RELAX NG Common Annotations

Working Draft�3 August 2001

This version:
Working Draft: 3 August 2001
Editors:
James Clark�<jjc@jclark.com>, Makoto MURATA�<mura034@attglobal.net>

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Abstract

This specification defines elements and attributes that may be used as annotations in RELAX NG schemas.

Status of this Document

This is a working draft constructed by the editors. It is not an official committee work product and may not reflect the consensus opinion of the committee. Comments on this document may be sent to relax-ng-comment@lists.oasis-open.org.

Table of Contents

1 Introduction
2 Conformance
3 Attribute default values
4 ID, IDREF and IDREFS
5 Documentation

Appendixes

A RELAX NG schema
References

1. Introduction

RELAX NG provides an annotation capability. In a RELAX NG schema, RELAX NG-defined elements can be annoated with child elements and attributes from other namespaces. This specification defines some useful annotations, emphasizing compatibility with XML 1.0.

The elements and attributes defined in this specification have the namespace URI.

http://relaxng.org/ns/annotation/0.9

Examples in this specification follow the convention of using the prefix a to refer to this namespace URI.

2. Conformance

This specification defines three features:

  • attribute default value
  • ID/IDREF/IDREFS
  • documentation

Conformance is defined separately for each feature. A conformant implementation can support any combination of features. There are also two levels of conformance.

  1. Level 1 requires validation only. A RELAX NG processor that supports a feature at level 1 is only required to check that the schema uses the feature correctly and that the instance is valid with respect to the schema's use of the feature.
  2. Level 2 requires transformation of the infoset, in addition to the validation required by level 1.

A conformant implementation may support different features at different levels.

3. Attribute default values

An a:defaultValue attribute on a RELAX NG attribute element specifies the default value for the attribute.

If an attribute element has an a:defaultValue attribute, then, after schema simplification,

  • the value of the a:defaultValue attribute must match the pattern contained in the attribute element
  • the pattern in the attribute element must not contain data or value elements with context-dependent datatypes
  • it must not have an a:attributeType attribute (see Section 4)
  • its first child must be a name element
  • it must not have a oneOrMore ancestor
  • any ancestor that is a choice element must have one child that is an empty element
  • it must have at least one choice ancestor
  • if the containing definition competes with another definition, then that other definition must also contain an attribute element with the same name and with an a:defaultValue attribute with the same value. A definition
    <define name="ln1">
  <element>
    nc1
    p1
  </element>
</define>

    competes with a definition

    <define name="ln2">
  <element>
    nc2
    p2
  </element>
</define>

    if there is a name n that belongs to both nc1 and nc2.

A RELAX NG processor that supports this feature at level 2 must transform the infoset by adding default attributes appropriately.

Editorial Note

Define this more precisely.

4. ID, IDREF and IDREFS

An a:attributeType attribute on a RELAX NG attribute element must have the value ID, IDREF or IDREFS. It specifies the XML 1.0 attribute type of the attribute and corresponds to the [attribute type] infoset property.

Editorial Note

Should we allow other attribute types such as NOTATION?

Leading and trailing whitespace is ignored in the value of the a:attributeType element during schema simplification.

If an attribute element has an a:attributeType attribute, then, after schema simplification,

  • if the value of the a:attributeType attribute is ID, then
    • the first child of the attribute element must be a name element, and
    • there must not be a definition that competes with the definition containing the attribute element and that contains an attribute element that has a different name and an a:attributeType attribute with value ID. Note that a definition competes with itself.

    This implies that in the instance if two attributes are both IDs and have a parent element with the same name, then the two attributes must have the same name.

  • any competing attribute element must have an a:attributeType attribute with the same value. Two attribute elements
    <attribute> nc1 p1 </attribute>

    and

    <attribute> nc2 p2 </attribute>

    compete if and only if the containing definitions compete and there is a name n that belongs to both nc1 and nc2. Note that a definition competes with itself.

  • it must not have an a:defaultValue attribute (see Section 3)

An instance is valid with respect to the a:attributeType attributes in the schema if the attribute values in the instance declared by a:attributeType attributes in the schema to be of type ID, IDREF or IDREFS meet the validity constraints specified in [XML 1.0] for values of that type, after normalizing the values by applying the normalizeWhiteSpace function defined in [RELAX NG].

A RELAX NG processor that supports this feature at level 2 must transform the infoset by changing the [attribute type] of attribute information items appropriately and by transforming the [normalized value] by applying the normalizeWhiteSpace function.

Editorial Note

Define this more precisely.

5. Documentation

The a:documentation element can be used to specify human-readable documentation. An a:documentation element must not contain any elements. It can have any attributes whose namespace URI is neither the empty string, the RELAX NG namespace URI nor the RELAX NG annotation namespace URI.

The documentation specified in an a:documentation element applies to the parent of the a:documentation element. To apply documentation to a value element, wrap the value element in a group element. To apply documentation to a name element, wrap the name element in a choice element.

Editorial Note

Is there a better solution? Allow an a:documentation attribute as an alternative?

For any RELAX NG element, all a:documentation child elements must precede all child elements from the RELAX NG namespace.

A. RELAX NG schema

To be supplied.

References

James Clark, Makoto MURATA, editors. RELAX NG Specification. OASIS, 2001.

Tim Bray, Jean Paoli, and C. M. Sperberg-McQueen, Eve Maler, editors. Extensible Markup Language (XML) 1.0 Second Edition. W3C (World Wide Web Consortium), 2000.

John Cowan, Richard Tobin, editors. XML Information Set. W3C (World Wide Web Consortium), 2001.