Advanced XML Schema Patterns for Databinding

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This specification provides a set of commonly used patterns known to cause issues with some state of the art databinding implementations. The patterns in conjunction with the may be used to describe XML representations of commonly used data structures. The data structures described are intended to be independent of any particular programming language, database or modelling environment.

Version 1.0

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XML &pubday; &pubmonth; &pubyear; http://www.w3.org/2002/ws/databinding/edcopy/advanced/advanced.html Jonathan Calladine BT George Cowe Origo Services Limited Paul Downey BT Yves Lafon W3C

This section describes the status of this specification at the time of its publication. Other specification may supersede this specification. 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 a public Working Group Note produced by the XML Schema Patterns for Databinding Working Group, which is part of the W3C Web Services Activity. This publication as a Working Group Note coincides with the end of the Working Group's charter period, and represents the culmination of the group's work.

This document was built using evidence and experience gained examining the interoperability of a significant number of state of the art databinding implementations using a test suite, see the Advanced Patterns Implementation Report and a collection of implementation reports including the collection of patterns detected from "the wild".

The Working Group also produced an accompanying document, which includes patterns in common use, but which were discovered to be well supported by state of the art databinding implementations.

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

This document was produced by a Working Group operating under the 5 February 2004 W3C Patent Policy. The W3C maintains a public list of any patent disclosures made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) must disclose the information in accordance with section 6 of the W3C Patent Policy.

US English

Introduction

A databinding tool generates a mapping between XML documents which conform to an schema and an internal data representation. For example, a Web services databinding tool may use descriptions inside a document to produce and consume messages in terms of data structures in a programming language or data held inside a database.

State of the art databinding implementations have displayed uneven and inconsistent support of the W3C Recommendation. XML Schema provides a wide variety of methods for describing the same XML structure, conversely a concept such as "null" may be represented in a wide variety of different ways.

The result of these issues is impaired interoperability and a poor user experience of databinding tools:

rejecting valid XML Schema documents, rejecting valid XML instance documents, and making the content of valid XML instance documents unavailable in mapped data structures.

This specification provides a advanced set of example constructs and types in the form of concrete expressions. These patterns are known to be in widespresd use and considered to be compatible with databinding implementations.

Implementers of databinding tools may find these patterns useful to represent simple and common place data structures. Ensuring tools recognise at least these simple patterns and present them in terms most appropriate to the specific language, database or environment will provide an improved user experience when using databinding tools. It is inappropriate to use this specification to constrain the use of the Recommendation.

¬ations; &namespaces; Document Conformance

A Document claiming conformance to this specification:

MUST use either the UTF-8 or UTF-16 encoding. MAY include the Byte Order Mark (). MUST be a Well-formed document MUST conform to the Recommendation MUST only contain element nodes and attribute nodes which form a part of one or more complete patterns contained in this and the specifications. MAY contain additional comment nodes and processing instruction nodes. Implementation Conformance

An implementation that claims conformance to this specification:

MUST be able to consume any valid Document. MUST be able to process any Document conforming to this specification MUST produce a data model exposing all of the element node and attribute node content described by the originating Document. MUST be able to consume any Well-formed Document which satisfies local-schema validity against the originating Document exposing all of the element node and attribute node content in the data model. MUST be able to produce Well-formed instance documents which satisfy local-schema validity against the originating Document containing values exposed in the data model. MAY consume Well-formed instance documents which do not satisfy local-schema validity against the originating Document. MAY allow the production of Well-formed instance documents containing values exposed in the data model which do not satisfy local-schema validity against the originating Document.

Describing the form of the data model provided by a databinding implementation is beyond the scope of this specification. For example, the unconstrained built-in numeric primitive types, xs:decimal, xs:integer, xs:negativeInteger, xs:positiveInteger, xs:nonNegativeInteger and xs:nonPositiveInteger, do not map directly to native types in many programming languages and are likely to be presented as a toolkit specific construct or more generalised ways, such as a 'string'.

Note that although the patterns contained in this document are defined using , there is no requirement for a conformant implementation to support .

Schema Patterns &patterns-intro;

Note, this specification places no particular semantics on the difference between annotating an element with xsi:nil and the absence of an element.

Note, best current practice for the use of the xs:language type is described in .

&patterns; Data Types & Structures

This section offers one or more patterns which may be used to represent an abstract data structure. Each data structure presented is intended to be independent of any particular programming language, database or modeling environment. No semantics are implied by the order in which patterns are listed for a given abstract data structure.

Default Value Definition A preselected value used by when no alternative is explicitly specified. Patterns Map

pdowney2006-10-25ISSUE-25: need to incorporate examples for Hash tables and maps

Extensible Enumeration

pdowney2006-10-25ISSUE-5: need to incorporate extensible enum examples

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