xml schema vinod kumar kayartaya. what is xml schema? xml schema is an xml based alternative to dtd...

XML SchemaXML Schema

Vinod Kumar Kayartaya

What is XML Schema?What is XML Schema?

XML Schema is an XML based alternative to DTD

An XML schema describes the structure of an XML document

The purpose of an XML Schema is to define the legal building blocks of an XML document, just like a DTD

XML Schemas support data types, which DTDs do not

The XML Schema language is also referred to as XML Schema Definition (XSD)

XML documents can have a reference to a DTD or an XML Schema

What Does XML Schema Define?What Does XML Schema Define?

An XML Schema:– 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 data types for elements and attributes – defines default values for elements and

attributes

XML Schema SpecificationXML Schema Specification

XML Schema specification consists of two parts:– Structures– Datatypes

http://www.w3.org/TR/xmlschema-0/ (Primer)

http://www.w3.org/TR/xmlschema-1/ (Structures)

http://www.w3.org/TR/xmlschema-2/ (Datatypes)

XML TermsXML Terms

Instance Document – an XML document that is valid according to a particular schema

Schema – the XML document that has structural rules defined for an XML document

Instance Document (.xml file)

Schema (.xsd file)

Schema Validator

Building Blocks of SchemaBuilding Blocks of Schema

Element declarations – Complex type definitions – Simple type definitions

Attribute declarations

Schema ElementsSchema Elements

Simple Elements:– they do not contain other elements<xs:element name="name" type="type"/>

Complex Elements– they contain other elements<xs:element name="name">

<xs:complexType> . . element content . </xs:complexType> </xs:element>

Schema – Example 1Schema – Example 1<!ELEMENT note (to, from,

heading, body)> <!ELEMENT to (#PCDATA)> <!ELEMENT from (#PCDATA)> <!ELEMENT heading (#PCDATA)> <!ELEMENT body (#PCDATA)>

<!ELEMENT note (to, from, heading, body)>

<!ELEMENT to (#PCDATA)> <!ELEMENT from (#PCDATA)> <!ELEMENT heading (#PCDATA)> <!ELEMENT body (#PCDATA)>

<?xml version="1.0"?> <xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"><xsd:element name="note"> <xsd:complexType> <xsd:sequence> <xsd:element name="to" type="xsd:string"/> <xsd:element name="from" type="xsd:string"/> <xsd:element name="heading" type="xsd:string"/> <xsd:element name="body" type="xsd:string"/> </xsd:sequence> </xsd:complexType> </xsd:element></xsd:schema>

<?xml version="1.0"?> <note> <to>Mary</to> <from>John</from> <heading>Reminder</heading> <body>Don't forget me this

weekend!</body> </note> www.w3schools.com

<?xml version="1.0"?> <note> <to>Mary</to> <from>John</from> <heading>Reminder</heading> <body>Don't forget me this

weekend!</body> </note> www.w3schools.com

The NamespacesThe Namespaces

XML Schema Namespace– The elements and datatypes that are used

to construct schemas (schema, element, complexType, sequence, string, etc.) come from the http://www.w3.org/2001/XMLSchema namespacehttp://www.w3.org/2001/XMLSchema

elementcomplexType

schema

sequence

string

integer

boolean

The Namespaces…The Namespaces…

Reference to the schema in the instance document

<?xml version="1.0"?><note xmlns:xsi=

"http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation= "note.xsd">

<to>Mary</to> <from>John</from> <heading>Reminder</heading> <body>Don't forget me this weekend!</body> </note>

Reference to the schema in the instance document

<?xml version="1.0"?><note xmlns:xsi=

"http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation= "note.xsd">

<to>Mary</to> <from>John</from> <heading>Reminder</heading> <body>Don't forget me this weekend!</body> </note>

The Namespaces…The Namespaces…

XML Schema-instance Namespace

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

schemaLocationtype

noNamespaceSchemaLocation

The Levels of ValidationThe Levels of Validation

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

Validate that note.xmlconforms to the rules describedin note.xsd

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

Common XML Schema Data TypesCommon XML Schema Data Types

XML Schema has a lot of built-in data types. Some of them:– xs:string – xs:decimal – xs:integer – xs:boolean – xs:date – xs:time

Schema – Example 2Schema – Example 2

<!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)>

<!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)>

Schema – Example 2…Schema – Example 2…<?xml version="1.0"?><xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"> <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>

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

Reusing declarations with the

ref attribute

Schema – Example 2…Schema – Example 2…

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

Inline Element Declarations

Anonymous type

Occurrence Constraints on Occurrence Constraints on ElementsElements The attributes minOccurs and maxOccurs can

be used to indicate the number of times an element can appear

The default value for both the attributes minOccurs and maxOccurs is 1. If both the attributes are omitted, the element should appear exactly once.

Default and Fixed Values for Simple Default and Fixed Values for Simple Elements Elements

Elements can have either a default value OR a fixed value set

A default value is automatically assigned to the element when no other value is specified

A fixed value is also automatically assigned to the element when no other value is specified

But, unlike default values, if you specify another value than the fixed value, the document is considered invalid

<xs:element name="color" type="xs:string" default="red"/>

<xs:element name="color" type="xs:string" fixed="red"/>

<xs:element name="color" type="xs:string" default="red"/>

<xs:element name="color" type="xs:string" fixed="red"/>

Complex TypesComplex Types

Complex Types – Named TypesComplex Types – Named Types

The complex type definitions create new complex types, which can be reused in the element declarations

New complex types are defined using the complexType element

ComplexType definition typically contains a set of – element declarations, – element references, and – attributes declarations

Example –Complex (Named) Type Example –Complex (Named) Type DefinitionDefinition

Instance Document

<?xml version="1.0"?>

<note>

<heading>Reminder</heading>

<body>Don't forget me this weekend!</body>

</note>

Instance Document

<note>

<heading>Reminder</heading>

<body>Don't forget me this weekend!</body>

</note>

Example –Complex (Named) Type Example –Complex (Named) Type Definition…Definition…

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

<xs:element name="note" type="noteType"/>

<xs:complexType name="noteType">

<xs:sequence>

<xs:element name="to" type="xs:string"/>

<xs:element name="from" type="xs:string"/>

<xs:element name="heading" type="xs:string"/>

<xs:element name="body" type="xs:string"/>

</xs:sequence>

</xs:complexType>

</xs:schema>

<xs:element name="note" type="noteType"/>

<xs:complexType name="noteType">

<xs:sequence>

<xs:element name="to" type="xs:string"/>

<xs:element name="from" type="xs:string"/>

<xs:element name="heading" type="xs:string"/>

<xs:element name="body" type="xs:string"/>

</xs:sequence>

</xs:complexType>

</xs:schema>

Simple TypesSimple Types

Simple types could be – Built-in simple types (xs:string, xs:int, etc.)– Those derived from simple types or

existing derived ones• Deriving can be done by restricting the values

that the new type can take on, as a subset of the values of the existing simple type

• Restricting the range of values for the new simple type can be done with the xsd:restriction element

• Facets constrain the values

Derived Simple TypesDerived Simple Types

A new simple type salaryType derived from the integer type:

<xsd:element name="salary" type="salaryType"/>

<xsd:simpleType name="salaryType">

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

<xsd:minInclusive value="5000"/>

<xsd:maxInclusive value="10000"/>

</xsd:restriction>

</xsd:simpleType>

<xsd:element name="salary" type="salaryType"/>

<xsd:simpleType name="salaryType">

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

<xsd:minInclusive value="5000"/>

<xsd:maxInclusive value="10000"/>

</xsd:restriction>

</xsd:simpleType>

Derived Simple Types…Derived Simple Types…

A new simple type bookType derived using the enumeration facet

<xs:element name="book" type="bookType"/><xs:simpleType name="bookType"> <xs:restriction base="xs:string"> <xs:enumeration value="Technical"/> <xs:enumeration value="Managerial"/> <xs:enumeration value="Fiction"/> </xs:restriction> </xs:simpleType>

The type "carType" can be

used by other elements because it is not a part of

the "car" element

The type "carType" can be

used by other elements because it is not a part of

the "car" element

An Anonymous Simple Type An Anonymous Simple Type

This simple type cannot be reused as it is part of the element declaration

<xs:element name="book"> <xs:simpleType> <xs:restriction base="xs:string"> <xs:enumeration value="Technical"/> <xs:enumeration value="Managerial"/> <xs:enumeration value="Fiction"/> </xs:restriction> </xs:simpleType></xs:element>

Summary – Declaring ElementsSummary – Declaring Elements

A simple type(e.g., xs:string)or the name ofa complexType(e.g., noteType)

<xs:element name="name" minOccurs="int" maxOccurs="int"> <xs:complexType> … </xs:complexType></xs:element>

<xs:element name="name" type="type" minOccurs="int" maxOccurs="int"/>

A nonnegative integer

A nonnegative integer or the value “unbounded”

Summary – Declaring Elements…Summary – Declaring Elements…

<xs:element name="name" minOccurs="int" maxOccurs="int"> <xs:simpleType> … </xs:simpleType></xs:element>

Summary – Defining Reusable Summary – Defining Reusable TypesTypes

<xs:complexType name="name"> <xs:sequence> … </xs:sequence></xs:complexType>

<xs:simpleType name="name"> <xs:restriction> … </xs:restriction></xs:simpleType>

Schema AttributesSchema Attributes

An element that has an attribute should always be declared as complex type

The attribute declaration must reference simple types always

<book category="technical"

xmlns:xsi=

"http://www.w3.org/2001/XMLSchema-instance"

xsi:noNamespaceSchemaLocation= "book.xsd">

<title>XML Schemas</title>

</book>

<book category="technical"

xmlns:xsi=

"http://www.w3.org/2001/XMLSchema-instance"

xsi:noNamespaceSchemaLocation= "book.xsd">

<title>XML Schemas</title>

</book>

Book.xml

Schema Attributes…Schema Attributes…<?xml version="1.0"?>

<xs:element name="book" type="bookType"/>

<xs:complexType name="bookType">

<xs:sequence>

<xs:element name="title" type="xs:string"/>

<xs:element name="ISBN" type="ISBNType"/>

<xs:element name="price" type="priceType"/>

</xs:sequence>

<xs:attribute name="category" type="xs:string"/>

</xs:complexType>

<xs:simpleType name="ISBNType">

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

<xs:pattern value="\d{3}-[A-Z]{4}"/>

</xs:restriction>

</xs:simpleType>

<xs:complexType name="priceType">

<xs:simpleContent>

<xs:extension base="xs:decimal">

<xs:attribute name="currency" type="xs:string"/>

</xs:extension>

</xs:simpleContent>

</xs:complexType>

</xs:schema>

<xs:element name="book" type="bookType"/>

<xs:complexType name="bookType">

<xs:sequence>

<xs:element name="ISBN" type="ISBNType"/>

<xs:element name="price" type="priceType"/>

</xs:sequence>

<xs:attribute name="category" type="xs:string"/>

</xs:complexType>

<xs:simpleType name="ISBNType">

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

<xs:pattern value="\d{3}-[A-Z]{4}"/>

</xs:restriction>

</xs:simpleType>

<xs:complexType name="priceType">

<xs:simpleContent>

<xs:extension base="xs:decimal">

<xs:attribute name="currency" type="xs:string"/>

</xs:extension>

</xs:simpleContent>

</xs:complexType>

</xs:schema>

Book.xsd

Attribute DefaultsAttribute Defaults

Attributes can have either a default value OR a fixed value specified

<xs:attribute name="currency" type="xs:string" default="INR"/>

<xs:attribute name="currency" type="xs:string" fixed="INR"/>

Attribute OccurrenceAttribute Occurrence

Attribute occurrence (once or none) is indicated by use attribute

Values for use attribute:– required, optional, prohibited– Default value is optional

<xs:attribute name="currency" type="xs:string" use="optional"/>

<xs:attribute name="currency" type="xs:string" use="required"/>

Complex Types – More Complex Types – More Element Content ModelsElement Content Models

Complex Elements – More Complex Elements – More ExamplesExamples Element Contents

– Elements containing only a simple type value (text)

– Elements containing other elements– Elements containing other elements and

attributes– Empty elements (with or without

attributes)– Elements containing simple type value

(text) and attributes

Empty ElementsEmpty Elements

The existence of an attribute makes an element complex type, though it may not contain any content at all

<xs:element name="phone"><xs:complexType> <xs:attribute name="ftype" type="xs:string"/> <xs:attribute name="number" type="xs:string"/>

</xs:complexType></xs:element>

<xs:element name="phone"><xs:complexType> <xs:attribute name="ftype" type="xs:string"/> <xs:attribute name="number" type="xs:string"/>

</xs:complexType></xs:element>

Element with Text and Attribute Element with Text and Attribute

<xs:element name="phone"> <xs:complexType> <xs:simpleContent>

<xs:extension base="xs:string"> <xs:attribute name="ftype" type="xs:string"/> </xs:extension> </xs:simpleContent> </xs:complexType> </xs:element>

<xs:element name="phone"> <xs:complexType> <xs:simpleContent>

<xs:extension base="xs:string"> <xs:attribute name="ftype" type="xs:string"/> </xs:extension> </xs:simpleContent> </xs:complexType> </xs:element>

Using anyTypeUsing anyType

anyType allows for no constraints on the content at all

If you do not specify any type in the declaration, it defaults to anyType

<xs:element name="elem1" type="xs:anyType"/> <xs:element name="elem1" type="xs:anyType"/>

<xs:element name="elem1"/> <xs:element name="elem1"/>

Element Occurrence – Order Element Occurrence – Order IndicatorsIndicators You can use the following indicators to

mention how the elements should occur within a complex element/type– All

• Indicates that the child elements can appear in any order, but each can occur at most once (minOccurs=0, maxOccurs=1)

– Choice• Indicates either of the child elements only can

– Sequence• Indicates that the child elements should occur

only in the order specified

Element Occurrence Indicator - AllElement Occurrence Indicator - All

<PersonInfo

xmlns:xsi= "http://www.w3.org/2001/XMLSchema-instance"

xsi:noNamespaceSchemaLocation= "personinfo-all.xsd">

<title>Executive</title>

<dept>Sales</dept>

</person>

<title>Manager</title>

<dept>Sales</dept>

</person>

</PersonInfo>

<PersonInfo

xsi:noNamespaceSchemaLocation= "personinfo-all.xsd">

<dept>Sales</dept>

</person>

<dept>Sales</dept>

</person>

</PersonInfo>

Element Occurrence Indicator – Element Occurrence Indicator – All…All…

<xs:element name="PersonInfo">

<xs:complexType>

<xs:sequence>

<xs:element name="person" maxOccurs="unbounded">

<xs:complexType>

<xs:all>

<xs:element name="name" type="xs:string"/>

<xs:element name="dept" type="xs:string"/>

<xs:element name="email" type="xs:string"/>

<xs:element name="phone" type="xs:string"/>

</xs:all>

</xs:complexType>

</xs:element>

</xs:sequence>

</xs:complexType>

</xs:element></xs:schema>

<xs:element name="PersonInfo">

<xs:complexType>

<xs:sequence>

<xs:element name="person" maxOccurs="unbounded">

<xs:complexType>

<xs:all>

<xs:element name="dept" type="xs:string"/>

<xs:element name="email" type="xs:string"/>

<xs:element name="phone" type="xs:string"/>

</xs:all>

</xs:complexType>

</xs:element>

</xs:sequence>

</xs:complexType>

</xs:element></xs:schema>

Element Occurrence Indicator – Element Occurrence Indicator – ChoiceChoice

<employees

xsi:noNamespaceSchemaLocation= "employee-choice.xsd">

</employee>

</employee>

</employees>

<employees

</employee>

</employee>

</employees>

Element Occurrence Indicator – Choice…Element Occurrence Indicator – Choice…

<employees

<valid-till>2005-06-30</valid-till>

</contract>

<name>Sunil</name>

</contract>

</employees>

<employees

</contract>

<name>Sunil</name>

</contract>

</employees>

Element Occurrence Indicator – Choice…Element Occurrence Indicator – Choice…

<xs:element name="employees">

<xs:complexType>

<xs:choice>

<xs:element name="employee" type="regularType" maxOccurs="unbounded"/>

<xs:element name="contract" type="contractType" maxOccurs="unbounded"/>

</xs:choice>

</xs:complexType>

</xs:element>

<xs:complexType name="regularType">

<xs:sequence>

<xs:element name="salary" type="xs:integer"/>

</xs:sequence>

</xs:complexType>

<xs:complexType name="contractType">

<xs:sequence>

<xs:element name="rate" type="xs:integer"/>

<xs:element name="valid-till" type="xs:date"/>

</xs:sequence>

</xs:complexType>

</xs:schema>

<xs:element name="employees">

<xs:complexType>

<xs:choice>

<xs:element name="employee" type="regularType" maxOccurs="unbounded"/>

<xs:element name="contract" type="contractType" maxOccurs="unbounded"/>

</xs:choice>

</xs:complexType>

</xs:element>

<xs:complexType name="regularType">

<xs:sequence>

<xs:element name="salary" type="xs:integer"/>

</xs:sequence>

</xs:complexType>

<xs:complexType name="contractType">

<xs:sequence>

<xs:element name="rate" type="xs:integer"/>

<xs:element name="valid-till" type="xs:date"/>

</xs:sequence>

</xs:complexType>

</xs:schema>

xml schema vinod kumar kayartaya. what is xml schema? xml schema is an xml based alternative to dtd...

dtdan xml schema

schemas schema

valid schema document

notthe xml schema language

xml schemawhat

time schema example

simple elements elements

ref attribute schema

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