AttributeValue> </Attribute> </Subject> ... </Request> <AttributeSelector RequestContextPath="Subject/Attribute[AttributeId = '...subject-id']/AttributeValue"/> should return "123" that must be an integer from the DataType attribute. When "subject-id" matches two attributes, then the both value must be integers. 3. I think that the following XPath returns a boolean type: boolean ("Subject/Attribute[AttributeId='...subject-id']/AttributeValue"). 4. I agree. So the first sentence should be "If the XPath 1.0 expression evaluates to a node-set, then each node may consist of seven kinds of nodes as defined in XPath 1.0 specification." Best Michiharu Kudo IBM Tokyo Research Laboratory, Internet Technology Tel. +81 (46) 215-4642 Fax +81 (46) 273-7428 |---------+----------------------------> | | John Merrells | | | <merrells@jiffyso| | | ftware.com> | | | | | | 2002/11/25 10:54 | | | | |---------+----------------------------> >--------------------------------------------------------------------------------------------------------------| | | | To: xacml-comment <xacml-comment@lists.oasis-open.org> | | cc: | | Subject: [xacml-comment] 5.31 Element <AttributeSelector> | | | | | >--------------------------------------------------------------------------------------------------------------| 1. "The AttributeSelector element's RequestContextPath XML attribute SHALL contain a legal XPath expression over the <xacml-context:Request> element." The phrase 'over the' made me think for a while. This could be made clearer by using the 'context node' term from the XPath specification. XPath evaluation occurs with respect to a context node, the context node for this XPath expression is the <xacml-context:Request> element. 2. "In the case where the XPath expression matches attributes in the request context by AttributeId, it must also match the attribute's data-type with the selector's DataType." Does the 'it' above mean the XPath expression? So, it's saying that if you write an xpath expression to select an attribute from the context, and the expression includes a predicate for matching with an AttributeID, then that expression MUST also include a predicate that matches the selectors data type with the data type of the selected attribute...? 3. "In the case of using XPath 1.0, the value of the XPath expression is either a node-set, string value, numeric value, or boolean value." This may seem a quibble, and it probably is, but even though the XPath specification says that the result of an expression can be a primitive... I do not believe there's any way to form an expression that actually returns one. In my experience all XPath 1.0 expressions return a node-set. (I'd be very interested to be corrected on this point. I just looked in the o'reilly xpath book and it has some examples that are plain literal values like, 2002, or "hello", but if you follow the grammar of the language they're just not valid expressions.) 4. "If the XPath 1.0 expression evaluates to a node-set, then each node may consist of a string, numeric or boolean value, or a child node (i.e. structured node). In this case, each node is logically converted to string data by applying the "string" function defined in the XPath 1.0 specification, resulting in a sequence of string data." This is correct in spirit, but not actually correct. In XPath 1.0 an expression evaluates to a node-set. There are seven kinds of node (root, element, text, attribute, namespace, processing instruction, and comment). The XPath specification describes a way of determining a <b>string-value</b> for each type of node. John ---------------------------------------------------------------- To subscribe or unsubscribe from this elist use the subscription manager: <http://lists.oasis-open.org/ob/adm.pl>
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