Web Services Metadata Exchange (WS-MetadataExchange)

2.1 Requirements

This specification intends to meet the following requirements:

• Define a mechanism for retrieving metadata about a Web service endpoint.

• Define an encapsulation format for metadata.

• Treat the metadata about a Web service endpoint as [WS-Transfer] resources, or as an HTTP reachable resource.

• Define a bootstrap mechanism for retrieving metadata.

• Support future versions of known metadata formats.

• Allow new metadata formats to be added.

2.2 Examples

Example 2-1 illustrates a sample GetWSDL request for the WSDL metadata document of a service.

(01)  <s11:Envelope
(02)     xmlns:s11='http://schemas.xmlsoap.org/soap/envelope/'
(03)     xmlns:wsa='http://www.w3.org/2005/08/addressing'>
(04)     xmlns:wst='http://www.w3.org/2011/03/ws-tra'>
(05)    <s11:Header>
(06)      <wsa:Action>
(07)        http://www.w3.org/2011/03/ws-mex/GetWSDL
(08)      </wsa:Action>
(09)      <wsa:To>http://services.example.org/stockquote</wsa:To>
(10)      <wsa:ReplyTo>
(11)        <wsa:Address>http://client.example.org</wsa:Address>
(12)      </wsa:ReplyTo>
(13)      <wsa:MessageID>
(14)        urn:uuid:1cec121a-82fe-41da-87e1-3b23f254f128
(15)      </wsa:MessageID>
(16)    </s11:Header>
(17)    <s11:Body>
(18)      <mex:GetWSDL/>
(19)    </s11:Body>
(20)  </s11:Envelope> 

Example 2-2 lists a sample response to the request in Example 2-1.

(01)   <s11:Envelope
(02)      xmlns:s11='http://schemas.xmlsoap.org/soap/envelope/'
(03)      xmlns:wsa='http://www.w3.org/2005/08/addressing'
(04)      xmlns:wsp='http://www.w3.org/ns/ws-policy'
(05)      xmlns:mex='http://www.w3.org/2011/03/ws-mex'>
(06)    <s11:Header>
(07)      <wsa:To>http://client.example.org</wsa:To>
(08)      <wsa:Action>
(09)        http://www.w3.org/2011/03/ws-mex/GetWSDLResponse
(10)      </wsa:Action>
(11)      <wsa:RelatesTo>
(12)        urn:uuid:73d7edfc-5c3c-49b9-ba46-2480caee43e9
(13)      </wsa:RelatesTo>
(14)    </s11:Header>
(15)    <s11:Body>
(16)      <mex:GetWSDLResponse>
(17)        <wsdl:definitions ...>
(18)          <!-- WSDL data removed for brevity -->
(19)        </wsdl:definitions>
(18)      </mex:GetWSDLResponse>
(19)    </s11:Body>
(20)  </s11:Envelope> 

Lines 17-19 in Example 2-2 is the WSDL of the service.

Example 2-3 illustrates a sample [WS-Transfer] Get request for a resource' s representation.

(01)  <s11:Envelope
(02)     xmlns:s11='http://schemas.xmlsoap.org/soap/envelope/'
(03)     xmlns:wsa='http://www.w3.org/2005/08/addressing'>
(04)     xmlns:wst='http://www.w3.org/2011/03/ws-tra'>
(05)    <s11:Header>
(06)      <wsa:Action>
(07)        http://www.w3.org/2011/03/ws-tra/Get
(08)      </wsa:Action>
(09)      <wsa:To>http://services.example.org/stockquote/metadata</wsa:To>
(10)      <wsa:ReplyTo>
(11)        <wsa:Address>http://client.example.org</wsa:Address>
(12)      </wsa:ReplyTo>
(13)      <wsa:MessageID>
(14)        urn:uuid:1cec121a-82fe-41da-87e1-3b23f254f128
(15)      </wsa:MessageID>
(16)    </s11:Header>
(17)    <s11:Body>
(18)      <wst:Get/>
(19)    </s11:Body>
(20)  </s11:Envelope>

The sample request message of Example 2-3 is a [WS-Transfer] request for the retrieval of a resource's representation. In this case, the requested representation is the WS-MetadataExchange Metadata element about a Web service endpoint. The fact that the resource's representation is a mex:Metadata element might be known to the requestor but is not explicitly encoded in the request message.

Example 2-4 illustrates a sample response to the request of Example 2-3.

(01)  <s11:Envelope
(02)      xmlns:s11='http://schemas.xmlsoap.org/soap/envelope/'
(03)      xmlns:xs='http://www.w3.org/2001/XMLSchema'
(04)      xmlns:wsa='http://www.w3.org/2005/08/addressing'
(05)      xmlns:mex='http://www.w3.org/2011/03/ws-mex'
(06)      xmlns:wsp='http://www.w3.org/ns/ws-policy'
(07)      xmlns:wst='http://www.w3.org/2011/03/ws-tra'
(08)      xmlns:wsdl='http://schemas.xmlsoap.org/wsdl/'>
(09)    <s11:Header>
(10)      <wsa:Action>
(11)        http://www.w3.org/2011/03/ws-tra/GetResponse
(12)      </wsa:Action>
(13)      <wsa:To>http://client.example.org</wsa:To>
(14)      <wsa:RelatesTo>
(15)        urn:uuid:1cec121a-82fe-41da-87e1-3b23f254f128
(16)      </wsa:RelatesTo>
(17)    </s11:Header>
(18)    <s11:Body>
(19)      <wst:GetResponse>
(20)        <mex:Metadata>
(21)          <mex:MetadataSection Dialect='wsdl:definitions'>
(22)            <wsdl:definitions>
(23)              <!-- WSDL data removed for brevity -->
(24)            </wsdl:definitions>
(25)          </mex:MetadataSection>
(26)          <mex:MetadataSection
(27)              Dialect='xs:schema'
(28)              Identifier='http://services.example.org/stockquote/schemas'>
(29)            <mex:MetadataLocation>
(30)              http://services.example.org/stockquote/schemas
(31)            </mex:MetadataLocation>
(32)          </mex:MetadataSection>
(33)          <mex:MetadataSection
(34)              Dialect='wsp:Policy'
(35)              Identifier='http://services.example.org/stockquote/policy'>
(36)            <mex:MetadataReference>
(37)              <wsa:Address>
(38)                http://services.example.org/stockquote/policy
(39)              </wsa:Address>
(40)            </mex:MetadataReference>
(41)          </mex:MetadataSection>
(42)        </mex:Metadata>
(43)      </wst:GetResponse>
(44)    </s11:Body>
(45)  </s11:Envelope>

The message of Example 2-4 is a [WS-Transfer] response message to the request of Example 2-3. The content of the [Body] (lines 18-44) is a mex:Metadata element with metadata about the Web service endpoint (lines 20-42). The mex:Metadata contains three MetadataSections. The first MetadataSection (lines 21-25) contains the [WSDL11] of the Web service endpoint. The second MetadataSection (lines 26-32) contains the location of the XML Schemas [XMLSchema - Part 1], [XMLSchema - Part 2] used by the WSDL document. The schemas can be retrieved through an HTTP GET request at the identified URL (lines 29-31). The third MetadataSection (lines 33-41) contains the [WS-Addressing] endpoint reference (lines 36-40) of a [WS-Transfer] resource the representation of which is a [WS-Policy] document as indicated by the Dialect attribute (line 34).

While the WS-Policy of the Web service endpoint could be retrieved using a WS-Transfer Get request directed to the endpoint identified by the mex:MetadataReference element in lines 36-40 of Example 2-4, some endpoints MAY support explicit requests for metadata via the GetMetadata operation. Example 2-5 illustrates a sample GetMetadata request for the [WS-Policy].

(01)  <s11:Envelope
(02)      xmlns:s11='http://schemas.xmlsoap.org/soap/envelope/'
(03)      xmlns:wsa='http://www.w3.org/2005/08/addressing'
(04)      xmlns:wsp='http://www.w3.org/ns/ws-policy'
(05)      xmlns:mex='http://www.w3.org/2011/03/ws-mex' >
(06)    <s11:Header>
(07)      <wsa:To>http://services.example.org/stockquote</wsa:To>
(08)      <wsa:Action>
(09)        http://www.w3.org/2011/03/ws-mex/GetMetadata
(10)      </wsa:Action>
(11)      <wsa:MessageID>
(12)        urn:uuid:73d7edfc-5c3c-49b9-ba46-2480caee43e9
(13)      </wsa:MessageID>
(14)      <wsa:ReplyTo>
(15)        <wsa:Address>http://client.example.org</wsa:Address>
(16)      </wsa:ReplyTo>
(17)    </s11:Header>
(18)    <s11:Body>
(19)      <mex:GetMetadata>
(20)        <mex:Dialect Type='{http://www.w3.org/ns/ws-policy}Policy'
(21)          Identifier='http://services.example.org/stockquote/policy'/>
(22)      </mex:GetMetadata>
(23)    </s11:Body>
(24)  </s11:Envelope>

Lines 8-10 in Example 2-5 indicate this is a GetMetadata request. As lines 19-22 indicate, this request is for the policy of the Web service endpoint (line 7).

Example 2-6 lists a sample response to the request in Example 2-5.

(01)   <s11:Envelope
(02)      xmlns:s11='http://schemas.xmlsoap.org/soap/envelope/'
(03)      xmlns:wsa='http://www.w3.org/2005/08/addressing'
(04)      xmlns:wsp='http://www.w3.org/ns/ws-policy'
(05)      xmlns:mex='http://www.w3.org/2011/03/ws-mex'>
(06)    <s11:Header>
(07)      <wsa:To>http://client.example.org</wsa:To>
(08)      <wsa:Action>
(09)        http://www.w3.org/2011/03/ws-mex/GetMetadataResponse
(10)      </wsa:Action>
(11)      <wsa:RelatesTo>
(12)        urn:uuid:73d7edfc-5c3c-49b9-ba46-2480caee43e9
(13)      </wsa:RelatesTo>
(14)    </s11:Header>
(15)    <s11:Body>
(16)      <mex:GetMetadataResponse>
(17)        <mex:Metadata>
(18)          <mex:MetadataSection
(19)              Dialect='wsp:Policy'
(20)              Identifier='http://services.example.org/stockquote/policy'>
(21)            <wsp:Policy>
(22)              <wsp:ExactlyOne>
(23)                <!-- Policy alternatives -->
(24)              </wsp:ExactlyOne>
(25)            </wsp:Policy>
(26)          </mex:MetadataSection>
(27)        </mex:Metadata>
(28)      </mex:GetMetadataResponse>
(29)    </s11:Body>
(30)  </s11:Envelope>

Lines 8-10 in Example 2-6 indicate this message is a response to a GetMetadata request, and lines 11-13 indicate that it is a response to the request in Example 2-5. Lines 17-26 contain a single MetadataSection (lines 18-26); line 19 indicates that the metadata in this section is of type, or Dialect, WS-Policy while line 20 identifies a specific policy document. Line 23 would have contained the policy expressions for the Web service endpoint to which the GetMetadata request of Example 2-5 was directed.

3.1 Notational Conventions

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 [RFC 2119].

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

• 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.

• The characters "[" and "]" are used to call out references and property names.

• Ellipses (i.e., "...") indicate points of extensibility.

• XML namespace prefixes (see Table 3-1) are used to indicate the namespace of the element being defined.

In addition to Message Information Header properties [WS-Addressing], this specification uses the following properties to define messages:

[Headers]

Unordered message headers.

[Action]

The value to be used for the wsa:Action IRI.

[Body]

A message body.

These properties bind to a SOAP Envelope as follows:

<s:Envelope>
  <s:Header>
    [Headers]
    <wsa:Action>[Action]</wsa:Action>
    ...
  </s:Header>
  <s:Body>[Body]</s:Body> 
</s:Envelope>

This specification can be used in terms of XML Information Set (Infoset) [XML Infoset], even though the specification uses XML 1.0 terminology. Valid Infoset for this specification is the one serializable in XML 1.0, hence the use of XML 1.0.

The term "generate" is used in relation to the various faults defined by this specification to imply that a fault is produced and no further processing SHOULD be performed. In these cases the fault SHOULD be transmitted. However, there might be reasons when a compliant implementation can choose not to transmit the fault - for example, security concerns - in these situations the service MAY choose not to transmit the fault.

3.2 Considerations on the Use of Extensibility Points

The elements defined in this specification MAY be extended at the points indicated by their outlines and schema. Implementations MAY add child elements and/or attributes at the indicated extension points but MUST NOT contradict the semantics of the parent and/or owner, respectively. If a receiver does not recognize an extension, the receiver SHOULD ignore that extension. Senders MAY indicate the presence of an extension that has to be understood through the use of a corresponding SOAP Header with a soap:mustUnderstand attribute with the value "1".

In cases where it is either desirable or necessary for the receiver of a request that has been extended to indicate that it has recognized and accepted the semantics associated with that extension, it is RECOMMENDED that the receiver add a corresponding extension to the response message. The definition of an extension SHOULD clearly specify how the extension that appears in the response correlates with that in the corresponding request.

Extension elements and attributes MUST NOT use the Web Services Metadata Exchange namespace URI.

3.3 Terminology

Service Endpoint

A Web service that is addressable using a WS-Addressing endpoint reference. Within the context of this specification, it is assumed that the consumer's primary goal is to interact with this service.

Metadata Resource

A specialized Web service that is addressable using either a WS-Addressing endpoint reference or a URL and whose main purpose is to expose the XML representation of a piece of metadata associated with a Service Endpoint.

While technically a single Web service can be both a 'Service Endpoint' as well as a 'Metadata Resource', for the purposes of clarifying the various expectations of these two types Web services, this specification will discuss these two concepts (or roles) as distinct entities.

3.4 Compliance

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 3.5 XML Namespaces) within SOAP Envelopes unless it is compliant with this specification.

Normative text within this specification takes precedence over the XML Schema and WSDL descriptions, which in turn take precedence over outlines, which in turn take precedence over examples.

All messages defined by this specification MUST conform to the WS-Addressing specifications and be sent to a Web service that is addressable by an EPR (see [WS-Addressing]).

Unless otherwise noted, all IRIs are absolute IRIs and IRI comparison MUST be performed according to [RFC 3987] section 5.3.1.

For any message defined by this specification, any OPTIONAL elements or attributes in the message MAY be used by senders of the message; however receivers of those messages MUST support those OPTIONAL elements and attributes, unless other behavior is explicitly defined by this specification.

Support for the GetMetadata operation by a Web service is OPTIONAL. If metadata about a Web service endpoint is referenced by a MetadataReference, which is a [WS-Addressing] endpoint reference, then the MetadataReference MUST refer to a [WS-Transfer] resource. The referred resource MAY also support other resource management and access specifications (e.g. HTTP, WS-ResourceFramework).

Implementations are expected to support both UTF-8 and UTF-16 as described in XML 1.0.

Implementations of this specification MUST conform to the corrected version of WSDL as defined by the 'WSDL Correction' sections of WS-I Basic Profile 1.2 [BP12] and WS-I Basic Profile 2.0 [BP20].

3.5 XML Namespaces

The XML namespace URI that MUST be used by implementations of this specification is:

http://www.w3.org/2011/03/ws-mex

Table 3-1 lists XML namespaces that are used in this specification. The choice of any namespace prefix is arbitrary and not semantically significant.

The working group intends to update the value of the Web Services Metadata Exchange namespace URI each time a new version of this document is published until such time that the document reaches Candidate Recommendation status. Once it has reached Candidate Recommendation status, the working group intends to maintain the value of the Web Services Metadata Exchange namespace URI that was assigned in the Candidate Recommendation unless significant changes are made that impact the implementation or break post-CR implementations of the specification. Also see http://www.w3.org/2001/tag/doc/namespaceState.html and http://www.w3.org/2005/07/13-nsuri .

6.1 GetWSDL

A requester MAY send a GetWSDL request message to an endpoint to retrieve the service's WSDL metadata document. This operation MUST be supported by compliant WS-MetadataExchange service endpoints. Note, the GetWSDL operation is a SOAP-based equivalent feature to the commonly supported HTTP GET targeted at an endpoint's URL appended with "?wsdl".

Through examination of this WSDL document, and by following any references within it, a requester MUST be able to retrieve any metadata needed to interact with the service. For example, the schema used by the service might be embedded within the WSDL or could be available by following a xs:import element. Likewise, as discussed in 9 Exposing Metadata for Implicitly Defined Features through the inclusion of policy assertions and nested metadata (or metadata references) within those policy assertions, a requester MUST be able to determine the set of implicit features available and any related metadata associated with those features.

The normative outline for a GetWSDL request is:

[Action]
  http://www.w3.org/2011/03/ws-mex/GetWSDL

[Body]
  <mex:GetWSDL ...>
    xs:any*
  </mex:GetWSDL> 

If the endpoint accepts a GetWSDL request, it MUST reply with a GetWSDLResponse message. The normative outline for a GetWSDLResponse is:

[Action]
  http://www.w3.org/2011/03/ws-mex/GetWSDLResponse

[Body]
  <mex:GetWSDLResponse ...>
    xs:any*
  </mex:GetWSDLResponse> 

The following describes additional, normative constraints on the outline listed above:

[Body]/mex:GetWSDLResponse/xs:any

When the GetWSDLResponse element contains any child elements, the first element MUST either be the WSDL metadata document, or a reference to the WSDL metadata document, of the endpoint. While an endpoint MAY choose to return a reference to the WSDL, it is STRONGLY RECOMMENDED that the WSDL metadata document itself be returned. If a requester would like a reference to the WSDL then it can use the GetMetadata operation specifying the appropriate Content URI.

Any extension elements MUST appear after the WSDL document/reference. The absence of any child elements indicates that the endpoint does not have any WSDL document, or additional metadata, associated with it.

[Body]/mex:GetWSDLResponse/wsdl:definitions

When present this OPTIONAL element contains the WSDL metadata document of the endpoint.

[Body]/mex:GetWSDLResponse/mex:Location

When present this OPTIONAL element contains a reference to the WSDL metadata document of the endpoint.

[Body]/mex:GetWSDLResponse/mex:Reference

When present this OPTIONAL element contains a reference to the WSDL metadata document of the endpoint.

This operation is safe; it will not result in any side effect imputable to the requester. This means that in case of an underlying protocol error that might get unnoticed, resending the same request can be done automatically.

6.2 GetMetadata

A requester MAY send a GetMetadata request message to an endpoint to retrieve the metadata associated with that endpoint. This operation MAY be supported by WS-MetadataExchange compliant service endpoints. Observe that, in the case where a service endpoint is also a [WS-Transfer] resource, the [WS-Transfer] Get operation allows requesters to retrieve the resource representation associated with that endpoint (i.e. the "data"), while the GetMetadata operation can be used to retrieve that endpoint's metadata. The normative outline for a GetMetadata request is:

[Action]
  http://www.w3.org/2011/03/ws-mex/GetMetadata

[Body]
  <mex:GetMetadata Content='xs:any' ? ...>
    <mex:Dialect Type='mex:QNameSerialization'
                 Identifier='xs:anyURI' ?
                 Content='xs:anyURI' ? .../> *
    xs:any*
  </mex:GetMetadata> 

The following describes additional, normative constraints on the outline listed above:

[Body]/mex:GetMetadata@Content

This OPTIONAL attribute, when present, specifies the default content form IRI for this request. When this attribute is not present, the default content form IRI is 'http://www.w3.org/2011/03/ws-mex/Content/Any'.

If no dialect elements are present in the request, the response MUST only include MetadataSections of the content form specified by this attribute.

If the specified content form is not available, or not known, then the response MUST include zero MetadataSections of the specified form.

This specification defines the following content form IRIs:

Content Form IRI	Form
http://www.w3.org/2011/03/ws-mex/Content/EPR	A MetadataReference element is returned
http://www.w3.org/2011/03/ws-mex/Content/URI	A MetadataLocation element is returned
http://www.w3.org/2011/03/ws-mex/Content/Metadata	The metadata is embedded
http://www.w3.org/2011/03/ws-mex/Content/Any	The service is free to choose any content form
http://www.w3.org/2011/03/ws-mex/Content/All	The service MUST return all available content forms

[Body]/mex:GetMetadata/mex:Dialect

When this repeating OPTIONAL element is present, the response MUST include only MetadataSections corresponding to metadata specified by the combination of the QName, Identifier and Content attributes of each of the Dialect elements. For each Dialect element if there is no metadata for that combination of attributes then the response MUST NOT include any MetadataSections for that Dialect element.

When this element is not present, the endpoint MUST return all available metadata.

[Body]/mex:GetMetadata/mex:Dialect@Type

This REQUIRED attribute specifies the Metadata Dialect. The response MUST only include MetadataSections corresponding to the Dialect specified by this QName. If the receiver does not have any MetadataSections of this indicated Dialect, the response MUST include zero MetadataSections for this QName.

Note: the QName is serialized as {namespace-uri}localName.

[Body]/mex:GetMetadata/mex:Dialect@Identifier

When this OPTIONAL attribute is present, the response MUST include only MetadataSections with the indicated identifier; if the receiver does not have any MetadataSections of the indicated identifier, the response MUST include zero MetadataSections for this QName/Identifier pair. When this attribute is not present, the implied value is any identifier. If multiple MetadataSections have the indicated Dialect and Identifier then all of them MUST be returned. Note that the absence of this attribute is not equivalent to its presence with a value of "" - which indicates a request to retrieve all metadata whose Identifier is the empty string.

[Body]/mex:GetMetadata/mex:Dialect@Content

For the dialect indicated, the response MUST include only MetadataSections of the content form specified by this attribute.

When this OPTIONAL attribute is not present, it defaults to the value of the [Body]/mex:GetMetadata@Content attribute.

If the specified content form is not available, or not known, then the response MUST include zero MetadataSections of the specified form for this QName/Identifier pair.

Subject to authorization restrictions, services MUST return all the MetadataSections corresponding to the GetMetadata request. Note that there can be multiple MetadataSections returned for any one combination of Dialect, Identifier and Content values.

If an endpoint accepts a GetMetadata request, it MUST reply with a GetMetadataResponse message. The normative outline for a GetMetadataResponse is:

[Action]
  http://www.w3.org/2011/03/ws-mex/GetMetadataResponse

[Body]
  <mex:GetMetadataResponse ...>
    <mex:Metadata ...> ... </mex:Metadata>
    xs:any*
  </mex:GetMetadataResponse>

The following describes additional, normative constraints on the outline listed above:

[Body]/mex:GetMetadataResponse/mex:Metadata

The body of the response message MUST contain one mex:Metadata element as defined in 4 Web Services Metadata Collection.

Note, in cases where the requester, through the use of @Content and/or mex:Dialect sub-elements in the GetMetadata request, has excluded all the metadata maintained by the service, this element will be empty.

This operation is safe; it will not result in any side effect imputable to the requester. This means that in case of an underlying protocol error that might get unnoticed, resending the same request can be done automatically.

6.3 PutMetadata

A requester MAY send a PutMetadata request message to an endpoint to update the metadata associated with that endpoint. This operation MAY be supported by WS-MetadataExchange compliant service endpoints. Observe that, in the case where a service endpoint is also a [WS-Transfer] resource, the [WS-Transfer] Put operation allows requesters to update the resource representation associated with that endpoint (i.e. the "data"), while the PutMetadata operation can be used to update that endpoint's metadata.

The normative outline for a PutMetadata request is:

[Action]
  http://www.w3.org/2011/03/ws-mex/PutMetadata
 
[Body]
  <mex:PutMetadata ...>
    <mex:Metadata ...> ... </mex:Metadata>
    xs:any*
  </mex:PutMetadata>

The following describes additional, normative constraints on the outline listed above:

[Body]/mex:PutMetadata

This REQUIRED element MUST have as its first child element an element that comprises the representation of the metadata that is to be replaced. Additional extension elements MAY be included after the element representing the metadata to be updated.

[Body]/mex:PutMetadata/mex:Metadata

The body of the PutMetadata message MUST contain one mex:Metadata element as defined in 4 Web Services Metadata Collection.

The mex:Metadata element contains one MetadataSection child for each distinct unit of metadata to be updated. All resource metadata (identified by the Dialect, Identifier and Content values) specified by each metadata section MUST be replaced in its entirety by the metadata specified in the PutMetadata request message; the service MUST treat the incoming MetadataSections as the complete set of metadata for the specified Dialect, Identifier and Content values and any metadata previously associated with that triplet of values MUST be removed.

If there is no Metadata associated with the resource that corresponds to a MetadataSection child contained within the mex:Metadata element, the endpoint MUST create the Metadata if the MetadataSection has a dialect that is supported by the endpoint and if the creation of the Metadata will not invalidate the endpoint.

When storing references, the endpoint MUST NOT resolve the references in an attempt to persist the actual metadata document itself.

An endpoint MUST reject a PutMetadata request if it is unable to process all of the metadata updates requested. If the dialect, identifier or content form specified in one or more MetadataSections is unsupported by the endpoint, the endpoint MUST generate a mex:UnsupportedMetadata fault. If the creation or update of the endpoint's Metadata will render the endpoint invalid (either because the metadata is of an invalid syntax for the dialect or because the metadata will cause a semantic conflict with the endpoint's definition), the endpoint MUST generate an mex:InvalidMetadata fault.

If an endpoint accepts a PutMetadata request, it MUST reply with a PutMetadataResponse message. The normative outline for a PutMetadataResponse is:

[Action]
  http://www.w3.org/2011/03/ws-mex/PutMetadataResponse
 
[Body]
  <mex:PutMetadataResponse>
    <mex:Metadata ...> ... </mex:Metadata> ?
    xs:any*
  </mex:PutMetadataResponse>

The following describes additional, normative constraints on the outline listed above:

[Body]/mex:PutMetadataResponse

This REQUIRED element, if it contains any child elements, MUST have as its first child element, a mex:Metadata element that comprises the representation of the metadata that has been updated. Additional extension elements MAY be included after the element representing the metadata updates.

As an optimization and as a service to the requester, if there are no extension elements this element SHOULD be empty if the updated representation does not differ from the representation sent in the PutMetadata request message; that is, if the service accepted the new representation (including all Metadata updates) verbatim.

Such a response (an empty mex:PutMetadataResponse) implies that the update request was successful in its entirety (assuming no intervening mutating operations are performed). A service MAY return the current representation of the resource as the child of the mex:PutMetadataResponse element even in this case, however.

[Body]/mex:PutMetadataResponse/mex:Metadata

This OPTIONAL element comprises the representation of all the metadata sections of the resource that have been updated during the PutMetadata operation.

6.4 DeleteMetadata

A requester MAY send a DeleteMetadata request message to an endpoint to delete the metadata associated with that endpoint. This operation MAY be supported by WS-MetadataExchange compliant service endpoints. Observe that, in the case where a service endpoint is also a [WS-Transfer] resource, the [WS-Transfer] Delete operation allows requesters to update the resource representation associated with that endpoint (i.e. the "data"), while the DeleteMetadata operation can be used to update that endpoint's metadata.

The normative outline for a DeleteMetadata request is:

[Action]
  http://www.w3.org/2011/03/ws-mex/DeleteMetadata
 
[Body]
  <mex:DeleteMetadata ...>
    <mex:Dialect Type='mex:QNameSerialization'
                 Identifier='xs:anyURI'? 
                 Content='xs:anyURI'? .../> +
    xs:any*
  </mex:DeleteMetadata>

The following describes additional, normative constraints on the outline listed above:

[Body]/mex:DeleteMetadata

This REQUIRED element MUST have as its first children elements one or more elements that comprise the representation of the metadata that is to be deleted. Additional extension elements MAY be included after the element representing the metadata to be deleted.

[Body]/mex:DeleteMetadata/mex:Dialect

This REQUIRED (optionally repeating) element specifies the metadata to be deleted.

[Body]/mex:DeleteMetadata/mex:Dialect@Type

This REQUIRED attribute specifies the Metadata Dialect of the metadata to be deleted.

Note: the QName is serialized as {namespace-uri}localName.

[Body]/mex:DeleteMetadata/mex:Dialect@Identifier

When this OPTIONAL attribute is present, only metadata with the indicated identifier is to be deleted. Absence of this attribute indicates that all metadata matching the specified Dialect and Content MUST be removed.

[Body]/mex:DeleteMetadata/mex:Dialect@Content

When this OPTIONAL attribute is present, only metadata of the specific content form is to be deleted. Absence of this attribute indicates that all metadata matching the specified Dialetc and Identifier MUST be removed.

An endpoint MUST reject a DeleteMetadata request if it is unable to process all of the metadata deletes requested. If the dialect, identifier or content form specified in one or more of the Dialect elements is unsupported by the endpoint, the endpoint MUST generate a mex:UnsupportedMetadata fault. If the deletion of the specified Metadata will render the endpoint invalid, the endpoint MUST generate an mex:InvalidMetadata fault. Note that an otherwise valid request that refers to metadata that does not exist is not considered an error condition. Rather, the service MUST continue as if it had successfully processed that one delete request.

If an endpoint accepts a DeleteMetadata request, it MUST reply with a DeleteMetadataResponse message. The normative outline for a DeleteMetadataResponse is:

[Action]
  http://www.w3.org/2011/03/ws-mex/DeleteMetadataResponse
 
[Body]
  <mex:DeleteMetadataResponse>
    xs:any*
  </mex:DeleteMetadataResponse>

There are no additional, normative constraints on the outline listed above.

7.1 mex:Location

The mex:Location element MAY be used to specify a reference to an HTTP metadata resource. A requester MAY use an HTTP GET to the indicated URL to retrieve the metadata.

The outline for the mex:Location element is:

<mex:Location URL="xs:anyURI" Type="mex:QNameSerialization" 
              Identifier="xs:anyURI" ...>
  xs:any*
<mex:Location> 

The following describes additional constraints on the outline listed above:

/mex:Location

This element contains a reference to an HTTP metadata resource.

/mex:Location@URL

This REQUIRED attribute contains the URL of an HTTP metadata resource. This resource MUST support retrieval of the metadata via an HTTP GET request.

/mex:Location@Type

This REQUIRED attribute indicates the QName of the referenced metadata. This can be used in deciding whether or not to retrieve the metadata.

Note: the QName is serialized as {namespace-uri}localName.

/mex:Location@Identifier

This REQUIRED attribute indicates the Identifier for the metadata being referenced. Identifier is an absolute IRI.

7.2 mex:Reference

The mex:Reference element MAY be used to specify a reference to a WS-Transfer metadata resource. A requester MAY use a WS-Transfer Get to the indicated EPR to retrieve the metadata

The outline for the mex:Reference element is:

<mex:Reference Type="mex:QNameSerialization" 
               Identifier="xs:anyURI" ...>
  endpoint-reference-type
<mex:Reference> 

The following describes additional constraints on the outline listed above:

/mex:Reference

This element is an endpoint reference to a metadata resource. This resource MUST support retrieval of the metadata via a WS-Transfer Get request.

/mex:Reference@Type

This REQUIRED attribute indicates the QName of the referenced metadata. This can be used in deciding whether or not to retrieve the metadata.

Note: the QName is serialized as {namespace-uri}localName.

/mex:Reference@Identifier

This REQUIRED attribute indicates the Identifier for the metadata being referenced. Identifier is an absolute IRI.

7.3 Examples

The following examples show how metadata might appear in various locations:

(01) <wsa:Endpoint ...>
(02)    <wsa:Address> http://example.com </wsa:Address>
(03)    <wsa:Metadata>
(04)      <wsdl:definitions>
(05)        ...
(06)      </wsdl:definitions>
(07)    </wsa:Metadata>
(08)  </wsa:Endpoint> 

Example 7-1 shows an endpoint reference with the endpoint's WSDL embedded. This saves the user of this EPR from having to retrieve the WSDL. This same endpoint reference might have been constructed by using a metadata reference instead, as shown in Example 7-2:

(01) <wsa:Endpoint ...>
(02)   <wsa:Address> http://example.com </wsa:Address>
(03)   <wsa:Metadata>
(04)     <mex:Location URL="http://example.com?wsdl"
(05)                     Type="{http://schemas.xmlsoap.org/wsdl/}definitions"
(06)                     Indentifier="..."/>
(07)   </wsa:Metadata>
(08) </wsa:Endpoint> 

Example 7-2 shows the same endpoint reference but rather than embedding the endpoint's WSDL directly in the EPR a mex:Location is used to indicate that if the user of the EPR needs the service's WSDL then it can retrieve it from the specified URL.

The following example WSDL shows how support for a particular feature might be indicated:

(01) <wsdl:definitions>
(02)   ...
(03)   <wsdl:service name="stockQuote">
(04)     <wsdl:port binding="..." name="...">
(05)       <soap:address location="http://example.com"/>
(06)     </wsdl:port>
(07)     <wsp:Policy>
(08)       <wse:EventSource>
(09)         <wse:FormatName uri="http://www.w3.org/2011/03/ws-evt/DeliveryFormats/Unwrap"/>
(10)         <wsdl:definitions>
(11)           ...
(12)           <wsdl:service ...>
(13)             ...
(14)             <wsp:Policy xmlns:wsp="..." wmlns:sp="...">
(15)               <sp:SymmetricBinding>
(16)                 <wsp:Policy>
(17)                   <sp:ProtectionToken>
(18)                     <wsp:Policy>
(19)                       <sp:SecureConversationToken ...>
(20)                         ...
(21)                       </sp:SecureConversationToken>
(22)                     </wsp:Policy>
(23)                   </sp:ProtectionToken>
(24)                 </wsp:Policy>
(25)               </sp:SymmetricBinding>
(26)             </wsp:Policy>
(27)           </service>
(28)         </wsdl:definitions>
(29)       </wse:EventSource>
(30)     </wsp:Policy>
(31)   </wsdl:service>
(32) </wsdl:definitions> 

This example shows the WSDL for a stockQuote service. As indicated on lines (08) through (29), this endpoint also acts as a WS-Eventing event source. The endpoint supports sending notification in the "Unwrapped" format - line (09). Line (10) through (28) provides the WSDL for the WS-Eventing features. In particular, lines (14) through (26) indicates that the WS-Eventing messages need to be protected using WS-SecureConversation.

This example could have also been written by using metadata references:

(01) <wsdl:definitions>
(02)   ...
(03)   <wsdl:service name="stockQuote">
(04)     <wsdl:port binding="..." name="...">
(05)       <soap:address location="http://example.com"/>
(06)     </wsdl:port>
(07)     <wsp:Policy>
(08)       <wse:EventSource>
(09)         <wse:FormatName uri="http://www.w3.org/2011/03/ws-evt/DeliveryFormats/Unwrap"/>
(10)         <mex:Location URL="http://example.com/EventingWSDL"
(11)                       Type="{http://schemas.xmlsoap.org/wsdl/}definitions"
(12)                       Identifier="..." />
(13)       </wse:EventSource>
(14)     </wsp:Policy>
(15)   </wsdl:service>
(16) </wsdl:definitions> 

In this case the embedded WS-Eventing WSDL that is supported by the stockQuote service has been replaced by a mex:Location element. The WSDL can now be retrieved via an HTTP GET to the URL specified on line (10).

8.1 Endpoint References Containing Metadata

The issuer of a WS-Addressing endpoint reference MAY include metadata for that service inside the endpoint reference itself. This mechanism simplifies the bootstrapping of the service interaction on the requester side by avoiding additional calls to retrieve the Web service metadata for the service endpoint.

Embedding the metadata (including a mex:Metadata element) inside an endpoint reference's wsa:Metadata element allows the issuer of the endpoint reference to include metadata by value or by reference, according to the options described in 4 Web Services Metadata Collection and 7 Metadata References. The outline of a [WS-Addressing] endpoint reference which includes Web services metadata is as follows:

<wsa:EndpointReference ...>
     <wsa:Address>xs:anyURI</wsa:Address>
     <wsa:ReferenceParameters> xs:any* </wsa:ReferenceParameters> ?
     <wsa:Metadata>
       ( <mex:Location .../> |
         <mex:Reference ...> ... </mex:Reference> |
         <mex:Metadata ...> ... </mex:Metadata> ) *
         xs:any*
     </wsa:Metadata> ?
     xs:any*
</wsa:EndpointReference>

/wsa:EndpointReference/wsa:Metadata/mex:Location

This repeating OPTIONAL element MAY appear as a direct child of the wsa:Metadata endpoint reference element.

/wsa:EndpointReference/wsa:Metadata/mex:Reference

This repeating OPTIONAL element MAY appear as a direct child of the wsa:Metadata endpoint reference element.

/wsa:EndpointReference/wsa:Metadata/mex:Metadata

This repeating OPTIONAL element MAY appear as a direct child of the wsa:Metadata endpoint reference element. Note: It MAY also be possible to combine multiple mex:Metadata elements into one mex:Metadata element, however, it is RECOMMENDED that multiple mex:Metadata elements be used.

/wsa:EndpointReference/wsa:Metadata/xs:any

This extensibility point, defined by WS-Addressing, can be used for embedding additional metadata.

In example Example 8-1, a [WS-Addressing] endpoint reference contains WSDL metadata by value that identifies the binding used to access the service endpoint:

(01) <wsa:EndpointReference
(02)     xmlns:wsa='http://www.w3.org/2005/08/addressing'>
(03)   <wsa:Address>http://services.example.org/stockquote</wsa:Address>
(04)   <wsa:Metadata>
(05)     <wsdl:definitions
(06)         name='StockQuote'
(07)         targetNamespace='http://services.example.org/stockquote'
(08)         xmlns:tns='http://services.example.org/stockquote'
(09)         xmlns:wsoap='http://schemas.xmlsoap.org/wsdl/soap/'
(10)         xmlns:wsdl='http://schemas.xmlsoap.org/wsdl/'
(11)         xmlns:wsp='http://www.w3.org/ns/ws-policy'
(12)         xmlns:msgs='http://services.example.org/stockquote/schemas
(13)         xmlns:xs='http://www.w3.org/2001/XMLSchema'>
(14)       <wsdl:import
(15)           namespace='http://services.example.org/stockquote'
(16)           location='http://services.example.org/stockquote/schemas'/>
(17)       <wsdl:portType name='StockQuotePortType'>
(18)         <wsdl:operation name='GetLastTradePrice'>
(19)           <wsdl:input message='msgs:GetLastTradePriceInput'
(20)                       name='GetLastTradePriceInput'/>
(21)           <wsdl:output message='msgs:GetLastTradePriceOutput'
(22)                        name='GetLastTradePriceOutput'/>
(23)         </wsdl:operation>
(24)       </wsdl:portType>
(25)       <wsdl:binding name='StockQuoteBinding'
(26)             type='tns:StockQuotePortType'>
(27)         <wsp:PolicyReference
(28)             URI='http://services.example.org/stockquote/policy' />
(29)         <wsoap:binding style='document'
(30)                  transport='http://schemas.xmlsoap.org/soap/http'/>
(31)         <wsdl:operation name='GetLastTradePrice'>
(32)           <wsoap:operation soapAction='http://services.example.org/stockquote/GetLastTradePrice' />
(33)           <wsdl:input name='GetLastTradePriceInput'>
(34)             <wsoap:body use='literal'/>
(35)           </wsdl:input>
(36)           <wsdl:output name='GetLastTradePriceOutput'>
(37)             <wsoap:body use='literal'/>
(38)           </wsdl:output>
(39)         </wsdl:operation>
(40)       </wsdl:binding>
(41)       <wsdl:service name='StockQuoteService'>
(42)         <wsdl:port name='StockQuotePort'
(43)                    binding='tns:StockQuoteBinding' >
(44)           <wsoap:address
(45)                 location='http://services.example.org/stockquote'/>
(46)         </wsdl:port>
(47)       </wsdl:service>
(48)     </wsdl:definitions>
(49)   </wsa:Metadata>
(50) </wsa:EndpointReference> 

Lines 5-48 show the way the WSDL of the Web service endpoint is included 'by value'.

(01) <wsa:EndpointReference ...>
(02)   <wsa:Address>http://services.example.org/stockquote</wsa:Address>
(03)   <wsa:Metadata>
(04)     <mex:Reference Type="{http://www.w3.org/2011/03/ws-mex}Metadata" Identifier="">
(05)       <wsa:Address>
(06)         http://services.example.org/stockquote/metadata
(07)       </wsa:Address>
(08)       <wsa:Metadata>
(09)         <wsdl:definitions ...>
(10)           <!-- WS-Transfer WSDL portType plus binding -->
(11)         </wsdl:definitions>
(12)       </wsa:Metadata>
(13)     </mex:Reference>
(14)   </wsa:Metadata>
(15) </wsa:EndpointReference> 

Example 8-2 shows an example of a Web service endpoint reference in which the Metadata element contains a single mex:Reference element to a metadata resource (lines 4-13) the representation of which is mex:Metadata as hinted by the value of the Type attribute (line 4). The metadata reference contains a Metadata element (lines 8-12) which contains the necessary metadata for interacting with the metadata resource through [WS-Transfer] operations. Since the mex:Reference is an endpoint reference to a [WS-Transfer] resource, the embedded metadata includes the [WS-Transfer] WSDL portType and the necessary binding information for communicating with that resource.

(01) <wsa:EndpointReference ...>
(02)   <wsa:Address>http://services.example.org/stockquote</wsa:Address>
(03)   <wsa:Metadata>
(04)     <mex:Reference Type='{http://www.w3.org/2011/03/ws-mex}Metadata' Identifier=''>
(05)       <wsa:Address>
(06)         http://services.example.org/stockquote/metadata
(07)       </wsa:Address>
(08)       <wsa:Metadata>
(09)         <!-- Ref to the WS-Transfer WSDL -->
(10)         <mex:Location URL='http://example.org/sq/TransferWSDL'
(11)                       Type='{http://schemas.xmlsoap.org/wsdl/}definitions' Identifier='...'/>
(12)       </wsa:Metadata>
(13)     </mex:Reference>
(14)   </wsa:Metadata>
(15) </wsa:EndpointReference> 

Example 8-3 shows an alternative way to represent Example 8-2. It shows an example of a Web service endpoint reference in which the Metadata element contains a single mex:Reference element to a metadata resource (lines 4-13) the representation of which is mex:Metadata as hinted by the value of the Type attribute (line 4). The metadata reference contains a Metadata element (lines 8-12) which contains the necessary metadata for interacting with the metadata resource through [WS-Transfer] operations. Since the mex:Reference is an endpoint reference to a [WS-Transfer] resource, the mex:Location element is a reference to the [WS-Transfer] WSDL which includes the portType and the necessary binding information for communicating with that resource.

In example Example 8-4, an endpoint reference to a service endpoint contains the metadata to allow requesters to issue a GetWSDL request against it.

(01) <wsa:EndpointReference ...>
(02)   <wsa:Address>http://services.example.org/stockquote</wsa:Address> 
(03)   <wsa:Metadata> 
(04)     <wsp:PolicyAttachment>
(05)       <wsp:AppliesTo>                       
(06)         <!-- Following according to: http://www.w3.org/TR/ws-policy-attach/#uri-domain-expression --> 
(07)         <!-- with URI syntax from:
(08)              http://www.w3.org/TR/wsdl11elementidentifiers/ -->
(09)         <wsp:URI> 
(10)           http://www.w3.org/2011/03/ws-mex#wsdl1.PortTypeOperation(GetWSDL) 
(11)         </wsp:URI>
(12)       </wsp:AppliesTo> 
(13)       <wsp:Policy> ... </wsp:Policy>  
(14)     </wsp:PolicyAttachment>            
(15)   </wsa:Metadata>
(16) </wsa:EndpointReference> 

Example 8-4 shows an example of an endpoint reference to a service endpoint. The endpoint reference contains metadata associated with the service endpoint (lines 3-15) and the Policy metadata (lines 4-14) which contains the necessary metadata for interacting with the endpoint through WS-MetadataExchange. The metadata for the WS-MetadataExchange interaction is of policy attachment (line 4). The policy attachment (lines 4-14) defines the policy (line 13) and the GetWSDL operation to which the policy applies (lines 5-12).

Alternatively, Example 8-4 could have been written with the WS-MetadataExchange Policy Assertion embedded directly into the EPR along with the necessary Policy Assertions, as shown in Example 8-5:

(01) <wsa:EndpointReference ...>
(02)   <wsa:Address>http://services.example.org/stockquote</wsa:Address> 
(03)   <wsa:Metadata> 
(04)     <wsp:Policy>
(05)       <mex:MetadataExchange>
(06)         <wsp:Policy> ... </wsp:Policy>
(07)       </mex:MetadataExchange>
(08)     </wsp:Policy>
(09)   </wsa:Metadata>
(10) </wsa:EndpointReference> 

Example 8-5 shows an example of a endpoint reference to a service endpoint. The endpoint reference contains Policy metadata that can be used to properly interact with the service. In this case the Policy contains the mex:MetadataExchange Policy Assertion (lines 5-7) indicating that it supports the WS-MetadataExchange specification. Line 6 contains a Policy Assertion that further qualifies how a requester would invoke the WS-MetadataExchange operations. For example, the Policy Assertion on line 6 might contain assertions to indicate how all WS-MetadataExchange messages are to be consturcted.

8.2 Associating Policies with Endpoint References

It is desirable for components that provide EPRs to other components to be able to efficiently communicate the effective policies of the endpoints referenced by those EPRs. For example, a subscriber might wish to indicate to an event source that the notification messages sent as part of a subscription needs to be digitally signed. Although the mechanisms described in 8.1 Endpoint References Containing Metadata can be used to communicate the complete set of policies associated with an endpoint, the relationship of these policies to specific bindings, operations, or messages cannot be determined without additional information such as WSDL documents or wsp:PolicyAttachment elements.

A single wsp:Policy or wsp:PolicyReference element MAY appear as a child of the /wsa:EndpointReference/wsa:Metadata element.

<wsa:EndpointReference>
  <wsa:Address> xs:anyURI </wsa:Address>
  <wsa:ReferenceParameters> xs:any* </wsa:ReferenceParameters>
  <wsa:Metadata>
    ( <wsp:Policy ...> ... </wsp:Policy> |
      <wsp:PolicyReference ...> ... </wsp:PolicyReference> ) ?
  </wsa:Metadata>
</wsa:EndpointReference>

If multiple alternatives are desired, the operators defined in [WS-Policy] can be used to specify such alternatives within the single wsp:Policy element or the element referenced by the wsp:PolicyReference.

Policies that appear in an endpoint reference in this manner have Endpoint Policy Subject. Endpoint Policy Subject is defined as follows:

The wsp:Policy or wsp:PolicyReference element, when present, represents the capabilities and requirements of the endpoint referenced by the EPR as defined by Section 3, "Policy Model", in the [WS-Policy] specification. Policy attached to an EPR in this manner MUST be applicable to all message exchanges using the endpoint referenced by that EPR.

(01) <wse:NotifyTo xmlns:wsa="http://www.w3.org/2005/08/addressing"
(02)               xmlns:wse="http://www.w3.org/2011/03/ws-evt">
(03)   <wsa:Address>http://www.example.com/EventSink/OnPriceChange</wsa:Address>
(04)   <wsa:ReferenceParameters>
(05)     ...
(06)   </wsa:ReferenceParameters>
(07)   <wsa:Metadata>
(08)     <wsp:Policy xmlns:wsp="..." wmlns:sp="...">
(09)       <sp:SymmetricBinding>
(10)         <wsp:Policy>
(11)           <sp:ProtectionToken>
(12)             <wsp:Policy>
(13)               <sp:SecureConversationToken ...>
(14)                 ...
(15)               </sp:SecureConversationToken>
(16)             </wsp:Policy>
(17)           </sp:ProtectionToken>
(18)         </wsp:Policy>
(19)       </sp:SymmetricBinding>
(20)     </wsp:Policy>
(21)   </wsa:Metadata>
(22) </wse:NotifyTo>

Example 8-6 shows a WS-Eventing NotifyTo EPR that refers to the endpoint to which an event source sends notification messages. Attached to this EPR is a Policy (lines 8-20) that indicates that WS-SecureConversation needs to be used when sending messages to this endpoint.

Note that in some cases the context in which an EPR appears might imply the version of SOAP that messages addressed to that EPR are to use. In this example, without an explicit use of the SOAP assertion, the Notifications will most likely be sent using the same version of SOAP that was used to carry the Subscribe message.

The [WS-Addressing] specification discusses caveats to the validity of Metadata information. These apply to policies contained within the wsa:Metadata element as discussed in this section.

The relationship, if any, between policies contained within the wsa:Metadata element and any other policies that might apply to the endpoint referred to by the containing EPR (e.g. policies that might appear in a WSDL document that describes one or more of the services offered by that endpoint) is not defined by this specification.

10.1 UnsupportedMetadata

This fault MUST be generated when one or more metadata dialect(s) specified on the request message are unsupported by the endpoint.

10.2 UnknownDialect

This fault MUST be generated when the metadata passed on the PutMetadata request message is invalid or when the Metadata would render the endpoint invalid.

11.1 Metadata and Security Bootstrapping

There are cases in which the metadata used to describe a service might be considered sensitive information. In these cases it is advisable for services to authenticate and authorize consumers as part of the processing of any requests for this metadata. However, because the security aspects of a service (e.g. supported protocols and token formats, cipher suites, etc.) are usually described using metadata (i.e. the constructs defined by WS-SecurityPolicy), there is an obvious dilemma when attempting to protect metadata in this way. Services wishing to protect access to their metadata are advised to use the mechanisms described in 13 Bootstrapping Metadata Retrieval to advertise the security requirements for clients wishing to access metadata via the mechanisms defined in this specification.

12.1 MetadataExchange Assertion

Services indicate support for the WS-MetadataExchange specification through the use of the Web Services Policy - Framework [WS-Policy] and Web Services Policy - Attachment [WS-PolicyAttachment] specifications.

This specification defines a policy assertion (mex:MetadataExchange). The normative outline of this assertion is:

<mex:MetadataExchange ...>
  <mex:GetMetadataSupported ...>
    <mex:MetadataExchangeDialect Type="mex:QNameSerialization" ...>
      <mex:MetadataContent URI="xs:anyURI" ...> 
        xs:any*
      </mex:MetadataContent> *
      xs:any*
    </mex:MetadataExchangeDialect> * 
    xs:any*
  </mex:GetMetadataSupported> ?
  <mex:PutMetadataSupported ...>
    <mex:MetadataExchangeDialect Type="mex:QNameSerialization" ...>
      <mex:MetadataContent URI="xs:anyURI" ...> 
        xs:any*
      </mex:MetadataContent> *
      xs:any*
    </mex:MetadataExchangeDialect> *
    xs:any*
  </mex:PutMetadataSupported> ?
  <mex:DeleteMetadataSupported ...>
    <mex:MetadataExchangeDialect Type="mex:QNameSerialization" ...>
      <mex:MetadataContent URI="xs:anyURI" ...> 
        xs:any*
      </mex:MetadataContent> *
      xs:any*
    </mex:MetadataExchangeDialect> *
    xs:any*
  </mex:DeleteMetadataSupported> ?
  xs:any*
</mex:MetadataExchange>

The following describes additional, normative constraints on the outline listed above:

/mex:MetadataExchange

This policy assertion has Endpoint Policy Subject. When present in a policy alternative, it indicates that the WS-MetadataExchange protocol MUST be used when communicating with this endpoint.

/mex:MetadataExchange/mex:GetMetadataSupported

When present, this OPTIONAL parameter indicates that the GetMetadata operation is supported by this endpoint.

/mex:MetadataExchange/mex:GetMetadataSupported/mex:MetadataExchangeDialect@Type

When present, this OPTIONAL parameter indicates support for the specified MetadataExchange Dialect QName by the GetMetadata operation.

Note: the QName is serialized as {namespace-uri}localName.

/mex:MetadataExchange/mex:GetMetadataSupported/mex:MetadataExchangeDialect/mex:MetadataContent

When present, this OPTIONAL parameter indicates support for the specified MetadataExchange content IRI by the GetMetadata operation for the dialect indicated.

/mex:MetadataExchange/mex:GetMetadataSupported/mex:MetadataExchangeDialect/mex:MetadataContent/xs:any

This extensibility point allows for additional MetadataContent specific metadata to be included within the policy assertion. Any metadata that appears is scoped to the use of the specified MetadataContent URI.

/mex:MetadataExchange/mex:GetMetadataSupported/mex:MetadataExchangeDialect/xs:any

This extensibility point allows for additional Metadata Dialect specific metadata to be included within the policy assertion. Any metadata that appears is scoped to the use of the specified Metadata Dialect QName.

/mex:MetadataExchange/mex:GetMetadataSupported/xs:any

This extensibility point allows for additional metadata specific to the GetMetadata operation to be included within the policy assertion. Any metadata that appears is scoped to the use of the GetMetadata operation.

/mex:MetadataExchange/mex:PutMetadataSupported

When present, this OPTIONAL parameter indicates that the PutMetadata operation is supported by this endpoint.

/mex:MetadataExchange/mex:PutMetadataSupported/mex:MetadataExchangeDialect@Type

When present, this OPTIONAL parameter indicates support for the specified MetadataExchange Dialect QName by the PutMetadata operation.

Note: the QName is serialized as {namespace-uri}localName.

/mex:MetadataExchange/mex:PutMetadataSupported/mex:MetadataExchangeDialect/mex:MetadataContent

When present, this OPTIONAL parameter indicates support for the specified MetadataExchange content IRI by the PutMetadata operation for the dialect indicated.

/mex:MetadataExchange/mex:PutMetadataSupported/mex:MetadataExchangeDialect/mex:MetadataContent/xs:any

This extensibility point allows for additional MetadataContent specific metadata to be included within the policy assertion. Any metadata that appears is scoped to the use of the specified MetadataContent URI.

/mex:MetadataExchange/mex:PutMetadataSupported/mex:MetadataExchangeDialect/xs:any

This extensibility point allows for additional Metadata Dialect specific metadata to be included within the policy assertion. Any metadata that appears is scoped to the use of the specified Metadata Dialect QName.

/mex:MetadataExchange/mex:PutMetadataSupported/xs:any

This extensibility point allows for additional metadata specific to the PutMetadata operation to be included within the policy assertion. Any metadata that appears is scoped to the use of the PutMetadata operation.

/mex:MetadataExchange/mex:DeleteMetadataSupported

When present, this OPTIONAL parameter indicates that the DeleteMetadata operation is supported by this endpoint.

/mex:MetadataExchange/mex:DeleteMetadataSupported/mex:MetadataExchangeDialect@Type

When present, this OPTIONAL parameter indicates support for the specified MetadataExchange Dialect QName by the DeleteMetadata operation.

Note: the QName is serialized as {namespace-uri}localName.

/mex:MetadataExchange/mex:DeleteMetadataSupported/mex:MetadataExchangeDialect/mex:MetadataContent

When present, this OPTIONAL parameter indicates support for the specified MetadataExchange content IRI by the DeleteMetadata operation for the dialect indicated.

/mex:MetadataExchange/mex:DeleteMetadataSupported/mex:MetadataExchangeDialect/mex:MetadataContent/xs:any

This extensibility point allows for additional MetadataContent specific metadata to be included within the policy assertion. Any metadata that appears is scoped to the use of the specified MetadataContent URI.

/mex:MetadataExchange/mex:DeleteMetadataSupported/mex:MetadataExchangeDialect/xs:any

This extensibility point allows for additional Metadata Dialect specific metadata to be included within the policy assertion. Any metadata that appears is scoped to the use of the specified Metadata Dialect QName.

/mex:MetadataExchange/mex:DeleteMetadataSupported/xs:any

This extensibility point allows for additional metadata specific to the DeleteMetadata operation to be included within the policy assertion. Any metadata that appears is scoped to the use of the DeleteMetadata operation.

/mex:MetadataExchange/xs:any

This extensibility point allows for additional WS-MetadataExchange specific metadata to be included within the policy assertion - e.g. WS-MetadataExchange WSDL, or nested policy assertions related to the WS-MetadataExchange message exchanges. Any metadata that appears is scoped to the operations and features of the WS-MetadataExchange specification.

15.1 Normative References

BP12

WS-I Profile, Basic Profile Version 1.2 , R. Chumbley, et al, Editors. Web Services Interoperability Organization (WS-I), 9 November 2010. Available at http://ws-i.org/profiles/BasicProfile-1.2-2010-11-09.html.

BP20

WS-I Profile, Basic Profile Version 2.0 , R. Chumbley, et al, Editors. Web Services Interoperability Organization (WS-I), 9 November 2010. Available at http://ws-i.org/profiles/BasicProfile-2.0-2010-11-09.html.

RFC 2119

Key words for use in RFCs to Indicate Requirement Levels , S. Bradner, Author. Internet Engineering Task Force, March 1997. Available at http://www.ietf.org/rfc/rfc2119.txt.

RFC 3987

Internationalized Resource Identifiers (IRIs) , M. Duerst and M. Suignard, Authors. Internet Engineering Task Force, January 2005. Available at http://www.ietf.org/rfc/rfc3987.txt.

SOAP11

W3C Note, "Simple Object Access Protocol (SOAP) 1.1" , D. Box, et al, Editors. World Wide Web Consortium (W3C), 8 May 2000. Available at http://www.w3.org/TR/2000/NOTE-SOAP-20000508/.

SOAP12

W3C Recommendation, "SOAP Version 1.2 Part 1: Messaging Framework" , M. Gudgin, M. Hadley, N. Mendelsohn, J-J. Moreau, H. Frystyk Nielson, Editors. World Wide Web Consortium (W3C), 27 April 2007. Available at http://www.w3.org/TR/soap12-part1/.

WS-Addressing

W3C Recommendation, "Web Services Addressing 1.0 (WS-Addressing)" , M. Gudgin, M. Hadley, T. Rogers, Editors. World Wide Web Consortium (W3C), 9 May 2006. Available at http://www.w3.org/TR/ws-addr-core.

WS-Addressing 1.0 SOAP Binding

W3C Recommendation, "Web Services Addressing 1.0 - SOAP Binding" , M. Gudgin, M. Hadley, T. Rogers, Editors. World Wide Web Consortium (W3C), 9 May 2006. Available at http://www.w3.org/TR/ws-addr-soap.

WS-SOAPAssertions

W3C Working Group Draft, "Web Services SOAP Assertions (WS-SOAPAssertions) 1.0" , D. Davis, et al., Editors. World Wide Web Consortium (W3C), 15 September 2009. Available at http://www.w3.org/TR/ws-soap-assertions.

WS-Policy

W3C Recommendation, "Web Services Policy (WS-Policy) 1.5 - Framework" , A. Vedamuthu, et al., Editors. World Wide Web Consortium (W3C), 4 September 2007. Available at http://www.w3.org/TR/ws-policy/.

WS-PolicyAttachment

W3C Recommendation, "Web Services Policy (WS-Policy) 1.5 - Attachment" , A. Vedamuthu, et al., Editors. World Wide Web Consortium (W3C), 4 September 2007. Available at http://www.w3.org/TR/ws-policy-attach/.

WS-Transfer

W3C Working Group Draft, "Web Services Transfer (WS-Transfer) 1.1" , D. Davis, et al., Editors. World Wide Web Consortium (W3C), 15 September 2009. Available at http://www.w3.org/TR/ws-transfer.

WSDL11

W3C Note, "Web Services Description Language (WSDL) 1.1" , E. Christensen, et al., Editors. World Wide Web Consortium (W3C), 15 March 2001 Available at http://www.w3.org/TR/2001/NOTE-wsdl-20010315.

XML Infoset

W3C Recommendation, "XML Information Set (Second Edition)" , J. Cowan, R. Tobin, Editors. World Wide Web Consortium (W3C), 4 February 2004. Available at http://www.w3.org/TR/xml-infoset.

XMLSchema - Part 1

W3C Recommendation, "XML Schema Part 1: Structures (Second Edition)" , H. Thompson, et al., Editors. World Wide Web Consortium (W3C), 28 October 2004. Available at http://www.w3.org/TR/xmlschema-1/.

XMLSchema - Part 2

W3C Recommendation, "XML Schema Part 2: Datatypes (Second Edition)" , P. Biron, A. Malhotra, Editors. World Wide Web Consortium (W3C), 28 October 2004. Available at http://www.w3.org/TR/xmlschema-2/.