XML Schema Tutorial:

Additional Materials [*]

Henry S. Thompson

Language Technology Group,
Human Communication Research Centre
University of Edinburgh

London, 15 December 1999

Introduction

This document contains additional illustrative and reference material to accompany the narrative presentation in the slide documents.

DISCLAIMER

Some of the material contained herein is drawn from internal working drafts of the XML Schema Working Group of the W3C. Those WG-internal drafts are due to be published in the next few days, but may change in the interim, and in any case errors may have been introduced in copying and formatting. Only material identified as W3C publications is a reliable or quotable* source of information about XML Schema or any other W3C activity.

_______

*Note that employees of W3C member companies (that's you) are enjoined from distributing W3C-internal materials to non-W3C members: these materials are covered by that injunction!

XML Schema Goals

“The purpose of an XML Schema: Structures schema is to define and describe a class of XML documents by using [schema] constructs to constrain and document the meaning, usage and relationships of their constituent parts: datatypes, elements and their content, attributes and their values. Schema constructs may also provide for the specification of additional information such as default values. Schemas are intended to document their own meaning, usage, and function through a common documentation vocabulary. Thus, XML Schema: Structures can be used to define, describe and catalogue XML vocabularies for classes of XML documents”

“[XML Schema: Datatypes] addresses the need of both document authors and applications writers for a robust, extensible datatype system for XML which could be incorporated into XML processors. As discussed below, these datatypes could be used in other XML-related standards as well.”

The Structures draft TOC

1 Introduction
1.1 Documentation Conventions
1.2 Purpose
1.3 Relationship To Other Work
1.4 Terminology
2 Conceptual Framework
2.1 Kinds of XML Documents
2.2 On schemas, constraints and contributions
2.3 Schemas, Types and Elements
2.4 Schemas and their component parts
2.5 Names and Symbol Spaces
2.6 Referencing Schema Components
2.7 Association of components with a target namespace
2.7.1 Association of definitions with a target namespace
2.7.2 Providing a target namespace for definitions and declarations
2.8 Abstract and Concrete Syntax
3 Schema Definitions and Declarations
3.1 The Schema
3.2 The Document and its Root
3.3 References to Schema Constructs
3.4 Types, Elements and Attributes
3.4.1 Simple Type Definition
3.4.2 Complex Type Definition
3.4.3 Attribute Declaration
3.4.4 Attribute Group Definition
3.4.5 Element Content Model
3.4.6 Rich Content Models
3.4.7 Mixed Content
3.4.8 Named Model Group
3.4.9 Element Declaration
3.5 Wildcards
3.6 Deriving Type Definitions
3.6.1 Deriving type definitions by extension
3.6.2 Deriving type definitions by restriction
3.6.3 Controlling derivation
3.6.4 Reinterpreting Content Models
3.6.5 Element Equivalence Classes
3.6.6 The ur-type
3.6.7 Graveyard for stale syntax, here to avoid breaking IDREFs elsewhere *
3.7 Unique, key and key reference constraints
3.8 Notations
3.8.1 Notation Declaration
4 Schema Access and Composition
4.1 Layer 1: Summary of the schema-validation core
4.2 Layer 2: Schema definitions in XML
4.2.1 Assembling a schema for a single namespace from multiple schema definition documents
4.2.2 References to schema components across namespaces
4.3 Layer 3: Web-interoperability
4.3.1 Standards for representation and retrieval of schema definitions on the Web
4.3.2 How schema definitions are located on the Web
5 Annotating schemas
6 Conformance *
6.1 Schema Validity *
6.2 Detailed validity constraints and definitions *
6.2.1 The Schema *
6.2.2 References to Schema Constructs *
6.2.3 Types, Elements and Attributes *
6.2.4 Type Refinement *
6.2.5 Import Restrictions *
6.2.6 Schema Inclusion *
6.2.7 Schema Validity *
6.3 Responsibilities of Schema-aware processors *
6.4 Lexical representation *
6.5 Information set *

Appendices

A (normative) Schema for Schemas
B (normative) DTD for Schemas
C Glossary (normative) *
D References (normative) *
E Acknowledgments (non-normative)
F Sample Schema (non-normative)
G Tabulation of changes
H Open Issues

Datatypes draft TOC

1 Introduction
1.1 Purpose
1.2 Requirements
1.3 Scope
1.4 Terminology
2 Type System
2.1 Datatype
2.2 Value space
2.3 Lexical space
2.4 Datatype dichotomies
2.4.1 Atomic vs. aggregate datatypes
2.4.2 Primitive vs. generated datatypes
2.4.3 Built-in vs. user-generated datatypes
2.5 Facets
2.5.1 Fundamental facets
2.5.2 Constraining or Non-fundamental facets
3 Built-in datatypes
3.1 Namespace considerations
3.2 Primitive datatypes
3.2.1 string
3.2.2 boolean
3.2.3 float
3.2.4 double
3.2.5 decimal
3.2.6 timeInstant
3.2.7 timeDuration
3.2.8 recurringInstant
3.2.9 binary
3.2.10 uri
3.3 Generated datatypes
3.3.1 language
3.3.2 NMTOKEN
3.3.3 NMTOKENS
3.3.4 Name
3.3.5 QName
3.3.6 NCName
3.3.7 ID
3.3.8 IDREF
3.3.9 IDREFS
3.3.10 ENTITY
3.3.11 ENTITIES
3.3.12 NOTATION
3.3.13 integer
3.3.14 non-negative-integer
3.3.15 positive-integer
3.3.16 non-positive-integer
3.3.17 negative-integer
3.3.18 date
3.3.19 time
4 Defining Generated Datatypes
5 Conformance

Appendices

A Schema for Datatype Definitions (normative)
B DTD for Datatype Definitions (normative)
C Datatypes and Facets
C.1 Fundamental Facets
C.2 Constraining Facets
D ISO 8601 Date and Time Formats
D.1 ISO 8601 Conventions
D.2 Truncated Formats
D.3 Deviations from ISO 8601 Formats
D.3.1 Sign Allowed
D.3.2 More Than 9999 Years
E Regular Expressions
F References
F.1 Normative
F.2 Non-normative
G Acknowledgments (non-normative)
H Open Issues
I Revisions from Previous Draft

Simple XML Schema example

First the instance

<PurchaseOrder orderDate="1999-05-20">

<shipTo type="US">

<name>Alice Smith</name>

<street>123 Maple Street</street>

<city>Mill Valley</city>

<state>CA</state>

<zip>90952</zip>

</shipTo>

<billTo type="UK">

<name>Trevor Mostyn</name>

<street>12, The Gables</street>

<city>Bourton-on-the-Water</city>

<state>Glous.</state>

<zip>GL3 2BB</zip>

</billTo>

<shipDate>1999-05-25</shipDate>

<comment>Get these things to me in a hurry, my lawn is going wild!</comment>

<Items>

<Item pno="333-333">

<productName>Lawnmower,

model BUZZ-1</productName>

<quantity>1</quantity>

<price>148.95</price>

<comment>Please confirm this is the electric model</comment>

</Item>

<Item pno="444-444">

<productName>Baby Monitor,

model SNOOZE-2</productName>

<quantity>1</quantity>

<price>39.98</price>

</Item>

</Items>

</PurchaseOrder>

Then the schema

<schema
targetNamespace='http://…/PurchaseOrder'
xmlns:po='http://…/PurchaseOrder'

xmlns='http://www.w3.org/1999/XMLSchema'>

<element name='PurchaseOrder'

type='po:PurchaseOrderType'/>

<element name='comment' type='string'/>

<type name='PurchaseOrderType'>

<element name='shipTo' type='po:Address'/>

<element name='billTo' type='po:Address'/>

<element name='shipDate' type='date'/>

<element ref='po:comment' minOccurs='0'/>

<element name='Items' type='po:Items'/>

<attribute name='orderDate' type='date'/>

</type>

<type name='Address'>

<element name='name' type='string'/>

<element name='street' type='string'/>

<element name='city' type='string'/>

<element name='state' type='string'/>

<element name='zip' type='integer'/>

<attribute name='type' type='string'/>

</type>

<type name='Items'>

<element name='Item'
minOccurs='0' maxOccurs='*'>

<type>

<element name='productName'
type='string'/>

<element name='quantity'>

<datatype source='integer'>

<minExclusive value='0'/>

</datatype>

</element>

<element name='price' type='decimal'/>

<element ref='po:comment' minOccurs='0'/>
<attribute name='pno' type='string'/>

</type>

</element>

</type>

</schema>

Schema example:
type derivation and element equivalence classes

The schema

<xsd:type name='animalFriends'>

<xsd:any equivClass='pet' maxOccurs='*'/>

</xsd:type>

<xsd:type name='pet'>

<xsd:attribute name='name'/>

<xsd:attribute name='owner' minOccurs='0'/>

</xsd:type>

<xsd:element name=’pet’ type='pet'
abstract=’yes’/>

<xsd:element name='cat' equivClass='pet'/>
<xsd:type source='pet' derivedBy='extension'>

<xsd:element name='kittens' minOccurs='0'/>

<xsd:attribute name='lives'/>

</xsd:type>

</xsd:element>

<xsd:element name='dog' class='pet'/>
<xsd:type source='pet' derivedBy='extension'>

<xsd:element name='puppies' minOccurs='0'/>

<xsd:attribute name='breed'/>

</xsd:type>
</xsd:element>

A valid instance
<anima

<animalFriends>

<cat name='Fluffy' lives='9'/>

<dog name='Gromit' owner='Wallace'
breed='mutt'/>

</animalFriends>

The Schema for Datatypes

See disclaimer on page 2

<!-- XML Schema schema for XML Schemas:
Part 2: Datatypes -->

<!-- Note this schema is NOT the normative
datatypes schema - - the prose copy in the
datatypes REC is the normative version (which

shouldn't differ from this one except for
this comment and entity

expansions, but just in case -->

<!DOCTYPE schema PUBLIC
"-//W3C//DTD XMLSCHEMA 19991216//EN"
"structures.dtd" >

<schema xmlns="http://www.w3.org/1999/XMLSchema"

targetNamespace="http://www.w3.org/1999/XMLSchema"
version="$Id: datatypes.xsd,v 1.2 1999/12/04 12:09:08 aqw Exp $">

<type name="datatype"
source="annotated" derivedBy="extension">

<element ref="facet"
minOccurs="0" maxOccurs="*"/>

<attribute name="name" type="NCName">

<annotation>

<info>Will be restricted to
required or forbidden</info>

</annotation>

</attribute>

<attribute name="source" type="QName"
minOccurs="1"/>

</type>

<element name="datatype" equivClass="schemaTop">

<type source="datatype"
derivedBy="restriction">

<annotation>

<info>This is the top-level type element,
as ref'ed in &lt;schema</info>

</annotation>

<attribute name="name" minOccurs="1">

<annotation>
<info>Required at the top level</info>

</annotation>

</attribute>

</type>

</element>

<type name="facet"
source="annotated"
derivedBy="extension">

<attribute name="value" minOccurs="1"/>

</type>

<element name="facet" type="facet"
abstract="true"/>

<element name="minBound" abstract="true"

equivClass="facet"/>

<element name="minExclusive"

equivClass="minBound"/>

<element name="minInclusive"

equivClass="minBound"/>

<element name="maxBound" abstract="true"

equivClass="facet"/>

<element name="maxExclusive"

equivClass="maxBound"/>

<element name="maxInclusive"

equivClass="maxBound"/>

<type name="numFacet" source="facet"

derivedBy="restriction">

<attribute name="value"

type="non-negative-integer"/>

</type>

<element name="precision" type="numFacet"

equivClass="facet"/>

<element name="scale" type="numFacet"

equivClass="facet"/>

<element name="length" type="numFacet"

equivClass="facet"/>

<element name="maxLength" type="numFacet"

equivClass="facet"/>

<!-- the following datatype is used to limit the

possible values for the encoding facet on

the binary datatype -->

<datatype name="encodings" source="NMTOKEN">

<enumeration value="hex">

<annotation>

<info>each (8-bit) byte is encoded as

a sequence of 2 hexidecimal

digits</info>

</annotation>

</enumeration>

<enumeration value="base64">

<annotation>

<info>value is encoded in Base64 as

defined in the MIME RFC</info>

</annotation>

</enumeration>

</datatype>

<element name="encoding" equivClass="facet">

<type source="facet" derivedBy="restriction">

<attribute name="value" type="encodings"/>

</type>

</element>

<element name="period" equivClass="facet">

<type source="facet" derivedBy="restriction">

<attribute name="value" type="timeDuration"/>

</type>

</element>

<element name="enumeration"
equivClass="facet"/>

<element name="pattern" equivClass="facet"/>

<!-- built-in generated datatypes -->

<!-- only has a few for now, eventually needs to have all of them -->

<datatype name="integer" source="decimal">

<scale value="0"/>

</datatype>

<datatype name="non-negative-integer"

source="integer">

<minInclusive value="0"/>

</datatype>

<datatype name="positive-integer"

source="non-negative-integer">

<minInclusive value="1"/>

</datatype>

<datatype name="non-positive-integer"

source="integer">

<maxInclusive value="0"/>

</datatype>

<datatype name="negative-integer"

source="non-positive-integer">

<maxInclusive value="-1"/>

</datatype>

<datatype name="date"
source="recurringInstant">

<period value="000000T2400"/>

</datatype>

<datatype name="time"
source="recurringInstant">

<period value="000000T2400"/>

</datatype>

<datatype name="NMTOKENS" source="string">

<pattern value="\c+(\s\c+)*">

<annotation>

<info source="http://www.w3.org/TR/REC-xml#NT-Nmtokens">

pattern matches production 8

from the XML spec

</info>

</annotation>

</pattern>

</datatype>

<datatype name="NMTOKEN" source="NMTOKENS">

<pattern value="\c+">

<annotation>

<info source="http://www.w3.org/TR/REC-xml#NT-Nmtoken">

pattern matches production 7 from the XML spec

</info>

</annotation>

</pattern>

</datatype>

<datatype name="Name" source="NMTOKEN">

<pattern value="\i\c*">

<annotation>

<info source="http://www.w3.org/TR/REC-xml#NT-Name">

pattern matches production 5 from the XML spec

</info>

</annotation>

</pattern>

</datatype>

<datatype name="ID" source="NCName">

<annotation>

<info source="http://www.w3.org/TR/REC-xml#id">
values of this datatype must be unique
within a document

</info>

</annotation>

</datatype>

<datatype name="IDREFS" source="string">

<pattern
value="[\i-[:]][\c-[:]]*(\s[\i-[:]][\c-[:]]*)*">

<annotation>

<info
source="http://www.w3.org/TR/REC-xml#NT-Names">

pattern matches production 6 from the XML spec

modified as required by the

Conformance section in

Namespaces in XML
(http://www.w3.org/TR/REC-xml-names#conformance)

</info>

<info
source="http://www.w3.org/TR/REC-xml#idref">
values of this datatype must have occured within
a document as the value of some component
of type ID

</info>

</annotation>

</pattern>

</datatype>

<datatype name="IDREF" source="IDREFS">

<pattern value="[\i-[:]][\c-[:]]*">

<annotation>

<info source="http://www.w3.org/TR/REC-xml-names#NT-NCName">
pattern matches production 4 from the
Namespaces in XML spec

</info>

<info
source="http://www.w3.org/TR/REC-xml#idref">
values of this datatype must have occured within
a document as the value of some component
of type ID

</info>

</annotation>

</pattern>

</datatype>

<datatype name="ENTITIES" source="string">

<pattern
value="[\i-[:]][\c-[:]]*(\s[\i-[:]][\c-[:]]*)*">

<annotation>

<info
source="http://www.w3.org/TR/REC-xml#NT-Names">

pattern matches production 6 from
the XML spec

(modified as required by the

Conformance section in

Namespaces in XML
(http://www.w3.org/TR/REC-xml-names#conformance)

</info>

<info
source="http://www.w3.org/TR/REC-xml#entname">
values of this datatype must match the name of
an unparsed entity declared in the schema

</info>

</annotation>

</pattern>

</datatype>

<datatype name="ENTITY" source="ENTITIES">

<pattern value="[\i-[:]][\c-[:]]*">

<annotation>

<info source="http://www.w3.org/TR/REC-xml-names#NT-NCName">
pattern matches production 4 from
the Namespaces in XML spec

</info>

<info
source="http://www.w3.org/TR/REC-xml#entname">
values of this datatype must match the name of

an unparsed entity declared in the schema

</info>

</annotation>

</pattern>

</datatype>

<datatype name="NCName" source="Name">

<pattern value="[\i-[:]][\c-[:]]*">

<annotation>

<info source="http://www.w3.org/TR/REC-xml-names/#NT-NCName">
pattern matches production 4 from
the Namespaces in XML spec

</info>

</annotation>

</pattern>

</datatype>

<datatype name="QName" source="Name">

<pattern
value="([\i-[:]][\c-[:]]*:)?[\i-[:]][\c-[:]]*">

<annotation>

<info source="http://www.w3.org/TR/REC-xml-names/#NT-QName">
pattern matches production 6 from
the Namespaces in XML spec

</info>

</annotation>

</pattern>

</datatype>

</schema>

The Schema for Schemas

See disclaimer on page 2

<?xml version='1.0'?>

<!-- XML Schema schema for

XML Schemas: Part 1: Structures -->

<!-- Note this schema is NOT the normative structures schema - - the prose copy in the structures REC is the normative version (which
shouldn't differ from this one except for this comment and entity expansions, but just in case-->

<!DOCTYPE schema PUBLIC "-//W3C//DTD XMLSCHEMA 19991216//EN" "structures.dtd" [

<!ATTLIST schema xmlns:x CDATA #IMPLIED> <!-- keep this schema XML1.0 valid -->

]>

<schema xmlns="http://www.w3.org/1999/XMLSchema"
targetNamespace="http://www.w3.org/1999/XMLSchema"
xmlns:x="http://www.w3.org/XML/1998/namespace"
version="Id: structures.xsd,v 1.26 1999/12/10 16:08:42 aqw Exp ">

<!-- get access to the xml: attribute
groups for xml:lang -->

<import namespace="http://www.w3.org/XML/1998/namespace"
schemaLocation="http://www.w3.org/XML/1998/xml.xsd"
/>

<!-- The datatype element and all of its
members are defined

in XML Schema: Part 2: Datatypes -->

<include
schemaLocation="http://www.w3.org/XML/Group/xmlschema-current/datatypes/datatypes.xsd"/>

<type name="annotated">

<annotation>

<info>This type is extended by all types
which allow annotation

other than &lt;schema> itself</info>

</annotation>

<element ref="annotation" minOccurs="0"/>

</type>

<element name="schemaTop" abstract="true" type="annotated">

<annotation>

<info>This abstract element defines an
equivalence class over the

elements which occur freely at the top
level of schemas.

These are: datatype, type, element,
attributeGroup, group, notation

All of their types are based on the
"annotated" type by extension.</info>

</annotation>

</element>

<!-- schema element -->

<element name="schema">

<annotation>

<info>The obnoxious duplication in the
content model below is to avoid

infringing the no-ambiguity constraint
while still allowing

annotation virtually anywhere.</info>

</annotation>

<type>

<group order="choice" minOccurs="0"
maxOccurs="*">

<element ref="include"/>

<element ref="import"/>

<element ref="annotation"/>

</group>

<element ref="schemaTop"/>

<group order="choice" minOccurs="0"
maxOccurs="*">

<element ref="annotation"/>

<element ref="schemaTop"/>

</group>

<attribute name="targetNamespace" type="uri"/>

<attribute name="version" type="string"/>

<attribute name="finalDefault"
type="derivationSet"/>

<attribute name="exactDefault"
type="exactSet"/>

</type>

</element>

<!-- annotation element -->

<element name="annotation">

<type>

<group order="choice" minOccurs="0"
maxOccurs="*">

<element name="appinfo">

<type content="mixed">

<any minOccurs="0" maxOccurs="*"/>

<attribute name="source" type="uri"/>

</type>

</element>

<element name="info">

<type content="mixed">

<any minOccurs="0" maxOccurs="*"/>

<attribute name="source" type="uri"/>

<attributeGroup ref="x:lang"/>

</type>

</element>

</group>

</type>

</element>

<!-- For references to a type -->

<!-- 'element', 'attribute' and 'any'
all use this -->

<attributeGroup name="typeRef">

<attribute name="type" type="QName"/>

</attributeGroup>

<!-- For 'element' and 'attribute' -->

<attributeGroup name="valueConstraint">

<attribute name="default" type="string"/>

<attribute name="fixed" type="string"/>

</attributeGroup>

<!-- for all particles -->

<attributeGroup name="occurs">

<attribute name="minOccurs"
type="non-negative-integer" default="1"/>

<attribute name="maxOccurs" type="string"/> <!-- allows '*', so integer won't do -->

</attributeGroup>