W3C

SOAP Resource Representation Header

W3C Working Draft 8 June 2004

This version:
http://www.w3.org/TR/2004/WD-soap12-rep-20040608/
Latest version:
http://www.w3.org/TR/soap12-rep/
Previous version:
http://www.w3.org/TR/2004/WD-soap12-rep-20040428/
Editors:
Anish Karmarkar, Oracle Corp.
Martin Gudgin, Microsoft
Yves Lafon, W3C

Abstract

This document describes the semantics and serialization of a SOAP header block for carrying resource representations in SOAP messages.

Status of this Document

This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at http://www.w3.org/TR/.

This is the W3C Last Call Working Draft of the SOAP Resource Representation Header document. It has been produced by the XML Protocol Working Group (WG), which is part of the Web Services Activity.

Discussion of this document takes place on the public xml-dist-app@w3.org mailing list (public archive) under the email communication rules in the XML Protocol Working Group Charter .

Comments on this document are welcome. Send them before 29 June 2004 to xmlp-comments@w3.org mailing list (public archive). Note that all outstanding issues against this document are documented in the Working Group Last Call Issues List. If the feedback on this document is positive, the WG plans to submit it for consideration as a W3C Candidate Recommendation.

This document has been produced under the 24 January 2002 CPP as amended by the W3C Patent Policy Transition Procedure. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) with respect to this specification should disclose the information in accordance with section 6 of the W3C Patent Policy. Patent disclosures relevant to this specification may be found on the Working Group's patent disclosure page.

Publication as a Working Draft does not imply endorsement by the W3C Membership. This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress.

Table of Contents

1 Introduction
    1.1 Notational Conventions
    1.2 Relation to other specifications
        1.2.1 Relationship to the SOAP Processing model
2 Representation Header
    2.1 Introduction
    2.2 Representation header block Constructs
        2.2.1 rep:Representation element
        2.2.2 resource attribute
        2.2.3 reinsert attribute
        2.2.4 rep:Data element
    2.3 Extensibility of the Representation header block
        2.3.1 SOAP header block Attributes
        2.3.2 Specifying the media type
        2.3.3 HTTP headers

Appendices

A References
B Acknowledgements (Non-Normative)


1 Introduction

This document describes the semantics and serialization of a SOAP header block for carrying resource representations in SOAP messages.

1.1 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 a number of namespace prefixes throughout; they are listed in [Prefixes and Namespaces used in this specification.]. Note that the choice of any namespace prefix is arbitrary and not semantically significant (see XML Infoset [XML InfoSet]).

Prefixes and Namespaces used in this specification.
PrefixNamespace
Notes
env"http://www.w3.org/2003/05/soap-envelope"
A normative XML Schema [XML Schema Part 1], [XML Schema Part 2] document for the "http://www.w3.org/2003/05/soap-envelope" namespace can be found at http://www.w3.org/2003/05/soap-envelope.
rep"http://www.w3.org/2004/02/representation"
A normative XML Schema [XML Schema Part 1], [XML Schema Part 2] document for the "http://www.w3.org/2004/02/representation" namespace can be found at http://www.w3.org/2004/02/representation.
xs"http://www.w3.org/2001/XMLSchema"
The namespace of XML Schema data types (see [XML Schema Part 2]).
xmlmime"http://www.w3.org/2004/06/xmlmime"
The namespace for representing MIME media-types in XML (see [Assigning Media Types to Binary Data in XML]).

2 Representation Header

This section describes a SOAP header block, the Representation header block, that allows a SOAP message to carry representations of Web resources.

2.1 Introduction

The Representation header block is designed to allow applications to carry a representation of a Web resource in a SOAP message. Applications of this header include cases where the receiver has limited ability to get the representation using other means, for example because of access restrictions or because the overhead would be unacceptable. The representation header is also required when multiple references to the same extracted content are required but duplication of extracted content is undesirable. See UC2 and UC6 [SOAP Optimized Serialization Use Cases and Requirements] for details.

The meaning of the Representation header block, when present in a SOAP message, is to make available the contained representation of the resource it carries to the processing SOAP node. The SOAP node MAY use this representation when dereferencing the URI of the resource instead of making a network request to the given resource. Note that implementations MAY need to process a Representation header block before processing other header blocks that require dereferencing of a URI whose representation is carried in the Representation header block.

Several occurences of the Representation header block MAY be present in the same SOAP Message to carry representations of several Web resource or several representation of the same Web resource.

Several occurences of the Representation header block having the same value for the role and resource attribute information item (see 2.2.2 resource attribute) MAY be present in the same SOAP Message. Such Representation header blocks SHOULD NOT have the same metadata (such as media-type). If such Representation header blocks have the same metadata then any one of them may be used.

An example SOAP Envelope using the Representation header block is given below.

2.2 Representation header block Constructs

2.2.1 rep:Representation element

The Representation element information item has:

The rep:Representation element information item contains a representation of a Web resource. The value of the resource element information item is the URI identifying the Web resource. The value of the rep:Data element information item is a base64-encoded representation of the Web resource.

2.2.3 reinsert attribute

The reinsert attribute information item has:

The type of the reinsert attribute information item is xs:boolean. When this attribute is specified on the Representation header block with a value of "true", it indicates that a SOAP forwarding intermediary node processing the header block must reinsert the header block. This means that when used in conjunction with the relay attribute, defined in [SOAP Part 1] 5.2.4 SOAP Relay Attribute, with a value of "true", the Representation header block will always be relayed by a SOAP forwarding intermediary. When this attribute is specified on the Representation header block with a value of "false", the behavior of the SOAP node processing the header block is the same as that when the attribute is not specified, and normal SOAP processing rules apply. The presence of this attribute has no effect on the processing of a Representation header by a SOAP endpoint.

2.3 Extensibility of the Representation header block

The Representation header block is built to be extensible. This section describes several possible usage of this extensibility.

2.3.1 SOAP header block Attributes

Attributes defined in [SOAP Part 1] 5. SOAP Message Construct for SOAP header blocks MAY be used with the Representation header block.

Adding a env:mustUnderstand attribute information item with a value of "true" in the [attributes] property of the rep:Representation element information item ensures that the SOAP receiver is aware that the Web resource representation is available to it.

A env:role attribute information item in the [attributes] property of the rep:Representation element information item indicates the SOAP node for which the Web resource representation is intended.

2.3.2 Specifying the media type

An xmlmime:contentType attribute information item (See [Assigning Media Types to Binary Data in XML]) MAY be used to convey the media type of the representation conveyed by a header. Media type information can be useful in determining whether a given representation is suitable for processing and if it is, how best to interpret the representation provided. If used, the xmime:contentType attribute information item MUST appear within the [attribute] property of the rep:Data element information item. An example of this usage is show in Example Example.

2.3.3 HTTP headers

A receiving SOAP node MAY act as a resolver, with all the rules pertaining to HTTP caches, for some or all of the http: scheme URIs for which representations have been provided. To enable this, one or more element information items MAY be added to the [children] property of the rep:Representation element information item to transmit the information needed at the HTTP level.

To avoid requiring that all SOAP senders understand HTTP caching mechanism, all the data required by a processor that wants to act as a local cache needs to be carried along with the message. This includes the complete request, reply as well as the time the original HTTP request has been sent and the time the HTTP response has been received.

Note that if the clocks of the SOAP sender and the SOAP recipient are not synchronized, all the expiration/age computed at the receiving side will not accurately reflect what could have been computed at the SOAP sender side.

A References

SOAP Part 1
W3C Recommendation "SOAP Version 1.2 Part 1: Messaging Framework", M. Gudgin, M. Hadley, N. Mendelsohn, J-J. Moreau, H. F. Nielsen, May 2003. (See http://www.w3.org/TR/soap12-part1/.)
SOAP Part 2
W3C Recommendation "SOAP Version 1.2 Part 2: Adjuncts", M. Gudgin, M. Hadley, N. Mendelsohn, J-J. Moreau, H. F. Nielsen, May 2003. (See http://www.w3.org/TR/soap12-part2/.)
XOP
W3C Working Draft "XML-binary Optimized Packaging", N. Mendelsohn, M. Nottingham, H. Ruellan, June 2004. (See http://www.w3.org/TR/2004/WD-xop10-20040608/.)
SOAP 1.2 Attachment Feature
W3C Working Group Note "SOAP 1.2 Attachment Feature", H. F. Nielsen, H. Ruellan, June 2004. (See http://www.w3.org/TR/2004/NOTE-soap12-af-20040608/.)
SOAP Optimized Serialization Use Cases and Requirements
W3C Working Draft "SOAP Optimized Serialization Use Cases and Requirements", M. A. Jones, Tony Graham, Anish Karmarkar, June 2004. (See http://www.w3.org/TR/2004/WD-soap12-os-ucr-20040608/.)
XML 1.0
W3C Recommendation "Extensible Markup Language (XML) 1.0 (Second Edition)", Tim Bray, Jean Paoli, C. M. Sperberg-McQueen, Eve Maler, 6 October 2000. (See http://www.w3.org/TR/2000/REC-xml-20001006.)
Namespaces in XML
W3C Recommendation "Namespaces in XML", Tim Bray, Dave Hollander, Andrew Layman, 14 January 1999. (See http://www.w3.org/TR/1999/REC-xml-names-19990114/.)
XML InfoSet
W3C Recommendation "XML Information Set", John Cowan, Richard Tobin, 24 October 2001. (See http://www.w3.org/TR/2001/REC-xml-infoset-20011024/.)
XML Schema Part 1
W3C Recommendation "XML Schema Part 1: Structures", Henry S. Thompson, David Beech, Murray Maloney, Noah Mendelsohn, 2 May 2001. (See http://www.w3.org/TR/2001/REC-xmlschema-1-20010502/.)
XML Schema Part 2
W3C Recommendation "XML Schema Part 2: Datatypes", Paul V. Biron, Ashok Malhotra, 2 May 2001. (See http://www.w3.org/TR/2001/REC-xmlschema-2-20010502/.)
XML Schema Part 2 Errata
W3C Internal Working Draft 7 March 2003 Id: datatypes-with-errata.xml,v 1.5 2003/03/07 19:54:00 (See http://www.w3.org/XML/Group/2002/09/xmlschema-2/datatypes-with-errata.html.)
XML Query Data Model
"XQuery 1.0 and XPath 2.0 Data Model", Mary Fernández, Ashok Malhotra, Jonathan Marsh, Marton Nagy, Norman Walsh, November 2003. (See http://www.w3.org/TR/xpath-datamodel/.)
RFC 2119
IETF "RFC 2119: Keywords for use in RFCs to Indicate Requirement Levels", S. Bradner, March 1997. (See http://www.ietf.org/rfc/rfc2119.txt.)
RFC 2387
IETF "The MIME Multipart/Related Content-type", E. Levinson, August 1998. (See http://www.ietf.org/rfc/rfc2387.txt.)
PASWA
"Proposed Infoset Addendum to SOAP Messages with Attachments", April 2003. (See http://www.gotdotnet.com/team/jeffsch/paswa/paswa61.html.)
Assigning Media Types to Binary Data in XML
W3C Working Draft "Assigning Media Types to Binary Data in XML", Anish Karmarkar, Ümit Yalçınalp, June 2004. (See http://www.w3.org/TR/2004/WD-xml-media-types-20040608.)

B Acknowledgements (Non-Normative)

This specification is the work of the W3C XML Protocol Working Group.

Participants in the Working Group are (at the time of writing, and by alphabetical order): TBD

Previous participants were: TBD

This document has its genesis as a separate section in the SOAP Message Transmission Optimization Mechanism (MTOM) document. The editors of the MTOM document, specifically Mark Nottingham and Hervé Ruellan are gratefully acknowledged.

The people who have contributed to discussions on xml-dist-app@w3.org are also gratefully acknowledged.