Web Services Fragment (WS-Fragment)

1.1 Requirements

This specification intends to meet the following requirement:

• Provide an extension mechanism to WS-Transfer that allows for subsets (parts or fragments) of a resource to be retrieved or modified.

• Provide an extension framework for defining expression languages.

• Provide a set of expression languages that implementations can leverage.

2.1 Terminology

Expression

A Language specific set of tokens that resolves to a location in a resource that contains a subset of the resource.

Fragment

A subset of a resource.

2.2 XML Namespaces

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

http://www.w3.org/2009/10/ws-fra

Table 2-1 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 Fragment 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 Fragment 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 .

2.3 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.

• Ellipsis (i.e. "...") indicate points of extensibility.

• XML namespace prefixes (see Table 2-1) 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.

In the outlines, bold text is used to indicate those parts of the message that are defined as part of this specification and are extensions to the WS-Transfer messages.

2.4 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 Fragment namespace URI.

2.5 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 2.2 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 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.

3.1 Get

To retrieve a subset of a resource a client MUST specify the WS-Fragment Dialect IRI in the wst:Get request.

The Get request message MUST be of the following form:

[Action]
  http://www.w3.org/2009/09/ws-tra/Get

[Body]
  <wst:Get Dialect="http://www.w3.org/2009/10/ws-fra" ...>
    <wsf:Expression Language="xs:anyURI" ...>
      xs:any *
    </wsf:Expression>
    
    xs:any *
  </wst:Get>

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

[Body]/wst:Get@Dialect

This attribute MUST be set to http://www.w3.org/2009/10/ws-fra.

[Body]/wst:Get/wsf:Expression

This element identifies which fragment in the resource this operation applies to. If the value of this element does not conform to the syntax of the language specified in the Language attribute, or is semantically invalid, a wsf:InvalidExpression fault MUST be generated.

[Body]/wst:Get/wsf:Expression@Language

This IRI indicates which expression language will be used to identify the subset of the resource this operation applies to. A resource MUST generate a wsf:UnsupportedLanguage Fault if it does not support the specified Language.

If the resource accepts a Get request, it MUST reply with a response of the following form:

[Action]
  http://www.w3.org/2009/09/ws-tra/GetResponse

[Body]
  <wst:GetResponse ...>
    <wsf:Value ...> xs:any * </wsf:Value>
    
    xs:any *
  </wst:GetResponse>

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

[Body]/wst:GetResponse/wsf:Value

This element encompasses the fragment response corresponding to the wsf:Expression in the request and MUST contain the subset of the resource identified by the wsf:Expression element in the corresponding Get request. If the Expression evaluates to a fragment with no value, then this element MAY be empty.

Other components of the outline above are not further constrained by this specification.

3.2 Put

To update a subset of a resource a client MUST specify the WS-Fragment IRI in the wst:Put request.

The Put request message MUST be of the following form:

[Action]
  http://www.w3.org/2009/09/ws-tra/Put

[Body]
  <wst:Put Dialect="http://www.w3.org/2009/10/ws-fra" ...>
    <wsf:Fragment ...>
      <wsf:Expression Language="xs:anyURI" Mode="xs:anyURI"? ...>
        xs:any *
      </wsf:Expression> 
      <wsf:Value ...>
        xs:any *
      </wsf:Value> ?
    </wsf:Fragment>
    
    xs:any *
  </wst:Put>

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

[Body]/wst:Put@Dialect

This attribute MUST be set to http://www.w3.org/2009/10/ws-fra.

[Body]/wst:Put/wsf:Fragment

This element contains an expression that identifies the location of a fragment in the resource and a value for the fragment. If the contents of this element are invalid a wsf:InvalidFragment fault MUST be generated.

[Body]/wst:Put/wsf:Fragment/wsf:Expression

This element identifies which fragment in the resource this operation applies to. If the value of this element does not conform to the syntax of the language specified in the Language attribute, or is semantically invalid, a wsf:InvalidExpression fault MUST be generated.

This element identifies the fragment in the resource as it appears after successfully processing the Put request.

[Body]/wst:Put/wsf:Fragment/wsf:Expression@Language

This IRI indicates which expression language will be used to identify the subset of the resource this operation applies to. A resource MUST generate a wsf:UnsupportedLanguage fault if it does not support the specified Language.

[Body]/wst:Put/wsf:Fragment/wsf:Expression@Mode

This OPTIONAL attribute indicates the type of update to be performed on this fragment. The implied value for this attribute is "http://www.w3.org/2009/10/ws-fra/Modes/Replace". A resource MUST generate a wsf:UnsupportedMode fault if the specified Mode is not supported.

[Body]/wst:Put/wsf:Fragment/wsf:Expression@Mode="http://www.w3.org/2009/10/ws-fra/Modes/Replace"

When the Mode attribute is set to a value of "http://www.w3.org/2009/10/ws-fra/Modes/Replace" the resource representation specified within the Value element MUST replace the entire resource representation referenced by the children of the Expression element, if it exists.

[Body]/wst:Put/wsf:Fragment/wsf:Expression@Mode="http://www.w3.org/2009/10/ws-fra/Modes/Insert"

When the Mode attribute is set to a value of "http://www.w3.org/2009/10/ws-fra/Modes/Insert" the resource representation specified within the Value element MUST be added to the resource representation. If the expression targets a repeated element (maxOccurs > 1), the fragment MUST be added at the end. If the expression targets a non-repeated element (maxOccurrs = 1) that already exists, the resource MUST generate a wst:InvalidRepresentation fault. If the expression targets an existing item of a repeated element, the fragment MUST be added before the existing item.

[Body]/wst:Put/wsf:Fragment/wsf:Expression@Mode="http://www.w3.org/2009/10/ws-fra/Modes/Remove"

When the Mode attribute is set to a value of "http://www.w3.org/2009/10/ws-fra/Modes/Remove" the resource representation referenced by the children of the Expression element MUST be deleted from the resource representation.

Note: the Value element MUST NOT be present if this attribute has a value of "http://www.w3.org/2009/10/ws-fra/Modes/Remove".

[Body]/wst:Put/wsf:Fragment/wsf:Value

This OPTIONAL element contains the fragment resource representation corresponding to the subset of the resource identified by the wsf:Expression element.

This element MUST NOT be present if the Mode attribute has a value of "http://www.w3.org/2009/10/ws-fra/Modes/Remove". This element MUST be present if the Mode attribute has a value of either "http://www.w3.org/2009/10/ws-fra/Modes/Replace" or "http://www.w3.org/2009/10/ws-fra/Modes/Insert". When present, this element can either be empty or non-empty.

If the resource accepts a Put request, it MUST reply with a response of the following form:

[Action]
  http://www.w3.org/2009/09/ws-tra/PutResponse

[Body]
  <wst:PutResponse ...>
    xs:any *
  </wst:PutResponse>

There are no additional constraints beyond what WS-Transfer defines.

3.3 Delete

This specification does not extend the Delete operation defined in WS-Transfer.

3.4 Create

This specification does not extend the Create operation defined in WS-Transfer.

4.1 Examples

In the following examples, and Expression Language definitions, the following representation of a resource is used for informational purposes:

<ab:AddressBook xmlns:ab="http://example.com/address">
  <ab:owner>Me</owner>
  <ab:size>2</size>
  <ab:contact>
    <ab:name>Joe Brown</name>
    <ab:address>123 Main Street</address>
    <ab:city>AnyTown</city>
    <ab:state>CA</state>
    <ab:zip>90210</zip>
    <ab:email>joe@example.com</email>
  </ab:contact>
  <ab:contact>
    <ab:name>Mary Smith</name>
    <ab:address>345 South Pine</address>
    <ab:city>AnyTown</city>
    <ab:state>CA</state>
    <ab:zip>90210</zip>
    <ab:email>mary@example.com</email>
  </ab:contact>
</ab:AddressBook>

The following shows a sample SOAP envelope containing a Get request:

<s:Envelope  
    xmlns:s="http://www.w3.org/2003/05/soap-envelope" 
    xmlns:wsa="http://www.w3.org/2005/08/addressing" 
    xmlns:ex="http://www.example.com/" >
  <s:Header>
    <wsa:To>http://www.example.org/resourceABC</wsa:To>
    <wsa:Action>
      http://www.w3.org/2009/09/ws-tra/Get
    </wsa:Action>
    <wsa:MessageID>
      uuid:00000000-0000-0000-C000-000000000046
    </wsa:MessageID>
  </s:Header>
  <s:Body>
    <wst:Get Dialect="http://www.w3.org/2009/10/ws-fra">
      <wsf:Expression Language="http://www.w3.org/2009/10/ws-fra/QName">
        ab:contact
      </wsf:Expression>
    </wst:Get>
  </s:Body>
</s:Envelope>

The following shows the corresponding response message:

<s:Envelope  
    xmlns:s="http://www.w3.org/2003/05/soap-envelope" 
    xmlns:wsa="http://www.w3.org/2005/08/addressing" 
    xmlns:ex="http://www.example.com/" >
  <s:Header>
    <wsa:Action>
      http://www.w3.org/2009/09/ws-tra/GetResponse
    </wsa:Action>
    <wsa:MessageID>
      uuid:0000010e-0000-0000-C000-000000000047
    </wsa:MessageID>
    <wsa:RelatesTo>
      uuid:00000000-0000-0000-C000-000000000046
    </wsa:RelatesTo>
  </s:Header>
  <s:Body>
    <wst:GetResponse>
      <wsf:Value>
        <ab:contact>
          <ab:name>Joe Brown</name>
          <ab:address>123 Main Street</address>
          <ab:city>AnyTown</city>
          <ab:state>CA</state>
          <ab:zip>90210</zip>
          <ab:email>joe@example.com</email>
        </ab:contact>
        <ab:contact>
          <ab:name>Mary Smith</name>
          <ab:address>345 South Pine</address>
          <ab:city>AnyTown</city>
          <ab:state>CA</state>
          <ab:zip>90210</zip>
          <ab:email>mary@example.com</email>
        </ab:contact>
      </wsf:Value>
    </wst:GetResponse>
  </s:Body>
</s:Envelope>

8.1 UnsupportedLanguage

This fault is generated when a service detects an unknown or unsupported Language IRI in a request message.

8.2 InvalidFragment

This fault is generated when a service determines that the fragment (contents of the wsf:Fragment element) specified in a request is invalid.

8.3 InvalidExpression

This fault is generated when a service determines that the Language expression specified in a request does not conform to the syntax of the language specified in the Language attribute or is semantically invalid.

8.4 UnsupportedMode

This fault is generated when a service detects a Mode in a Put request that is not supported.

9.1 Fragment Assertion

The mechanism for indicating that a binding or endpoint conforms to the WS-Fragment specification is through the use of the Web Services Policy - Framework [WS-Policy] and Web Services Policy - Attachment [WS-Policy Attachment] specifications.

This specification defines a policy assertion (wsfrp:Fragment). The wsfrp:Fragment policy assertion applies to the endpoint policy subject.

For WSDL 1.1, these assertions may be attached to wsdl11:port or wsdl11:binding. For WSDL 2.0, they may be attached to wsdl20:endpoint or wsdl20:binding. A policy expression containing the wsfrp:Fragment policy assertion MUST NOT be attached to a wsdl:portType or wsdl20:interface.

The wsfrp:Fragment policy assertion is a nested policy container assertion. The meaning of this assertion, when present in a policy alternative, is that WS-Fragment is required to communicate with the subject and that the subject is a WS-Transfer Resource.

In order to indicate that the subject supports WS-Fragment but does not require its use, an additional policy alternative should be provided which does not contain this assertion. The compact authoring style for an optional policy assertion (the wsp:Optional attribute) provided by WS-Policy may be used to indicate two policy alternatives, one which contains the policy assertion, and another which does not.

The normative outline of this assertion is:

<wsfrp:Fragment ...>
  <wsfrp:Language ...> xs:anyURI </wsfrp:Language> * 
  ... 
</wsfrp:Fragment>

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

/wsfrp:Fragment

A policy assertion that specifies that WS-Fragment protocol MUST be used when communicating with this endpoint. This assertion has Endpoint Policy Subject.

/wsfrp:Fragment/wsfrp:Language

When present, this parameter indicates support for the specified Language IRI.

11.1 Normative References

RFC 2119

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

RFC 3986

Uniform Resource Identifier (URI): Generic Syntax , T. Berners-Lee, R. Fields and L. Masinter, Authors. Network Working Group, January 2005. (See http://www.ietf.org/rfc/rfc3986.txt.)

RFC 3987

Internationalized Resource Identifiers (IRIs) , M. Duerst and M. Suignard, Authors. Internet Engineering Task Force, January 2005. (See 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. (See 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. (See 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. (See 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. (See http://www.w3.org/TR/ws-addr-soap.)

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. (See http://www.w3.org/TR/ws-policy/.)

WS-Policy Attachment

W3C Recommendation, "Web Services Policy (WS-Policy) 1.5 - Attachment" , A. Vedamuthu, et al., Editors. World Wide Web Consortium (W3C), 4 September 2007. (See 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. (See 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 (See 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. (See 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. (See 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. (See http://www.w3.org/TR/xmlschema-2/.)

XPath1.0

W3C Recommendation, "XML Path Language (XPath) Version 1.0" , J. Clark, S. DeRose, Editors. World Wide Web Consortium (W3C), 16 November 1999. (See http://www.w3.org/TR/xpath.)