Web Services Policy 1.5 - Attachment

2.1 Notational Conventions

This specification uses the following syntax within normative outlines:

• The syntax appears as an XML instance, but values in italics indicate data types instead of literal 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.

• This document relies on the XML Information Set [XML Information Set]. Information items properties are indicated by the style [infoset property].

• XML namespace prefixes (see Table 2-1) are used to indicate the namespace of the element or attribute being defined.

• The ellipses characters "…" are used to indicate a point of extensibility that allows other Element or Attribute Information Items.

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 http://www.w3.org/ns/ws-policy 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. namespace.

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

2.2 XML Namespaces

This specification uses a number of namespace prefixes throughout; they are listed in Table 2-1. Note that the choice of any namespace prefix is arbitrary and not semantically significant (see [XML Namespaces]).

All information items defined by this specification are identified by the XML namespace URI [XML Namespaces] http://www.w3.org/ns/ws-policy. A normative XML Schema [XML Schema Structures, XML Schema Datatypes] document can be obtained indirectly by dereferencing the namespace document at the WS-Policy 1.5 namespace URI.

In this document reference is made to the wsu:Id attribute in a utility schema (http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-utility-1.0.xsd). The wsu:Id attribute was added to the utility schema with the intent that other specifications requiring such an Id could reference it (as is done here).

It is the intent of the W3C Web Services Policy Working Group that the Web Services Policy 1.5 - Framework and Web Services Policy 1.5 - Attachment XML namespace URI will not change arbitrarily with each subsequent revision of the corresponding XML Schema documents as the specifications transition through Candidate Recommendation, Proposed Recommendation and Recommendation status. However, should the specifications revert to Working Draft status, and a subsequent revision, published as a WD, CR or PR draft, results in non-backwardly compatible changes from a previously published WD, CR or PR draft of the specification, the namespace URI will be changed accordingly.

Under this policy, the following are examples of backwards compatible changes that would not result in assignment of a new XML namespace URI:

• Addition of new global element, attribute, complexType and simpleType definitions.

• Addition of new elements or attributes in locations covered by a previously specified wildcard.

• Modifications to the pattern facet of a type definition for which the value-space of the previous definition remains valid or for which the value-space of the preponderance of instance would remain valid.

• Modifications to the cardinality of elements for which the value-space of possible instance documents conformant to the previous revision of the schema would still be valid with regards to the revised cardinality rule.

2.3 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 [IETF RFC 2119].

We introduce the following terms that are used throughout this document:

collection

The items in a collection in this specification are unordered and may contain duplicates.

effective policy

The effective policy, for a given policy subject, is the combination of relevant policies. The relevant policies are those attached to policy scopes that contain the policy subject.

element policy

The element policy is the policy attached to the policy subjects associated with the element information item that contains it.

ignorable policy assertion

An ignorable policy assertion is an assertion that may be ignored for purposes of determining the compatibility of alternatives in policy intersection in a lax mode (as defined in 4.5 Policy Intersection).

merge

A merge consists of serializing each policy as a policy expression, replacing their wsp:Policy element with a wsp:All element, and placing each as children of a wrapper wsp:Policy element.

policy

A policy is a potentially empty collection of policy alternatives.

policy alternative

A policy alternative is a potentially empty collection of policy assertions.

policy assertion

A policy assertion represents a requirement, a capability, or other property of a behavior.

policy attachment

A policy attachment is a mechanism for associating policy with one or more policy scopes.

policy expression

A policy expression is an XML Infoset representation of a policy, either in a normal form or in an equivalent compact form.

policy scope

A policy scope is a collection of policy subjects to which a policy may apply.

policy subject

A policy subject is an entity (e.g., an endpoint, message, resource, operation) with which a policy can be associated.

2.4 Example

This specification defines several mechanisms for associating policies (Web Services Policy 1.5 - Framework, [Web Services Policy Framework]) with various XML Web service entities. For brevity, we define two sample policy expressions that the remainder of this document references.

Example 2-1 indicates a policy for reliable messaging [WS-RM Policy]. Example 2-2 is a policy for securing messages using X509 certificates [WS-SecurityPolicy].

(01) <wsp:Policy
        xmlns:rmp="http://docs.oasis-open.org/ws-rx/wsrmp/200702"
        xmlns:wsp="http://www.w3.org/ns/ws-policy"
        xmlns:wsu="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-utility-1.0.xsd"
        wsu:Id="RmPolicy" >
(02)   <rmp:RMAssertion>
(03)    <wsp:Policy/>
(04)   </rmp:RMAssertion>
(05) </wsp:Policy>

(01) <wsp:Policy
        xmlns:sp="http://docs.oasis-open.org/ws-sx/ws-securitypolicy/200702"
        xmlns:wsp="http://www.w3.org/ns/ws-policy"
        xmlns:wsu="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-utility-1.0.xsd"
        wsu:Id="X509EndpointPolicy" >
(02)   <sp:AsymmetricBinding>
(03)     <wsp:Policy>
(04)       <sp:RecipientToken>
(05)         <wsp:Policy>
(06)           <sp:X509Token sp:IncludeToken="http://docs.oasis-open.org/ws-sx/ws-securitypolicy/200702/IncludeToken/Never">
(07)             <wsp:Policy>
(08)               <sp:WssX509V3Token10 />
(09)             </wsp:Policy>
(10)           </sp:X509Token>
(11)         </wsp:Policy>
(12)       </sp:RecipientToken>
(13)       <sp:InitiatorToken>
(14)         <wsp:Policy>
(15)           <sp:X509Token sp:IncludeToken="http://docs.oasis-open.org/ws-sx/ws-securitypolicy/200702/IncludeToken/AlwaysToRecipient" >
(16)             <wsp:Policy>
(17)               <sp:WssX509V3Token10 />
(18)             </wsp:Policy>
(19)           </sp:X509Token>
(20)         </wsp:Policy>
(21)       </sp:InitiatorToken>
(22)       <sp:AlgorithmSuite>
(23)         <wsp:Policy>
(24)           <sp:Basic256Rsa15 />
(25)         </wsp:Policy>
(26)       </sp:AlgorithmSuite>
(27)       <sp:Layout>
(28)         <wsp:Policy>
(29)           <sp:Lax />
(30)         </wsp:Policy>
(31)       </sp:Layout>
(32)       <sp:IncludeTimestamp />
(33)       <sp:OnlySignEntireHeadersAndBody />
(34)     </wsp:Policy>
(35)   </sp:AsymmetricBinding>
(36) </wsp:Policy>

The document containing both of these policy expressions is assumed to be located at http://www.example.com/policies.  Per Section 3.2 Policy Identification of Web Services Policy 1.5 - Framework [Web Services Policy Framework], the IRIs used for these policy expressions in the remainder of this document are http://www.example.com/policies#RmPolicy and http://www.example.com/policies#X509EndpointPolicy, for the examples in Example 2-1 and Example 2-2, respectively.

3.1 Effective Policy

Policies will often be associated with a particular policy subject using multiple policy attachments. For example, there may be attachments at different points in a WSDL description that apply to one policy subject, and other attachments may be made by UDDI and other mechanisms.

When multiple attachments are made, their relevent policies can be combined. [Definition: The effective policy, for a given policy subject, is the combination of relevant policies. The relevant policies are those attached to policy scopes that contain the policy subject.]

This combination can be achieved through a merge. [Definition: A merge consists of serializing each policy as a policy expression, replacing their wsp:Policy element with a wsp:All element, and placing each as children of a wrapper wsp:Policy element.] The resulting policy expression is considered to represent the combined policy of all of the attachments to that policy subject.

Such calculated policy expressions have no meaningful IRI of their own.

3.2 Policy Attachment Mechanisms

This section defines two general-purpose mechanisms for associating policies [Web Services Policy Framework] with one or more policy subjects. The first allows XML-based descriptions of resources to associate policy as part of their intrinsic definition. The second allows policies to be associated with arbitrary policy subjects independently from their definition.

The policy scope of an attachment is specific to the policy attachment Mechanism using it. Accordingly, any policy attachment mechanism MUST define the policy scope of the attachment.

3.3 XML Element Attachment

It is often desirable to associate policies with Web services policy subjects represented as XML elements (i.e., WSDL 1.1 elements - Section 4. Attaching Policies Using WSDL 1.1 for the specific details of WSDL attachment).

Since policy assertions are strongly typed by the authors, the precise semantics of how element policy is to be processed once discovered is domain-specific; however, implementations are likely to follow the precedent specified in the section below on WSDL [WSDL 1.1] and Policy.

This specification defines a global attribute that allows policy expressions to be attached to an arbitrary XML element. The following is the schema definition for the wsp:PolicyURIs attribute:

(01) <xs:schema>
(02)   <xs:attribute name="PolicyURIs">
(03)     <xs:simpleType>
(04) 	<xs:list itemType="xs:anyURI" />
(05)     </xs:simpleType>
(06)   </xs:attribute>
(07) </xs:schema>

The namespace URI [XML Namespaces] for this attribute is http://www.w3.org/ns/ws-policy.

The wsp:PolicyURIs attribute contains a white space-separated list of one or more IRIs [IETF RFC 3987]. When this attribute is used, each of the values identifies a policy expression as defined by [Web Services Policy Framework]. If more than one IRI is specified, the individual referenced policies need to be merged together to form a single element policy expression. The resultant policy is then associated with the element information item's element policy property. [Definition: The element policy is the policy attached to the policy subjects associated with the element information item that contains it.]

An example of element policy through the use of this global attribute is given below using the sample policies stated in Section 2.4 Example.

If the policies referenced by the following XML element

(01) <MyElement wsp:PolicyURIs="
(02)    http://www.example.com/policies#RmPolicy
(03)    http://www.example.com/policies#X509EndpointPolicy" />

have been processed and merged, it would result in an element policy whose XML 1.0 representation is listed in Example 3-1:

(01) <wsp:Policy
            xmlns:rmp="http://docs.oasis-open.org/ws-rx/wsrmp/200702"
            xmlns:sp="http://docs.oasis-open.org/ws-sx/ws-securitypolicy/200702"
            xmlns:wsp="http://www.w3.org/ns/ws-policy" >
(02)   <wsp:All>
(03)     <rmp:RMAssertion>
(04)        <wsp:Policy/>
(05)     </rmp:RMAssertion>
(06)   </wsp:All>
(07)   <wsp:All>
(08)     <sp:AsymmetricBinding>
(09)       <wsp:Policy>
(10)         <!-- Details omitted for readability -->
(11)         <sp:IncludeTimestamp />
(12)         <sp:OnlySignEntireHeadersAndBody />
(13)       </wsp:Policy>
(14)     </sp:AsymmetricBinding>
(15)   </wsp:All>
(16) </wsp:Policy>

Note that this element policy has no meaningful IRI.

The presence of the wsp:PolicyURIs attribute does not prohibit implementations from using additional mechanisms for associating policy expressions with XML-based constructs.

Alternatively, rather than using the global attribute, XML elements MAY use the wsp:Policy or wsp:PolicyReference elements directly as children, in order to support element policy (Per Section 4.3.4 Policy References of Web Services Policy 1.5 - Framework [Web Services Policy Framework]), and the semantics for this are the same as for the use of the global attribute. For example, an alternative way of attaching the policies in the above example, using child elements, would be as follows: 

(01) <MyElement>
(02)   <wsp:PolicyReference
(03)      URI="http://www.example.com/policies#RmPolicy" />
(04)   <wsp:PolicyReference
(05)      URI="http://www.example.com/policies#X509EndpointPolicy" />
(06) <MyElement/>

3.4 External Policy Attachment

This mechanism allows policies to be associated with a policy subject independent of that subject's definition and/or representation through the use of a wsp:PolicyAttachment element.

This element has three components: the policy scope of the attachment, the policy expressions being bound, and optional security information. The policy scope of the attachment is defined using one or more extensible domain expressions that identify policy subjects, typically using IRIs.

Domain expressions identify the domain of the association. That is, the set of policy subjects that will be considered for inclusion in the scope using an extensible domain expression model. Domain expressions identify policy subjects to be included within the policy scope. Domain expressions yield an unordered set of policy subjects for consideration.

For the purposes of attaching policy to a policy subject through this mechanism, any policy expression contained inside of the wsp:AppliesTo element MUST NOT be considered in scope. For example, an Endpoint Reference may be used as a domain expression, and it may contain policy expressions within it, but this policy expressions are not considered in scope with respect to the wsp:PolicyAttachment element using it.

The following is the pseudo-schema for the wsp:PolicyAttachment element:

(01) <wsp:PolicyAttachment … >
(02)   <wsp:AppliesTo>
(03)     <x:DomainExpression/> +
(04)   </wsp:AppliesTo>
(05)   ( <wsp:Policy>…</wsp:Policy> |
(06)     <wsp:PolicyReference>…</wsp:PolicyReference> ) +
(07)   <wsse:Security>…</wsse:Security> ?
(08)   …
(09) </wsp:PolicyAttachment>

The following describes the attributes and elements listed in the pseudo-schema outlined above:

/wsp:PolicyAttachment

This describes an external policy attachment.

/wsp:PolicyAttachment/wsp:AppliesTo

This required element's children describe the policy scope.

/wsp:PolicyAttachment/wsp:AppliesTo/{any}

These child elements MUST specify and/or refine the domain expression(s) that define the policy scope. They MUST NOT contradict the semantics of their root element; if an element is not recognized, it SHOULD be ignored. Domain expressions are XML elements that describe policy subjects within a policy scope. When more than one domain expression is present, the policy scope contains the union of the policy subjects identified by each expression.

/wsp:PolicyAttachment/wsp:Policy

This element is a policy expression representing a policy that is attached to the policy subjects within the policy scope.

/wsp:PolicyAttachment/wsp:PolicyReference

This element references a policy expression to be attached to the policy subjects that are in the policy scope. Refer to Web Services Policy 1.5 - Framework [Web Services Policy Framework] for additional details.

/wsp:PolicyAttachment/wsse:Security

This element is of type wsse:Security and allows security information such as signatures to be included. The syntax of this element is described in WS-Security [WS-Security 2004].

/wsp:PolicyAttachment/@{any}

Additional attributes MAY be specified but MUST NOT contradict the semantics of the [owner element]; if an attribute is not recognized, it SHOULD be ignored.

/wsp:PolicyAttachment/{any}

Other child elements for binding constructs MAY be specified but MUST NOT contradict the semantics of the parent element; if an element is not recognized, it SHOULD be ignored.

Domain expressions are used to identify entities such as endpoints, messages or resources with which a policy can be associated. For example, domain expressions may be used to refer to WSDL 1.1 definitions, WSDL 2.0 components, endpoint references, etc.

The following example illustrates the use of this mechanism with an EndpointReference domain expression for a deployed endpoint as defined in Web Services Addressing [WS-Addressing Core]:

(01) <wsp:PolicyAttachment>
(02)   <wsp:AppliesTo>
(03)     <wsa:EndpointReference>
(04)       <wsa:Address>http://www.example.com/acct</wsa:Address>
(05)     </wsa:EndpointReference>
(06)   </wsp:AppliesTo>
(07)   <wsp:PolicyReference
(08)      URI="http://www.example.com/policies#RmPolicy" />
(09) </wsp:PolicyAttachment>

In this example, the policy expression at http://www.example.com/policies#RmPolicy applies to all interactions with the endpoint at http://www.example.com/acct.

(01) <wsp:PolicyAttachment … >
(02)   <wsp:AppliesTo>
(03)     <wsp:URI … >xs:anyURI</wsp:URI> *
(04)   </wsp:AppliesTo>
(05)   …
(06) </wsp:PolicyAttachment>

(01) <wsp:PolicyAttachment>
(02)   <wsp:AppliesTo>
(03)     <wsp:URI>http://example.org/TicketAgent.wsdl20#wsdl.endpoint(TicketAgentService/Endpoint)</wsp:URI>
(04)   </wsp:AppliesTo>
(05)   <wsp:PolicyReference URI="http://www.example.com/policies#RmPolicy" />
(06)  </wsp:PolicyAttachment>

3.5 Use of IRIs in Policy Attachment

Policy attachment mechanisms use IRIs for some identifiers. This document does not define a base URI but relies on the mechanisms defined in XML Base [XML BASE] and RFCs 3023 [IETF RFC 3023], 3986 [IETF RFC 3986] and 3987 [IETF RFC 3987] for establishing a base URI against which relative IRIs can be made absolute.

4.1 Calculating Effective Policy in WSDL 1.1

Policy attachments in WSDL 1.1 can be used to associate policies with four different types of policy subject, identified as the service policy subject, the endpoint policy subject, the operation policy subject, and the message policy subject. These policy subjects should be considered as nested, due to the hierarchical nature of WSDL.

When attaching a policy to a WSDL element, a policy scope is implied for that attachment. The policy scope only contains the policy subject associated with that element and not those associated with the children of that element. Therefore, it is RECOMMENDED that each policy assertion contained within a WSDL element's element policy should have the correct semantic such that the policy subject for that assertion is that WSDL element. For example, assertions that describe behaviours regarding the manipulation of messages should only be contained within policies attached to WSDL message elements.

Figure 1 represents how the effective policies, with regard to WSDL, are calculated for each of these policy subjects. In the diagram, the dashed boxes represent policy scopes implied by WSDL elements. For a particular policy subject, the effective policy MUST merge the element policy of each element with a policy scope that contains the policy subject.

For abstract WSDL definitions, the element policy is considered an intrinsic part of the definition and applies to all uses of that definition. In particular, it MUST be merged into the effective policy of every implementation of that abstract WSDL definition.

Policies that are attached to a deployed resource (e.g., services or ports) are only considered in the effective policy of that deployed resource itself.

Figure 4-1. Effective Policy and Policy Scopes in WSDL

(This graphic is also available in SVG format here.)

When attaching policies at different levels of the WSDL hierarchy, care must be taken. A message exchange with an endpoint MAY be described by the effective policies in all four subject types simultaneously.

For example, in Figure 4-1, for a particular input message to a deployed endpoint, there are four policy subjects involved, each with their own effective policy. There is an effective policy for the message, as well as an effective policy for the parent operation of that message, an effective policy for the deployed endpoint, and the effective policy for the service as a whole. All four effective policies are applicable in relation to that specific input message.

It is RECOMMENDED that, where specific policy assertions associated with one policy subject are only compatible with specific policy assertions on another policy subject in the same hierarchical chain, the policies containing these assertions should be attached within a single WSDL binding hierarchy.

For any given port, the policy alternatives for each policy subject type SHOULD be compatible with each of the policy alternatives at each of the policy subjects parent and child policy subjects, such that choices between policy alternatives at each level are independent of each other.

The rest of this section describes these policy subject types, and how the effective policy for each policy subject is calculated.

(01) <wsdl11:definitions name="StockQuote"
        targetNamespace="http://www.example.com/stock/binding"
        xmlns:tns="http://www.example.com/stock/binding"
        xmlns:fab="http://www.example.com/stock"
        xmlns:rmp="http://docs.oasis-open.org/ws-rx/wsrmp/200702"
        xmlns:sp="http://docs.oasis-open.org/ws-sx/ws-securitypolicy/200702"
        xmlns:wsdl="http://schemas.xmlsoap.org/wsdl/"
        xmlns:wsoap12="http://schemas.xmlsoap.org/wsdl/soap12/"
        xmlns:wsp="http://www.w3.org/ns/ws-policy"
        xmlns:wsu="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-utility-1.0.xsd" >
(02)   <wsp:Policy wsu:Id="RmPolicy" >
(03)     <rmp:RMAssertion>
(04)       <wsp:Policy/>
(05)     </rmp:RMAssertion>
(06)   </wsp:Policy>
(07)     <wsp:Policy wsu:Id="X509EndpointPolicy" >
(08)       <sp:AsymmetricBinding>
(09)         <wsp:Policy>
               <!-- Details omitted for readability -->
(10)           <sp:IncludeTimestamp />
(11)           <sp:OnlySignEntireHeadersAndBody />
(12)         </wsp:Policy>
(13)       </sp:AsymmetricBinding>
(14)     </wsp:Policy>
(15)     <wsp:Policy wsu:Id="SecureMessagePolicy" >
(16)       <sp:SignedParts>
(17)         <sp:Body />
(18)       </sp:SignedParts>
(19)       <sp:EncryptedParts>
(20)         <sp:Body />
(21)       </sp:EncryptedParts>
(22)     </wsp:Policy>
(23)     <wsdl11:import namespace="http://www.example.com/stock"
            location="http://www.example.com/stock/stock.wsdl" />
(24)     <wsdl11:binding name="StockQuoteSoapBinding" type="fab:Quote" >
(25)       <wsoap12:binding style="document"
(26)          transport="http://schemas.xmlsoap.org/soap/http" />
(27)       <wsp:PolicyReference URI="#RmPolicy" wsdl11:required="true" />
(28)       <wsp:PolicyReference URI="#X509EndpointPolicy" wsdl11:required="true" />
(29)       <wsdl11:operation name="GetLastTradePrice" >
(30)         <wsoap12:operation soapAction="http://www.example.com/stock/Quote/GetLastTradePriceRequest" />
(31)           <wsdl11:input>
(32)             <wsoap12:body use="literal" />
(33)             <wsp:PolicyReference URI="#SecureMessagePolicy"
                                      wsdl11:required="true" />
(34)           </wsdl11:input>
(35)           <wsdl11:output>
(36)             <wsoap12:body use="literal" />
(37)             <wsp:PolicyReference URI="#SecureMessagePolicy"
(38)                                  wsdl11:required="true" />
(39)           </wsdl11:output>
(40)       </wsdl11:operation>
(41)     </wsdl11:binding>
(42) </wsdl11:definitions>

(01) <wsp:Policy
        xmlns:sp="http://docs.oasis-open.org/ws-sx/ws-securitypolicy/200702"
        xmlns:wsp="http://www.w3.org/ns/ws-policy"
        xmlns:wsu="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-utility-1.0.xsd"
        wsu:Id="SecureMessagePolicy" >
(02)   <sp:SignedParts>
(03)     <sp:Body />
(04)   </sp:SignedParts>
(05)   <sp:EncryptedParts>
(06)     <sp:Body />
(07)   </sp:EncryptedParts>
(08) </wsp:Policy>

5.1 Example

The example below illustrates the use of WS-Policy Attachment for WSDL 2.0:

(01) <wsdl20:description>
(02) …
(03)   <wsp:Policy wsu:Id="common">
(04)     <mtom:OptimizedMimeSerialization wsp:Optional="true"/>
(05)     <wsam:Addressing>…</wsam:Addressing>
(06)   </wsp:Policy>

(07)   <wsp:Policy wsu:Id="secure">
(08)     <wsp:ExactlyOne>
(09)       <sp:TransportBinding>…</sp:TransportBinding>
(10)       <sp:AsymmetricBinding>…</sp:AsymmetricBinding >
(11)     </wsp:ExactlyOne>
(12)   </wsp:Policy>

(13)   <wsdl20:binding name="SecureBinding"
(14)       interface="tns:RealTimeDataInterface" >
(15)     <wsp:PolicyReference URI="#secure" />
(16)     <wsdl20:operation name="GetRealQuote" >…</wsdl20:operation>
(17)     …
(18)   </wsdl20:binding>

(19)   <wsdl20:service name="RealTimeDataService"
(20)        interface="tns:RealTimeDataInterface" >
(21)     <wsdl20:endpoint name="RealTimeDataPort" 
(22)          binding="tns:SecureBinding">
(23)       <wsp:PolicyReference URI="#common" />
(24)       …
(25)     </wsdl20:endpoint>
(26)   </wsdl20:service>
(27) …
(28) </wsdl20:description>

The SecureBinding WSDL binding description describes a binding for an interface that provides real-time quotes and book information on securities. (The prefixes wsdl20 and tns are used here to denote the Web Services Description Language 2.0 XML Namespace and the target namespace of this WSDL document respectively.) To require the use of security for these offerings, a policy expression that requires the use of either transport-level or message-level security is attached to the binding description. The policy expression applies to any message exchange associated with any endpoint that supports this binding description.

The RealTimeDataPort WSDL endpoint description describes an endpoint that supports the SecureBinding WSDL binding description. To require the use of addressing and allow the use of optimization (Optimized MIME Serialization as defined in the MTOM specification [MTOM]), a policy expression that represents the addressing requirement and optimization capability is attached to the endpoint description. The policy expression applies to any message exchange associated with the RealTimeDataPort endpoint.

In the above example, the #secure and #common policy expressions attached to the SecureBinding WSDL binding and RealTimeDataPort WSDL endpoint descriptions collectively apply to any message exchange associated with the RealTimeDataPort endpoint. The example below represents the combination of these two policies, that is, the effective policy for the RealTimeDataPort endpoint.

(01) <wsp:Policy>
(02)   <wsp:All>
(03)     <wsp:Policy>
(04)       <mtom:OptimizedMimeSerialization wsp:Optional="true"/>
(05)       <wsam:Addressing>…</wsam:Addressing>
(06)     </wsp:Policy>
(07)     <wsp:Policy>
(08)       <wsp:ExactlyOne>
(09)         <sp:TransportBinding>…</sp:TransportBinding>
(10)         <sp:AsymmetricBinding>…</sp:AsymmetricBinding >
(11)       </wsp:ExactlyOne>
(12)     </wsp:Policy>
(13)   </wsp:All>
(14) </wsp:Policy>

5.2 Attaching Policy Expressions

Policy attachment points in a WSDL 2.0 document are:

• wsdl20:service

• wsdl20:endpoint

• wsdl20:binding

• wsdl20:binding/wsdl20:operation

• wsdl20:binding/wsdl20:fault

• wsdl20:binding/wsdl20:operation/wsdl20:input

• wsdl20:binding/wsdl20:operation/wsdl20:output

• wsdl20:binding/wsdl20:operation/wsdl20:infault

• wsdl20:binding/wsdl20:operation/wsdl20:outfault

• wsdl20:interface

• wsdl20:interface/wsdl20:operation

• wsdl20:interface/wsdl20:fault

• wsdl20:interface/wsdl20:operation/wsdl20:input

• wsdl20:interface/wsdl20:operation/wsdl20:output

• wsdl20:interface/wsdl20:operation/wsdl20:infault and

• wsdl20:interface/wsdl20:operation/wsdl20:outfault.

Any of these elements MAY have one or more wsp:Policy or wsp:PolicyReference child elements.

Policy attachment points in a WSDL document are associated with specific policy subjects as described in the table below. There are four policy subjects in WSDL: the service policy subject, the endpoint policy subject, the operation policy subject and the message policy subject. When a policy expression is attached to a policy subject in a WSDL document, capabilities and requirements represented by the policy expression apply to any message exchange or message associated with (or described by) the policy subject.

For a WSDL component, the attached policy (extension to the WSDL component model is described in 5.3 Extension to WSDL Component Model) is considered an intrinsic part of the WSDL component definition and applies to all uses of that definition. For example, when attached to a WSDL Interface component, capabilities and requirements represented by a policy apply to all the use of this WSDL Interface description. When attached to a WSDL Binding component, capabilities and requirements represented by a policy apply to all the Endpoints that support this binding description.

A policy associated with a service policy subject applies to any message exchange (that is explicitly described by the Interface component in the Service component's {interface} property) using any of the endpoints offered by that service.

Policies associated with an endpoint policy subject apply to any message exchange (that is explicitly described by the Interface component in the Service component’s {interface} property of the Endpoint component’s {parent} property) made using that endpoint. Given that a WSDL Interface component may be used by one or more binding descriptions, it is RECOMMENDED that only a policy containing policy assertions that apply to any possible binding description should be attached.

Policies associated with an operation policy subject apply to the message exchange described by that operation. Given that a WSDL Interface Operation component may be used by one or more binding descriptions, it is RECOMMENDED that only a policy containing policy assertions that apply to any possible binding description should be attached.

Policies associated with a message policy subject apply to that message (input, output or fault). Given that a WSDL Interface Message Reference, Interface Fault, Interface Fault Reference components may be used by one or more binding descriptions, it is RECOMMENDED that only a policy containing policy assertions that apply to any possible binding should be attached.

Policies MAY be attached at different levels of the WSDL component hierarchy. A message exchange with an endpoint MAY be described by the policies in all four policy subjects simultaneously.

The common mechanism of associating a policy expression with a policy subject is to attach a reference to the policy expression to the policy subject. As described in the WS-Policy specification [Web Services Policy Framework], a reference to a policy expression is represented using the wsp:PolicyReference element. A policy attachment to a WSDL element is represented by attaching a wsp:PolicyReference element as a child element of the WSDL element.

Policy expressions can be included within a WSDL document or may reside external to a WSDL document. If including policy expressions with a WSDL document is the chosen approach, it is RECOMMENDED that the wsp:Policy elements are included as children of the wsdl20:description element after the wsdl20:types element and referenced using the wsp:PolicyReference elements.

To mandate the processing of a policy expression attached to a policy attachment point in a WSDL document, the expression MUST be marked as required using the @wsdl20:required flag.

If the wsp:Policy elements are included as children of the wsdl20:description element, these Policy elements MUST NOT be marked as required using the @wsdl20:required. (Note: these policy expressions may be included as children of the wsdl20:description element and may not be attached to any policy attachment point in a WSDL document.)

5.3 Extension to WSDL Component Model

This document adds an optional {policy} property to the following WSDL components:

• Service

• Endpoint

• Binding

• Binding Operation

• Binding Fault

• Binding Message Reference

• Binding Fault Reference

• Interface

• Interface Operation

• Interface Fault

• Interface Message Reference

• Interface Fault Reference

The {policy} property, when present, represents the capabilities and requirements as a policy. The value of the {policy} property is a policy as defined by Section 3 - Policy Model in the WS-Policy specification [Web Services Policy Framework]. The following table describes the mapping from XML representation to the {policy} property.

Two {policy} properties are equivalent when they represent policies that contain the same number of policy alternatives, and each policy alternative in the first policy is equivalent to some policy alternative in the second policy, and conversely.

Two policy alternatives are equivalent when each policy assertion in the first policy alternative is equivalent to some policy assertion in the second policy alternative, and conversely. If either policy alternative contains multiple policy assertions of the same type, policy alternative equality is dependent on the semantics of that assertion type.

Two policy assertions are equivalent if they have the same QName, if either policy assertion is an ignorable policy assertion, both assertions must be ignorable policy assertions and, if either policy assertion has a nested policy, both assertions must have a nested policy and the nested policies must be equal. If either assertion contains policy assertion parameters, then the policy assertion parameters SHOULD be compared for equality. Comparing policy assertion parameters for equality is not defined by this document, but policy assertion equality may be further refined by the corresponding policy assertion specification.

5.4 Effective Policy

The following diagram illustrates the four policy subjects in WSDL and how the effective policy is calculated for each of these policy subjects.

Figure 5-1. Policy Subjects and Effective Policy in WSDL 2.0

If multiple policies are attached to WSDL components that collectively represent a policy subject then the effective policy of these policies applies. (For example, there is a policy attached to an Endpoint component that describes the component and there is a policy attached to the Binding component in the Endpoint component’s {binding} property.) The effective policy is the merge of the policies that are attached to the same policy subject. The rest of this section describes how the effective policy is calculated for each of these policy subjects.

6.1 Calculating Effective Policy and Element Policy in UDDI

When attaching a policy to a UDDI entity a policy scope is implied for that attachment. The policy scope only contains the policy subjects associated with that entity, and not those associated with the children of that entity. This policy is the entity's element policy.

Each policy assertion contained within a UDDI entity's element policy should have the correct semantic such that the policy subject for that assertion is that UDDI entity. For example, assertions that describe behaviours regarding a service provider should only be contained within policies attached to a businessEntity structure.

For UDDI tModels that represent Web service types, the element policy is considered an intrinsic part of the tModel and applies to all uses of that tModel. In particular, it MUST be merged into the effective policy of every bindingTemplate that references that tModel.

Policies that apply to deployed Web services (bindingTemplates) are only considered in the effective policy of that deployed resource itself.

Each of these entities MAY have an element policy per Section 3. Policy Attachment. The remainder of this section defines how that element policy is interpreted to calculate the effective policy.

6.2 Referencing Remote Policy Expressions

UDDI tModels provide a generic mechanism for associating arbitrary metadata with services and other entities in a UDDI registry. To properly integrate Web Services Policy into the UDDI model, Web Services Policy 1.5 - Attachment pre-defines one tModel that is used to associate a remotely accessible policy with an entity in a UDDI registry.

This new tModel is called the remote policy reference category system and is defined in Appendix B.1 Remote Policy Reference Category System.

UDDI registries MUST use the (UDDI V2 [UDDI Data Structure 2.0]) tModelKey uuid:2ea5f9d3-9b84-39f9-b334-e9d5f535b4c1 to uniquely identify this tModel so that UDDI registry users can expect the same behavior across different UDDI registries.

The tModel's valid values are those IRIs that identify external policy expressions; that is, when referencing this category system in a categoryBag, the corresponding keyValue of the keyedReference is the IRI of the policy expression.

Using the remote policy reference category system, one can then associate a policy expression with a businessEntity, a businessService, and a tModel using the entity's categoryBag. For example, associating the policy expression that is identified by the IRI http://www.example.com/myservice/policy with a businessService is done as follows: 

(01) <businessService serviceKey="…" >
(02)   <name>…</name>
(03)   <description>…</description>
(04)   <bindingTemplates>…</bindingTemplates>
(05)   <categoryBag>
(06)     <keyedReference
(07)        keyName="Policy Expression for example's Web services"
(08)        keyValue="http://www.example.com/myservice/policy"
(09)        tModelKey="uuid:2ea5f9d3-9b84-39f9-b334-e9d5f535b4c1" />
(10)   </categoryBag>
(11) </businessService>

The tModelKey of the keyedReference MUST match the fixed tModelKey from the remote policy reference category system. The keyValue MUST be the IRI that identifies the policy expression.

A different approach has to be taken to associate a policy expression with a bindingTemplate, since bindingTemplates do not contain a categoryBag in UDDI Version 2. Therefore, the bindingTemplate's tModelInstanceInfo and instanceParms MUST be used as follows: 

(01) <bindingTemplate bindingKey="…" >
(02)   <accessPoint>…</accessPoint>
(03)   <tModelInstanceDetails>
(04)     <tModelInstanceInfo
(05)        tModelKey="uuid:2ea5f9d3-9b84-39f9-b334-e9d5f535b4c1" >
(06)       <instanceDetails>
(07)         <instanceParms>
(08)           http://www.example.com/myservice/policy
(09)         </instanceParms>
(10)       </instanceDetails>
(11)     </tModelInstanceInfo>
(12)   </tModelInstanceDetails>
(13) </bindingTemplate>

The tModelKey of the tModelInstanceInfo MUST match the fixed tModelKey from the remote policy reference category system as defined above. The instanceParms MUST be the IRI that identifies the policy expression.

6.3 Registering Reusable Policy Expressions

In addition to using the approach outlined in the section above, publishers may register a specific policy expression in a UDDI registry as a distinct tModel. To properly categorize tModels as policy expressions, Web Services Policy 1.5 - Attachment pre-defines the Web Services Policy Types category system as a tModel. This tModel is defined in Appendix B.2 Web Services Policy Types Category System.

The following illustrates a tModel for the policy expression identified by the IRI http://www.example.com/myservice/policy.

(01) <tModel tModelKey="uuid:04cfa…">
(02)   <name>…</name>
(03)   <description xml:lang="EN">
(04)     Policy Expression for example's Web services
(05)   </description>
(06)   <overviewDoc>
(07)     <description xml:lang="EN">Web Services Policy Expression</description>
(08)     <overviewURL>http://www.example.com/myservice/policy</overviewURL>
(09)   </overviewDoc>
(10)   <categoryBag>
(11)     <keyedReference
(12)        keyName="Reusable policy Expression"
(13)        keyValue="policy"
(14)        tModelKey="uuid:90eda65e-ffd7-33df-965f-98ebb1c2a941" />
(15)     <keyedReference
(16)        keyName="Policy Expression for example's Web services"
(17)        keyValue="http://www.example.com/myservice/policy"
(18)        tModelKey="uuid:2ea5f9d3-9b84-39f9-b334-e9d5f535b4c1" />
(19)   </categoryBag>
(20) </tModel>

The first keyedReference specifies that the tModel represents a policy expression — rather than only being associated with one — by using the Web Services Policy Types category system's built-in category "policy", which is its single valid value. This is necessary in order to enable UDDI inquiries for policy expressions in general. The second keyedReference designates the policy expression the tModel represents by using the approach from the section above. This is necessary in order to enable UDDI inquiries for particular policy expressions based on their IRI.

Note that the policy expression IRI is also specified in the tModel's overview URL to indicate that it is a resolvable URL to actually retrieve the policy expression.

Web Services Policy 1.5 - Attachment pre-defines another tModel that is used to associate such a pre-registered, locally available policy expressions with an entity in a UDDI registry

This new tModel is called the local policy reference category system and is defined in Appendix B.3 Local Policy Reference Category System.

UDDI registries MUST use the tModelKey uuid:5da4fc61-a302-35ad-91d3-775150429035 to uniquely identify this tModel so that UDDI registry users can expect the same behavior across different UDDI registries.

The local policy reference category system is based on tModelKeys. The valid values of this category system are those tModelKeys identifying tModels that

• exist in the same UDDI registry

• and are categorized as "policy" using the Web Services Policy Types category system.

That is, when referencing this category system in a category bag, the corresponding keyValue of the keyedReference is the tModelKey of the tModel that represents the policy expression.

Given the local policy reference category system, one can then associate a policy expression tModel with a businessEntity, a businessService, and a tModel using the entity's categoryBag. For example, associating the policy expression tModel with the tModelKey "uuid:04cfa…" from above with a businessService is done as follows: 

(01) <businessService serviceKey="…" >
(02)   <name>…</name>
(03)   <description>…</description>
(04)   <bindingTemplates>…</bindingTemplates>
(05)   <categoryBag>
(06)     <keyedReference
(07)        keyName="Policy Expression for example's Web services"
(08)        keyValue="uuid:04cfa…"
(09)        tModelKey="uuid:5da4fc61-a302-35ad-91d3-775150429035" />
(10)   </categoryBag>
(11) </businessService>

The tModelKey of the keyedReference MUST match the fixed tModelKey from the local policy reference category system. The keyValue MUST be the tModelKey of the policy expression that is registered with the UDDI registry.

A different approach has to be taken to associate a policy expression with a bindingTemplate, since bindingTemplates do not contain a categoryBag in UDDI Version 2. Therefore, the bindingTemplate's tModelInstanceInfo and instanceParms MUST be used as follows: 

(01) <bindingTemplate bindingKey="…" >
(02)   <accessPoint>…</accessPoint>
(03)   <tModelInstanceDetails>
(04)     <tModelInstanceInfo
(05)        tModelKey="uuid:5da4fc61-a302-35ad-91d3-775150429035" >
(06)       <instanceDetails>
(07)         <instanceParms>uuid:04cfa…</instanceParms>
(08)       </instanceDetails>
(09)     </tModelInstanceInfo>
(10)   </tModelInstanceDetails>
(11) </bindingTemplate>

The tModelKey of the tModelInstanceInfo MUST match the fixed tModelKey from the local policy reference category system. The instanceParms MUST be the tModelKey of the policy expression that is registered with the UDDI registry.

6.4 Registering Policies in UDDI Version 3

UDDI Version 3 [UDDI 3.0] provides a number of enhancements in the areas of modeling and entity keying. Special considerations for UDDI multi-version support are outlined in chapter 10 of [UDDI 3.0]. The changes with respect to the previous sections are as follows.

First, the tModelKeys of the pre-defined tModels are migrated to domain-based keys. The migration is unique since the Version 2 keys introduced in this specification are already programmatically derived from the Version 3 keys given below.

The tModelKey for the remote policy reference tModel changes from "uuid:2ea5f9d3-9b84-39f9-b334-e9d5f535b4c1" to "uddi:w3.org:ws-policy:v1.5:attachment:remotepolicyreference".

The tModelKey for the Web Services Policy Types tModel changes from "uuid:90eda65e-ffd7-33df-965f-98ebb1c2a941" to "uddi:w3.org:ws-policy:v1.5:attachment:policytypes".

The tModelKey for the local policy reference tModel changes from "uuid:5da4fc61-a302-35ad-91d3-775150429035" to "uddi:w3.org:ws-policy:v1.5:attachment:localpolicyreference".

Second, rather than putting policy expression references in a bindingTemplate's tModelInstanceInfo, they are added to the bindingTemplate's categoryBag, analogous to the mechanism described for other UDDI entities. For example, the example bindingTemplate from section 6.1 Calculating Effective Policy and Element Policy in UDDI would be changed as follows: 

(01) <bindingTemplate bindingKey="…" >
(02)   <accessPoint>…</accessPoint>
(03)   <tModelInstanceDetails>…</tModelInstanceDetails>
(04)   <categoryBag>
(05)     <keyedReference
(06)        keyName="Policy Expression for example's Web services"
(07)        keyValue="http://www.example.com/myservice/policy"
(08)        tModelKey="uddi:w3.org:ws-policy:v1.5:attachment:remotepolicyreference"
(09)     />
(10)   </categoryBag>
(11) </bindingTemplate>

Third, inquiries for reusable policy expression tModels described in Section 6.3 Registering Reusable Policy Expressions and UDDI tModel entities that are associated with remote policy expression is enhanced by the wildcard mechanism for keyValues in keyedReferences. For example, searching for all policy expression tModels whose IRI starts with http://www.example.com/, the following find_tModel API call can be used: 

(01) <find_tModel 
        xmlns="urn:uddi-org:api_v3" >
(02)   <categoryBag>
(03)     <keyedReference
(04)        keyValue="http://www.example.com/"
(05)        tModelKey="uddi:w3.org:ws-policy:v1.5:attachment:remotepolicyreference"
(06)     />
(07)   </categoryBag>
(08)   <findQualifiers>
(09)     <findQualifier>approximateMatch</findQualifier>
(10)   </findQualifiers>
(11) </find_tModel>

Fourth, all UDDI entities may be digitally signed using XML digital signatures [XML-Signature]. Publishers who want to digitally sign their policy expression tModels or policy expression references in UDDI MUST use the Schema-centric canonicalization algorithm [SCC14N].

8.1 External Policy Attachment Conformance

An element information item whose namespace name is "http://www.w3.org/ns/ws-policy" and whose local part is PolicyAttachment conforms to this specification if it is valid according to the XML Schema [XML Schema Structures] for that element as defined by this specification (http://www.w3.org/2007/02/ws-policy.xsd) and additionally adheres to all the constraints contained in Section 3.4 External Policy Attachment of this specification. Such a conformant element information item constitutes an external policy attachment.

8.2 WSDL 1.1 Attachment Conformance

A WSDL 1.1 [WSDL 1.1] description conforms to this specification when it incorporates one or more element policies and additionally adheres to all the constraints contained in section 4. Attaching Policies Using WSDL 1.1

8.3 WSDL 2.0 Attachment Conformance

A WSDL 2.0 [WSDL 2.0 Core Language] description conforms to this specification when it incorporates one or more element policies and additionally adheres to all the constraints contained in section 5. WS-Policy Attachment for WSDL 2.0