W3C Architecture Domain Web Services Activity

Charter of the XML Schema Patterns for Databinding Working Group

[October 2005]

Paul Downey, Chair, BT
Yves Lafon, Team Contact

The Working Group follows the rules and requirements of the latest operative version of the World Wide Web Consortium Process Document. In the event of a conflict between this document and the W3C Process Document, the W3C Process Document shall take precedence.


Table of Contents

  1. Mission
  2. Scope and Goals
  3. Out of Scope
  4. Deliverables and duration
  5. Expected milestones
  6. Coordination with Other Groups
  7. Working Group participation
  8. Meetings
  9. Communication
  10. Confidentiality
  11. Patent Policy

Mission

The mission of this Working Group is to define a set of XML Schema patterns that will be efficiently implementable by the broad community who use XML databindings. Patterns which may prove useful to model include abstractions of structures common across a wide variety of programming environments, such as hash tables, vectors, and collections. There are several ways of representing such abstracted data structures and Web Services toolkits are currently using ad hoc technologies to infer the most suitable language mapping when processing XML Schemas. Agreeing on a set of XML Schema patterns for which databinding optimizations can be made will facilitate the ability of Web services and other toolkits to expose a more comprehensible data model to the developer.

Scope and Goals

The Working Group should identify a set of common data abstractions and define a set of recommended XML Schema patterns for them for the purpose of simplifying the mapping of XML Schemas to the identified data structures. Those patterns must be independent of any particular programming language, database or processing environment. For example, keys from a hash table can be represented using the ID derived type, the xs:key component, or the xs:unique component, and possibly in other ways. The Group will also develop a method of identifying the usage of those patterns so that conformance of an XML Schema to those patterns can be verified.

This group will also look at the issue of versioning of data structures and the impact on the XML Schema patterns. For example, suppose a programmer uses one version of a class and a later version of that class adds a new property. Consider an application that uses one version of a schema pattern for which a later version adds a new elements and/or attributes. The Working Group will examine how such a change might affect applications as Web Services compatibility, and what approach developer may adopt to reduce the risk of incompatibility across versions when accessing the corresponding datastructures.

As the TAG and other groups have discussed, it is important to consider evolution goals early in the design process. The Technical Architecture Group, the Web Services Description Working Group, and the XML Schema Working Group (see XML Schema Versioning Use Cases) are all studying versioning and extensibility issues. It is therefore expected that this Working Group will follow the results of those discussions, or take active part in them.

Out of scope

Profiling XML Schema for Web Services is out of scope: While the recommended patterns are not expected to use every possible feature of XML Schema, Web Services toolkits are expected to provide full support of XML Schema.

Direct mapping from the patterns into a specific programming language, database or other environment are out of scope; the goal is to provide interoperability across different programming languages, database and processing environments each with their own native data representations.

Roadmap, deliverables and duration

Roadmap

We expect this work to unfold in two successive set of patterns:

  1. First, the group will focus on “basic” patterns. The group would target data structures that can be represented and preserved with XML Schema 1.0, such as collections, vectors, or maps, and that would not require the use of XML Schema annotations in order to preserve them. We expect the work on “basic patterns” to be relatively short, restricting itself to today’s state of the art. The Group will accept as input the document started in the Web Services Description Working Group: XML Schema Patterns for Common Data Structures.
  2. In the second phase, the group will proceed to address more “advanced” patterns, using techniques such as XML Schema annotations when appropriate. Consider the example of graphs: an XML Schema document using advanced patterns might include XML Schema annotations to indicate that the data structure is a graph and should be preserved as such when represented in a processing environment. The Group will also consider the issue of versioning of data structures and XML Schema patterns, as outlined in the scope section.

Deliverables

Duration

The expiration date of this charter is 30 September 2007.

Expected milestones

The milestones follow the roadmap, outlined above.

September 2005
Working Group created
November/December 2005
First face-to-face meeting.
January 2006
First public Working Group draft for the XML Schema patterns for databinding (“basic” patterns) specification.
March 2006
Last Call for the XML Schema patterns for databinding (“basic”) patterns specification.
June 2006
Candidate Recommendation for the XML Schema patterns for databinding (“basic” patterns) specification. First public Working Draft for the XML Schema patterns for databinding (“advanced” patterns and versioning of data structures) specification.
August 2006
Proposed Recommendation for the XML Schema patterns for databinding (“basic” patterns) specification.
September 2006
Last Call for the XML Schema patterns for databinding (“advanced” patterns and versioning of data structures) specification.
November 2006
Candidate Recommendation for the XML Schema patterns for databinding (“advanced” patterns and versioning of data structures) specification.
February 2007
Proposed Recommendation for the XML Schema patterns for databinding (“advanced” patterns and versioning of data structures) specification.

Coordination with Other Groups

W3C Groups

The Working Group should coordinate its efforts with the W3C Working Groups involved in the Web Services and XML Activities, in particular the Web Services Description Working Group and the XML Schema Working Group, as well as the Technical Architecture Group.

External Groups

Web Services Interoperability Organization
The Web Services Interoperability Organization is an open industry effort chartered to promote Web Services interoperability across platforms, applications, and programming languages through the development of profiles, any one of which could be relevant.

Various efforts have been accomplished outside W3C in order to map the XML Schema constructions in different programming languages (C#, Java, Python, …). The Working Group will also take those external efforts into account.

Working Group participation

Effective participation is expected to consume one workday per week for each Working Group participant; two days per week for editors. The Chair shall ensure that the criteria for Good Standing are understood and followed.

To be successful, we expect the Working Group to have 10 or more active participants for its duration.

Chair

The initial Chair of this Working Group is Paul Downey, BT.

W3C Team resources

The initial W3C Team contact is Yves Lafon. It is expected that this Working Group would consume about 0.2 FTE, including administrative logistics.

Meetings

The Working Group will have distributed and face-to-face meetings.

Communication

The Working Group will use a public mailing list, public-xsd-databinding@w3.org.

A Member-only mailing list member-xsd-databinding@w3.org is also available for administrative purposes only.

Confidentiality

The proceedings of this Working Group are public, subject to exceptions made by the Chair, after consultation with the Working Group.

Patent Policy

This Working Group operates under the W3C Patent Policy (5 February 2004 Version). To promote the widest adoption of Web standards, W3C seeks to issue Recommendations that can be implemented, according to this policy, on a Royalty-Free basis.


Philippe Le H├ęgaret, Yves Lafon
Last modified $Date: 2005/10/28 20:19:17 $