Update 2008-06-20 A memo from W3C AC Representatives Steve Holbrook (IBM), Jeff Mischkinsky (Oracle), Kazunori Iwasa (Fujitsu), and Paul Lipton (CA) recommends the creation of new Working Group "Web Services Resource Access Working Group (suggested) to four Web services specifications: WS-Transfer, WS-Enumeration, WS-MetadataExchange, WS-ResourceTransfer. See the text of memo and draft Working Group Charter.

Update 2006-08-16 Version 1.1 of the Web Services Metadata Exchange (WS-MetadataExchange) specification was released in August 2006. It "adds the ability to 'push' metadata along with an Endpoint Reference (of either version), replaces its locally-defined 'Get' request-reply message pair with the one from WS-Transfer, brings in WS-Addressing 1.0 Core, updates examples," etc.

[September 21, 2004] Microsoft announced the release of a second public version of Web Services Metadata Exchange (WSMetadataExchange), adding new functionality and broader industry support.

The September 2004 version of WSMetadataExchange is co-authored by Computer Associates International, Sun Microsystems, and webMethods, together with authors named on the previous version of March 2004 (BEA Systems, IBM, Microsoft Corporation, and SAP AG).

WSMetadataExchange is designed to define a bootstrap mechanism for metadata-driven message exchange, including XML Schema, WSDL, and WS-Policy. It is also intended to "support future versions of known metadata formats, allowing new metadata formats to be added. It is supposed to leverage other Web service specifications for secure, reliable, transacted message delivery. The design supports both SOAP 1.1 and and SOAP 1.2 Envelopes, and enables description in WSDL 1.1." The protocol binding by default is SOAP 1.1 over HTTP, and adherence to constraints expressed by the WS-I Basic Profile 1.0 is recommended as a means of bootstrapping communication.

The previous version of WSMetadataExchange defined a Get Policy request, Get WSDL request, and Get Schema request as methods for retrieving metadata. These have been generalized in the updated specification to provide more flexible endpoint metadata access and to support versioning. The specification now defines request-response messages to retrieve arbitrary types of metadata; these metadata can be returned inline or by reference.

Metadata retrieval is implemented in the 2004-09 version of WSMetadataExchange by 'Get Metadata' and 'Get': "to retrieve a service's metadata, a requester may send a Get Metadata request message to an endpoint. To retrieve a referenced Metadata Section, a requester may send a Get request message to a Metadata Reference. 'Get' fetches a one-time snapshot of the metadata, according to the metadata type (@Dialect) and identifier specified in the Metadata Section. To facilitate intelligent intermediaries, all implementations of the Get operation must be 'safe', as defined in RFC 2616; specifically, safe operations are required to have no significant semantic side-effects on the service, including such actions as the acquisition of long-lived locks."

A new appendix for "Dialect URI Definitions" has been added, defining several values for @Dialect; "other specifications are expected to define values for @Dialect for other metadata formats and/or versions." Dialect URIs are defined for the following formats/versions: XML Schema Version 1.0, WSDL 1.1, WS-Policy expression, WS-PolicyAttachment [wsp:PolicyAttachment] and WSMetadataExchange [mex, for Metadata elements nested within a metadata section, or referenced via wsx:MetadataReference and wsx:Location].

As a member of the composable suite of 'WS-*' Web services specifications, WSMetadataExchange "relies on other Web services specifications to provide secure, reliable, and/or transacted message delivery and to express Web service and client policy."

In the updated copyright notice for WSMetadataExchange, the authors are said to "each agree to grant you a license, under royalty-free and otherwise reasonable, non-discriminatory terms and conditions, to their respective essential patent claims that they deem necessary to implement the WSMetadataExchange Specification."

Bibliographic Information

• Web Services Metadata Exchange (WSMetadataExchange). September 2004. 23 pages (PDF). Copyright (c) 2004 BEA Systems Inc., Computer Associates International, Inc., International Business Machines Corporation, Microsoft Corporation, Inc., SAP AG, Sun Microsystems, and webMethods. Authors: Keith Ballinger (Microsoft), Don Box (Microsoft), Francisco Curbera (Editor, IBM), Srinivas Davanum (Computer Associates), Don Ferguson (IBM), Steve Graham (IBM), Canyang Kevin Liu (SAP), Frank Leymann (IBM), Brad Lovering (Microsoft), Anthony Nadalin (IBM), Mark Nottingham (BEA Systems), David Orchard (BEA Systems), Claus von Riegen (SAP), Jeffrey Schlimmer (Editor, Microsoft), Igor Sedukhin (Computer Associates), John Shewchuk (Microsoft), Bill Smith (Sun Microsystems Inc), Greg Truty (IBM), Sanjiva Weerawarana (IBM), and Prasad Yendluri (webMethods).

  Acknowledgements: "This specification has been developed as a result of joint work with many individuals and teams, including: Luis Felipe Cabrera (Microsoft), Erik Christensen (Microsoft), Timm Falter (SAP), Jeffrey Frey (IBM), Omri Gazitt (Microsoft), Alan Geller (Microsoft), Martin Gudgin (Microsoft), Maryann Hondo (IBM), Chris Kaler (Microsoft), Dave Langworthy (Microsoft), Andrew Layman (Microsoft), Steve Millet (Microsoft), Henrik Frystyk Nielsen (Microsoft), Sanjay Patil (SAP), Vladimir Savchenko (SAP), Ramesh Seshadri (Microsoft), Chris Sharp (IBM), Eugene Sindambiwe (SAP), Tony Storey (IBM), Marvin Theimer (Microsoft), Sara Wong (Microsoft), Alexander Zubev (SAP)."

• Previous version: Web Services Metadata Exchange (WS-MetadataExchange). Edited by Francisco Curbera (IBM) and Jeffrey Schlimmer (Microsoft). Authors: Keith Ballinger (Microsoft), Don Box (Microsoft), Francisco Curbera (Editor, IBM), Steve Graham (IBM), Canyang Kevin Liu (SAP), Brad Lovering (Microsoft), Anthony Nadalin (IBM), Mark Nottingham (BEA Systems), David Orchard (BEA Systems), Claus von Riegen (SAP), Jeffrey Schlimmer (Editor, Microsoft), John Shewchuk (Microsoft), Greg Truty (IBM), and Sanjiva Weerawarana (IBM). March 2004. 28 pages. XML Namespace URI: http://schemas.xmlsoap.org/ws/2004/03/mex. Copyright (c) 2004 BEA Systems Inc., International Business Machines Corporation, Microsoft Corporation, Inc, and SAP AG.

  Acknowledgements: "This specification has been developed as a result of joint work with many individuals and teams, including: Luis Felipe Cabrera (Microsoft), Erik Christensen (Microsoft), Timm Falter (SAP), Don Ferguson (IBM), Jeffrey Frey (IBM), Maryann Hondo (IBM), Chris Kaler (Microsoft), Dave Langworthy (Microsoft), Frank Leymann (IBM), Brad Lovering (Microsoft), Steve Millet (Microsoft), Sanjay Patil (SAP), Chris Sharp (IBM), Eugene Sindambiwe (SAP), Tony Storey (IBM), Sara Wong (Microsoft)."

  From the copyright statement: "...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..." and status statement: "This specification is an initial public draft release and is provided for review and evaluation only. The authors hope to solicit your contributions and suggestions in the near future. The authors make no warrantees or representations regarding the specifications in any manner whatsoever..."

About Web Services Metadata Exchange (WSMetadataExchange)

Web services use metadata to describe what other endpoints need to know to interact with them. Specifically, WS-Policy describes the capabilities, requirements, and general characteristics of Web services; WSDL describes abstract message operations, concrete network protocols, and endpoint addresses used by Web services; XML Schema (XML Schema Part 1, Part 2) describes the structure and contents of XML-based messages received by and sent by Web services.

To bootstrap communication with Web services and to retrieve these and other types of metadata, this specification defines two request-response interactions. When the type of metadata sought is clearly known, e.g., WS-Policy, a requester may indicate that only that type should be returned; where additional types of metadata are being used, or are expected, or when a requester needs to retrieve all of the metadata relevant to subsequent interactions with an endpoint, a requester may indicate that all available metadata, regardless of their types, are expected.

The interactions defined herein are intended for the retrieval of metadata (i.e., service description information) only. They are not intended to provide a general purpose query or retrieval mechanism for other types of data associated with a service, such as state data, properties and attribute values, etc..." [from the 2004-09 specification Introduction]

"WSDL and WS-Policy both define formats for metadata but do not specify mechanisms for acquiring or accessing metadata for a given service. In general, service metadata can be discovered using a variety of techniques. To enable services to be self-describing, Web services architecture defines SOAP-based access protocols for metadata in WS-MetadataExchange. The GetMetadata operation is used to retrieve metadata that is found at the endpoint reference of the request. The Get operation is similar but is designed to retrieve metadata that is referenced in a metadata section, and is to be retrieved at the endpoint reference where it is stored. The metadata exchanged using WS-MetadataExchange can be described as a resource. A resource is defined as any entity addressable by an endpoint reference where the entity can provide an XML representation of itself. Resources form the basis needed to build state management in Web services..." [from Microsoft's September 2004 Web Services Architecture document]

WS-MetadataExchange Feedback Workshop 2004-10-14

BEA, Computer Associates, IBM, Microsoft, SAP, Sun and webMethods, authors of the WS-MetadataExchange specification, are hosting a one-day Feedback Workshop on Thursday, October 14 2004 from 9:00 AM to 3:00 PM with breakfast available from 8:00 AM.

The one-day Feedback Workshop is an open forum for spec authors to share background information on the design of the specifications and to receive feedback and for software vendors and other interested parties to discuss their ideas about the practicality of implementing these and related Web Services specifications.

Note that in order to attend this event, a feedback agreement must be reviewed and signed by each attendee — either before or at the workshop event. The purpose of the feedback agreement is to ensure that everyone involved in influencing the specification is committed to keeping the specification royalty free.

This workshop will be held at webMethods campus in Sunnyvale, California. Address: 432 Lakeside Dr., sunnyvale, CA, USA 94085, +1 408-962-5000. [detailed information from webMethods]