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Created: March 11, 2004.
News: Cover StoriesPrevious News ItemNext News Item

Reliable Messaging: Recent Versions of WS-Reliability and WS-ReliableMessaging.

Update 2005-02-18: BEA Systems, IBM, Microsoft, and TIBCO have released a revised version of "WS-ReliableMessaging." WS-RM is now published as two separate specifications: one for the core protocol elements and one for the related policy assertion (WS-RM Policy). This release, updating the March 2004 version and offered for use on royalty-free licensing terms, has been improved based upon user feedback from a May 2004 Interoperability Workshop and subsequent endpoint testing. See "New Release of Web Services Reliable Messaging Protocol (WS-ReliableMessaging)."

Update 2004-09-10:: See "OASIS WSRM TC Releases Web Services Reliable Messaging (WS-Reliability) Version 1.1." On August 24, 2004 members of the OASIS Web Services Reliable Messaging TC voted: (1) to approve WSRM Spec Draft Version 1.086 as a Committee Draft, and (2) to submit this Committee Draft to OASIS administration for an OASIS member vote.

Update 2004-03-17: The WS-Reliability specification version .992 referenced as "balloted for approval as a TC Committee Draft" has been approved by members of the OASIS Web Services Reliable Messaging TC. The Committee Draft was released for 30-day public review thorough April 19, 2004 in anticipation its submission to the OASIS membership for approval as an OASIS Standard.

Contents

[March 11, 2004] The Web Services Reliability (WS-Reliability) specification "is a SOAP-based protocol for exchanging SOAP messages with guaranteed delivery (acknowledgment messages, re-sending of messages), no duplicates, and guaranteed message ordering using a sequence number mechanism. WS-Reliability is defined as SOAP header extensions, and is independent of the underlying protocol. This specification contains a binding to HTTP."

WS-Reliability is being developed by the OASIS Web Services Reliable Messaging (WSRM) Technical Committee which was chartered in February 2003. The Version 0.992 of March 10, 2004 prose specification is accompanied by two XML Schemas. It addresses a recognized problem, viz., that "SOAP 1.2 over HTTP is not sufficient when an application-level messaging protocol must also address reliability and security. The specification is intended as an initial proposal for defining reliability in the context of current Web Services standards. It borrows from previous work in messaging and transport protocols, e.g., SOAP and the OASIS ebXML Message Service Specification Version 2.0. A version 0.992 WS-Reliability working draft (prose specification and two XML Schemas for SOAP 1.1/1.2) is being balloted for approval as a TC Committee Draft. Royalty-free software which implements the Web Services Reliability specification has been made available by Fujitsu, Hitachi, and NEC.

The Web Services Reliable Messaging Protocol (WS-ReliableMessaging) "describes a protocol that allows messages to be delivered reliably between distributed applications in the presence of software component, system, or network failures. The protocol is described in this specification in a transport-independent manner allowing it to be implemented using different network technologies. To support interoperable Web services, a SOAP binding is defined within this specification. This specification integrates with and complements the WS-Security, WS-Policy, and other Web services specifications. Combined, these allow for a broad range of reliable, secure messaging options."

The March 09, 2004 revised draft of WS-ReliableMessaging from BEA, IBM, Microsoft Corporation, and TIBCO Software updates the original publication of March 13, 2003. As of March 9, 2004 no public indication had yet been given that the WS-ReliableMessaging specification was submitted to a standards body; the copyright notice reads (in part) "... except for the copyright license granted above, the authors do not grant, either expressly or impliedly, a license to any intellectual property, including patents, they own or control."

Bibliographic Information for WS-Reliability

  • WS-Reliability. Edited by Kazunori Iwasa (Fujitsu Limited). Produced by members of the OASIS Web Services Reliable Messaging TC. Working Draft version 0.992. 10-March-2004. Document identifier: 'wd-web services reliable messaging tc-ws-reliability-0.992'. 77 pages. [source PDF, OpenOffice]

    Subsequent to its approval as an OASIS Committee Draft, the version 0.992 specification was reprinted to reflect the approval date, 17-March-2004. See WS-Reliability. Produced by the OASIS Web Services Reliable Messaging TC. Edited by Kazunori Iwasa (Fujitsu Limited). Approved Committee Draft. Version 0.992. 17-March-2004. Document identifier: wd-web services reliable messaging tc-ws-reliability-0.992. 78 pages. With SOAP 1.1 XML Schema and SOAP 1.2 XML Schema. [source, cache]

    The following individuals were members of the committee during the development of this specification: David Ingham, Arjuna Technologies Limited; Joseph Chiusano, Booz Allen Hamilton; Peter Furniss, Choreology Ltd; Jeff Turpin, Cyclone Commerce; Pramila Mullan, France Telecom; Jacques Durand, Fujitsu; Kazunori Iwasa (Secretary), Fujitsu; Tom Rutt (Chair), Fujitsu; Jishnu Mukerji, Hewlett-Packard; Robert Freund, Hitachi; Eisaku Nishiyama, Hitachi; Nobuyuki Yamamoto, Hitachi; Ben Bloch, Individual; Mark Hansen, Individual; Paolo Romano, Individual; Dock Allen, Mitre Corporation; Junichi Tatemura, NEC Corporation; Alan Weissberger, NEC Corporation; Magdolna Gerendai, Nokia; Szabolcs Payrits, Nokia; Mark Peel, Novell; Sunil Kunisetty (Secretary), Oracle; Anish Karmarkar, Oracle; Jeff Mischkinsky, Oracle; Marc Goodner (Secretary), SAP; Pete Wenzel, SeeBeyond Technology Corporation; Doug Bunting (Secretary), Sun Microsystems; Tony Graham, Sun Microsystems; Chi-Yuen Ng, University of Hong Kong; Patrick Yee, University of Hong Kong; Prasad Yendluri, webMethods, Inc.; Scott Werden, WRQ, Inc.

  • Schema for WS-Reliability Protocol Headers. Reference: 'ws-reliability.xsd'. Version: 0.62. Date: 2004-March-08. Edited by Sunil Kunisetty and Scott Werden. [source .ZIP]

  • Schema for WS-Reliability Protocol Headers for SOAP 1.2 protocol. Reference: 'ws-reliability-soap12.xsd'. Version: 0.62b. Date: 2004-March-10. Edited by Sunil Kunisetty and Scott Werden. A SOAP 1.2 version of the schema based on 0.62 version; this (first exemplar) is versioned as 0.62b. [source .ZIP]

WS-Reliability Overview

Purpose: "The purpose of WS-Reliability is to address reliable messaging requirements, which become critical, for example, when using Web Services in B2B applications. SOAP 1.2 over HTTP is not sufficient when an application-level messaging protocol must also address reliability and security. This specification is intended as an initial proposal for defining reliability in the context of current Web Services standards. The specification borrows from previous work in messaging and transport protocols, e.g., SOAP, and the ebXML Message Service (OASIS ebXML Message Service Specification 2.0).

Scope and Definition of Reliable Messaging: The focus of this specification is on the SOAP layer and envelope. In the current specification, we will define reliable messaging as the mechanism supporting any of the following requirements:

  • Guaranteed message delivery, or At-Least-Once delivery semantics
  • Guaranteed message duplicate elimination, or At-Most-Once delivery semantics
  • Guaranteed message delivery and duplicate elimination, or Exactly-Once delivery semantics
  • Guaranteed message ordering for delivery, within a context delimited using a group ID

Within the scope of this specification, the following features are investigated:

  • Asynchronous messaging at the application level
  • Three reliability features: Guaranteed Delivery, Duplicate Elimination, and Guaranteed Message Ordering

Some messaging features are not mentioned in this specification. They are considered out of scope, yet the design of this specification is preserving compatibility with some of them. They are:

  • Application level synchronous messaging. Synchronous messaging applications that require immediate knowledge of the error status instead of waiting for the messaging layer to resend the message when an error is returned.
  • Routing features. This specification addresses end-to-end reliability, and is not concerned with intermediaries. The mechanisms described are orthogonal to routing techniques, and can be used in combination with these.

Out of Scope: The OASIS WSRM TC does not attempt to cover all aspects of Reliable Messaging. Several fundamental questions on reliability need to be addressed in subsequent work, and are only partially addressed in this specification:

  • Given that some reliability objectives cannot always be guaranteed or attainable, should a reliability contract include advanced quality of service elements (which may translate into specifying quantitative thresholds, e.g., Rate of delivery success, scope of a duplicate check, size of a message archive)? How could these quantitative parameters adjust to resource availability — memory, storage, computing — which depends on the communication system (mobile device, messaging hub, etc.)?
  • Beyond the specified qualities of message delivery (Guaranteed Delivery, Duplicate Elimination, and Guaranteed Message Ordering), how much of the synchronization between sender and receiver applications can and should be supported (i.e., the degree to which both sender and receiver parties share the same understanding about the outcome of a reliable exchange)?

Model: The Reliable Messaging Model described in this document makes the following assumptions:

  • Reliability is a contract between two messaging nodes, with respective roles of sender and receiver: (1) the sender RMP on which the submit message operation is invoked, and (2) the receiver RMP which invokes the deliver message operation. Intermediaries are transparent to this specification. Signal messages resulting from a reliable exchange, such as Acknowledgment message or Reliable Messaging Fault message are sent from the receiving RMP to the sender RMP.
  • The underlying protocol is a request-response protocol. In other words, this specification assumes the underlying protocol distinguishes two kinds of messages: requests and responses. Under normal conditions, a response is always sent back for each request. This assumption is not essential to the reliable features described here: these could be reformulated without this assumption..." [adapted from the v.992 spec Section 1]

"The WS-Reliability specification was created based on the ebXML Message Service's reliability functions for all types of Web Service. The reliability techniques developed in ebXML were not limited in scope to B2B applications. They have been improved in WS-Reliability. WS-Reliability has the following characteristics:

  1. Standardized by OASIS: WS-Reliability has been created by the Web Services Reliable Messaging Technical Committee in the standard organization OASIS. It is an open and royalty free specification. It is in the final stage[s] of its standardization process in OASIS and it is expected that OASIS will adopt WS-Reliability as an OASIS Standard in the second quarter of 2004.
  2. Support for the most common Reliable Messaging features: WS-Reliability provides required QoS (Quality of Service) for reliable messaging:
    • Guarantee of message delivery: When a message fails to be delivered to the target system, the failure is detected and the message is resent automatically, until the message arrives or a timeout is reached.
    • Prevention of Message Duplication: When duplicate messages are received by the target system, duplicate messages are removed automatically. The combination of the 'Guarantee of message delivery' and this function 'Prevention of Duplication Message' realizes 'exactly-once' semantics.
    • Guarantee of Message Order: Messages are delivered to the target application in the same order they were submitted by the sending application.
  3. Support for both Synchronous and Asynchronous communication: WS-Reliability supports not only asynchronous communication semantics for reliable messaging but also synchronous communication semantics.
  4. Compliance with SOAP 1.1: WS-Reliability is compliant with SOAP 1.1 specification.
  5. Combination with other Web Service Specifications: WS-Reliability can be used with other Web Service specifications (e.g., with WS-Security)..." [adapted from the RM4GS Overview by Fujitsu, Hitachi and NEC]

WS-Reliability Sample Software (RM4GS)

"A highly reliable message delivery infrastructure is necessary in e-business where important information, such as purchase orders and billing, is exchanged. The delivery of an incorrect purchase order or the non-delivery of an order cancellation could cause serious problems for a company. In order to avoid such problems in e-business executed using Web services, it is necessary to provide a highly reliable messaging infrastructure for Web services. To encourage the swift and wide-ranging implementation of such an infrastructure, its technology should be both open and royalty-free... To achieve the goals set out above, Fujitsu, in cooperation with other IT vendors, has promoted the standardization of WS-Reliability: an open and royalty-free specification that provides a highly reliable message delivery infrastructure for Web services..."

"In addition to standardizing the specification, Fujitsu has developed WS-Reliability-compatible sample software jointly with Hitachi, Ltd., and NEC Corporation in order to help the spread of the highly reliable messaging infrastructure. This sample software demonstrates the fact that WS-Reliability is a high quality specification that is ready for implementation. The sample software was developed as part of the 'Business Grid Computing Project' hosted by the Japanese Ministry of Economy, Trade and Industry..." [from Fujitsu]

"Fujitsu Limited, Hitachi, Ltd., and NEC Corporation today [March 09, 2004] announced that they are making available on their respective websites sample software that implements Web Services Reliability (WS-Reliability), a messaging specification for web services designed to ensure superior reliability. URL links to the royalty-free software downloads from each company's website are listed below.

WS-Reliability has been proposed as the standard specification for open and highly reliable messaging in the provision of web services. In providing the sample software, the companies hope to accelerate the spread of a reliable data transmission environment for the web services market and enable customers to develop systems for reliable web services more quickly..."

On January 9, 2003, a group of IT vendors including the three companies published a draft specification for WS-Reliability, and on April 7, 2003, the group submitted it to OASIS, the international standards-setting organization. The specification is now in the final stage of the process for becoming a standard. Today's move demonstrates that the WS-Reliability specification is close to completion and is now ready for actual implementation. [from the announcement, "Fujitsu, Hitachi and NEC Offer Sample Reliable Messaging Software for Web Services"]

System Requirements for use of the "RM4GS alpha version" WS-Reliability sample software: (1) Red Hat Linux 8.0 or later; (2) Java2 SDK, Enterprise Edition Developer Release 1.4; (3) Java2 SDK, Standard Edition 1.4.2; (4) PostgreSQL 7.4; (5) Apache Axis 1.1

URLs for the RM4GS alpha version implementation (based upon WS-Reliability Version 0.54):

About the OASIS Web Services Reliable Messaging TC

The OASIS Web Services Reliable Messaging Technical Committee (WSRM TC) was chartered in February 2003 to "create a generic and open model for ensuring reliable message delivery for Web services. This TC defines reliable message delivery as the ability to guarantee message delivery to software applications — Web services or Web service client applications — with a chosen level of quality of service (QoS). For this TC effort, QoS will be defined as the ability to determine the following aspects of message delivery: Message persistence; Message acknowledgement and resending; Elimination of duplicate messages; Ordered delivery of messages; Delivery status awareness for sender and receiver applications. The TC will specify rules for combining these features and their parameters.

Essential elements of web services are SOAP and WSDL. The specification to be created will provide WSDL definitions for reliable messaging and the message formats will be specified as SOAP headers and/or body content. The resulting specification must be programming language-neutral and platform-neutral. Lastly, the TC will address the dependencies between the capacity of the messaging nodes (persistence, message processing) and the level of QoS that can be provided...

In no event shall this Technical Committee finalize or approve any technical specification if it believes that the use, distribution, or implementation of such specification would necessarily require the unauthorized infringement of any third party rights known to the Technical Committee, and such third party has not agreed to provide necessary license rights on perpetual, royalty-free, non-discriminatory terms..."

The WSRM TC Chair is Mr. Tom Rutt (Coast Enterprises). Secretaries include Doug Bunting (Sun), Marc Goodner (SAP), Kazunori Iwasa (Fujitsu), and Sunil Kunisetty (Oracle).

Related: Web Services Reliable Messaging

Bibliographic Information for WS-ReliableMessaging

  • Web Services Reliable Messaging Protocol (WS-ReliableMessaging). March 09, 2004. 40 pages. Edited by Christopher Ferris (IBM) and David Langworthy (Microsoft). XML Namespace URI: http://schemas.xmlsoap.org/ws/2004/03/rm. Contributions by Ruslan Bilorusets, BEA; Adam Bosworth, BEA; Don Box, Microsoft; Luis Felipe Cabrera, Microsoft; Derek Collison, TIBCO Software; Donald Ferguson, IBM; Tom Freund, IBM; Mary Ann Hondo, IBM; John Ibbotson, IBM; Chris Kaler, Microsoft; Amelia Lewis, TIBCO Software; Rodney Limprecht, Microsoft; Steve Lucco, Microsoft; Matt Mihic, BEA; Don Mullen, TIBCO Software; Anthony Nadalin, IBM; Mark Nottingham, BEA; David Orchard, BEA; Shivajee Samdarshi, TIBCO Software; John Shewchuk, Microsoft; Tony Storey, IBM. Also credited: Keith Ballinger, Microsoft; Allen Brown, Microsoft; Michael Conner, IBM; Francisco Curbera, IBM; Steve Graham, IBM; Pat Helland, Microsoft; Rick Hill, Microsoft; Scott Hinkelman, IBM; Tim Holloway, IBM; Efim Hudis, Microsoft; Johannes Klein, Microsoft; Frank Leymann, IBM; Martin Nally, IBM; Peter Niblett, IBM; Jeffrey Schlimmer, Microsoft; James Snell, IBM; Keith Stobie, Microsoft; Satish Thatte, Microsoft; Stephen Todd, IBM; Sanjiva Weerawarana, IBM; Roger Wolter, Microsoft. Copyright (c) 2002-2004 BEA Systems Inc., International Business Machines Corporation, Microsoft Corporation, Inc, and TIBCO Software Inc. With WSDL and XSD files.

  • [2003-03] Web Services Reliable Messaging Protocol (WS-ReliableMessaging). March 13, 2003. Edited by Christopher Ferris (IBM) and David Langworthy (Microsoft). Copyright BEA, IBM, Microsoft, and TIBCO Software. 33 pages (PDF). Authors: Ruslan Bilorusets (BEA), Adam Bosworth (BEA), Don Box (Microsoft), Felipe Cabrera (Microsoft), Derek Collison (TIBCO Software), Jon Dart (TIBCO Software), Donald Ferguson (IBM), Christopher Ferris (IBM, Editor), Tom Freund (IBM), Mary Ann Hondo (IBM), John Ibbotson (IBM), Chris Kaler (Microsoft), David Langworthy (Microsoft, Editor), Amelia Lewis (TIBCO Software), Rodney Limprecht (Microsoft), Steve Lucco (Microsoft), Don Mullen (TIBCO Software), Anthony Nadalin (IBM), Mark Nottingham (BEA), David Orchard (BEA), John Shewchuk (Microsoft), and Tony Storey (IBM).

WS-ReliableMessaging Overview

This [March 09, 2004] specification (WS-ReliableMessaging) "describes a protocol that allows messages to be delivered reliably between distributed applications in the presence of software component, system, or network failures. The updates are based upon the suggestions collected from the WS-ReliableMessaging Feedback Workshop held in July 2003 and the Interoperability Workshop help in October 2003. The protocol is described in this specification in an independent manner allowing it to be implemented using different network transport technologies. To support interoperable Web services, a SOAP binding is defined within this specification. The protocol defined in this specification depends upon other Web services specifications for the identification of service endpoint addresses and policies. How these are identified and retrieved are detailed within those specifications and are out of scope for this document..." [IBM reference page]

"It is often a requirement for two Web services that wish to communicate to do so reliably in the presence of software component, system, or network failures. The primary goal of this specification is to create a modular mechanism for reliable message delivery. It defines a messaging protocol to identify, track, and manage the reliable delivery of messages between exactly two parties, a source and a destination. It also defines a SOAP binding that is required for interoperability. Additional bindings may be defined. This mechanism is extensible allowing additional functionality, such as security, to be tightly integrated. This specification integrates with and complements the WS-Security, WS-Policy, and other Web services specifications. Combined, these allow for a broad range of reliable, secure messaging options..." [spec 2004 Introduction]

"The WS-ReliableMessaging protocol facilitates the successful transmission of messages from a source to a destination, and ensures that error conditions are detectable. The protocol is transport-independent, allowing it to be implemented using different network technologies. Implementations of this protocol hide intermittent communication failures from the application, and may provide recoverability in case of system failures...

WS-ReliableMessaging Mechanisms Used for Reliable Delivery. The main mechanisms used in the implementation are:

  • Sequences: The messages sent from the source to the destination are scoped using a sequence. Sequences are distinguished using a unique identifier (a URI) for each sequence. It is important to note that the term sequence does not imply any processing order.
  • Message Numbers: Every message sent in the context of a sequence has a unique identifier in the context of the sequence. This identifier is a monotonically increasing integer number, starting with 1 and increasing by exactly 1 for each message. In a typical implementation the numbering would be performed "under the covers" by the messaging infrastructure, and the applications sending the messages would not be aware of it. This numbering scheme makes it simple to detect missing or duplicate messages, and simplifies acknowledgement generation and processing.
  • Acknowledgements: An acknowledgement is an indication that a message was successfully transferred to the destination. Messages are acknowledged using acknowledgement ranges. For example, acknowledging 1 through 4 and 6 through 13 will indicate that messages number 1 through 13 were received, with the exception of message number 5. An acknowledgement does not necessarily indicate that the message was processed. Indication of successful processing, or the reporting of processing errors, requires a separate, higher-level protocol. This protocol will often be application-specific.
  • Persistence: Message persistence (durability) considerations do not affect the wire protocol and are not addressed by it. As mentioned above (in the discussion about acknowledgements), WS-RM ensures transfer, not processing. Persistence requirements have to do with the storing of the message on the destination until it is processed, and are thus the responsibility of the implementation... [from the Microsoft paper "Reliable Messaging in a Service Oriented Architecture"]

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