Issue #87 CORE ERRATA: resource:xpath needs to be added in B.6, plusfix needed for 4.2.2 example - updated

[Rich Levinson <rich.levinson@oracle.com>]

Note: the previous version of this issue accidentally went to xacml-demo-tech.
 
Note: this issue should be reviewed carefully to make sure we end up with a
consistent picture of how xpath is described in the core spec. It appears that
the changes in section B.6 Resource Attributes from V1.1 to V2.0 were
incomplete. The suggestion in the issue I believe will make the spec self-consistent,
however as the note at the end of part 1 implies, there may have been another
intention, which might be a cleaner way to handle it.

    Thanks,
    Rich

87. CORE ERRATA: resource:xpath needs to be added in B.6, plus fix needed for 4.2.2 example

Part 1: Xacml core V2.0 apparently inadvertently left out resource:xpath in section B.6. (This identifier is used in a number of places in the examples: lines 1172, 1337, 1496, 1658) The following lines (inside the quotes), which are modified from the XACML V1.1 spec (4555-4556) to take into account the ResourceContextPath, should be inserted to the XACML V2.0 spec after line 5046:

"This identifier indicates that the resource is specified by an XPath expression and that the default RequestContextPath for the parent attribute is "//xacml-context:Request/xacml-context:Resource/xacml-context:ResourceContent".

• urn:oasi:names:tc:xacml:1.0:resource:xpath"

It has been deduced from analysis of section B.6 (lines 5041-5045) description of "resource:target-namespace", plus the fact that the "resource:xpath" identifier apparently was inadvertently left out of XACML 2.0, plus examination of the XPaths in the examples that begin with "/md:record" require that the statement about the about the <xacml-context:Request> element being the context node for every XPath expression (Sec A.3.15 lines 4907-4908) be overridden in order to set the ResourceContextPath to the <ResourceContent> element. See analysis in this email: http://lists.oasis-open.org/archives/xacml-dev/200710/msg00005.html

In addition, to understand this situation please refer to lines 1155-1176 of Rule 1:

• <Resources>

  • <Resource>

    • <ResourceMatch MatchId="urn:oasis:names:tc:xacml:1.0:function:string-equal">

      • <AttributeValue DataType="http://www.w3.org/2001/XMLSchema#string">

        • http://www.med.example.com/schemas/record.xsd

        </AttributeValue> <ResourceAttributeDesignator

        • AttributeId="urn:oasis:names:tc:xacml:2.0:resource:target-namespace" DataType="http://www.w3.org/2001/XMLSchema#string"/>

      </ResourceMatch> <ResourceMatch MatchId="urn:oasis:names:tc:xacml:1.0:function:xpath-node-match">

      • <AttributeValue DataType="http://www.w3.org/2001/XMLSchema#string">

        • /md:record

        </AttributeValue> <ResourceAttributeDesignator

        • AttributeId="urn:oasis:names:tc:xacml:1.0:resource:xpath" DataType="http://www.w3.org/2001/XMLSchema#string"/>

      </ResourceMatch>

    </Resource>

  </Resources>

Note: that the 2nd ResourceMatch is a somewhat "odd" construct in that it uses an AttributeDesignator to specify an XPath. Be that as it may, it is clear that the intent of the resource:xpath identifier is implicitly make the <ResourceContent> node the xpath context node, which is consistent with intention of the resource:target-namespace identifier as well, which is used in the first ResourceMatch.

Note: an alternative solution might be to not use the resource:xpath identifier at all and simply modify the description of the resource:target-namespace to say that it implies that the ResourceContent element is the xpath context node. However, it might be too late for that, although we could add both and mark the resource:xpath as deprecated.

Part 2: In addition, on line 1064 there is a typo 4.2.2 Example request that should be fixed:

• "xmlns:(md=:Resource/ResourceContent/xpointer"

should be changed to read:

• "xmlns:(md=http:www.med.example.com/schemas/record.xsd) xpointer"

Note: it had been decided before to fix this: http://lists.oasis-open.org/archives/xacml/200702/msg00001.html and it has been brought up again independently: http://lists.oasis-open.org/archives/xacml-dev/200710/msg00000.html, http://lists.oasis-open.org/archives/xacml-dev/200710/msg00002.html with a preliminary response: http://lists.oasis-open.org/archives/xacml/200710/msg00009.html

Part 3: Finally, some clarifying text about requirements for whether XPointer needs to be supported should be added in section 3.3.1.1 "Rule Target" lines 657-658 where it is explicitly referenced. It shows up in the example on line 1064. i.e. apparently providing XPath capabilities does not implicitly include XPointer, and we should say something about how to include it if desired. Note: in the example it comes in as part of the request. What behavior would be expected if the PDP did not support it?

Status: OPEN

Champions: Rich