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Last modified: August 03, 2001
W3C XML Protocol

[December 23, 2000] From the XML Protocol Activity statement: As part of the W3C's Architecture Domain, the W3C XML Protocol Activity is designed to address the problem of "standardized application-to-application messaging." The problem domain description: "Data transport is as central to modern computing as data storage and display in the networked, decentralized, and distributed environment of the Internet and Web. Following the adoption of XML (Extensible Markup Language) for data processing, the challenge is for both sides of a session to agree on an application-layer transfer protocol, whether between software programs, between machines, or between organizations. Even though it accounts for most Web surfing, interactive browsing by human beings operating user agents can accomplish only so much alone...The search is on for common ground that can meet the heavyweight, commercial demands of business to business e-commerce systems, and at the same time satisfy aesthetic requirements for a lightweight, simple network protocol for distributed applications."

The XML Protocol Working Group "is chartered to design four things and to produce a Recommendation based on them: (1) An envelope to encapsulate XML data for transfer in an interoperable manner that allows for distributed extensibility, evolvability, as well as intermediaries like proxies, caches, and gateways (2) In cooperation with the IETF (Internet Engineering Task Force), an operating system-neutral convention for the content of the envelope when used for RPC (Remote Procedure Call) applications (3) A mechanism to serialize data based on XML Schema datatypes (4) In cooperation with the IETF, a non-exclusive mechanism layered on HTTP transport." Principal contacts include Yves Lafon (W3C Team Contact), Hugo Haas (Alternate W3C Team Contact), and David Fallside (XML Protocol Working Group Chair).

[July 09, 2001]   W3C Publishes XML Protocol Abstract Model and Glossary.    An initial draft specification XML Protocol Abstract Model has been published by the W3C XML Protocol Working Group. The draft document has been developed "in order to provide a useful framework for the evaluation of candidate protocols and for reasoning about the development of the protocol itself." According to the WD, "the challenge of crafting a protocol specification is to create a description of behaviour that is not tied to any particular approach to implementation. There is a need to abstract away from some of the messy implementation details of buffer management, data representation and specific APIs. However, in order to describe the behaviour of a protocol one has to establish a set of (useful) concepts that can be used in that description. An abstract model is one way to establish a consistent set of concepts. An abstract model is a tool for the description of complex behaviour -- it is not a template for an implementation... although it should not stray so far away from reality that it is impossible to recognise how the required behaviours would be implemented... As the XML Protocol Working Group labored on the XML Protocol Requirements document and the emerging specification, they also set out to describe how such a technology might ultimately be designed at an abstract level. The resulting Working Draft, the XML Protocol Abstract Model, also provides a shared vocabulary for both members of the Working Group, and other developers already at work on applications that make use of earlier versions of SOAP. Section 2 of the working draft presents an overview of the abstract model; Section 3 presents a model for the services provided by the XML protocol layer to XML protocol applications; Section 4 presents a model for the extensible processing of XML protocol messages; Section 5 presents a model for the binding of XML protocol to underlying protocol layers." [Full context]


  • XML Protocol Home Page

  • W3C XML Protocol Working Group

  • W3C XML Protocol Activity

  • XML Protocol Abstract Model. Working Draft 2001-07-09 (or later)

  • 'xml-dist-app' mailing list

  • 'xml-dist-app' mailing list archives

  • XML Protocol Working Group Charter

  • A Matrix of XML Protocol Comparisons

  • XML Protocols Shakedown. A W3C-organized panel at the WWW9 conference in Amsterdam

  • [March 24, 2001]   W3C Publishes Revised XML Protocol (XMLP) Requirements.    The W3C XML Protocol Working Group has released a revised working draft document for the XML Protocol (XMLP) Requirements. This WD updates the previous version of 2000-12-19, and "describes the W3C XML Protocol Working Group's requirements for the XML Protocol (XMLP) specification." XMLP "allows two or more peers to communicate in a distributed environment using XML as its encapsulation language. The XMLP framework can accommodate an open-ended set of XMLP modules defining a large variety of functions and services. Typical functions and services defined by XMLP modules can range from generic mechanisms for handling security, caching, routing, and eventing to specific functions like submitting a purchase order. While XMLP itself is intended to be as simple and lightweight as possible, XMLP modules can be designed and composed to perform arbitrarily complex operations allowing the core protocol to remain simple." The working draft articulates external requirements from XForms and P3P in addition to the general requirements and related requirements areas (simplicity and stability; data encapsulation and evolvability; intermediaries; data representation; protocol bindings; convention for RPC). A Glossary in the document overviews the general protocol concepts, data encapsulation concepts, message sender and receiver concepts, and data representation concepts. The draft also specifies usage scenarios, intended to provide representative examples of situations where XMLP might be applicable. [Full context]

  • [August 03, 2001] "WSDL for Defining Web Services." By Don Kiely. In XML Magazine Volume 2, Number 4 (August/September 2001). ['Achieving fully distributed Web services has yet to be realized, partly because a lack of standards has fragmented development efforts. The W3C's XML Protocol Working Group hopes to change that with initiatives that include WSDL as a complement to SOAP and UDDI. With the W3C's XML Protocol Working Group and industry heavyweights behind it, will WSDL reach Recommendation status?'] "The big news in Web development over the last year has been Web services. Microsoft made it mainstream with its early work on Simple Object Access Protocol (SOAP), using it as the basis for its vision of Web services in the .Net framework. During that time many groups submitted their own standards proposals to provide key pieces of the XML middleware story. Fundamentally, these networked service requests are a way to request XML-related functionality from a remote machine over a network such as the Internet. The more notable standards entries for Web services include Web Distributed Data eXchange (WDDX), XML Remote Procedure Call (XML-RPC), and SOAP. There also have been proposals for defining the descriptions and structure of such content, including Information Content Exchange (ICE) and the RDF (Resource Description Framework) Site Summary (RSS). Many developers have also done very well using the common Internet standard of Multipurpose Internet Mail Extensions (MIME). At the same time, Web developers have plugged away building applications with plain old HTTP. But many other XML protocol initiatives are floating around the W3C and elsewhere, so the W3C has a new XML Protocol Working Group for addressing these issues (see Resources). The group has begun defining its charter and pulling together the proposed standards that ultimately will be the backbone of this new generation of Web features. Here's an excerpt from the group's charter: A broad range of applications will eventually be interconnected through the Web. The initial focus of this Working Group is to create simple protocols that can be ubiquitously deployed and easily programmed through scripting languages, XML tools, interactive Web development tools, etc. The goal is a layered system which will directly meet the needs of applications with simple interfaces (e.g. getStockQuote, validateCreditCard), and which can be incrementally extended to provide the security, scalability, and robustness required for more complex application interfaces. Experience with SOAP, XML-RPC, WebBroker, etc. suggests that simple XML-based messaging and remote procedure call (RPC) systems, layered on standard Web transports such as HTTP and SMTP, can effectively meet these requirements..."

  • [December 19, 2000] XML Protocol Requirements. Reference: W3C Working Draft 19-December-2000. The document "describes the XML Protocol Working Group's requirements for the XML Protocol specification." Revisions from the previous draft of 7-December-2000 are presented in a color-coded diff document. Included among the general requirements delineated in the new working draft document: "(1) The specification will make reasonable efforts to support (but not define) a broad range of programming models suitable for the applications intended for XP. (2) The specification will make reasonable efforts to support (but not define) a broad range of protocol bindings between communicating peers. (3) The specification developed by the Working Group must support either directly or via well defined extension mechanisms different messaging patterns and scenarios. The specification will directly support One-way and Request-response patterns as part of permanently and intermittently connected scenarios. The specification will not preclude the development of other patterns at either the application or transport layers. Examples of such patterns may include publish-subscribe or multicast delivery. All patterns and scenarios will be described by relevant use cases. (4) The Working Group will coordinate with W3C XML Activities through the XML Coordination Group and shall use available XML technologies whenever possible. If there are cases where this is not possible, the reasons must be documented thoroughly. (5) The specification developed by the Working Group shall be as lightweight as possible keeping parts that are mandatory to the minimum. Optional parts of the specification should be orthogonal to each other allowing non-conflicting configurations to be implemented. (6) The specification must be suitable for use between communicating parties that do not have a priori knowledge of each other. (7) The specification must focus on the encapsulation and representation of data being transferred between parties capable of generating and/or accepting an XP protocol envelope."

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