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

<!-- 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 <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"/>

<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 -->

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

<!ATTLIST schema xmlns:x CDATA #IMPLIED> 

<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 ">

<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 <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>

<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>

<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>

<attributeGroup name="typeRef">

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

</attributeGroup>

<attributeGroup name="valueConstraint">

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

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

</attributeGroup>

<attributeGroup name="occurs">

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

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

</attributeGroup>

<attributeGroup name="defRef">

<attribute name="name" type="NCName"
minOccurs="0"/>

<attribute name="ref" type="QName"
minOccurs="0"/>

</attributeGroup>

<group name="particle" order="choice">

<element name="element" type="element"/>

<element name="group" type="anonGroup"/>

<element ref="any"/>

</group>

<group name="restrictionParticle"
order="choice">

   <element name="sic">
    <type content="empty"/>
   </element>

<group ref="particle"/>

</group>

<group name="attrDecls">

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

<element ref="attribute"/>

<element ref="attributeGroup"/>

</group>

<element name="anyAttribute"
type="namespaceList" minOccurs="0"/>

</group>

<type name="type" source="annotated" derivedBy="extension" abstract="true">

<group order="choice">

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

<group>

<group ref="particle" minOccurs="0"
maxOccurs="*"/>

<group ref="attrDecls"/>

</group>

<attribute name="name" type="NCName" minOccurs="0">

<annotation>

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

</annotation>

</attribute>

<attribute name="content">

<datatype source="NMTOKEN">

<enumeration value="elementOnly"/>

<enumeration value="textOnly"/>

<enumeration value="mixed"/>

<enumeration value="empty"/>

</datatype>

</attribute>

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

<attribute name="derivedBy"
type="derivationChoice"/>

<attribute name="abstract" type="boolean"
default="false"/>

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

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

</type>

<type name="namedType" source="type" derivedBy="restriction">

<annotation>

<info>This is for the top-level type element,
daughter of <schema</info>

</annotation>

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

<annotation>

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

</annotation>

</attribute>

</type>

<type name="anonType" source="type" derivedBy="restriction">

<annotation>

<info>This is for the nested type element,
daughter of <element</info>

</annotation>

<attribute name="name" maxOccurs="0">

<annotation>

<info>Forbidden when nested</info>

</annotation>

</attribute>

</type>

<element name="type" equivClass="schemaTop"
type="namedType"/>

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

<enumeration value="extension"/>

<enumeration value="restriction"/>

</datatype>

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

<annotation>

    <info>Should be a sequence drawn from the
          values of derivationChoice plus
          'equivClass', or #all -- regexp
              is only an approximation</info>

</annotation>

<pattern value="#all?|(equivClass|extension|restriction| )*"/>

</datatype>

<datatype name="derivationSet" source="exactSet">

<annotation>

<info>Should be a sequence drawn from the
values of derivationChoice,

or #all -- regexp is only
an approximation</info>

</annotation>

<pattern value="#all?|(extension|restriction| )*"/>

</datatype>

<element name="restrictions">

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

<group order="choice">

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

<group ref="restrictionParticle"
minOccurs="0" maxOccurs="*"/>

</group>

<group ref="attrDecls"/>

</type>

</element>

<!-- The element element can be used either

        at the toplevel to define an element-type
        binding globally, or within a content
        model to either reference a globally-
        defined element or type or declare an
        element-type binding locally.

The ref form is not allowed at
the top level -->

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

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

<element name="datatype"
type="anonDatatype"/>

<element name="type" type="anonType"/>

</group>

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

<element ref="unique"/>

<element ref="key"/>

<element ref="keyref"/>

</group>

<attributeGroup ref="defRef"/>

<attributeGroup ref="typeRef"/>

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

<attributeGroup ref="occurs"/>

<attributeGroup ref="valueConstraint"/>

<attribute name="nullable" type="boolean"
default="false"/>

<attribute name="abstract" type="boolean"
default="false"/>

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

</type>

<type name="namedElement" source="element"
derivedBy="restriction">

<restrictions>

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


<attribute name="ref" maxOccurs="0"/>


</restrictions>

</type>

<element name="element" type="namedElement"
equivClass="schemaTop"/>

<type name="group" source="annotated"
derivedBy="extension" abstract="true">

<group ref="particle" minOccurs="0"
maxOccurs="*"/>

<attributeGroup ref="defRef"/>

<attributeGroup ref="occurs"/>

<attribute name="order" default="seq">

<datatype source="NMTOKEN">

<enumeration value="choice"/>

<enumeration value="seq"/>

<enumeration value="all"/>


</datatype>

</attribute>

</type>

<type name="namedGroup" source="group"
derivedBy="restriction">

<restrictions>

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


<attribute name="ref" maxOccurs="0"/>


</restrictions>

</type>

<type name="anonGroup" source="group"
derivedBy="restriction">

<restrictions>

<attribute name="name" maxOccurs="0"/>


</restrictions>

</type>

<element name="group" equivClass="schemaTop"
type="namedGroup"/>

<element name="any">

<type content="empty">

<attribute name="namespace"
type="namespaceList"/>

<attributeGroup ref="occurs"/>

</type>

</element>

<!-- simple type for the value of the
'namespace' attr of 'any' and

'anyAttribute' -->

<!-- Value is

               ##any     - - any non-conflicting
                             WFXML/attribute
                             at all

##other - - any non-conflicting
WFXML/attribute from

namespace other than
targetNS

one or - - any non-conflicting
more URI WFXML/attribute from

references the listed namespaces

(space separated)

               ##targetNamespace may appear in
               the above list, to refer to the
      targetNamespace of the enclosing schema -->

<datatype name="namespaceList"
source="string"/>

<element name="attribute">

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

<element name="datatype" minOccurs="0">

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

<attribute name="name" maxOccurs="0">

       <annotation>
         <info>must benameless</info>
       </annotation>

</attribute>

</type>

</element>

<attribute name="name" type="NCName"
minOccurs="1"/>

<attributeGroup ref="typeRef"/>

<attribute name="minOccurs" default="0">

<datatype source="non-negative-integer">

<enumeration value="0"/>

<enumeration value="1"/>

</datatype>

</attribute>

<attribute name="maxOccurs" default="1">

<datatype source="non-negative-integer">

<enumeration value="0"/>

<enumeration value="1"/>

</datatype>

</attribute>

<attributeGroup ref="valueConstraint"/>

</type>

</element>

<type name="attributeGroup" source="annotated"
derivedBy="extension" abstract="true">

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

<element ref="attribute"/>

<element name="attributeGroup"
type="anonAttributeGroup"/>

</group>

<element name="anyAttribute"
type="namespaceList" minOccurs="0"/>

<attributeGroup ref="defRef"/>

</type>

<type name="namedAttributeGroup" source="attributeGroup"

derivedBy="restriction">

<restrictions>

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


<attribute name="ref" maxOccurs="0"/>


</restrictions>

</type>

<type name="anonAttributeGroup"
source="attributeGroup"
derivedBy="restriction">

<restrictions>

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


<attribute name="name" maxOccurs="0"/>


</restrictions>

</type>

<element name="attributeGroup"
type="namedAttributeGroup"

equivClass="schemaTop"/>

<element name="include">

<type content="empty">

<attribute name="schemaLocation" type="uri"
minOccurs="1"/>

</type>

</element>

<element name="import">

<type content="empty">

<attribute name="namespace" type="uri"
minOccurs="1"/>

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

</type>

</element>

<type name="keybase">

<element name="selector"/>

<element name="field" minOccurs="1"
maxOccurs="*"/>

<attribute name="name" type="NCName"
minOccurs="1"/>

</type>

<element name="unique" type="keybase"/>

<element name="key" type="keybase"/>

<element name="keyref">

<type source="keybase">

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

</type>

</element>

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

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

<attribute name="name" type="NCName"
minOccurs="1"/>

<attribute name="public" type="public"
minOccurs="1"/>

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

</type>

</element>

<datatype name="public" source="string"/>

<notation name="XMLSchemaStructures"
public="structures"
system="http://www.w3.org/XML/Group/xmlschema-current/structures/structures.xsd"/>

<notation name="XML" public="REC-xml-19980210" system="http://www.w3.org/TR/1998/REC-xml-19980210"/>

</schema>

The DTD for Datatypes

See disclaimer on page 2

<!-- Note this DTD is NOT the normative datatypes DTD - - 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 -->

<!ENTITY % p ''> <!-- can be overriden in the internal subset of a

schema document to establish a namespace prefix -->

<!ENTITY % datatype "%p;datatype">

<!ENTITY % maxExclusive "%p;maxExclusive">

<!ENTITY % minExclusive "%p;minExclusive">

<!ENTITY % maxInclusive "%p;maxInclusive">

<!ENTITY % minInclusive "%p;minInclusive">

<!ENTITY % precision "%p;precision">

<!ENTITY % scale "%p;scale">

<!ENTITY % length "%p;length">

<!ENTITY % maxLength "%p;maxLength">

<!ENTITY % enumeration "%p;enumeration">

<!ENTITY % literal "%p;literal">

<!ENTITY % pattern "%p;pattern">

<!ENTITY % lexical "%p;lexical">

<!ENTITY % encoding "%p;encoding">

<!ENTITY % period "%p;period">

<!ENTITY % annotation "%p;annotation">

<!ENTITY % appinfo "%p;appinfo">

<!ENTITY % info "%p;info">

<!ENTITY % URI "CDATA">

<!ENTITY % URIList "CDATA">

<!ENTITY % QName "CDATA">

<!ENTITY % NCName "NMTOKEN">

<!ENTITY % non-negative-integer "NMTOKEN">

<!ENTITY % boolean "(true|false)">

<!ENTITY % meansChoice "(restriction|extension)">

<!ENTITY % meansSeq "CDATA"> 

<!-- Note that the use of 'facet' below is less restrictive than is

really intended: There should in fact be no more than one of each of

minInclusive, minExclusive, maxInclusive, maxExclusive,

precision, scale,

length, maxLength, encoding, period within datatype,

and the min- and max- variants of Inclusive and Exclusive are

mutually exclusive.

On the other hand, pattern and enumeration may repeat -->

<!ENTITY % minBound '(%minInclusive; | %minExclusive;)'>

<!ENTITY % maxBound '(%maxInclusive; | %maxExclusive;)'>

<!ENTITY % bounds '%minBound; | %maxBound;'>

<!ENTITY % numeric '%precision; | %scale;'>

<!ENTITY % ordered '%bounds; | %numeric;'>

<!ENTITY % unordered

'%pattern; | %enumeration; | %length; | %maxLength;

| %encoding; | %period;'>

<!ENTITY % facet '%ordered; | %unordered;'>

<!ENTITY % facetAttr 'value CDATA #REQUIRED'>

<!ENTITY % facetModel '(%annotation;)?'>

<!ELEMENT %datatype; ((%annotation;)?,(%facet;)*)>

<!ATTLIST %datatype;

name %NCName; #IMPLIED

source %QName; #REQUIRED>

<!ELEMENT %maxExclusive; %facetModel;>

<!ATTLIST %maxExclusive; %facetAttr;>

<!ELEMENT %minExclusive; %facetModel;>

<!ATTLIST %minExclusive; %facetAttr;>

<!ELEMENT %maxInclusive; %facetModel;>

<!ATTLIST %maxInclusive; %facetAttr;>

<!ELEMENT %minInclusive; %facetModel;>

<!ATTLIST %minInclusive; %facetAttr;>

<!ELEMENT %precision; %facetModel;>

<!ATTLIST %precision; %facetAttr;>

<!ELEMENT %scale; %facetModel;>

<!ATTLIST %scale; %facetAttr;>

<!ELEMENT %length; %facetModel;>

<!ATTLIST %length; %facetAttr;>

<!ELEMENT %maxLength; %facetModel;>

<!ATTLIST %maxLength; %facetAttr;>

<!ELEMENT %enumeration; %facetModel;>

<!ATTLIST %enumeration; %facetAttr;>

<!ELEMENT %pattern; %facetModel;>

<!ATTLIST %pattern; %facetAttr;>

<!ELEMENT %encoding; %facetModel;>

<!ATTLIST %encoding; %facetAttr;>

<!ELEMENT %period; %facetModel;>

<!ATTLIST %period; %facetAttr;>

<!-- By having these here they are available for datatypes as well

as all the structures elements -->

<!ELEMENT %annotation; (%appinfo; | %info;)*>

<!-- User must define annotation elements in internal subset for this

to work -->

<!ELEMENT %appinfo; ANY> 

<!ATTLIST %appinfo;

source %URI; #IMPLIED>

<!ELEMENT %info; ANY> 

<!ATTLIST %info;

source %URI; #IMPLIED

xml:lang CDATA #IMPLIED>

The DTD for Schemas

See disclaimer on page 2

<!-- Note this DTD is NOT the normative structures DTD - - 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 -->

<!ENTITY % versionEntities SYSTEM "../versionInfo.ent">

%versionEntities; 

<!-- The the datatype element and its components

are defined in XML Schema: Part 2: Datatypes -->

<!ENTITY % xs-datatypes PUBLIC 'datatypes'

'datatypes.dtd' >

%xs-datatypes;

<!ENTITY % schema "%p;schema">

<!ENTITY % type "%p;type">

<!ENTITY % restrictions "%p;restrictions">

<!ENTITY % element "%p;element">

<!ENTITY % group "%p;group">

<!ENTITY % any "%p;any">

<!ENTITY % anyAttribute "%p;anyAttribute">

<!ENTITY % sic "%p;sic">

<!ENTITY % attribute "%p;attribute">

<!ENTITY % attrGroup "%p;attrGroup">

<!ENTITY % include "%p;include">

<!ENTITY % import "%p;import">

<!ENTITY % notation "%p;notation">

<!ELEMENT %schema; ((%include; | %import; | %annotation;)*,

(%datatype; | %type;

| %element;

| %attrGroup; | %group;

| %notation; ),

(%annotation;

| %datatype; | %type;

| %element;

| %attrGroup; | %group;

| %notation; )* )>

<!ATTLIST %schema;

targetNamespace %URI; #IMPLIED

version CDATA #IMPLIED

xmlns %URI; #FIXED '&XMLSchemaNS;'>

<!-- a type is a named content type specification which allows attribute

declarations-->

<!ELEMENT %type; ((%annotation;)?, (%restrictions;)?,

(%element;| %group;| %any;)*,

(%attribute;| %attrGroup;)*,

(%anyAttribute;)?)>

<!ATTLIST %type;

name %NCName; #IMPLIED

content (textOnly|mixed|elemOnly|empty) #IMPLIED

abstract %boolean; 'false'

final %meansSeq; ''

intolerant %meansSeq; ''

means %meansChoice; #IMPLIED

source %QName; #IMPLIED>

<!-- content defaults to basetype's if there is a complex basetype,

textonly if there's a simple basetype,

'mixed' if no basetype (because that's the urType's content)

and no content daughters,

'elemOnly' otherwise -->

<!-- should we replace content='empty' with content='elemOnly'

final='#all' plus no content? -->

<!-- If one top-level group, that IS the content model, otherwise

an implicit group obtains.

This is

<group order='seq' minOccurs='1' maxOccurs='1'>

unless content='mixed', in which case it's

<group order='choice' minOccurs='0' maxOccurs='*'> -->

<!-- If anyAttribute appears in one or more referenced attrGroups

and/or explicitly, the intersection of the permissions is used -->

<!-- A text-only type with no attributes differs from a datatype with

the same basetype qualified the same way in regard to the impact on

attributes of anyAttribute -->

<!ELEMENT %restrictions; ((%annotation;)?,

((%facet;)*|

(%element;| %group;| %any;| %sic;)*),

(%attribute;| %attrGroup;)*,

(%anyAttribute;)?)>

<!-- (element|group|any|sic) allowed only if basetype refers to an

elemOnly or mixed type, the sequence and GI must match point for

point with (an initial sub-sequence of) the content model of

the basetype, restricting in each case, except that 'sic' is

allowed to "copy through" a single particle.

Only the top-level content model can be restricted,

e.g. the content model of an anonymous embedded 'type' within

an 'element' particle cannot be restricted piecemeal. -->

<!-- attributes to be restricted are identified by name, without order

constraints.

Attributes incorporated into basetypes via attrGroups may be

restricted by name. -->

<!-- If anyAttribute appears in one or more referenced attrGroups

and/or explicitly, the intersection of the permissions with the

inherited permission (which must exist) is used -->

<!-- an element is declared by either:

a name and a type (either nested or referenced via the type attribute)

or:

a ref to an existing element declaration -->

<!ELEMENT %element; ((%annotation;)?, (%type;| %datatype;)?)>

<!ATTLIST %element;

name %NCName; #IMPLIED

ref %QName; #IMPLIED

type %QName; #IMPLIED

minOccurs %non-negative-integer; '1'

maxOccurs CDATA #IMPLIED

nullable %boolean; 'false'

equivClass %QName; #IMPLIED

abstract %boolean; 'false'

default CDATA #IMPLIED

fixed CDATA #IMPLIED>

<!-- type and ref are mutually exclusive.

name and ref are mutually exculsive, one is required -->

<!ELEMENT %group; ((%annotation;)?, (%element;| %group;| %any;)*)>

<!ATTLIST %group;

minOccurs %non-negative-integer; '1'

maxOccurs CDATA #IMPLIED

order (choice|seq|all) 'seq'

name %NCName; #IMPLIED

ref %QName; #IMPLIED>

<!-- an anonymous grouping in a model, or

a top-level named group definition, or a reference to same -->

<!-- Note that if order is 'all', group is not allowed inside.

If order is 'all' THIS group must be alone (or referenced along) at

the top level of a content model -->

<!ELEMENT %any; EMPTY>

<!ATTLIST %any;

type %QName; #IMPLIED

namespace CDATA #IMPLIED

tag %QName; #IMPLIED

equivClass %QName; #IMPLIED

means %meansSeq; '#all'

minOccurs %non-negative-integer; '1'

maxOccurs CDATA #IMPLIED>

<!-- type, equivClass and namespace are mutually exclusive,

if none present, i.e. <any/>, default is namespace='##any'.

tag required if type.

means only if tag and type or equivClass, consists of 1 or more allowed

derivation means. -->

<!-- namespace is interpreted as follows:

##any - - any non-conflicting WFXML at all

##other - - any non-conflicting WFXML from namespace other

than targetNamespace

one or - - any non-conflicting WFXML from

more URI the listed namespaces

references

##targetNamespace may appear in the above list, with the

obvious meaning -->

<!ELEMENT %anyAttribute; EMPTY>

<!ATTLIST %anyAttribute;

namespace CDATA #REQUIRED>

<!-- for use inside basetype to copy down corresponding content

model particle from the basetype's content model -->

<!ELEMENT %sic; EMPTY>

<!ELEMENT %attribute; ((%annotation;)?, (%datatype;)?)>

<!ATTLIST %attribute;

name %NCName; #REQUIRED

type %QName; 'string'

maxOccurs (0|1) '1'

minOccurs (0|1) '0'

default CDATA #IMPLIED

fixed CDATA #IMPLIED>

<!-- an attrGroup is a named collection of attribute decls, or a

reference thereto -->

<!ELEMENT %attrGroup; ((%annotation;)?,

(%attribute; | %attrGroup;)*,

(%anyAttribute;)?) >

<!ATTLIST %attrGroup;

name %NCName; #IMPLIED

ref %QName; #IMPLIED>

<!ELEMENT %include; EMPTY>

<!ATTLIST %include; schemaLocation %URI; #REQUIRED>

<!ELEMENT %import; EMPTY>

<!ATTLIST %import; namespace %URI; #REQUIRED

schemaLocation %URI; #IMPLIED>

<!ELEMENT %notation; EMPTY>

<!ATTLIST %notation;

name %NCName; #REQUIRED

public CDATA #REQUIRED

system %URI; #IMPLIED>

<!NOTATION XMLSchemaStructures PUBLIC 'structures'

'&XSP1.URI;.xsd' >

<!NOTATION XML PUBLIC 'REC-xml-1998-0210'

'http://www.w3.org/TR/1998/REC-xml-19980210' >

Resources

The W3C is at

http://www.w3.org/

XED, my free XML editor, can be found at

http://www.ltg.ed.ac.uk/~ht/xed.html

Pointers to many more useful links, can be found at Robin Cover’s SGML/XML web page:

http://www.oasis-open.org/cover/

Note: This HTML version converted from the canonical '.DOC' file; see additional notes (.doc)

Introduction

XML Schema Goals

The Structures draft TOC

Datatypes draft TOC

Simple XML Schema example

Schema example: type derivation and element equivalence classes

The Schema for Datatypes

The Schema for Schemas

The DTD for Datatypes

The DTD for Schemas

Resources

Schema example:
type derivation and element equivalence classes