Table of contents

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1.1 Purpose

1.2 Dependencies on Other Specifications

1.3 Documentation Conventions and Terminology

2 Conceptual Framework

2.1 Overview of XML Schema

2.2 XML Schema Abstract Data Model

2.2.1 Type Definition Components

2.2.2 Declaration Components

2.2.3 Model Group Components

2.2.4 Identity-constraint Definition Components

2.2.5 Group Definition Components

2.2.6 Annotation Components

2.3 Constraints and Validation Rules

2.4 Conformance

2.5 Names and Symbol Spaces

2.6 Schema-Related Markup in Documents Being Validated

2.6.1 xsi:type

2.6.2 xsi:nil

2.6.3 xsi:schemaLocation, xsi:noNamespaceSchemaLocation

2.7 Representation of Schemas on the World Wide Web

3 Schema Component Details

3.1 Introduction

3.1.1 Components and Properties

3.1.2 XML Representations of Components

3.1.3 The Mapping between XML Representations and Components

3.1.4 White Space Normalization during Validation

3.2 Attribute Declarations

3.2.1 The Attribute Declaration Schema Component

3.2.2 XML Representation of Attribute Declaration Schema Components

3.2.3 Constraints on XML Representations of Attribute Declarations

3.2.4 Attribute Declaration Validation Rules

3.2.5 Attribute Declaration Information Set Contributions

3.2.6 Constraints on Attribute Declaration Schema Components

3.2.7 Built-in Attribute Declarations

3.3 Element Declarations

3.3.1 The Element Declaration Schema Component

3.3.2 XML Representation of Element Declaration Schema Components

3.3.3 Constraints on XML Representations of Element Declarations

3.3.4 Element Declaration Validation Rules

3.3.5 Element Declaration Information Set Contributions

3.3.6 Constraints on Element Declaration Schema Components

3.4 Complex Type Definitions

3.4.1 The Complex Type Definition Schema Component

3.4.2 XML Representation of Complex Type Definitions

3.4.3 Constraints on XML Representations of Complex Type Definitions

3.4.4 Complex Type Definition Validation Rules

3.4.5 Complex Type Definition Information Set Contributions

3.4.6 Constraints on Complex Type Definition Schema Components

3.4.7 Built-in Complex Type Definition

3.5 AttributeUses

3.5.1 The Attribute Use Schema Component

3.5.2 XML Representation of Attribute Use Components

3.5.3 Constraints on XML Representations of Attribute Uses

3.5.4 Attribute Use Validation Rules

3.5.5 Attribute Use Information Set Contributions

3.5.6 Constraints on Attribute Use Schema Components

3.6 Attribute Group Definitions

3.6.1 The Attribute Group Definition Schema Component

3.6.2 XML Representation of Attribute Group Definition Schema Components

3.6.3 Constraints on XML Representations of Attribute Group Definitions

3.6.4 Attribute Group Definition Validation Rules

3.6.5 Attribute Group Definition Information Set Contributions

3.6.6 Constraints on Attribute Group Definition Schema Components

3.7 Model Group Definitions

3.7.1 The Model Group Definition Schema Component

3.7.2 XML Representation of Model Group Definition Schema Components

3.7.3 Constraints on XML Representations of Model Group Definitions

3.7.4 Model Group Definition Validation Rules

3.7.5 Model Group Definition Information Set Contributions

3.7.6 Constraints on Model Group Definition Schema Components

3.8 Model Groups

3.8.1 The Model Group Schema Component

3.8.2 XML Representation of Model Group Schema Components

3.8.3 Constraints on XML Representations of Model Groups

3.8.4 Model Group Validation Rules

3.8.5 Model Group Information Set Contributions

3.8.6 Constraints on Model Group Schema Components

3.9 Particles

3.9.1 The Particle Schema Component

3.9.2 XML Representation of Particle Components

3.9.3 Constraints on XML Representations of Particles

3.9.4 Particle Validation Rules

3.9.5 Particle Information Set Contributions

3.9.6 Constraints on Particle Schema Components

3.10 Wildcards

3.10.1 The Wildcard Schema Component

3.10.2 XML Representation of Wildcard Schema Components

3.10.3 Constraints on XML Representations of Wildcards

3.10.4 Wildcard Validation Rules

3.10.5 Wildcard Information Set Contributions

3.10.6 Constraints on Wildcard Schema Components

3.11 Identity-constraint Definitions

3.11.1 The Identity-constraint Definition Schema Component

3.11.2 XML Representation of Identity-constraint Definition Schema Components

3.11.3 Constraints on XML Representations of Identity-constraint Definitions

3.11.4 Identity-constraint Definition Validation Rules

3.11.5 Identity-constraint Definition Information Set Contributions

3.11.6 Constraints on Identity-constraint Definition Schema Components

3.12 Notation Declarations

3.12.1 The Notation Declaration Schema Component

3.12.2 XML Representation of Notation Declaration Schema Components

3.12.3 Constraints on XML Representations of Notation Declarations

3.12.4 Notation Declaration Validation Rules

3.12.5 Notation Declaration Information Set Contributions

3.12.6 Constraints on Notation Declaration Schema Components

3.13 Annotations

3.13.1 The Annotation Schema Component

3.13.2 XML Representation of Annotation Schema Components

3.13.3 Constraints on XML Representations of Annotations

3.13.4 Annotation Validation Rules

3.13.5 Annotation Information Set Contributions

3.13.6 Constraints on Annotation Schema Components

3.14 Simple Type Definitions

3.14.1 (non-normative) The Simple Type Definition Schema Component

3.14.2 (non-normative) XML Representation of Simple Type Definition Schema Components

3.14.3 (non-normative) Constraints on XML Representations of Simple Type Definitions

3.14.4 Simple Type Definition Validation Rules

3.14.5 Simple Type Definition Information Set Contributions

3.14.6 Constraints on Simple Type Definition Schema Components

3.14.7 Built-in Simple Type Definition

3.15 Schemas as a Whole

3.15.1 The Schema Itself

3.15.2 XML Representations of Schemas

3.15.3 Constraints on XML Representations of Schemas

3.15.4 Validation Rules for Schemas as a Whole

3.15.5 Schema Information Set Contributions

3.15.6 Constraints on Schemas as a Whole

4 Schemas and Namespaces: Access and Composition

4.1 Layer 1: Summary of the Schema-validity Assessment Core

4.2 Layer 2: Schema Documents, Namespaces and Composition

4.2.1 Assembling a schema for a single target namespace from multiple schema definition documents

4.2.2 Including modified component definitions

4.2.3 References to schema components across namespaces

4.3 Layer 3: Schema Document Access and Web-interoperability

4.3.1 Standards for representation of schemas and retrieval of schema documents on the Web

4.3.2 How schema definitions are located on the Web

5 Schemas and Schema-validity Assessment

5.1 Errors in Schema Construction and Structure

5.2 Assessing Schema-Validity

5.3 Missing Sub-components

5.4 Responsibilities of Schema-aware Processors

Appendices

A Schema for Schemas (normative)

B References (normative)

C Outcome Tabulations (normative)

C.1 Validation Rules

C.2 Contributions to the post-schema-validation infoset

C.3 Schema Representation Constraints

C.4 Schema Component Constraints

D Required Information Set Items and Properties (normative)

E Schema Components Diagram (non-normative)

F Glossary (non-normative)

G DTD for Schemas (non-normative)

H Analysis of the Unique Particle Attribution Constraint (non-normative)

I References (non-normative)

J Acknowledgements (non-normative)

2.3 Constraints and Validation Rules

Constraints and Validation Rules

The [ref-xml] specification describes two kinds of constraints on XML documents: well-formedness and validity constraints. Informally, the well-formedness constraints are those imposed by the definition of XML itself (such as the rules for the use of the < and > characters and the rules for proper nesting of elements), while validity constraints are the further constraints on document structure provided by a particular DTD.

The preceding section focused on valid, that is the constraints on information items which schema components supply. In fact however this specification provides four different kinds of normative statements about schema components, their representations in XML and their contribution to the valid of information items:

Schema Component Constraint: Constraints on the schema components themselves, i.e. conditions components must satisfy to be components at all. Located in the sixth sub-section of the per-component sections of [Schema Component Details] and tabulated in [Schema Component Constraints].
Schema Representation Constraint: Constraints on the representation of schema components in XML beyond those which are expressed in [Schema for Schemas (normative)]. Located in the third sub-section of the per-component sections of [Schema Component Details] and tabulated in [Schema Representation Constraints].
Validation Rules: Contributions to valid associated with schema components. Located in the fourth sub-section of the per-component sections of [Schema Component Details] and tabulated in [Validation Rules].
Schema Information Set Contribution: Augmentations to post-schema-validation infosets expressed by schema components, which follow as a consequence of valid and/or assessment. Located in the fifth sub-section of the per-component sections of [Schema Component Details] and tabulated in [Contributions to the post-schema-validation infoset].

The last of these, schema information set contributions, are not as new as they might at first seem. XML 1.0 validation augments the XML 1.0 information set in similar ways, for example by providing values for attributes not present in instances, and by implicitly exploiting type information for normalization or access. (As an example of the latter case, consider the effect of NMTOKENS on attribute white space, and the semantics of ID and IDREF.) By including schema information set contributions, this specification makes explicit some features that XML 1.0 left implicit.

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