· eXtensible Access Control Markup Language (XACML) Version 3.0. 22 January 2013. OASIS Standard. http://docs.oasis-open.org/xacml/3.0/xacml-3.0-core-spec-os-en.html.

Abstract:

This specification defines a profile for the use of XACML in a RESTful architecture.

Status:

This document was last revised or approved by the OASIS eXtensible Access Control Markup Language (XACML) TC on the above date. The level of approval is also listed above. Check the “Latest version” location noted above for possible later revisions of this document.

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Citation format:

When referencing this specification the following citation format should be used:

[XACML-REST-v1.0]

REST Profile of XACML v3.0 Version 1.0. 07 February 2013. OASIS Committee Specification Draft 02. http://docs.oasis-open.org/xacml/xacml-rest/v1.0/csd02/xacml-rest-v1.0-csd02.html.

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Table of Contents

1 Introduction. 5

1.1 Terminology. 5

1.2 Glossary. 5

1.3 Normative References. 5

1.4 Non-Normative References. 6

1.5 Rationale. 7

1.5.1 Externalization of Access Control 7

1.5.2 Cloud Computing. 7

1.5.3 REST. 7

1.5.4 RESTful Authorization as a Service. 8

1.6 Use Cases. 8

1.6.1 PEP ↔ PDP. 8

2 RESTful Services. 9

2.1 Network Transport 9

2.2 Resources. 9

2.2.1 Entry Point 9

2.2.2 Policy Decision Point 9

2.3 Representations. 10

2.3.1 Linking. 10

2.3.2 Entry Point 11

2.3.3 XACML versions, Representation Formats, and Content Negotiation. 11

2.4 Examples. 11

2.4.1 Obtain an Access Decision. 11

3 Security Considerations. 12

3.1 Network Transport 12

3.2 Authentication. 12

3.3 Authorization. 12

3.4 Non-Repudiation. 12

4 Conformance. 13

4.1 Conformance Clauses. 13

4.2 Test Assertions. 13

4.2.1 Network Transport 13

4.2.2 Entry Point 13

4.2.3 Policy Decision Point 14

Appendix A. Acknowledgments. 16

Appendix B. Revision History. 17

1 Introduction

{Non-normative}

This specification defines a profile for the use of the OASIS eXtensible Access Control Markup Language (XACML), versions 3.0 [XACMLv3] and earlier. Use of this profile requires no changes or extensions to the XACML standard.

This specification begins with a non-normative discussion of the topics and terms of interest in this profile. The normative section of the specification describes the details of web services that conforming implementations must support.

This specification assumes the reader is somewhat familiar with XACML. A brief overview of XACML is available in [XACMLIntro].

1.1 Terminology

The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “MAY”, and “OPTIONAL” in this document are to be interpreted as described in [RFC2119].

1.2 Glossary

Client

The agent that initiates requests to a server.

Representation

A sequence of bytes, in a given format, that represents a resource in some way.

Request

The HTTP request message sent from the client to the server [HTTP]. Note that this is not the same concept as a XACML request [XACMLv3].

Resource

A service that is offered by the server [REST]. This can be static, like a document, or dynamic, like a search. Note that this is not the same concept as a XACML resource [XACMLv3].

Response

The HTTP response message returned from the server to the client [HTTP]. Note that this is not the same concept as a XACML response [XACMLv3].

Server

The agent that handles requests from a client.

1.3 Normative References

[Atom] The Atom Syndication Format. December 2005. IETF RFC 4287. http://tools.ietf.org/html/rfc4287

[HTTP] Hypertext Transfer Protocol. June 1999. IETF RFC 2616. http://tools.ietf.org/html/rfc2616

[RFC2119] Key words for use in RFCs to Indicate Requirement Levels. March 1997. IETF RFC 2119. http://tools.ietf.org/html/rfc2119

[TAG] Test Assertions Part 1 - Test Assertions Model Version 1.0. 30 November 2011. OASIS Committee Specification 02. http://docs.oasis-open.org/tag/model/v1.0/cs02/testassertionsmodel-1.0-cs02.pdf

[URI] Uniform Resource Identifier (URI): Generic Syntax. January 2005. IETF RFC 3986. http://tools.ietf.org/html/rfc3986

[WebLink] Web Linking. October 2010. IETF RFC 4287. http://tools.ietf.org/html/rfc5988

[XACMLMedia] eXtensible Access Control Markup Language (XACML) Media Type. 14 September 2012. IETF Draft 00. http://tools.ietf.org/html/draft-sinnema-xacml-media-type-00

[XACMLv3] eXtensible Access Control Markup Language (XACML) Version 3.0. 8 August 2012. OASIS Committee Specification 02. http://docs.oasis-open.org/xacml/3.0/xacml-3.0-core-spec-cs02-en.pdf

1.4 Non-Normative References

[Admin] XACML v3.0 Administration and Delegation Profile Version 1.0. 10 August 2010. OASIS Committee Specification 01. http://docs.oasis-open.org/xacml/3.0/xacml-3.0-administration-v1-spec-en.pdf

[Cloud] The NIST Definition of Cloud Computing. September 2011. National Institute of Standards and Technology. http://csrc.nist.gov/publications/nistpubs/800-145/SP800-145.pdf

[HomeDocument] Home Documents for HTTP APIs. May 2012. Internet-Draft. http://tools.ietf.org/html/draft-nottingham-json-home-00

[HTTPAuthN] HTTP Authentication: Basic and Digest Access Authentication. June 1999. IETF RFC 2617. http://tools.ietf.org/html/rfc2617

[HTTPS] HTTP over TLS. May 2000. IETF RFC 2818. http://tools.ietf.org/html/rfc2818

[Media] MIME Media Types. http://www.iana.org/assignments/media-types/index.html

[OpenID] OpenID Authentication 2.0. 5 December 2007. http://openid.net/specs/openid-authentication-2_0.html

[REST] Roy Fielding, Architectural Styles and the Design of Network-based Software Architectures. 2000. http://www.ics.uci.edu/~fielding/pubs/dissertation/fielding_dissertation.pdf

[SAMLv2] Security Assertion Markup Language (SAML) Version 2.0. 15 March 2005. OASIS Standard. http://docs.oasis-open.org/security/saml/v2.0/saml-core-2.0-os.pdf

[SAML4XACML] SAML 2.0 Profile of XACML, Version 2.0. 10 August 2010. OASIS Committee Specification 01. http://docs.oasis-open.org/xacml/3.0/xacml-profile-saml2.0-v2-spec-cs-01-en.pdf

[SASL] Simple Authentication and Security Layer (SASL). June 2006. IETF RFC 4422. http://tools.ietf.org/html/rfc4422

[SecaaS] Security as a Service: Defined Categories of Service, October 10 2011. https://cloudsecurityalliance.org/wp-content/uploads/2011/09/SecaaS_V1_0.pdf

[XACMLIntro] A Brief Introduction to XACML. 14 March 2003, http://www.oasis-open.org/committees/download.php/2713/Brief_Introduction_to_XACML.html

1.5 Rationale

1.5.1 Externalization of Access Control

XACML [XACMLIntro] can be used for controlling access within a single application. This removes hard-coded security constraints from the application code, making it easier to change them. It also makes it possible to use a standard Policy Decision Point (PDP), so that organizations can make a proper make-or-buy decision. For virtually all organizations, authorization is not their core business, so being able to use an off-the-shelf product is appealing.

Although these are substantial benefits, XACML really shines when authorization is completely externalized from the application. Policies can then be reused across many applications, each using the same PDP. This leads to greater consistency of access control rules and improved efficiency in maintaining them.

1.5.2 Cloud Computing

Once access control policies are externalized from the application, the PDP can become a service to be shared in a cloud computing scenario.

The National Institute of Standards and Technology (NIST) defines cloud computing as “a model for enabling ubiquitous, convenient, on-demand network access to a shared pool of configurable computing resources (e.g., networks, servers, storage, applications, and services) that can be rapidly provisioned and released with minimal management effort or service provider interaction.“ [Cloud].

Applying the ideas of cloud computing to access control leads to Authorization as a Service (AZaaS). The Cloud Security Alliance sees this as part of the Identity and Access Management category of service that they distinguish in the Security as a Service field [SecaaS]. Note that AZaaS requires a much heavier load on servers than Authentication as a Service, since authentication happens only once for a user session, while authorization must occur on every user action.

1.5.3 REST

In cloud computing, services are shared and must therefore be accessed over a computer network. Cloud infrastructure will thus by definition have a network-addressable API. Such an API can be built on RESTful principles.

REpresentational State Transfer (REST) is a system of architectural constraints that govern the interaction between a client and a server [REST]. In cloud computing, the client is the cloud service consumer, and the server is the cloud service itself. The constraints that REST adds to a client-server system are:

Statelessness: Each request from client to server must contain all of the information necessary to understand the request, and cannot take advantage of any stored context on the server. It improves visibility, reliability and scalability.
Cache: Data within a response to a request must be implicitly or explicitly labeled as cacheable or non-cacheable. It improves efficiency and scalability.
Uniform interface: Client and server interact through a generalized interface. It improves visibility, simplicity and evolvability, at the expense of efficiency. This is the distinguishing feature of REST. The constraints on the generalized interface are:

i. Identification of resources: The key abstraction of information in REST is a resource. Any information that can be named can be a resource: a document or image, a temporal service, a collection of other resources, a non-virtual object, and so on. Each resource is identified by a resource identifier. In practice, this will be a Uniform Resource Identifier [URI].

ii. Manipulation of resources through representations: Actions on resources are performed on representations of those resources. A representation is a sequence of bytes, plus representation metadata to describe those bytes. In practice, representations will be MIME media types [Media].

Self-descriptive messages: All the information required to process a request is available in the request. This includes the host, message control metadata (like Content-Length) , representation metadata and the resource representation.
Hypermedia as the engine of application state (HATEOAS): The client knows only the starting URL of the server. All future interactions are discovered from representations. This allows the server to evolve separately from the clients.

4. Layered system: Clients and servers can be composed of hierarchical layers such that each component cannot see beyond the immediate layer with which it is interacting. It improves simplicity and scalability at the expense of efficiency.

5. Code-on-demand: Client functionality can be extended by downloading and executing code in the form of applets or scripts. It improves simplicity and extensibility at the expense of visibility and security. This is an optional constraint.

The constraints of a RESTful architecture lead to simple, scalable, and evolvable systems. Simplicity means that few demands are placed on the cloud service consumer, whereas scalability and evolvability let the cloud service meet its rapid provisioning and releasing requirements, while incrementally expanding its services.

1.5.4 RESTful Authorization as a Service

Due to the pervasive nature of access control, Authorization-as-a-Service will result in many calls to the authorization servers. These servers must therefore perform and scale extremely well. Thus it makes sense to use a RESTful architecture for them.

This specification defines a profile for the use of XACML in a RESTful architecture, enabling the interoperability of RESTful Authorization-as-a-Service (AZaaS) solutions. The MIME media types [Media] available for representations of the various XACML constructs are defined separately [XACMLMedia].

1.6 Use Cases

This version of this profile will only consider the PEP and PDP. Later versions may involve other components of the XACML architecture, like the PAP and PIP.

1.6.1 PEP ↔ PDP

Line Of Business applications contain Policy Enforcement Points (PEPs) that interact with Policy Decision Points (PDPs) from various vendors. These PDPs may either be dedicated to the application, or be simultaneously offered to multiple applications (Authorization as a Service).

2 RESTful Services

{Normative}

2.1 Network Transport

The following URI SHALL be used as the identifier for the functionality specified in this section of this profile:

· urn:oasis:names:tc:xacml:3.0:profile:rest:http

Although not strictly required by REST, this specification mandates that HTTP MUST be used as the protocol to transport network messages [HTTP] between client and server.

For additional security, it is RECOMMENDED that SSL/TLS be used [HTTPS]. See section 3, Security Considerations, for more on securing the RESTful interactions.

Note that additional transport protocols are allowed but outside the scope of this profile.

2.2 Resources

The following sections describe the mandatory and optional resources that this profile defines. Each section defines which operations are supported on the resource, and what their requirements are. In particular, HTTP status codes [HTTP] define success or failure of the operation. See section 3, Security Considerations, for information on securing the RESTful interactions and representations.

2.2.1 Entry Point

The following URI SHALL be used as the identifier for the functionality specified in this section of this Profile:

· urn:oasis:names:tc:xacml:3.0:profile:rest:home

Operation	Request Body	Response Body	Description	Status Codes
GET		XACML entry point		200, 400, 401, 403, 406, 5xx

To enable the discoverability requirement, a RESTful XACML system MUST have a single entry point at a known location [HomeDocument]. It is RECOMMENDED that the location of the entry point remain fixed, even as the service evolves, to allow older clients to remain functional. Each implementation of this profile MUST document the location of the entry point.

Note that the XACML entry point MAY be part of a larger RESTful system. In that case, the entry point location is not known in advance, but discovered from the enclosing system. The link relation http://docs.oasis-open.org/ns/xacml/relation/home SHALL be used for links to this resource. The documentation SHOULD contain information on how to discover the XACML entry point using this link relation.

The XACML entry point representation that is returned SHOULD NOT contain anything other than links to other resources specified in this profile.

2.2.2 Policy Decision Point

The following URI SHALL be used as the identifier for the functionality specified in this section of this profile:

· urn:oasis:names:tc:xacml:3.0:profile:rest:pdp

The link relation type for links to this resource is
http://docs.oasis-open.org/ns/xacml/relation/pdp.

Operation	Request Body	Response Body	Description	Status Codes
POST	XACML request	XACML response	Makes an access control decision	200, 400, 401, 403, 406, 415, 5xx

A server MUST support <Request> from XACML core [XACMLv3] as the XACML request in the request body.

A server MAY additionally support <XACMLAuthzDecisionQuery> from the SAML Profile [SAML4XACML] as the XACML request. When <XACMLAuthzDecisionQuery> is used, requests and responses can be correlated using the request’s ID and the response’s InResponseTo attributes. When <Request> is used, this additional functionality is not available and the PEP must either use a new TCP/IP session, or wait with sending a request over the current session until the response for the previous request is received.

The processing and response MUST be as specified in the respective specification, either [XACMLv3] or [SAML4XACML].

Note that success of the HTTP operation (i.e. status code 200) doesn’t mean that authorization is granted. It means that the response body is valid, and that the response body contains the XACML decision, which could be Deny. Likewise, a status code of 403 doesn’t imply a XACML decision of Deny, but instead means that the user is not allowed to ask the PDP for an access decision.

Also note that, although this operation uses POST, it is both idempotent and safe [HTTP].

2.3 Representations

MIME media types defined for XACML in [XACMLMedia] or elsewhere MUST be used to represent resources. Whenever a representation is not available in that specification, a conforming implementation MAY chose its own representation. However, this specification will define constraints that such a representation MUST adhere to.

2.3.1 Linking

A fundamental concept in a RESTful architecture is that of linking between resources [REST].

For XML based representations, links MUST follow the Atom Syndication Format [Atom]. The link relation types [WebLink] for the services in this specification are given in their respective sections below. For instance, a link to the PDP could be

<atom:link rel=”http://docs.oasis-open.org/ns/xacml/relation/pdp”
href=”/authorization/pdp”/>

For JSON based representations, links MUST map from Atom XML to JSON. For instance, a link to the PDP could be

“link”: {
rel: “http://docs.oasis-open.org/ns/xacml/relation/pdp”,
href: “/authorization/pdp”
}

Likewise, other representations SHOULD follow Atom as closely as possible.

Whenever it is not possible to add links to a representation, for instance because the representation must conform to a schema that doesn’t support links, or because the representation is binary, links MUST be added using the Link HTTP header [WebLink]. In case of multiple links, the title attribute of the Link header field MAY be used to correlate the link to an item in the representation.

2.3.2 Entry Point

The representation of the entry point resource SHOULD NOT contain anything other than links to other resources specified by this profile.

2.3.3 XACML versions, Representation Formats, and Content Negotiation

This profile is agnostic to the version and format of XACML used. Clients and servers SHOULD use content negotiation [HTTP] to agree on the version and format of XACML used in their exchanges. XACML media types [Media] MUST support a version parameter for this purpose. See the Examples section for the use of the Accept and Content-Type headers [HTTP] used in content negotiation.

2.4 Examples

2.4.1 Obtain an Access Decision

The following is a sequence of REST calls to obtain an authorization decision from a PDP. The client starts by accessing the entry point:

GET /authorization HTTP/1.0
Host: www.example.com

Accept: application/xml
Content-Length: 0

To which the server responds:

HTTP/1.0 200 OK
Content-Type: application/xml
Content-Length: <nnnn>

<resources xmlns=”http://ietf.org/ns/home-documents”
xmlns:atom=”http://www.w3.org/2005/Atom”>
<resource rel=”http://docs.oasis-open.org/ns/xacml/relation/pdp”>
<atom:link href=”/authorization/pdp”/>
</resource>
</resources>

The client looks for a resource with relation type http://docs.oasis-open.org/ns/xacml/relation/pdp and posts the XACML request to it:

POST /authorization/pdp HTTP/1.0
Host: www.example.com
Accept: application/xacml+xml; version=3.0
Content-Type: application/xacml+xml; version=3.0
Content-Length: <nnnn>

<Request xmlns=”urn:oasis:names:tc:xacml:3.0:core:schema:wd-17”>

</Request>

And finally the server responds with the access decision:

HTTP/1.0 200 OK
Content-Type: application/xacml+xml; version=3.0
Content-Length: <nnnn>

<Response xmlns=”urn:oasis:names:tc:xacml:3.0:core:schema:wd-17”>

</Response>

3 Security Considerations

{Non-normative}

Security and privacy considerations for the use of XACML in general are defined in [XACMLv3]. This section describes some additional considerations that have to do with the networked nature of a RESTful architecture, together with the administrative capabilities set out by this profile.

3.1 Network Transport

The use of SSL/TLS [HTTPS] is RECOMMENDED to protect data as it is transferred across the network.

3.2 Authentication

This specification leaves the issue open of how to authenticate. Implementations MUST document how they handle authentication.

HTTP status code 401 (Unauthorized) [HTTP] MAY be used to indicate that an operation on a resource is denied because the requestor is not authenticated. However, the problem of authentication over HTTP is not completely solved. [HTTPAuthN] defines Basic and Digest authentication. Basic authentication MUST NOT be used, since it sends the password in plain text over the network. Digest authentication MAY be used.

Additional standards like [OpenID], [SAMLv2] or [SASL] MAY be used instead of or in addition to HTTP Digest authentication.

3.3 Authorization

This specification RECOMMENDS that authorization be implemented using XACML. Implementations can perform authorization based upon the identity of the requestor, as well as on any appropriate additional, trusted, attribute. The use of the XACML Administration and Delegation Profile [Admin] is RECOMMENDED.

HTTP status code 403 (Forbidden) [HTTP] MUST be used to indicate that an operation on a resource is denied because the requestor is not authorized.

Authorization SHOULD be used to exclude from the response any links to resources that the requestor is not allowed to retrieve.

3.4 Non-Repudiation

In some situations it is important to have an audit trail of access decisions that were made. This audit trail must be at least tamper-evident. For this purpose, the SAML Profile for XACML [SAML4XACML] can be used to sign the access request and response.

4 Conformance

{Non-normative}

4.1 Conformance Clauses

This section lists those portions of the specification that MUST be included in an implementation of a server that claims to conform to this profile.

Identifier	M/O
urn:oasis:names:tc:xacml:3.0:profile:rest:http urn:oasis:names:tc:xacml:3.0:profile:rest:home	M M
urn:oasis:names:tc:xacml:3.0:profile:rest:pdp	M

4.2 Test Assertions

This section lists test assertions [TAG] that help verify conformance to this specification.

4.2.1 Network Transport

Id	urn:oasis:names:tc:xacml:3.0:profile:rest:assertion:http:client
Normative Source	The client must use HTTP when communicating with the server (From the more general source: HTTP MUST be used as the protocol to transport network messages between client and server)
Target	Network message from the client
Predicate	The [message] starts with an HTTP request line [HTTP]
Prescription Level	mandatory

Id	urn:oasis:names:tc:xacml:3.0:profile:rest:assertion:http:server
Normative Source	The server must use HTTP when communicating with the client (From the more general source: HTTP MUST be used as the protocol to transport network messages between client and server)
Target	Network message from the server
Predicate	The [message] starts with an HTTP response line [HTTP]
Prescription Level	Mandatory

4.2.2 Entry Point

Id	urn:oasis:names:tc:xacml:3.0:profile:rest:assertion:home:documentation
Normative Source	A RESTful XACML system MUST have a single entry point at a known location Each implementation of this profile MUST document the location of the entry point
Target	server documentation
Predicate	The [documentation] lists a (procedure for discovering a) single entry point URL at which the server can be accessed
Prescription Level	mandatory

Id	urn:oasis:names:tc:xacml:3.0:profile:rest:assertion:home:status
Normative Source	GET on the home location MUST return status code 200
Target	Response to GET request on the home location
Predicate	The HTTP status code in the [response] is 200
Prescription Level	mandatory

Id	urn:oasis:names:tc:xacml:3.0:profile:rest:assertion:home:body
Normative Source	GET on the home location MUST return a home document
Target	Response to GET request on the home location
Predicate	The HTTP body in the [response] follows the home document schema [HomeDocument]
Prescription Level	mandatory

Id	urn:oasis:names:tc:xacml:3.0:profile:rest:assertion:home:pdp
Normative Source	The XACML entry point representation SHOULD contain a link to the PDP
Target	Response to GET request on the home location
Predicate	The home document in the [response] body contains a resource with link relation http://docs.oasis-open.org/ns/xacml/relation/pdp and a valid URL
Prescription Level	mandatory

4.2.3 Policy Decision Point

Id	urn:oasis:names:tc:xacml:3.0:profile:rest:assertion:pdp:xacml:status
Normative Source	POST on the PDP with a valid XACML request MUST return status code 200
Target	Response to POST request on the PDP location with valid XACML request in the body
Predicate	The HTTP status code in the [response] is 200
Prescription Level	mandatory

Id	urn:oasis:names:tc:xacml:3.0:profile:rest:assertion:pdp:xacml:body
Normative Source	POST on the PDP with a valid XACML request MUST return a valid XACML response in the body
Target	Response to POST request on the PDP location with valid XACML request in the body
Predicate	The HTTP body in the [response] is a valid XACML response
Prescription Level	mandatory

Id	urn:oasis:names:tc:xacml:3.0:profile:rest:assertion:pdp:xacml:invalid
Normative Source	POST on the PDP with an invalid XACML request MUST return status code 400 (Bad Request)
Target	Response to POST request on the PDP location with invalid XACML request in the body
Predicate	The HTTP status code in the [response] is 400
Prescription Level	mandatory

Id	urn:oasis:names:tc:xacml:3.0:profile:rest:assertion:pdp:saml:status
Normative Source	POST on the PDP with a valid XACML request MUST return status code 200
Target	Response to POST request on the PDP location with valid XACML request wrapped in a xacml-samlp:XACMLAuthzDecisionQuery in the body
Predicate	The HTTP status code in the [response] is 200
Prescription Level	optional

Id	urn:oasis:names:tc:xacml:3.0:profile:rest:assertion:pdp:saml:body
Normative Source	POST on the PDP with a valid XACML request MUST return a valid XACML response in the body
Target	Response to POST request on the PDP location with valid XACML request wrapped in a xacml-samlp:XACMLAuthzDecisionQuery in the body
Predicate	The HTTP body in the [response] is a valid XACML response wrapped in a samlp:Response
Prescription Level	optional

Id	urn:oasis:names:tc:xacml:3.0:profile:rest:assertion:pdp:saml:invalid
Normative Source	POST on the PDP with an invalid XACML request MUST return status code 400 (Bad Request)
Target	Response to POST request on the PDP location with invalid XACML request wrapped in a xacml-samlp:XACMLAuthzDecisionQuery in the body
Predicate	The HTTP status code in the [response] is 400
Prescription Level	optional

Appendix A. Acknowledgments

The following individuals have participated in the creation of this specification and are gratefully acknowledged:

Participants:

David Brossard, Axiomatics

Jean-Paul Buu-Sao, TSCP
David Chadwick, Individual
Jacques Durand, Fujitsu

Craig Forster, IBM
Hal Lockhart, Oracle
Danny Thorpe, Dell
Erik Wilde, EMC

Appendix B. Revision History

Revision	Date	Editor	Changes Made
WD01	2012-02-14	Rémon Sinnema	Defined use cases
WD02	2012-04-24	Rémon Sinnema	Initial full draft
WD03	2012-05-03	Rémon Sinnema	Fixed typos Renamed Use Cases section to Rationale Introduced Use Cases section Moved everything representation related out of the section on resources Added examples Improved authorization section
WD04	2012-05-22	Rémon Sinnema	Conformance section should succinctly indicate what needs to be implemented Added platform use case Added policy version resource
WD05	2012-05-31	Rémon Sinnema	PDP is now optional, allowing PAP-only servers Added explanatory text for delete example Added note on policies contained within policy sets Added note that supplied policies must be valid according to the policy schema Improved wording in Security section Added “lost” paragraph from WD02 about the contents of the entry point resource Added text on different types of PAPs Added text on policy (version) equality Added use of HTTP to conformance section
WD06	2012-10-9	Rémon Sinnema	Added domain terms Added section on test assertions Removed policy administration related text Updated text to better fit the home document standard Added section on non-repudiation Replaced reference to XACML Media Types Profile with URL of Internet Draft Added text on embedding XACML REST in a larger RESTful system
WD07	2013-01-25	Rémon Sinnema	Added section on content negotiation