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Subject: [xacml] Updated list of Change Requests
I suggest that requests that have received heavy discussion on
the list should be re-submitted in their entirety, incorporating
any corrections and comments.
Title: Change Requests
Author: Anne Anderson
Version: 1.3, 02/09/06 (yy/mm/dd)
Original Source: /net/labeast.east/files2/east/info/projects/isrg/xacml/docs/SCCS/s.ChangeRequests.txt
0001. [Daniel] Add AttributeValue element to support sequence-of values
http://lists.oasis-open.org/archives/xacml/200208/msg00047.html
http://lists.oasis-open.org/archives/xacml/200208/msg00140.html
STATUS: POSTPONED (to discussion of functions #23)
Currently <attributeValue> element is an extension of
anyType, with specified DataType. XACML functions arguments
are, in general, a sequence of typed elements - as it can be
returned by a designator from context. While most accept
only single values (sequence of size 1), some set operation
functions have an arbitrary length sequence as an argument.
We need to provide syntax to express a sequence of values as
a literal argument in set operations (like union, member_of,
intersection..)
I propose adding element Value, of anyType, and defining
<AttributeValueType> as sequence of <Value>, with DataType
attribute, applicable to all elements in the sequence. It
supports 0 size of the sequence, to support empty set in
operations
<xs:element name="Value" type="xs:anyType"/>
<xs:element name="AttributeValue"/>
<xs:complexType name="AttributeValueType">
<xs:sequence minOccurs="0" maxOccurs="unbounded">
<xs:element ref="Value"/>
</xs:sequence>
<xs:attribute name="name" type="xs:anyURI" use="required"/>
</xs:complexType>
-------------------------------------
>2. Adding a separate construct to XACML policy schema to represent
>sequences of attribute values, such that you cannot create sequeences of
>sequences.
As an alternative to my proposal to modify schema element <attributevalue>,
I propose to define standard core function collection
<type>-sequence
of undefined arity, that takes arguments of singleton <type> kind and return
a sequence<type> value, a sequence of its argument values.
In this case, when a literal sequence definition is needed, this funciton
can be used. No schema modification is needed.
The drawback is that it can not be used to specify an argument of
sequence<type> kind for predicate functions that can be used in <Match>
elements.
0002. [Anne] Add mandatory action-id attribute
STATUS: APPROVED 8/29 (QUORUM)
Create a reserved attribute identifier
"urn:oasis:names:tc:xacml:1.0:action:action-id". Make
inclusion of an <Attribute> with AttributeId of this
identifier mandatory under the <Action> element of the
<Request> context. Change minOccurs for <Attribute> under
<Action> 1.
Rationale:
We had previously decided that <Action> would have a single
string value that would be the action id. Now we need a
specific AttributeId for this.
This is consistent with the way resource-id is handled. It
provides a consistent, interoperable way of specifying the
action. The <DataType> of the <Attribute> can specify
whether the action value is a string or URI.
0003. [Anne] Add optional action-namespace attribute
STATUS: APPROVED 8/29 (QUORUM)
Create a reserved attribute identifier
"urn:oasis:names:tc:xacml:1.0:action:action-namespace". Make
inclusion of an <Attribute> with AttributeId of this
identifier optional under the <Action> element of the
<Request> context.
Rationale:
We previously decided that an <Action> value might be
associated with a specific namespace, and that an XML
attribute was needed to express this.
0004. [Anne] Add optional action:implied-action identifier
STATUS: APPROVED 8/29 (QUORUM)
Create a reserved identifier
"urn:oasis:names:tc:xacml:1.0:action:implied-action" to
represent the value of an action that is implied by the
<Resource>
Rationale:
We have agreed to this concept, but have not reserved an
identifier for it.
0005. [Anne] Change <Result> ResourceURI xml attribute to ResourceId
STATUS: APPROVED 8/29 (QUORUM)
Rationale:
Since the Request <Resource> identifier is now called
resource-id, and can be of any data type, the <Result> should
be consistent.
0006. [Anne] Add missing-attribute identifier for StatusCode
STATUS: APPROVED 8/29 (QUORUM)
Rationale:
We have values for ok, processing-error, and syntax-error.
Although we discussed the use case for missing attributes
extensively, we have not defined a standard identifier for this
status.
0007. [Anne] Make context Resource Attribute minoccurs=1
STATUS: REJECTED 9/5 (NO QUORUM, BUT ANNE CONCURS)
Current value is minOccurs=0 maxOccurs=unbounded. Change this
to minOccurs=1 maxOccurs=unbounded.
Rationale:
Since Resource MUST contain a resource-id attribute, minimum
value should be 1.
0008. [Anne] list mandatory vs. non-mandatory functions
http://lists.oasis-open.org/archives/xacml/200208/msg00069.html
STATUS: POSTPONED
Add a list of all functions, with an indicator as to
whether the function is mandatory to implement, to the
Conformance Section.
This list should be updated based on the final resolution
of CR#23.
Rationale:
I forgot to include these when I created the original list.
Text to be inserted:
[complete list of functions in e-mail]
0009. [Daniel] Function naming convention
http://lists.oasis-open.org/archives/xacml/200208/msg00071.html
STATUS: REJECTED 8/29 (QUORUM)
Change function names to blah_blah
Rationale:
Dashes are not always supported.
0010. [Anne] allow more than two arguments to "add"
http://lists.oasis-open.org/archives/xacml/200208/msg00090.html
STATUS: APPROVED 8/29 (QUORUM)
Allow function:integer-add and function:decimal-add to take
more than two arguments.
Rationale:
This saves having to write nested statements for these simple
operations.
0011. [Carlisle] state *Match is matched against AttributeValue
http://lists.oasis-open.org/archives/xacml/200208/msg00094.html
STATUS: APPROVED 8/29 (QUORUM)
In section 5.7 (Element <SubjectMatch>), I think we need to
specify that whatever is returned by
SubjectAttributeDesignator or AttributeSelector is matched
against the value carried in AttributeValue. The same is
true for <ResourceMatch> and <ActionMatch> (sections 5.10 and
5.13).
Rationale:
This behaviour is not spelled out anywhere. (In fact,
AttributeValue is not even described in the "list of elements
contained in <SubjectMatch>" discussion; it only appears in
the schema fragment.)
0012. [Carlisle] <AttributeSelector> in <SubjectMatch> should be [optional]
http://lists.oasis-open.org/archives/xacml/200208/msg00094.html
STATUS: APPROVED 8/29 (QUORUM)
Make <AttributeSelector> in <SubjectMatch> [optional] rather
than [required].
Rationale:
Also, in the "list of elements contained in <SubjectMatch>"
discussion, why is <AttributeSelector> described as
[required]? I thought it was optional.
0013. [Carlisle] <SubjectMatch> in <SubjectAttributeDesignatorWhere> min/max
http://lists.oasis-open.org/archives/xacml/200208/msg00094.html
STATUS: APPROVED 9/5 (NO QUORUM)
Make minOccurs="1" and maxOccurs="unbounded" for
<SubjectMatch> in <SubjectAttributeDesignatorWhere>.
Rationale:
In section 5.26 (Element <SubjectAttributeDesignatorWhere>),
why does the element <SubjectMatch> have minOccurs="0"? If
this element was omitted, you wouldn't use
SubjectAttributeDesignatorWhere; you would just use
SubjectAttributeDesignator. In any case, the verbal
description says that SubjectMatch has [Any Number], so I
suspect that minOccurs="0" in the schema should be changed to
maxOccurs="unbounded".
0014. [Carlisle] 10. "Security and Privacy Considerations"
http://lists.oasis-open.org/archives/xacml/200208/msg00096.html
STATUS: APPROVED 9/5 (NO QUORUM)
Change title of Section 10 to "Security and Privacy
Considerations".
Rationale:
Should this be called "Security and Privacy Considerations"
instead of just "Security and Privacy"?
0015. [Carlisle] 10. "Statement Level Confidentiality": rules/policies
http://lists.oasis-open.org/archives/xacml/200208/msg00096.html
STATUS: NOT YET CONSIDERED
In the 10. "Statement Level Confidentiality" section, 1st
paragraph, say "... a PRP only needs access to the target
elements in order to find the appropriate policies".
Rationale:
Currently says: "... a PRP only needs access to the target
elements in order to find the appropriate rules". Should
this say "rules/policies", or just "policies", instead of
"rules"?
0016. [Carlisle] 10. "Policy Integrity": rule/policy
http://lists.oasis-open.org/archives/xacml/200208/msg00096.html
STATUS: NOT YET CONSIDERED
In the 10. "Policy Integrity" section, 4th paragraph, say
"The PDP SHOULD NOT request a policy based on who signed the
policy...".
Rationale:
In the "Policy Integrity" section, 4th paragraph, it
currently says "The PDP SHOULD NOT request a rule based on
who signed the rule...". Should both occurrences of "rule"
be "policy"?
0017. [Carlisle] 10. "Resource Matching": NotApplicable treated as Permit
http://lists.oasis-open.org/archives/xacml/200208/msg00096.html
STATUS: NOT YET CONSIDERED
In 10. "Resource Matching" section, say, 'although the
policy result of "Not Applicable" is treated as equivalent
to "Permit" by many web servers, this behavior is not
recommended.'
Rationale:
In the "Resource Matching" section, 1st paragraph, it says
"... the policy result of "Not Applicable" is treated as
equivalent to "Permit" as is common in many web servers".
I'm a bit surprised that this is true (although I probably
shouldn't be!). In any case, we probably don't want to
encourage this behaviour. Should we simply not mention
this, or should we at least say that this behaviour is not
recommended?
Hal's rejoinder:
First of all, this is intended as a cautionary
example. However, this is a real world problem that affects
my product, and all of our compeitors. I can show you
security holes posted to BUGTRAQ, for example, where this
occurred. We have struggled with it for years. The Not
Applicable == Permit behavior is not only standard for web
servers, it is embedded in the Java Servlet and JSP
specifications.
The logic is that only a small portion of the resources on
a public web server are protected, so people want to only
specify rules for those that are. If the namespace is not
conveniencely laid out (as most are not) it may require a
number of rules just to specify all the pages that are not
protected.
0018. [Carlisle] C.3 use "First Applicable"
http://lists.oasis-open.org/archives/xacml/200208/msg00099.html
STATUS: NOT YET CONSIDERED
Call Section C.3, "First Applicable" rather than "First
Applicable Rule Combining Algorithm".
In first sentence of C.3, change "First Determinate"
rule-combining algorithm to "First Applicable".
Rationale:
Section C.3, should this be called "First Applicable"
rather than "First Applicable Rule Combining Algorithm"?
This would be more consistent with both C.1 and C.2, and
would also be more consistent with the fact that C.3
contains both a rule combining algorithm and a policy
combining algorithm.
The first sentence of C.3 calls it the "First Determinate"
rule-combining algorithm; this should be changed to "First
Applicable".
0019. [Carlisle] C. consistent error behavior
http://lists.oasis-open.org/archives/xacml/200208/msg00099.html
STATUS: NOT YET CONSIDERED
Policy combiner should halt and return Indeterminate when
an error is encountered.
Rationale:
The behaviour specified in the policy-combining algorithm
when an error is encountered is different from the
behaviour specified in the rule-combining algorithm when an
error is encountered (the rule combiner says halt and
return Indeterminate, whereas the policy combiner says to
keep looking for an applicable policy). Is this what we
wanted?
More importantly, might the policy combiner behaviour not
lead to different answers for the same inputs? For
example, say there are two policies that are to be combined
using this algorithm. Given a particular set of input
values, the first policy would return a decision of
"Permit" and the second policy would return a decision of
"Deny". Now we give all the inputs to two different PDPs.
The first PDP retrieves the first policy, gets an answer of
"Permit", and returns this to the PEP. The second PDP has
trouble retrieving the first policy for whatever reason
and, according to the combining algorithm, retrieves the
second policy; it then returns a "Deny" to the PEP. Isn't
this the sort of result we want to avoid? Wouldn't the
behaviour specified in the rule combining algorithm be
preferable (that way, the first PDP would return "Permit"
and the second would return "Indeterminate", which seems
fine to me)?
0020. [Michiharu] B.10: Resource Attributes scope value
http://lists.oasis-open.org/archives/xacml/200208/msg00112.html
STATUS: NOT YET CONSIDERED
In B.10, the identifier indicates the scope of the request
with regard to the resource. When this attribute is
specified in the request, the value MUST be either
'Immediate', 'Children', or 'Descendant'.
0021. [Michiharu] 8.1 Operational Model: PDP description change
http://lists.oasis-open.org/archives/xacml/200208/msg00112.html
STATUS: NOT YET CONSIDERED
8.1 Policy Decision Point (PDP)
Given a valid XACML "Policy" or a "PolicySet", a compliant XACML PDP MUST
evaluate that statement in accordance to the semantics specified in Section
4,5, and 6 when applied to a specific input context. The PDP MUST return an
output context, with one value of "Permit", "Deny", "Indeterminate", or
"NotApplicable".
If a permit is returned, the PEP permit access to the requested resource.
If a denial is returned, the PEP denies access to the requested resource.
If a permit with one or more obligations is returned, the PEP permits
access provided that every obligations are fulfilled successfully. If a
denial with one or more obligations is returned, the PEP denies access but
still fulfills the obligations. In each case, when fulfilling obligations
failed, the PEP SHOULD raise an error. How the error is raised is out of
the scope of XACML. In any case, the PDP can return additional information
in the status code element in the response context. For 'Permit' decision,
it MAY specify which rules are used in decision making.
If an indeterminate is returned, it means that the PDP could not make
decision due to some reason. The PDP MAY return decision of "indeterminate"
with a status code of "urn:oasis:names:tc:xacml:1.0:missing-attribute",
signifying that more information is needed. In this case, the decision MAY
list the names of any attributes of the subject and the resource that are
needed by the PDP to refine its decision. A PEP MAY resubmit a refined
request context in response to a decision of "indeterminate" with a status
code of "missing-attribute" by adding attribute values for the attribute
names that are listed in the response. When the PDP returns an decision of
"indeterminate", with a status code of "missing-attribute", a PDP MUST NOT
list the names of any attribute of the subject or the resource of the
request for which values were already supplied in the request. Note, this
requirement forces the PDP to eventually return a decision of "permit",
"deny", or "indeterminate" with some other reason, in response to
successively-refined requests.
If not applicable is returned, it means that the PDP's policy does not
cover the request, implying that the PEP should ask another PDP.
XACML does not assume how top-level XACML policies should be configured.
For example, a top-level policy might be a 'Policy' element containing a
target element that matches every request, or it might be a 'Policy'
element containing a target element that matches only a specific subject.
0022. [Michiharu] 8.1 Operational Model: New sections
http://lists.oasis-open.org/archives/xacml/200208/msg00112.html
STATUS: NOT YET CONSIDERED
8.2 Hierarchical Resource
It is often the case that a target resource is organized as a hierarchy
(e.g. file system, XML document). Some applications may require access to
an entire subtree of the resource. XACML allows the PEP (or Context
Handler) to specify whether the access is just for a single resource or for
a subtree below the specified resource. The latter is equivalent to
repeating a single request for the entire subtree. When a request context
contains a resource attribute of
'urn:oasis:names:tc:xacml:1.0:resource:scope' with a value of 'Immediate',
or does not contain that attribute in the context, then it means that the
access is just for a single resource specified by 'ResourceId' attribute.
When 'urn:oasis:names:tc:xacml:1.0:resource:scope' attribute specifies a
value of 'Children', it means that the access is for both a specified
resource and its children resources. When
'urn:oasis:names:tc:xacml:1.0:resource:scope' attribute specifies a value
of 'Descendant', it means that the access is for both a specified resource
and all the descendant resources. In the case of 'Children' and
'Descendant', the access decision may include multiple results for the
multiple resources. XACML response can contain multiple result elements. In
such case, the status element SHOULD be included only in the first result
element (the remaining result elements SHOULD NOT include the status
element). Note that the method how PDP finds out whether the resource is
hierarchically organized or not is out of the scope of the XACML.
8.3 Propagation through Data Hierarchy
When the resource is hierarchically organized, it is often the case that an
access control rule associated to a certain node propagates down to the
descendant nodes. The XACML core rule combining algorithm does not support
such propagation with regard to access control rules. Policy writers who
need propagation MUST implement their own local algorithm and specify that
algorithm ID in RuleCombiningAlgId in policy element.
0023. [Daniel, Polar] function names, types, semantics
http://lists.oasis-open.org/archives/xacml/200208/msg00181.html
STATUS: NOT YET CONSIDERED
Daniel and Polar have developed a list of functions and
their semantics, attached to the above
e-mail. (XACML_functions0.8.DOC)
CR#8 should be updated based on the final list of functions
to show which are mandatory-to-implement.
0024. [Anne] Make "gregorian" functions non-mandatory
http://lists.oasis-open.org/archives/xacml/200208/msg00137.html
STATUS: NOT YET CONSIDERED
Text Changes:
Section 11.1.4(?) [Conformance] Functions
Remove "M" from left column of
urn:oasis:names:tc:xacml:1.0:function:gregorian-equal
Rationale:
We already support xs:date, so support for Gregorian is icing
on the cake. Also, I haven't found a standard for "gregorian",
so it is hard to develop tests for it.
0025. [Anne] remove NOTATION from supported types; remove assoc. functions
http://lists.oasis-open.org/archives/xacml/200208/msg00138.html
STATUS: NOT YET CONSIDERED
Text Changes:
Section 11. Conformance, DataTypes, remove:
line listing "xs:NOTATION"
Appendix A.1. Functions, remove:
function:NOTATION-equal
function:NOTATION-not-equal
Rationale:
XML Schema says
"It is an error for NOTATION to be used directly
in a schema. Only datatypes that are derived from NOTATION by
specifying a value for enumeration can be used in a schema.
For compatibility NOTATION should be used only on attributes."
Also, QName-equal and QName-not-equal can be used to compare
such data types if necessary.
I'm on thin ground here, since I don't know enough about XML
Schema to be sure I am interpreting the impact of this
correctly.
0026. [Michiharu] Add XPath functions as non-mandatory
http://lists.oasis-open.org/archives/xacml/200208/msg00142.html
STATUS: NOT YET CONSIDERED
[See referenced e-mail for function definitions]
I propose to include the following functions (all relevant to XPath) in the
spec as non-mandatory to implement functions. The original proposal (a
little different from this proposal) was posted on 29th July and it
described more in detail.
http://lists.oasis-open.org/archives/xacml/200207/msg00162.html
function:general-string-equal xs:boolean object(*1) object A
= B
function:node-boolean xs:boolean object
function:node-match xs:boolean object object
========================
(*1) "object" type is defined in Introduction section of [2] as:
"... object, which has one of the following four basic types:
node-set (an unordered collection of nodes without duplicates)
boolean (true or false)
number (a floating-point number)
string (a sequence of UCS characters)"
[1] XQuery 1.0 and XPath 2.0 Data Model,
http://www.w3.org/TR/xquery-operators/
[2] XPath 1.0, http://www.w3.org/TR/xpath
0027. [Michiharu] Change resource-uri to resource-id
http://lists.oasis-open.org/archives/xacml/200208/msg00143.html (A1)
STATUS: NOT YET CONSIDERED
urn:oasis:names:tc:xacml:1.0:resource:resource-uri
==>
urn:oasis:names:tc:xacml:1.0:resource:resource-id
0028. [Michiharu] Add identifier for resource:syntax
http://lists.oasis-open.org/archives/xacml/200208/msg00143.html (B1)
STATUS: NOT YET CONSIDERED
urn:oasis:names:tc:xacml:1.0:resource:syntax
This identifier indicates the syntax of the resource-id
(urn:oasis:names:tc:xacml:1.0:resource:resource-id). The valid values are
either 'String', 'URI' or 'XPointer'. If this attribute is omitted,
'String' syntax is assumed. 'URI' indicates that the syntax of the
resource-id is URI format. 'XPointer' indicates that the syntax of the
resource-id is XPointer format proposed in
http://www.w3.org/TR/2001/CR-xptr-20010911/.
0029. [Michiharu] Add identifier for resource:scope
http://lists.oasis-open.org/archives/xacml/200208/msg00143.html (B2)
STATUS: NOT YET CONSIDERED
urn:oasis:names:tc:xacml:1.0:resource:scope
This identifier indicates the scope of the resource. The valid values are
either 'Immediate', 'Children', or 'Descendant'. When 'Immediate', it
indicates that the scope of the resource is a target value specified by
urn:oasis:names:tc:xacml:1.0:resource:resource-id attribute. When
'Children', it indicates that the scope of the resource is a target value
specified by urn:oasis:names:tc:xacml:1.0:resource:resource-id attribute
and its children resource. When 'Descendant', it indicates that the scope
of the resource is a target value specified by
urn:oasis:names:tc:xacml:1.0:resource:resource-id attribute and all the
descendant resources.
0030. [Michiharu] Add identifier for resource:target-namespace
http://lists.oasis-open.org/archives/xacml/200208/msg00143.html (B3)
STATUS: NOT YET CONSIDERED
urn:oasis:names:tc:xacml:1.0:resource:target-namespace
This identifier indicates the target-namespace of the requested XML
document, that is a namespace URI associated with the root element of the
XML document.
0031. [Michiharu] Schema change of Defaults element
http://lists.oasis-open.org/archives/xacml/200208/msg00144.html
STATUS: NOT YET CONSIDERED
I propose to change the XPathVersion element and to add a new
"XPathNamespace" element as follows:
(1) Schema change request
<xs:element name="XPathVersion" type="xs:string" substitutionGroup
="xacml:AbstractDefaults"/>
==>
<xs:element name="XPathVersion" type="xs:anyURI" substitutionGroup
="xacml:AbstractDefaults"/>
(2) Schema addition request
See #0032 for change to XPathNamespace schema.
(3) Text change request
In Section 5.3, Element <PolicySetDefaults>, line 1487-1489,
<AbstractDefaults>[Any Number]
This is the head of substitution group to specify default parameters. The
elements in this substitution group defined at this time are <XPathVersion>
element and <XPathNamespace> element.
0032. [Michiharu] Schema change of AttributeSelector
http://lists.oasis-open.org/archives/xacml/200208/msg00145.html
http://lists.oasis-open.org/archives/xacml/200208/msg00146.html (example)
http://lists.oasis-open.org/archives/xacml/200208/msg00149.html (correction)
http://lists.oasis-open.org/archives/xacml/200208/msg00150.html (Simon)
STATUS: NOT YET CONSIDERED. NOTE: we need a current
statement of the complete proposal, taking into account
comments and corrections to date.
I propose to change the AttributeSelector element. The reason of this
change is described in a separate mail titled "[xacml] AttributeSelector
example".
<xs:complexType name="AttributeSelectorType">
<xs:attribute name="RequestContextPath" type="xs:anyURI" use="required"/>
<xs:attribute name="DataType" type="xs:anyURI" use="required"/>
<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:element ref="xacml:XPathNamespace" minOccurs="0" maxOccurs
="unbounded"/>
<xs:choice>
<xs:attribute name="RequestContextPath" type="xs:anyURI" use
="optional"/>
<xs:attribute name="RequestContextId" type="xs:string" use="optional"/>
</xs:choice>
<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: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>
Scope of the XPathNamespace for AttributeSelector element:
1. AttributeSelector element that includes XPathNamespace element,
XPathNamespace elements in PolicyDefaults or PolicySetDefaults elements
that include the AttributeSelector element.
For the precedence,
1. XPathNamespace elements in AttributeSelector take precedence over
XPathNamespace elements in PolicyDefaults in Policy element..
2. XPathNamespace elements in PolicyDefaults in Policy take precedence over
XPathNamespace elements in PolicySetDefaults in PolicySet element..
3. If there are two or more identical prefixes are specified under an
AttributeSelector, a PolicyDefaults or a PolicySetDefaults elements, the
last prefix takes precedence over the previous prefixes.
Others:
1. Global xmlns attribute is not used for resolving namespace-prefix pair
specified in XPath expression.
2. If no XPathNamespace element is found in valid scope, it means no
namespace-prefix pair is defined.
3. If Prefix attribute is missing, it means that default namespace is
defined.
0033. [Michiharu] Example two to separate document
http://lists.oasis-open.org/archives/xacml/200208/msg00147.html
STATUS: NOT YET CONSIDERED.
After looking at line 589-1102, I think that Section 3.2
policy specification in Example two is too complicated for
average readers. While my preference is to hold this example
in the spec, most readers would feel that XACML is difficult
to read and understand when they try to go through this
example. Besides, this example requires expertise about XPath
syntax and its data model that is basically different from
this specification. Honestly speaking, it is a little
difficult even for me... :-). So my suggestion is to move
this section to a separate document (say Primer document or
Use Case document).
0034. [Polar] Target Match Semantics Section 4 & 5
http://lists.oasis-open.org/archives/xacml/200208/msg00188.html
[long set of specific text changes included in e-mail]
http://lists.oasis-open.org/archives/xacml/200208/msg00189.html (correction)
STATUS: NOT YET CONSIDERED.
The semantics for the Target need to be updated. It doesn't seem to
describe how "Match" or "No-Match" are derived at. The document mentions
logical-AND and logical-OR, and they are not defined for Match and
No-Match. Also, we need to resolve the discovery and issue of the
inconsistency between the evaluation of Target and Condition with respect
to Indeterminate and NotApplicable, now that we are making progress on the
"functions" document.
I feel that if we refer to the Target evaluations with the same semantics
as Condition, we can leverage the use of True, False, and Indeterminate
that we have already defined, and then we can use the notions of
conjunctive sequence and disjunctive sequence as combinators of our
boolean values (true, false, indeterminate) with the normative
specifications of our functions "function:and" and "function:or" for the
combining rules. This will take care of the normative handling of error
conditions in the evaluation logic.
When the XACML Data Types, Functions, and Semantics gets put in the
document, I suggest making the following changes. Some changes are
editorial.
Note: There is some issue about <Target> and <Condition> of where they say
that they possible to be "empty", but I'm not sure if that means "omitted"
(i.e. minOccurs="0"), or <Target/>, or <Condition/>.
0035. [Michiharu] AttributeSelectorIndirect
http://lists.oasis-open.org/archives/xacml/200208/msg00190.html
http://lists.oasis-open.org/archives/xacml/200208/msg00201.html (followup)
http://lists.oasis-open.org/archives/xacml/200209/msg00016.html (more)
http://lists.oasis-open.org/archives/xacml/200209/msg00024.html (Polar)
http://lists.oasis-open.org/archives/xacml/200209/msg00030.html (Michiharu)
http://lists.oasis-open.org/archives/xacml/200209/msg00031.html (Polar)
http://lists.oasis-open.org/archives/xacml/200209/msg00035.html (Daniel)
http://lists.oasis-open.org/archives/xacml/200209/msg00036.html (Daniel)
http://lists.oasis-open.org/archives/xacml/200209/msg00040.html (Polar)
http://lists.oasis-open.org/archives/xacml/200209/msg00042.html (Daniel)
STATUS: NOT YET CONSIDERED. NOTE: we need a restatement of
the current complete proposal, taking into account comments
and corrections to date.
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
0036. [Michiharu] DataType attribute required?
http://lists.oasis-open.org/archives/xacml/200208/msg00192.html
STATUS: NOT YET CONSIDERED.
DataType attribute in AttributeDesignatorType is 'required'. But in most
cases, AttributeDesignator is used below the matching function (e.g.
string-match) and that function is type-specific. So I think "DataType"
attribute is not required. I propose to change it to "optional".
<xs:complexType name="AttributeDesignatorType">
<xs:attribute name="AttributeId" type="xs:anyURI" use="required"/>
<xs:attribute name="DataType" type="xs:anyURI" use="required"/>
<xs:attribute name="Issuer" type="xs:anyURI" use="optional"/>
</xs:complexType>
[should be]
<xs:complexType name="AttributeDesignatorType">
<xs:attribute name="AttributeId" type="xs:anyURI" use="required"/>
<xs:attribute name="DataType" type="xs:anyURI" use="optional"/>
<xs:attribute name="Issuer" type="xs:anyURI" use="optional"/>
</xs:complexType>
[Polar] Taking this approach to the extreme, means you really
need a typechecking compiler that not only "checks" the type
correctness of the policy, but to WILL HAVE TO "infer" the
types of the elements, which is a little bit of a harder
problem. However, in this simple type system (i.e. no
recursive, abstract types), it's not much harder.
So, if you go that far, you might as well eliminate DataType attribute
altogether from the schema, as it doesn't buy you anything but possible
confusion.
As as Michiharu says "In most cases...". However, I would say "In all
cases...." since we can see every expression only appears in a Target or
Condition. The top level expressions in a Target or a Condition in XACML
must result in xs:boolean, and as Michiharu states, the types of all
elements in the expression can be "inferred" from the functions applied to
them.
I would propose to remove the DataType attribute, in this case.
[Daniel] That is correct.
When we started discussion about functions, at least my
personal idea was that if you specify data type within
arguments - you can overload function names (so when you see
add(integer, integer) you know which add to use). But then
we decided to have argument type embedded into function
names, so now we have all string-sequence and
decimal-member-of. Type of the argument is indeed redundant
now - as the external source is not aware of XACML types and
PDP gets everything encoded as strings anyway..
But this will work as long as we do not allow any type
conversions ever. If we decide to specify that any functions
taking a decimal (numeric) can also take an integer, and
promote it to decimal, you may get yourself an ambiguous
situation with extensions.
If I remember correctly - that was exactly the reason - at
some point we have proposed implicit promotion between
numeric datatypes..
I think no much harm is done by having DataType embedded.
Simplifies some things.. May be more useful in the future..
[Polar] Such is the thingy with "optional" attributes. If we
don't need them now, why have them. You can always "add" an
optional attribute to the schema later, unless there is some
non-standard use for it. Otherwise if it exists, it just
holds redundant information.
[Daniel] ..which raises another issue.
Do we want to allow the same named attribute to be declared
of different types in different rules.
So that "AccountNumber" is used as integer in one rule, and
as <date> in another..
Having "DataType" specified, we may specify that within one
PolicySet, same AttributeId should be associated with one and
only one data type..
[Polar] Still, you can infer the type information from the
functions applied in the expression it appears in.
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