Ceng 520 XML Schemas. 10.03.200520.0 3.2003 IntroductionXML Schemas 2 Part 0: Introduction Why XML Schema?

Ceng 520

XML Schemas

10.03.200520.03.2003

IntroductionXML Schemas

2

Part 0: Introduction

Why XML Schema?

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Purpose of XML schemas

1-The structure of instance documents– defines elements that can appear in a document,

– defines attributes that can appear in a document,

– defines which elements are child elements,

– defines the sequence in which the child elements can appear,

– defines the number of child elements,

– defines whether an element is empty or can include text,

– defines default values for elements and attributes.

Describe document class’s logical structure.

defines:

2-The datatype of each element/attribute

Same Purpose is achieved with DTDSame Purpose is achieved with DTD

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Why XML Schemas ?

DTDs present several limitations:

– It's a different syntax• You write your XML (instance) document using one syntax and the DTD

using another syntax bad, inconsistent

– Limited data type capability• DTDs support a very limited capability for specifying data types (only

PCDATA). You can't, for example, impose that an element is an integer with a range of 0 to 100.

– Limited reuse capability (offer only ENTITY mechanism)– Constructors (“,” , “¦”) and occurrences indicators (“*”, “+”, “?”)

don’t offer a lot of possibilities to constraint element’s occurrences.

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XML Schemas Vs DTDs

•XML Schemas are a tremendous advancement over DTDs:

–Enhanced data types

•44+ versus 10

•Can create your own data types

–Written in the same syntax as instance documents

•You don't have to learn another language

•You can use your XML editor to edit your Schema files

•You can use your XML parser to parse your Schema files

•You can manipulate your Schema with the XML DOM

•You can transform your Schema with XSLT

–XML Schemas are Object-oriented (Extensible)

•Can extend or restrict a type (derive new type definitions on the basis of old ones)

•XML Schemas are extensible, just like XML, because they are written in XML.

•With an extensible Schema definition you can:

–Reuse your Schema in other Schemas

–Create your own data types derived from standard types

–Reference multiple schemas from the same document

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Example: BookStore.dtd

<!ELEMENT BookStore (Book)+><!ELEMENT Book (Title, Author, Date, ISBN, Publisher)><!ELEMENT Title (#PCDATA)><!ELEMENT Author (#PCDATA)><!ELEMENT Date (#PCDATA)><!ELEMENT ISBN (#PCDATA)><!ELEMENT Publisher (#PCDATA)>

ATTLIST

ELEMENT

ID

#PCDATA

NMTOKEN

ENTITY

CDATA

BookStore

BookTitle

Author

DateISBN

Publisher

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Example: BookStore.xsd

<?xml version="1.0"?><xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema" targetNamespace="http://www.books.org" xmlns="http://www.books.org" elementFormDefault="qualified"> <xsd:element name="BookStore"> <xsd:complexType> <xsd:sequence> <xsd:element ref="Book" minOccurs="1"

maxOccurs="unbounded"/> </xsd:sequence> </xsd:complexType> </xsd:element> <xsd:element name="Book"> <xsd:complexType> <xsd:sequence> <xsd:element ref="Title" minOccurs="1" maxOccurs="1"/> <xsd:element ref="Author" minOccurs="1" maxOccurs="1"/> <xsd:element ref="Date" minOccurs="1" maxOccurs="1"/> <xsd:element ref="ISBN" minOccurs="1" maxOccurs="1"/> <xsd:element ref="Publisher" minOccurs="1" maxOccurs="1"/> </xsd:sequence> </xsd:complexType> </xsd:element> <xsd:element name="Title" type="xsd:string"/> <xsd:element name="Author" type="xsd:string"/> <xsd:element name="Date" type="xsd:date"/> <xsd:element name="ISBN" type="xsd:string"/> <xsd:element name="Publisher" type="xsd:string"/></xsd:schema>

<!ELEMENT Title (#PCDATA)><!ELEMENT Author (#PCDATA)><!ELEMENT Date (#PCDATA)><!ELEMENT ISBN (#PCDATA)><!ELEMENT Publisher (#PCDATA)>

<!ELEMENT Book (Title, Author, Date, ISBN, Publisher)>

<!ELEMENT BookStore (Book)+>

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Let’s get started!

Data Types Type Derivation Name Spaces Advanced XML SchemaConception More XML Schema!!!!! Conclusions References

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Part 1: Name Spaces

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Name spaces

elementcomplexType

schema

sequence

http://www.w3.org/2001/XMLSchema

string

integer

boolean

BookStore

BookTitle

Author

Date

ISBNPublisher

http://www.books.org (targetNamespace)

This is the vocabulary that XML Schemas provide to define yournew vocabulary

One difference between XML Schemas and DTDs is that the XML Schema vocabularyis associated with a name (namespace). Likewise, the new vocabulary that you define must be associated with a name (namespace).

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Example: BookStore.xsd<?xml version="1.0"?>

<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"

targetNamespace="http://www.books.org" xmlns="http://www.books.org" elementFormDefault="qualified"> <xsd:element name="BookStore"> <xsd:complexType> <xsd:sequence> <xsd:element ref="Book" minOccurs="1" maxOccurs="unbounded"/> </xsd:sequence> </xsd:complexType> </xsd:element> <xsd:element name="Book"> <xsd:complexType> <xsd:sequence> <xsd:element ref="Title" minOccurs="1" maxOccurs="1"/> <xsd:element ref="Author" minOccurs="1" maxOccurs="1"/> <xsd:element ref="Date" minOccurs="1" maxOccurs="1"/> <xsd:element ref="ISBN" minOccurs="1" maxOccurs="1"/> <xsd:element ref="Publisher" minOccurs="1" maxOccurs="1"/> </xsd:sequence> </xsd:complexType> </xsd:element> <xsd:element name="Title" type="xsd:string"/> <xsd:element name="Author" type="xsd:string"/> <xsd:element name="Date" type="xsd:string"/> <xsd:element name="ISBN" type="xsd:string"/> <xsd:element name="Publisher" type="xsd:string"/></xsd:schema>

Elements and data types:

• schema• element• complex Type• sequence• string • boolean• integer • …etc

Come from the namespace:

http://www.w3.org/2001/XMLSchema

An XML schema has « schema » as root element

xsd = Xml-Schema Definition

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Target Name Space<?xml version="1.0"?><xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"

targetNamespace="http://www.books.org" xmlns="http://www.books.org" elementFormDefault="qualified"> <xsd:element name="BookStore"> <xsd:complexType> <xsd:sequence> <xsd:element ref="Book" minOccurs="1" maxOccurs="unbounded"/> </xsd:sequence> </xsd:complexType> </xsd:element> <xsd:element name="Book"> <xsd:complexType> <xsd:sequence> <xsd:element ref="Title" minOccurs="1" maxOccurs="1"/> <xsd:element ref="Author" minOccurs="1" maxOccurs="1"/> <xsd:element ref="Date" minOccurs="1" maxOccurs="1"/> <xsd:element ref="ISBN" minOccurs="1" maxOccurs="1"/> <xsd:element ref="Publisher" minOccurs="1" maxOccurs="1"/> </xsd:sequence> </xsd:complexType> </xsd:element> <xsd:element name="Title" type="xsd:string"/> <xsd:element name="Author" type="xsd:string"/> <xsd:element name="Date" type="xsd:string"/> <xsd:element name="ISBN" type="xsd:string"/> <xsd:element name="Publisher" type="xsd:string"/></xsd:schema>

Elements defined by this schema

- BookStore - Book - Title - Author - Date - ISBN - Publisher

are to go in this space name

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Default Name space

This is referencing a Book element declaration.Since there is no namespace qualifier it is referencing the Book element in the defaultNamespace.

The default namespace ishttp://www.books.orgwhich is the targetNamespace!

<?xml version="1.0"?><xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema" targetNamespace="http://www.books.org" xmlns="http://www.books.org" elementFormDefault="qualified"> <xsd:element name="BookStore"> <xsd:complexType> <xsd:sequence> <xsd:element ref="Book" minOccurs="1"

maxOccurs="unbounded"/> </xsd:sequence> </xsd:complexType> </xsd:element> <xsd:element name="Book"> <xsd:complexType> <xsd:sequence> <xsd:element ref="Title" minOccurs="1" maxOccurs="1"/> <xsd:element ref="Author" minOccurs="1" maxOccurs="1"/> <xsd:element ref="Date" minOccurs="1" maxOccurs="1"/> <xsd:element ref="ISBN" minOccurs="1" maxOccurs="1"/> <xsd:element ref="Publisher" minOccurs="1"

maxOccurs="1"/> </xsd:sequence> </xsd:complexType> </xsd:element> <xsd:element name="Title" type="xsd:string"/> <xsd:element name="Author" type="xsd:string"/> <xsd:element name="Date" type="xsd:string"/> <xsd:element name="ISBN" type="xsd:string"/> <xsd:element name="Publisher" type="xsd:string"/></xsd:schema>

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<?xml version="1.0"?><schema xmlns="http://www.w3.org/2001/XMLSchema" targetNamespace="http://www.books.org" xmlns:bk="http://www.books.org" elementFormDefault="qualified"> <element name="BookStore"> <complexType> <sequence> <element ref="bk:Book" maxOccurs="unbounded"/> </sequence> </complexType> </element> <element name="Book"> <complexType> <sequence> <element ref="bk:Title"/> <element ref="bk:Author"/> <element ref="bk:Date"/> <element ref="bk:ISBN"/> <element ref="bk:Publisher"/> </sequence> </complexType> </element> <element name="Title" type="string"/> <element name="Author" type="string"/> <element name="Date" type="string"/> <element name="ISBN" type="string"/> <element name="Publisher" type="string"/></schema>

Note that http://…/XMLSchemais the defaultnamespace.Consequently, thereare no namespacequalifiers on - schema - element - complexType - sequence - string

Default XMLSchema, Qualify targetNamespace

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Name Space: Conclusion

BookStore.xml BookStore.xsd

targetNamespace="http://www.books.org"schemaLocation="http://www.books.org BookStore.xsd"

- defines elements in namespace http://www.books.org

- uses elements from namespace http://www.books.org

A schema defines a new vocabulary. Instance documents use that new vocabulary.

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BookStore.xml BookStore.xsd XMLSchema.xsd(schema-for-schemas)

Validate that the xml documentconforms to the rules describedin BookStore.xsd

Validate that BookStore.xsd is a validschema document, i.e., it conformsto the rules described in theschema-for-schemas

Multiple levels of checking

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Part 2: Data Types

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Elements, Attributes and attribute group declaration (1)

Element Declaration:

<?xml version="1.0" encoding="ISO-8859-1"?>

<xsd:schema xmlns:xsd="http://www.w3.org/2000/10/XMLSchema">

<xsd:element name="contacts" type="typeContacts"/>

<xsd:element name="remarque" type="xsd:string"/>

<!—Types declaration here -->

</xsd:schema>

Attribute Declaration:





<xsd:complexType name="typeContacts">

<!—content declaration-->

<xsd:attribute name="maj" type="xsd:date"/>

</xsd:complexType>

</xsd:schema>

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<xsd:element name="Book" > <xsd:complexType> <xsd:sequence> <xsd:group ref="PublicationElements"/> <xsd:element name="ISBN" type="string"/> <xsd:element name="Reviewer" type="string"/> </xsd:sequence> </xsd:complexType></xsd:element><xsd:element name="CD" > <xsd:complexType> <xsd:sequence> <xsd:group ref="PublicationElements"/> <xsd:element name="RecordingStudio" type="string"/> </xsd:sequence> </xsd:complexType></xsd:element><xsd:group name="PublicationElements"> <xsd:sequence> <xsd:element name="Title" type="xsd:string"/> <xsd:element name="Author" type="xsd:string" maxOccurs="unbounded"/> <xsd:element name="Date" type="xsd:string"/> </xsd:sequence></xsd:group>

Element Group

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Attribute group






<!—content declaration here-->

<xsd:attributeGroup ref="InfosMaj"/>

</xsd:complexType>

<xsd:attributeGroup name="InfosMaj">


<xsd:attribute name="auteur" type="xsd:string"/>

</xsd:attributeGroup>

</xsd:schema>






<!—content declaration here-->


</xsd:complexType>

<xsd:attributeGroup name="InfosMaj">


<xsd:attribute name="auteur" type="xsd:string"/>

</xsd:attributeGroup>

</xsd:schema>

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Data Types

Simple Type or Complex Type

– Use the simpleType element when the element does not contain attributes or child elements.

– Use the complexType element when you want to define child elements and/or attributes of an element.

There are four kinds of complex elements:– empty elements

– elements that contain only other elements

– elements that contain only text

– elements that contain both other elements and text

Note: Each of these elements may contain attributes as well!

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Simple Types: Predefined Types

Complex Type

String Boolean Entity ID IDREF

negativeInteger

NonPositiveInteger

positiveinteger

unsignedByte

unsignedShort

unsignedInt

unsignedLong

NonNegativeInteger

byte

short

int

Long

Integer

Decimal Binary QName Float Time duration

date month year century

timeperiod time

reccuringduration

Simple Type

Data Types

Similar to programming language

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Simple type: examples

<xsd:element name="lastname" type="xsd:string"/>

<xsd:element name="age" type="xsd:integer"/>

<xsd:element name="date born" type="xsd:date"/>

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Complex types: Constructors and occurrence indicators

Sequence and choice

<?xml version="1.0"?><xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema" targetNamespace="http://www.binary.org" xmlns="http://www.binary.org" elementFormDefault="qualified"> <xsd:element name="life"> <xsd:complexType> <xsd:sequence minOccurs="0" maxOccurs="unbounded"> <xsd:sequence minOccurs="0" maxOccurs="unbounded"> <xsd:element name="work" type="xsd:string"/> <xsd:element name="eat" type="xsd:string"/> </xsd: sequence> <xsd:choice> <xsd:element name="work" type="xsd:string"/> <xsd:element name="play" type="xsd:string"/> </xsd:choice> <xsd:element name="sleep" type="xsd:string"/> </xsd:sequence> </xsd:complexType> </xsd:element></xsd:schema>

<!ELEMENT life ((work, eat)*, (work | play), sleep)* >DTD:

XML Schema:

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<?xml version="1.0"?><xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema" targetNamespace="http://www.books.org" xmlns="http://www.books.org" elementFormDefault="qualified"> <xsd:element name="BookStore"> <xsd:complexType> <xsd:sequence> <xsd:element name="Book" maxOccurs="unbounded"> <xsd:complexType> <xsd:all> <xsd:element name="Title" type="xsd:string"/> <xsd:element name="Author" type="xsd:string"/> <xsd:element name="Date" type="xsd:string"/> <xsd:element name="ISBN" type="xsd:string"/> <xsd:element name="Publisher" type="xsd:string"/> </xsd:all> </xsd:complexType> </xsd:element> </xsd:sequence> </xsd:complexType> </xsd:element>

XML Schema:

Problem: create an element, Book, which contains Author, Title, Date, ISBN, and Publisher, in any order (Note: this is very difficult and ugly with DTDs).

Expressing Any Order

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The default value for minOccurs is "1“

The default value for maxOccurs is "1"

<xsd:element ref="Title" minOccurs="1" maxOccurs="1"/> <xsd:element ref="Title"/>

DTD

*

+

?

MinOccursXML SCHEMA

MaxOccurs0 Unbounded

1 (default value) Unbounded

0 1 (default value)

MinOccurs And MaxOccurs

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Empty Complex Type

<?xml version="1.0"?><xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema" targetNamespace="http://www.photography.org" xmlns="http://www.photography.org" elementFormDefault="qualified"> <xsd:element name="gallery"> <xsd:complexType> <xsd:sequence> <xsd:element name="image" maxOccurs="unbounded"> <xsd:complexType> <xsd:attribute name="href" type="xsd:anyURI" use="required"/> </xsd:complexType> </xsd:element> </xsd:sequence> </xsd:complexType> </xsd:element></xsd:schema>

<image href="http://www.xfront.com/InSubway.gif"/>

Schema:

InstanceDoc:

<!ELEMENT image EMPTY><!ATTLIST image href CDATA #REQUIRED>

DTD:

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Type Attribute or ComplexType child element

An element declaration can have a type attribute, or a complexType child element, but it cannot have both a type attribute and a complexType child element.

<xsd:element name="A" type="foo"> <xsd:complexType> … </xsd:complexType></xsd:element>

ERROR

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<?xml version="1.0"?><xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema" targetNamespace="http://www.books.org" xmlns="http://www.books.org" elementFormDefault="qualified"> <xsd:element name="BookStore"> <xsd:complexType> <xsd:sequence> <xsd:element ref="Book" minOccurs="1" maxOccurs="unbounded"/> </xsd:sequence> </xsd:complexType> </xsd:element> <xsd:element name="Book"> <xsd:complexType> <xsd:sequence>

<xsd:element ref="Title" minOccurs="1" maxOccurs="1"/> <xsd:element ref="Author" minOccurs="1" maxOccurs="1"/> <xsd:element ref="Date" minOccurs="1" maxOccurs="1"/> <xsd:element ref="ISBN" minOccurs="1" maxOccurs="1"/> <xsd:element ref="Publisher" minOccurs="1" maxOccurs="1"/> </xsd:sequence> </xsd:complexType> </xsd:element>

<xsd:element name="Title" type="xsd:string"/> <xsd:element name="Author" type="xsd:string"/> <xsd:element name="Date" type="xsd:string"/> <xsd:element name="ISBN" type="xsd:string"/> <xsd:element name="Publisher" type="xsd:string"/></xsd:schema>

Referring Elements Declarations

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Inlining Element Declarations

<?xml version="1.0"?><xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema" targetNamespace="http://www.books.org" xmlns="http://www.books.org" elementFormDefault="qualified"> <xsd:element name="BookStore"> <xsd:complexType> <xsd:sequence> <xsd:element name="Book" maxOccurs="unbounded"> <xsd:complexType> <xsd:sequence> <xsd:element name="Title" type="xsd:string"/> <xsd:element name="Author" type="xsd:string"/> <xsd:element name="Date" type="xsd:string"/> <xsd:element name="ISBN" type="xsd:string"/> <xsd:element name="Publisher" type="xsd:string"/> </xsd:sequence> </xsd:complexType> </xsd:element> </xsd:sequence> </xsd:complexType> </xsd:element></xsd:schema>

Note that we have movedall the element declarationsinline, and we are nolonger referring to theelement declarations.This results in a much more compact schema!

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Part 3:Type Derivation

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Creating your own Datatypes

A new datatype can be defined from an existing datatype (called the "base" type) by specifying values for one or more of the optional facets for the base type.

Two techniques: Type restriction and Type extension.We can restrict and extend simple and complex types.Example. The integer data type has 8 optional facets:

• totalDigits

• pattern

• whitespace

• enumeration

• maxInclusive

• maxExclusive

• minInclusive

• minExclusive

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Restriction of Simple Types (facet)

<xsd:simpleType name= "EarthSurfaceElevation"> <xsd:restriction base="xsd:integer"> <xsd:minInclusive value="-1290"/> <xsd:maxInclusive value="29035"/> </xsd:restriction></xsd:simpleType>

This creates a new datatype called 'EarthSurfaceElevation'.Elements declared to be of this type can hold an integer. However, the integer is restricted to have a value between -1290 and 29035, inclusive.

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<xsd:simpleType name= "name"> <xsd:restriction base= "xsd:source"> <xsd:facet value= "value"/> <xsd:facet value= "value"/> … </xsd:restriction></xsd:simpleType>

Facets: - length - minlength - maxlength - pattern - enumeration - minInclusive - maxInclusive - minExclusive - maxExclusive ...

Sources: - string - boolean - number - float - double - duration - dateTime - time ...

General Form of restricting simple types by Specifying Facet Values

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Enumeration And Pattern facets

<xsd:simpleType name="US-Flag-Colors"> <xsd:restriction base="xsd:string"> <xsd:enumeration value="red"/> <xsd:enumeration value="white"/> <xsd:enumeration value="blue"/> </xsd:restriction></xsd:simpleType>

This creates a new type called US-Flag-Colors.An element declared to be of this typemust have either the value red, or white, or blue.

<xsd:simpleType name="Emailadress">

<xsd:restriction base="xsd:string">

<xsd:pattern value="(.)+@(.)+"/>

</xsd:restriction>

</xsd:simpleType>

This creates a new type called Emailadress.An element declared to be of this typemust have the form string@string.

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Restriction of Complex Types

<xsd:complexType name="typeContactsLimit">

<xsd:complexContent>

<xsd:restriction base="typeContacts">

<xsd:sequence>

<xsd:element name="personne"maxOccurs="50" type="typePersonne"/>

</xsd:sequence>


</xsd:restriction>

</xsd:complexContent>

</xsd:complexType>


<xsd:sequence>

<xsd:element name="personne" maxOccurs="unbounded" type="typePersonne"/>

</xsd:sequence>


</xsd:complexType>

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Extension of Simple types

Element with Simple Content (don’t contain other elements) and Attributes

Example: <elevation units="feet">5440</elevation>

<xsd:element name="elevation"> <xsd:complexType> <xsd:simpleContent> <xsd:extension base="xsd:integer"> <xsd:attribute name="units" type="xsd:string" use="required"/> </xsd:extension> </xsd:simpleContent> </xsd:complexType></xsd:element>

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Extension of Complex Types

<xsd:complexType name="Publication"> <xsd:sequence> <xsd:element name="Title" type="xsd:string" maxOccurs="unbounded"/> <xsd:element name="Author" type="xsd:string" maxOccurs="unbounded"/> <xsd:element name="Date" type="xsd:gYear"/> </xsd:sequence></xsd:complexType ><xsd:complexType name="BookPublication"> <xsd:complexContent> <xsd:extension base="Publication"> <xsd:sequence> <xsd:element name="ISBN" type="xsd:string"/> <xsd:element name="Publisher" type="xsd:string"/> </xsd:sequence> </xsd:extension> </xsd:complexContent></xsd:complexType >

Title

AuthorDate

Publication

ISBN

Publisher

BookPublication

Add elements or attributes to a complex type

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Example: Fixing a Facet Value

<xsd:simpleType name= "ClassSize"> <xsd:restriction base="xsd:nonNegativeInteger"> <xsd:minInclusive value="10" fixed="true"/> <xsd:maxInclusive value="60"/> </xsd:restriction></xsd:simpleType>

<xsd:simpleType name= "BostonIEEEClassSize"> <xsd:restriction base="ClassSize"> <xsd:minInclusive value="15"/> <xsd:maxInclusive value="60"/> </xsd:restriction></xsd:simpleType>

Error! Cannotchange the valueof a fixed facet!

Controlling Type Derivations

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Prohibiting Derivations

Sometimes we may want to create a type and disallow all derivations of it, or just disallow extension derivations, or disallow restriction derivations.– Rationale: "For example, I may create a complexType and make it publicly

available for others to use. However, I don't want them to extend it with their proprietary extensions or subset it to remove, say, copyright information." (Jon Cleaver)

<xsd:complexType name="Publication" final="#all" Publication cannot be extended nor restricted

<xsd:complexType name="Publication" final="restriction" Publication cannot be restricted

<xsd:complexType name="Publication" final="extension" Publication cannot be extended

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Type Derivation and Attributes

<xsd:element name="BookStore"> <xsd:complexType> <xsd:sequence> <xsd:element name="Book" maxOccurs="unbounded"> <xsd:complexType> <xsd:sequence> <xsd:element name="Title" type="xsd:string"/> <xsd:element name="Author" type="xsd:string" maxOccurs="unbounded"/> <xsd:element name="Date" type="xsd:string"/> <xsd:element name="ISBN" type="xsd:string"/> <xsd:element name="Publisher" type="xsd:string"/> </xsd:sequence> <xsd:attributeGroup ref="BookAttributes"/> </xsd:complexType> </xsd:element> </xsd:sequence> </xsd:complexType> </xsd:element> <xsd:attributeGroup name="BookAttributes"> <xsd:attribute name="Category" use="required"> <xsd:simpleType> <xsd:restriction base="xsd:string"> <xsd:enumeration value="autobiography"/> <xsd:enumeration value="non-fiction"/> <xsd:enumeration value="fiction"/> </xsd:restriction> </xsd:simpleType> </xsd:attribute> <xsd:attribute name="InStock" type="xsd:boolean" default="false"/> <xsd:attribute name="Reviewer" type="xsd:string" default=" "/> </xsd:attributeGroup>

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A Brief Summary

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<xsd:attribute name="name" type="simple-type" use="how-its-used" value="value"/>

requiredoptionalprohibited

xsd:stringxsd:integerxsd:boolean...

<xsd:attribute name="name" use="how-its-used" value="value"> <xsd:simpleType> <xsd:restriction base="simple-type"> <xsd:facet value="value"/> … </xsd:restriction> </xsd:simpleType></xsd:attribute>

1

2

Declaring Attributes

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1. Element with Simple Content.

Declaring an element using a built-in type:

<xsd:element name="numStudents" type="xsd:positiveInteger"/>

Declaring an element using a user-defined simpleType:

<xsd:simpleType name="US-Flag-Colors> <xsd:restriction base="xsd:string"> <xsd:enumeration value="red"/> <xsd:enumeration value="white"/> <xsd:enumeration value="blue"/> </xsd:restriction> </xsd:simpleType> <xsd:element name="flag" type="US-Flag-Colors"/>

An alternative formulation of the above flag example is to inline the simpleType definition :

<xsd:element name="flag"> <xsd:simpleType> <xsd:restriction base="xsd:string"> <xsd:enumeration value="red"/> <xsd:enumeration value="white"/> <xsd:enumeration value="blue"/> </xsd:restriction> </xsd:simpleType> </xsd:element>

Summary of Declaring Elements

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Summary of Declaring Elements (cont.)

2. Element Contains Child Elements

Defining the child elements inline:

<xsd:element name="Person"> <xsd:complexType> <xsd:sequence> <xsd:element name="Title" type="xsd:string"/> <xsd:element name="FirstName" type="xsd:string"/> <xsd:element name="Surname" type="xsd:string"/> </xsd:sequence> </xsd:complexType> </xsd:element>

An alternate formulation of the above Person example is to create a named complexType and then use that type:

<xsd:complexType name="PersonType"> <xsd:sequence> <xsd:element name="Title" type="xsd:string"/> <xsd:element name="FirstName" type="xsd:string"/> <xsd:element name="Surname" type="xsd:string"/> </xsd:sequence> </xsd:complexType> <xsd:element name="Person" type="PersonType"/>

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<xsd:complexType name="Publication"> <xsd:sequence> <xsd:element name="Title" type="xsd:string" maxOccurs="unbounded"/> <xsd:element name="Author" type="xsd:string" maxOccurs="unbounded"/> <xsd:element name="Date" type="xsd:gYear"/> </xsd:sequence> </xsd:complexType> <xsd:complexType name="BookPublication"> <xsd:complexContent> <xsd:extension base="Publication" > <xsd:sequence> <xsd:element name="ISBN" type="xsd:string"/> <xsd:element name="Publisher" type="xsd:string"/> </xsd:sequence> </xsd:extension> </xsd:complexContent> </xsd:complexType> <xsd:element name="Book" type="BookPublication"/>

3. Element Contains a complexType that is an Extension of another complexType

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<xsd:complexType name="Publication"> <xsd:sequence> <xsd:element name="Title" type="xsd:string" maxOccurs="unbounded"/> <xsd:element name="Author" type="xsd:string" maxOccurs="unbounded"/> <xsd:element name="Date" type="xsd:gYear"/> </xsd:sequence></xsd:complexType><xsd:complexType name= "SingleAuthorPublication"> <xsd:complexContent> <xsd:restriction base="Publication"> <xsd:sequence> <xsd:element name="Title" type="xsd:string" maxOccurs="unbounded"/> <xsd:element name="Author" type="xsd:string"/> <xsd:element name="Date" type="xsd:gYear"/> </xsd:sequence> </xsd:restriction> </xsd:complexContent></xsd:complexType><xsd:element name="Catalogue" type="SingleAuthorPublication"/>

4. Element Contains a complexType that is a Restriction of another complexType


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<xsd:element name="apple"> <xsd:complexType> <xsd:simpleContent> <xsd:extension base="xsd:string"> <xsd:attribute name="variety" type="xsd:string" use="required"/> </xsd:extension> </xsd:simpleContent> </xsd:complexType></xsd:element>

5. Element Contains Simple Content and Attributes

Summary of Declaring Elements

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Part 4:Advanced XML Schema

Conception

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Element Substitution

Oftentimes in daily conversation there are several ways to express something.

– In Boston we use the words "T" and "subway" interchangeably. For example, "we took the T into town", or "we took the subway into town".

• Thus, "T" and "subway" are substitutable. Which one is used may depend upon what part of the state you live in, what mood you're in, or any number of factors.

We would like to be able to express this substitutability in XML Schemas.

– That is, we would like to be able to declare in a schema an element called "subway", an element called "T", and state that "T"may be substituted for "subway". Instance documents can then use either <subway> or <T>, depending on their preference.

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Element Substitution (cont…)

<xsd:element name="subway" type="xsd:string"/> <xsd:element name="T" substitutionGroup="subway" type="xsd:string"/> <xsd:element name="transportation"> <xsd:complexType> <xsd:sequence> <xsd:element ref="subway"/> </xsd:sequence> </xsd:complexType> </xsd:element>

Schema:

Instance doc:

Alternative instance doc(substitute Tfor subway):

This example shows the <subway> element being substituted with the <T> element.

<transportation> <subway>Red Line</subway> </transportation>

<transportation> <T>Red Line</T> </transportation>

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An element may wish to block other elements from substituting with it. This is achieved by adding a block attribute.

<xsd:element name="…" type="…" block="substitution"/>

1. Transitive: if element A can substitute for element B, and element B can substitute for element C, then element A can substitute for element C.

A --> B --> C then A --> C

2. Non-symmetric: if element A can substitute for element B, it is not the case that element B can substitute for element A.

Note: Element Substitution is:

Blocking Element Substitution

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Anonymous types and Named Types

<xsd:element name="Book" maxOccurs="unbounded"> <xsd:complexType> <xsd:sequence> <xsd:element name="Title" type="xsd:string"/> <xsd:element name="Author" type="xsd:string"/> <xsd:element name="Date" type="xsd:string"/> <xsd:element name="ISBN" type="xsd:string"/> <xsd:element name="Publisher" type="xsd:string"/> </xsd:sequence> </xsd:complexType> </xsd:element>

<xsd:element name="Book" type="BookPublication" maxOccurs="unbounded"/> … … … …

<xsd:complexType name="BookPublication"> <xsd:sequence> <xsd:element name="Title" type="xsd:string"/> <xsd:element name="Author" type="xsd:string"/> <xsd:element name="Date" type="xsd:string"/> <xsd:element name="ISBN" type="xsd:string"/> <xsd:element name="Publisher" type="xsd:string"/> </xsd:sequence> </xsd:complexType>

AnonymousType

AnonymousType

NamedType

NamedType

Named Type can

be reused by otherelements

Named Type can

be reused by otherelements

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<?xml version="1.0"?><Library xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation= "http://www.book.org Book.xsd http://www.employee.org Employee.xsd"> <Books> <Book xmlns="http://www.book.org"> <Title>My Life and Times</Title> <Author>Paul McCartney</Author> <Date>1998</Date> <ISBN>1-56592-235-2</ISBN> <Publisher>Macmillan Publishing</Publisher> </Book> <Book xmlns="http://www.book.org"> <Title>Illusions The Adventures of a Reluctant Messiah</Title> <Author>Richard Bach</Author> <Date>1977</Date> <ISBN>0-440-34319-4</ISBN> <Publisher>Dell Publishing Co.</Publisher> </Book> <Book xmlns="http://www.book.org"> <Title>The First and Last Freedom</Title> <Author>J. Krishnamurti</Author> <Date>1954</Date> <ISBN>0-06-064831-7</ISBN> <Publisher>Harper & Row</Publisher> </Book> </Books> <Employees> <Employee xmlns="http://www.employee.org"> <Name>John Doe</Name> <SSN>123-45-6789</SSN> </Employee> <Employee xmlns="http://www.employee.org"> <Name>Sally Smith</Name> <SSN>000-11-2345</SSN> </Employee> </Employees></Library>

Library.xml

Validating againsttwo schemas

The <Book> elements aredefined in Book.xsd, andthe <Employee> elementsare defined in Employee.xsd.

1. A schema validator will validate each Book elementagainst Book.xsd. 2. It will validate each Employee element against Employee.xsd.

Assembling an Instance Document from Multiple Schema Documents

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<xsd:schema …> <xsd:include schemaLocation="LibraryBook.xsd"/> <xsd:include schemaLocation="LibraryEmployee.xsd"/> …</xsd:schema>

<xsd:schema …> <xsd:include schemaLocation="LibraryBook.xsd"/> <xsd:include schemaLocation="LibraryEmployee.xsd"/> …</xsd:schema>

Assembling a Schema from Multiple Schema Documents

The include element allows you to access components in other schemas– All the schemas you include must have the same namespace as your schema

(i.e., the schema that is doing the include)

– The net effect of include is as though you had typed all the definitions directly into the containing schema

LibraryBook.xsd LibraryEmployee.xsd

Library.xsd

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Assembling a Schema from Multiple Schema Documents with Different NamespacesThe import element allows you to access elements and types in

a different namespace

NamespaceA

NamespaceA

A.xsd

NamespaceB

NamespaceB

B.xsd

C.xsd

<xsd:schema …> <xsd:import namespace="A" schemaLocation="A.xsd"/> <xsd:import namespace="B" schemaLocation="B.xsd"/> …</xsd:schema>

<xsd:schema …> <xsd:import namespace="A" schemaLocation="A.xsd"/> <xsd:import namespace="B" schemaLocation="B.xsd"/> …</xsd:schema>

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<?xml version="1.0"?><xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema" targetNamespace="http://www.camera.org" xmlns:nikon="http://www.nikon.com" xmlns:olympus="http://www.olympus.com" xmlns:pentax="http://www.pentax.com" elementFormDefault="qualified"> <xsd:import namespace="http://www.nikon.com" schemaLocation="Nikon.xsd"/> <xsd:import namespace="http://www.olympus.com" schemaLocation="Olympus.xsd"/> <xsd:import namespace="http://www.pentax.com" schemaLocation="Pentax.xsd"/> <xsd:element name="camera"> <xsd:complexType> <xsd:sequence> <xsd:element name="body" type="nikon:body_type"/> <xsd:element name="lens" type="olympus:lens_type"/> <xsd:element name="manual_adapter" type="pentax:manual_adapter_type"/> </xsd:sequence> </xsd:complexType> </xsd:element><xsd:schema>

Camera.xsd

These importelements giveus access tothe componentsin these otherschemas.

Use of thebody_typethat isdefinedin the Nikonnamespace

Assembling a Schema from Multiple Schema Documents with Different Namespaces

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Redefining a Type from the Included Schema

The <redefine> element does the same thing as an <include> element (i.e., it allows you to access components in other schemas, provided they have the same namespace), plus it enables you to redefine one or more components (simpleType, complexType, attributeGroup, or group)

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<xsd:complexType name="BookType"> <xsd:sequence> <xsd:element name="Title" type="xsd:string"/> <xsd:element name="Author" type="xsd:string"/> <xsd:element name="Date" type="xsd:string"/> <xsd:element name="ISBN" type="xsd:string"/> <xsd:element name="Publisher" type="xsd:string"/> </xsd:sequence></xsd:complexType>

LibraryBook.xsd

<xsd:redefine schemaLocation="LibraryBook.xsd"> <xsd:complexType name="BookType"> <xsd:complexContent> <xsd:extension base="BookType"> <xsd:sequence> <xsd:element name="Summary" type="xsd:string"/> </xsd:sequence> </xsd:extension> </xsd:complexContent> </xsd:complexType></xsd:redefine>

Library.xsd

Redefining BookType toalso have a Summaryelement.

Redefining a Type from the Included Schema

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Annotating Schemas

The <annotation> element is used for documenting the schema, both for humans and for programs.– Use <documentation> for providing a comment to humans

– Use <appinfo> for providing a comment to programs• The content is any well-formed XML

Note that annotations have no effect on schema validation

<xsd:annotation> <xsd:documentation> The following constraint is not expressible with XML Schema: The value of element A should be greater than the value of element B. So, we need to use a separate tool (e.g., Schematron) to check this constraint. We will express this constraint in the appinfo section (below). </xsd:documentation> <xsd:appinfo> <assert test="A > B">A should be greater than B</assert> </xsd:appinfo><xsd:/annotation>

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Uniqueness & Keys

DTDs provide the ID attribute datatype for uniqueness (i.e., an ID value must be unique throughout the entire document, and the XML parser enforces this).

XML Schema has much enhanced uniqueness capabilities:– enables you to define element content to be unique.

– enables you to define non-ID attributes to be unique.

– enables you to define a combination of element content and attributes to be unique.

– enables you to distinguish between unique versus key.

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unique vs key

Key: an element or attribute (or combination) which is defined to be a key must: – always be present (minOccurs must be greater than zero)

– be non-nillable (i.e., nillable="false")

– be unique

Key implies unique, but unique does not imply key

Example:

In the BookStore we should be able to express that each Book's ISBN element is unique. Further, let's make the ISBN elements keys (i.e., both unique and required to exist).

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<xsd:element name="BookStore"> ... <xsd:key name="PK"> <xsd:selector xpath="bk:Book"/> <xsd:field xpath="bk:ISBN"/> </xsd:key> </xsd:element>

"Within <BookStore> we define a key, called PK. Select each <Book>, andwithin each <Book> the ISBN element isa key."

In other words, within <BookStore>each <Book> must have an <ISBN> andit must be unique.

Example 1

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Example 2

<?xml version="1.0"?><xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema" targetNamespace="http://www.books.org" xmlns="http://www.books.org" xmlns:bk="http://www.books.org" elementFormDefault="qualified"> <xsd:element name="BookStore"> <xsd:complexType> <xsd:sequence> <xsd:element name="Book" maxOccurs="unbounded"> <xsd:complexType> <xsd:sequence> <xsd:element name="Title" type="xsd:string"/> <xsd:element name="Author" type="xsd:string"/> <xsd:element name="Date" type="xsd:string"/> <xsd:element name="ISBN" type="xsd:string" minOccurs="0"/> <xsd:element name="Publisher" type="xsd:string"/> </xsd:sequence> </xsd:complexType> </xsd:element> </xsd:sequence> </xsd:complexType> <xsd:unique name="UNIQ"> <xsd:selector xpath="bk:Book"/> <xsd:field xpath="bk:ISBN"/> </xsd:unique> </xsd:element></xsd:schema>

Note: ISBNis optional

Requireevery ISBNbe unique.

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Part 5:Conclusions

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Conclusions (1)

Namespaces, data types…make XML Shema very powerful

However, it is not "all powerful". There are many constraints that it cannot express. Here are some examples:

• Ensure that the value of the aircraft <Elevation> element is greater than the value of the obstacle <Height> element.

• Ensure that: if the value of the attribute, mode, is "air", then the value of the

element, <Transportation>, is either airplane or hot-air balloon

if mode="water" then <Transportation> is either boat or hovercraft

if mode="ground" then <Transportation> is either car or bicycle.

• Ensure that the value of the <PaymentReceived> is equal to the value of <PaymentDue>, where these elements are in separate documents!

To check all our constraints we will need to supplement XML Schemas with another tool.

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Conclusions (2)

Two Approaches to Extending XML Schemas

XSLT/XPath– The first approach is to supplement the XSD document with a

stylesheet

Schematron– The second approach is to embed the additional constraints within

<appinfo> elements in the XSD document. Then, a tool (Schematron) will extract and process those constraints.

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Part 6:References

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XML Schema Validators Command Line Only

– XSV by Henry Thompson• ftp://ftp.cogsci.ed.ac.uk/pub/XSV/XSV12.EXE

Has a Programmatic API

– xerces by Apache• http://www.apache.org/xerces-j/index.html

– IBM Schema Quality Checker (Note: this tool is only used to check your schema. It cannot be used to validate an instance document against a schema.)

• http://www.alphaworks.ibm.com/tech/xmlsqc

– MSXML4.0• http://www.microsoft.com

GUI Oriented

– XML Spy• http://www.xmlspy.com

– Turbo XML• http://www.extensibility.com

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References

http://www.w3.org/TR/xmlschema-0/ (Primer) http://www.w3.org/TR/xmlschema-1/ (Structures)http://www.w3.org/TR/xmlschema-2/ (Datatypes)