1 Introduction

This specification defines a domain-specific policy assertion for reliable messaging for use with WS-Policy and WS-ReliableMessaging.

1.1 Terminology

The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [KEYWORDS].

This specification uses the following syntax to define normative outlines for messages:

The syntax appears as an XML instance, but values in italics indicate data types instead of values.
Characters are appended to elements and attributes to indicate cardinality:

"?" (0 or 1)
"*" (0 or more)
"+" (1 or more)

The character "|" is used to indicate a choice between alternatives.
The characters "[" and "]" are used to indicate that contained items are to be treated as a group with respect to cardinality or choice.
An ellipsis (i.e. "...") indicates a point of extensibility that allows other child, or attribute, content. Additional children and/or attributes MAY be added at the indicated extension points but MUST NOT contradict the semantics of the parent and/or owner, respectively. If an extension is not recognized it SHOULD be ignored.
XML namespace prefixes (see section 1.4) are used to indicate the namespace of the element being defined.

Elements and Attributes defined by this specification are referred to in the text of this document using XPath 1.0 [XPATH 1.0] expressions. Extensibility points are referred to using an extended version of this syntax:

An element extensibility point is referred to using {any} in place of the element name. This indicates that any element name can be used, from any namespace other than the wsrm: namespace.
An attribute extensibility point is referred to using @{any} in place of the attribute name. This indicates that any attribute name can be used, from any namespace other than the wsrm: namespace.

1.2 Normative

[KEYWORDS] S. Bradner, "Key words for use in RFCs to Indicate Requirement Levels," RFC 2119, Harvard University, March 1997.
http://www.ietf.org/rfc/rfc2119.txt

[SOAP 1.1] W3C Note, "SOAP: Simple Object Access Protocol 1.1" 08 May 2000.
http://www.w3.org/TR/2000/NOTE-SOAP-20000508/

[SOAP 1.2] W3C Recommendation, "SOAP Version 1.2 Part 1: Messaging Framework" June 2003.
http://www.w3.org/TR/2003/REC-soap12-part1-20030624/

[URI] T. Berners-Lee, R. Fielding, L. Masinter, "Uniform Resource Identifiers (URI): Generic Syntax," RFC 3986, MIT/LCS, U.C. Irvine, Xerox Corporation, January 2005.
http://ietf.org/rfc/rfc3986

[WS-RM] OASIS Standard, "Web Services Reliable Messaging (WS-ReliableMessaging)," February 2009.
http://docs.oasis-open.org/ws-rx/wsrm/200702/wsrm-1.2-spec-os.doc

[WSDL 1.1] W3C Note, "Web Services Description Language (WSDL 1.1)," 15 March 2001.
http://www.w3.org/TR/2001/NOTE-wsdl-20010315

[XML] W3C Recommendation, "Extensible Markup Language (XML) 1.0 (Fourth Edition)", September 2006.
http://www.w3.org/TR/REC-xml/

[XML-ns] W3C Recommendation, "Namespaces in XML," 14 January 1999.
http://www.w3.org/TR/1999/REC-xml-names-19990114/

[XML-Schema Part1] W3C Recommendation, "XML Schema Part 1: Structures," October 2004.
http://www.w3.org/TR/xmlschema-1/

[XML-Schema Part2] W3C Recommendation, "XML Schema Part 2: Datatypes," October 2004.
http://www.w3.org/TR/xmlschema-2/

[XPATH 1.0] W3C Recommendation, "XML Path Language (XPath) Version 1.0," 16 November 1999.
http://www.w3.org/TR/xpath

1.3 Non Normative

[RDDL 2.0] Jonathan Borden, Tim Bray, eds. “Resource Directory Description Language (RDDL) 2.0,” January 2004
http://www.openhealth.org/RDDL/20040118/rddl-20040118.html

[SecurityPolicy] OASIS Standard, "WS-SecurityPolicy 1.3", February 2009
http://docs.oasis-open.org/ws-sx/ws-securitypolicy/v1.3/os/ws-securitypolicy-1.3-spec-os.doc

[WS-Policy] W3C Recommendation, "Web Services Policy 1.5 - Framework," September 2007.
http://www.w3.org/TR/2007/REC-ws-policy-20070904

[WS-PolicyAttachment] W3C Recommendation, "Web Services Policy 1.5 - Attachment," September 2007.
http://www.w3.org/TR/2007/REC-ws-policy-attach-20070904

[WS-Security] Anthony Nadalin, Chris Kaler, Phillip Hallam-Baker, Ronald Monzillo, eds. "OASIS Web Services Security: SOAP Message Security 1.0 (WS-Security 2004)", OASIS Standard 200401, March 2004.
http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-soap-message-security-1.0.pdf

Anthony Nadalin, Chris Kaler, Phillip Hallam-Baker, Ronald Monzillo, eds. "OASIS Web Services Security: SOAP Message Security 1.1 (WS-Security 2004)", OASIS Standard 200602, February 2006.
http://docs.oasis-open.org/wss/v1.1/wss-v1.1-spec-os-SOAPMessageSecurity.pdf

1.4 Namespace

The XML namespace [XML-ns] URI that MUST be used by implementations of this specification is:

http://docs.oasis-open.org/ws-rx/wsrmp/200702

Dereferencing the above URI will produce the Resource Directory Description Language [RDDL 2.0] document that describes this namespace.

Table 1 lists the XML namespaces that are used in this specification. The choice of any namespace prefix is arbitrary and not semantically significant.

Table 1

Prefix	Namespace	Specification
wsdl	http://schemas.xmlsoap.org/wsdl/	[WSDL 1.1]
wsp	http://www.w3.org/ns/ws-policy	WS-Policy 1.5
wsrmp	http://docs.oasis-open.org/ws-rx/wsrmp/200702	This specification.
wsu	http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-utility-1.0.xsd	WS-Security-Utility Schema

The normative schema for WS-ReliableMessaging can be found linked from the namespace document that is located at the namespace URI specified above.

All sections explicitly noted as examples are informational and are not to be considered normative.

1.5 Conformance

An implementation is not compliant with this specification if it fails to satisfy one or more of the MUST or REQUIRED level requirements defined herein. A SOAP Node MUST NOT use the XML namespace identifier for this specification (listed in section 1.4) within SOAP Envelopes unless it is compliant with this specification.

Normative text within this specification takes precedence over normative outlines, which in turn take precedence over the XML Schema [XML-Schema Part1, XML-Schema Part2] descriptions.

2 RM Policy Assertions

WS-Policy Framework and WS-Policy Attachment [WS-PolicyAttachment] collectively define a framework, model and grammar for expressing the requirements, and general characteristics of entities in an XML Web services-based system. To enable an RM Destination and an RM Source to describe their requirements for a given Sequence, this specification defines a single RM policy assertion that leverages the WS-Policy framework.

2.1 Assertion Model

The RM policy assertion indicates that the RM Source and RM Destination MUST use WS-ReliableMessaging to ensure reliable delivery of messages. Specifically, the WS-ReliableMessaging protocol determines invariants maintained by the reliable messaging endpoints and the directives used to track and manage the delivery of a Sequence of messages.

2.2 Normative Outline

The normative outline for the RM assertion is:

<wsrmp:RMAssertion [wsp:Optional="true"]? ... >

<wsp:Policy>

[ <wsrmp:SequenceSTR/> |

<wsrmp:SequenceTransportSecurity/> ] ?

<wsrmp:DeliveryAssurance>

<wsp:Policy>

[ <wsrmp:ExactlyOnce/> |

<wsrmp:AtLeastOnce/> |

<wsrmp:AtMostOnce/> ]

<wsrmp:InOrder/> ?

</wsp:Policy>

</wsrmp:DeliveryAssurance> ?

</wsp:Policy>

...

</wsrmp:RMAssertion>

The following describes the content model of the RMAssertion element.

/wsrmp:RMAssertion

A policy assertion that specifies that WS-ReliableMessaging protocol MUST be used when sending messages.

/wsrmp:RMAssertion/@wsp:Optional="true"

Per WS-Policy, this is compact notation for two policy alternatives, one with and one without the assertion. The intuition is that the behavior indicated by the assertion is optional, or in this case, that WS-ReliableMessaging MAY be used.

/wsrmp:RMAssertion/wsp:Policy

This required element allows for the inclusion of nested policy assertions.

/wsrmp:RMAssertion/wsp:Policy/wsrmp:SequenceSTR

When present, this assertion defines the requirement that an RM Sequence MUST be bound to an explicit token that is referenced from a wsse:SecurityTokenReference in the CreateSequence message. See section 2.5.1.

/wsrmp:RMAssertion/wsp:Policy/wsrmp:SequenceTransportSecurity

When present, this assertion defines the requirement that an RM Sequence MUST be bound to the session(s) of the underlying transport-level protocol used to carry the CreateSequence and CreateSequenceResponse message. When present, this assertion MUST be used in conjunction with the sp:TransportBinding assertion, see section 2.5.2.

/wsrmp:RMAssertion/wsp:Policy/wsrmp:DeliveryAssurance

This expression, which may be omitted, describes the message delivery quality of service between the RM and application layer. When used by an RM Destination it expresses the delivery assurance in effect between the RM Destination and its corresponding application destination, and it also indicates requirements on any RM Source that transmits messages to this RM destination. Conversely when used by an RM Source it expresses the delivery assurance in effect between the RM Source and its corresponding application source, as well as indicating requirements on any RM Destination that receives messages from this RM Source. In either case the delivery assurance does not affect the messages transmitted on the wire. Absence of this expression from a wsrmp:RMAssertion policy assertion simply means that the endpoint has chosen not to advertise its delivery assurance characteristics.
Note that when there are multiple policy alternatives of the RM Assertion, the Delivery Assurance on each MUST NOT conflict.

/wsrmp:RMAssertion/wsp:Policy/wsrmp:DeliveryAssurance/wsp:Policy

This required element identifies additional requirements for the use of the wsrmp:DeliveryAssurance.

/wsrmp:RMAssertion/wsp:Policy/wsrmp:DeliveryAssurance/wsp:Policy/wsrmp:ExactlyOnce

This expresses the ExactlyOnce Delivery Assurance defined in [WS-RM].

/wsrmp:RMAssertion/wsp:Policy/wsrmp:DeliveryAssurance/wsp:Policy/wsrmp:AtLeastOnce

This expresses the AtLeastOnce Delivery Assurance defined in [WS-RM].

/wsrmp:RMAssertion/wsp:Policy/wsrmp:DeliveryAssurance/wsp:Policy/wsrmp:AtMostOnce

This expresses the AtMostOnce Delivery Assurance defined in [WS-RM].

/wsrmp:RMAssertion/wsp:Policy/wsrmp:DeliveryAssurance/wsp:Policy/wsrmp:InOrder

This expresses the InOrder Delivery Assurance defined in [WS-RM].

/wsrmp:RMAssertion/{any}

This is an extensibility mechanism to allow different (extensible) types of information, based on a schema, to be passed.

/wsrmp:RMAssertion/@{any}

This is an extensibility mechanism to allow different (extensible) types of information, based on a schema, to be passed.

2.3 Assertion Attachment

The RM policy assertion is allowed to have the following Policy Subjects [WS-PolicyAttachment]:

Endpoint Policy Subject
Message Policy Subject

WS-PolicyAttachment defines a set of WSDL/1.1 policy attachment points for each of the above Policy Subjects. Since an RM policy assertion specifies a concrete behavior, it MUST NOT be attached to the abstract WSDL policy attachment points.

The following is the list of WSDL/1.1 elements whose scope contains the Policy Subjects allowed for an RM policy assertion but which MUST NOT have RM policy assertions attached:

wsdl:message
wsdl:portType/wsdl:operation/wsdl:input
wsdl:portType/wsdl:operation/wsdl:output
wsdl:portType/wsdl:operation/wsdl:fault
wsdl:portType

The following is the list of WSDL/1.1 elements whose scope contains the Policy Subjects allowed for an RM policy assertion and which MAY have RM policy assertions attached:

wsdl:port
wsdl:binding
wsdl:binding/wsdl:operation/wsdl:input
wsdl:binding/wsdl:operation/wsdl:output
wsdl:binding/wsdl:operation/wsdl:fault

If an RM policy assertion is attached to any of:

wsdl:binding/wsdl:operation/wsdl:input
wsdl:binding/wsdl:operation/wsdl:output
wsdl:binding/wsdl:operation/wsdl:fault

then an RM policy assertion, specifying wsp:Optional=”true” MUST be attached to the corresponding wsdl:binding or wsdl:port, indicating that the endpoint supports WS-RM. Any messages, regardless of whether they have an attached Message Policy Subject RM policy assertion, MAY be sent to that endpoint using WS-RM. Additionally, the receiving endpoint MUST NOT reject any message belonging to a Sequence, simply because there was no Message Policy Subject RM policy assertion attached to that message. There might be certain RM implementations that are incapable of applying RM Quality of Service (QoS) semantics on a per-message basis. In order to ensure the broadest interoperability, when an endpoint decorates its WSDL with RM policy assertions using Message Policy Subject, it MUST also be prepared to accept that all messages sent to that endpoint might be sent within the context of an RM Sequence, regardless of whether the corresponding wsdl:input, wsdl:output or wsdl:fault had an attached RM policy assertion.

Rather than turn away messages that were unnecessarily sent with RM semantics, the receiving endpoint described by the WSDL MUST accept these messages.

By attaching an RM policy assertion that specifies wsp:Optional="true" to the corresponding endpoint that has attached RM policy assertions at the Message Policy Subject level, the endpoint is describing the above constraint in policy.

In the case where an optional RM Assertion applies to an output message, there is no requirement on the client to support an RM Destination implementation

2.4 Assertion Example

Table 2 lists an example use of the RM policy assertion.

Table 2: Example policy with RM policy assertion

(01)<wsdl:definitions

(02) targetNamespace="example.com"

(03) xmlns:tns="example.com"

(04) xmlns:wsdl="http://schemas.xmlsoap.org/wsdl/"

(05) xmlns:wsp="http://www.w3.org/ns/ws-policy"

(06) xmlns:wsrmp="http://docs.oasis-open.org/ws-rx/wsrmp/200702"

(07) xmlns:wsu="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-utility-1.0.xsd">

(08)

(09) <wsp:UsingPolicy wsdl:required="true" />

(10)

(11) <wsp:Policy wsu:Id="MyPolicy" >

(12) <wsrmp:RMAssertion>

(13) <wsp:Policy/>

(14) </wsrmp:RMAssertion>

(15)

(16) </wsp:Policy>

(17)

(18)

(19)

(20) <wsdl:binding name="MyBinding" type="tns:MyPortType" >

(21) <wsp:PolicyReference URI="#MyPolicy" />

(22)

(23) </wsdl:binding>

(24)

(25)</wsdl:definitions>

Line (09) in Table 2 indicates that WS-Policy is in use as a required extension.

Lines (11-16) are a policy expression that includes a RM policy assertion (lines 12-14) to indicate that WS-ReliableMessaging must be used.

Lines (20-23) are a WSDL binding. Line (21) indicates that the policy in lines (11-16) applies to this binding, specifically indicating that WS-ReliableMessaging must be used over all the messages in the binding.

2.5 Sequence Security Policy

WS-SecurityPolicy [SecurityPolicy] provides a framework and grammar for expressing the security requirements and characteristics of entities in a XML web services based system. The following assertions MAY be used in conjunction with WS-SecurityPolicy to express additional security requirements particular to RM Sequences.

2.5.1 RM Assertion with Sequence STR Assertion

This version of the RM assertion includes the requirement that an RM Sequence MUST be bound to an explicit token that is referenced from a wsse:SecurityTokenReference in the CreateSequence message.

This assertion MUST apply to [Endpoint Policy Subject]. The normative outline for this form of the Sequence STR Assertion is:

<wsrmp:RMAssertion [wsp:Optional="true"]? ...>

<wsp:Policy>

<wsrmp:SequenceSTR/>

<wsp:Policy>

</wsrmp:RMAssertion>

The following describes the content model of the SequenceSTR element.

/wsrmp:SequenceSTR

A policy assertion that specifies security requirements which MUST be used with an RM Sequence that are particular to WS-RM and beyond what can be expressed in WS-SecurityPolicy.

2.5.2 RM Assertion with Sequence Transport Security Assertion

This version of the RM assertion includes the requirement that an RM Sequence MUST be bound to the session(s) of the underlying transport-level security protocol (e.g. SSL/TLS) used to carry the CreateSequence and CreateSequenceResponse messages.

This assertion MUST apply to [Endpoint Policy Subject]. This assertion MUST be used in conjunction with the sp:TransportBinding assertion that requires the use of some transport-level security mechanism (e.g. sp:HttpsToken).

The normative outline for this form of the RM Assertion with the Sequence Transport Security Assertion is:

<wsp:Policy>

<wsp:ExactlyOne>

<wsp:All>

<wsrm:RMAssertion [wsp:Optional="true"]> ...>

<wsp:Policy>

<wsrmp:SequenceTransportSecurity/>

</wsp:Policy>

</wsrm:RMAssertion>

<sp:TransportBinding ...>

...

</sp:TransportBinding>

<wsp:All>

<wsp:ExactlyOne>

</wsp:Policy>

The following describes the content model of the SequenceTransportSecurity element.

/wsrmp:SequenceTransportSecurity

A policy assertion that specifies that any Sequences targeted to the indicated endpoint MUST be bound to the underlying session(s) of the transport-level security used to carry messages related to the Sequence.

This form of the RM Assertion says that an endpoint MAY have RM as an option but always requires HTTPS to be used. All the SequenceTransportSecurity assertion indicates is that RM's rules for protecting the Sequence over TLS are followed.

3 Security Considerations

It is strongly RECOMMENDED that policies and assertions be signed to prevent tampering.

It is RECOMMENED that policies SHOULD NOT be accepted unless they are signed and have an associated security token to specify the signer has proper claims for the given policy. That is, a relying party shouldn't rely on a policy unless the policy is signed and presented with sufficient claims to pass the relying parties acceptance criteria.

It should be noted that the mechanisms described in this document could be secured as part of a SOAP message using WS-Security [WS-Security] or embedded within other objects using object-specific security mechanisms.

Appendix A. Schema

A normative copy of the XML Schema [XML-Schema Part1, XML-Schema Part2] description for this specification may be retrieved from the following address:

http://docs.oasis-open.org/ws-rx/wsrmp/200702/wsrmp-1.1-schema-200702.xsd

The following copy is provided for reference.

OASIS trademark, IPR and other policies apply. -->
<xs:schema xmlns:tns="http://docs.oasis-open.org/ws-rx/wsrmp/200702" xmlns:xs="http://www.w3.org/2001/XMLSchema" targetNamespace="http://docs.oasis-open.org/ws-rx/wsrmp/200702" elementFormDefault="qualified" attributeFormDefault="unqualified">
<xs:element name="RMAssertion">

<xs:complexType>

<xs:sequence>

<xs:any namespace="##other" processContents="lax" minOccurs="0" maxOccurs="unbounded"/>

</xs:sequence>

<xs:anyAttribute namespace="##any" processContents="lax"/>

</xs:complexType>

</xs:element>

<xs:element name="SequenceSTR">

<xs:complexType>

<xs:sequence/>

<xs:anyAttribute namespace="##any" processContents="lax"/>

</xs:complexType>

</xs:element>

<xs:element name="SequenceTransportSecurity">

<xs:complexType>

<xs:sequence/>

<xs:anyAttribute namespace="##any" processContents="lax"/>

</xs:complexType>

</xs:element>

<xs:element name="DeliveryAssurance">

<xs:complexType>

<xs:sequence>

<xs:any namespace="##any" processContents="lax" minOccurs="0" maxOccurs="unbounded"/>

</xs:sequence>

</xs:complexType>

</xs:element>

<xs:element name="ExactlyOnce">

<xs:complexType>

<xs:sequence/>

</xs:complexType>

</xs:element>

<xs:element name="AtLeastOnce">

<xs:complexType>

<xs:sequence/>

</xs:complexType>

</xs:element>

<xs:element name="AtMostOnce">

<xs:complexType>

<xs:sequence/>

</xs:complexType>

</xs:element>

<xs:element name="InOrder">

<xs:complexType>

<xs:sequence/>

</xs:complexType>

</xs:element>
</xs:schema>

Appendix B. Acknowledgments

This document is based on initial contribution to OASIS WS-RX Technical Committee by the following authors: