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Subject: RE: [xacml] New issue: new attribute ids for xml multiple decisions
See comments inline. > -----Original Message----- > From: Jan Herrmann [mailto:herrmanj@in.tum.de] > Sent: Friday, November 20, 2009 03:01 > To: Tyson, Paul H > Cc: 'XACML TC' > Subject: AW: [xacml] New issue: new attribute ids for xml > multiple decisions > > Hi Paul, > > I like your proposal but I am wondering why you are not using > the resource-id attribute directly instead of adding the new > authorized-resource-id attribute. Let me explain: > > According to your proposal a multiple decision request and > one of derived decision requests will look like this: > > multiple decision request: > - resource-selector = xpath that selects a set of nodes > - scope = "XPath-expression" > - resource-id = empty? or not present? > What is the value of resource-id in a multiple decision request? The meaning and use of XACML "resource-id" is not well specified except in a few cases. I'm not sure it is necessary to specify the use of resource-id in this case. In practice, the only reasonable interpretation of resource-id in this context is as a primary identifier for the compound resource represented by the XML content. > > derived individual decision request: > authorized-resource-id = xpath to exactly one node (in the > set as specified by resource-selector and the scope value). > - resource-id ?? The individual decision requests would include the original resource-id, if present. > > It seems to me that we could also say that in a multiple > decision request the value of the resource-id attribute must > be empty (or even not present what seems to be allowed > following the schema for <Request>). Further we could say > that in the derived individual request the resource-id will > have a value equal to one of the individual resource (as > specified by resource-selector and the scope value). Thus > resource-id in the individual decision request will equal to > what your proposed authorized-resource-id will do. But that would prevent the use of resource-id that I suggested above: as an identifier of the resource represented by the XML content. For example, I might represent some product structure as an XML document. The product structure is an assembly, consisting of sub-assemblies and detail parts. The "resource-id" might be the part number of the top assembly. I want decisions about all the detail parts in the assembly. These would be the "authorized-resource-id" values in the individual decision requests. The top "resource-id" might participate in the policy evaluation, so it must be available in each individual request context. > > This solution will fulfil the problem 2 you pointed out (i.e. > overloaded resource-id meaning) and in case we exclude the > resource-id value in the multiple decision request than issue > 1 will also be addressed. > The advantage, reuse the existing resource-id attribute > instead of introducing a very similar new > authorized-resource-id. BTW why did you put authorized in the name? I'm not completely satisfied with the attribute name. We need something that means "identifier of the individual resource node about which the authorization decision was given". It is a sort of resource-id, so the name should include "resource-id". But none of the choices convey the meaning very well: "decision-node-resource-id", "individual-resource-id", etc. > > > Best regards > Jan > > > > -----Ursprüngliche Nachricht----- > > Von: Tyson, Paul H [mailto:PTyson@bellhelicopter.textron.com] > > Gesendet: Donnerstag, 19. November 2009 23:10 > > An: XACML TC > > Betreff: [xacml] New issue: new attribute ids for xml multiple > > decisions > > > > The cd-1 Multiple profile, lines 109-111, specifies that the > > resource-id attribute in a multiple decision request shall > be replaced > > with a > > (possibly) different value when creating individual > requests. The new > > value is the one that would be returned (if > IncludeInResult=true) in > > the result. > > > > There are a couple of problems with this. First, it breaks an > > implicit contract that prohibits the context handler from changing > > attribute values (it can provide more values, but should > never change > > or remove values from the original request context). Second, it > > overloads resource-id with a new meaning that is different from its > > initial purpose as a primary identifier of a resource. > When used in a > > multiple decision request for XML content, resource-id now means > > something like "resource selector" in the Request, but > reverts to its > > former meaning as "primary identifier" in the Response. > > > > I propose that the resource-id attribute should only be used as a > > persistent primary identifier for a singleton resource, and > that two > > new attributes be defined: one for requesting decisions on multiple > > nodes of XML content, and another for identifying those nodes in a > > XACML response. The proposed AttributeIds are: > > > > urn:oasis:names:tc:xacml:3.0:profile:multiple:xml:resource-selector > > > urn:oasis:names:tc:xacml:3.0:profile:multiple:xml:authorized-resource- > > id > > > > Sections 2.2.2 and 2.2.3 of the Multiple profile should be > rewritten > > as > > follows: > > > > ===================== > > 2.2.2 Original request context > > > > The original XACML request context <Attributes> element in the > > resource category SHALL contain a <Content> element and an > attribute > > with and AttributeId of > > > "urn:oasis:names:tc:xacml:3.0:profile:multiple:resource-selector" and > > a DataType of > > "urn:oasis:names:tc:xacml:3.0:data-type:xpathExpression", > > such that the <AttributeValue> of the "resource-selector" > attribute is > > an XPath expression that evaluates to a nodeset that represents > > multiple nodes in the resource category <Content> element. The > > <Attributes> element with the resource category SHALL contain a > > "scope" attribute with a value of "XPath-expression". > > > > 2.2.3 Semantics > > > > Such a request context SHALL be interpreted as a request for > > authorization decisions on multiple nodes in the nodeset > represented > > by the <AttributeValue> of the "resource-selector" attribute. Each > > such node SHALL represent an Individual Resource. > > > > Each Individual Decision Request SHALL be identical to the original > > request context with two exceptions: the "scope" attribute > SHALL NOT > > be present and an additional attribute with AttributeId of > > > "urn:oasis:names:tc:xacml:3.0:profile:multiple:authorized-resource-id" > > SHALL be present. The DataType of this attribute shall be > > "urn:oasis:names:tc:xacml:3.0:data-type:xpathExpression", and the > > value SHALL be an XPath expression that evaluates to a > single node in > > the <Content> element. The IncludeInResult XML attribute > SHALL be "true". > > The content XML node selected by this Attribute SHALL be the > > Individual Resource. If the "resource-selector" attribute in the > > original request context contained an Issuer, the > > "authorized-resource-id" attribute in the Individual > Resource Request SHALL contain the same Issuer. > > ============================== > > > > See these emails for previous comments on this issue: > > > > http://lists.oasis-open.org/archives/xacml/200910/msg00036.html > > http://lists.oasis-open.org/archives/xacml/200910/msg00052.html > > http://lists.oasis-open.org/archives/xacml/200911/msg00025.html > > > > Regards, > > --Paul > > > > > --------------------------------------------------------------------- > > To unsubscribe from this mail list, you must leave the > OASIS TC that > > generates this mail. Follow this link to all your TCs in OASIS at: > > > https://www.oasis-open.org/apps/org/workgroup/portal/my_workgroups.php > >
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