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More XML Schema

• The main source for these slides is “The XML Companion” by Bradley• Other resources: http://www.w3.org/TR/xmlschema-2/

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Three Major Uses – Same as DTD’s

1. Validation

2. Code Generation

3. Communication

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Better than DTD’s

• Good support for namespaces (namespaces came after DTD’s)

• Type Checking (DTD’s use #PCDATA)

See next slide

• XML Syntax (DTD’s are not XML)

• XML tools, like editors, will work with XSDL

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From W3CXML SchemaPart 2DataTypes

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// Validate.java using Xerces// Program written by Kunal Kavirajimport java.io.*;import org.xml.sax.ErrorHandler;import org.xml.sax.SAXException;import org.xml.sax.SAXParseException;import org.xml.sax.XMLReader;import org.xml.sax.InputSource;import org.xml.sax.helpers.XMLReaderFactory;import org.xml.sax.helpers.DefaultHandler;

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public class Validate implements ErrorHandler{ public static boolean valid = true;

public static void main (String argv []) throws SAXException, IOException { if (argv.length != 1) { System.err.println ("Usage: java Validate filename.xml"); System.exit (1); } // get a parser

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XMLReader reader = XMLReaderFactory.createXMLReader( "org.apache.xerces.parsers.SAXParser"); // request validation reader.setFeature("http://xml.org/sax/features/validation", true); reader.setFeature( "http://apache.org/xml/features/validation/schema",true);

reader.setErrorHandler(new Validate());

// associate an InputSource object with the file name

InputSource inputSource = new InputSource(argv[0]);

// go ahead and parse reader.parse(inputSource); System.out.println("Valid Document is " + valid); }

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public void warning(SAXParseException exception) { System.out.println("Validate:Warning" + exception); valid = false; } public void error(SAXParseException exception) { System.out.println("Validate:Error" + exception);

valid = false; } public void fatalError(SAXParseException exception) { System.out.println("Validate:fatalError" + exception);

valid = false; }}

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A Simple Purchase Order

<?xml version="1.0" encoding="UTF-8"?> <!-- po.xml -->

<purchaseOrder orderDate="07.23.2001" xmlns="http://www.cds-r-us.com" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.cds-r-us.com po.xsd">

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<recipient country="USA"> <name>Dennis Scannel</name> <street>175 Perry Lea Side Road</street> <city>Waterbury</city> <state>VT</state> <postalCode>15216</postalCode> </recipient>

<order> <cd artist="Brooks Williams" title="Little Lion" /> <cd artist="David Wilcox" title="What you whispered" /> </order>

</purchaseOrder>

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Purchase Order XSDL

<?xml version="1.0" encoding="utf-8"?> <!-- po.xsd --><xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns="http://www.cds-r-us.com" targetNamespace="http://www.cds-r-us.com" > XSDL Standard

namespaceTarget namespace

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<xs:element name="purchaseOrder">

<xs:complexType> <xs:sequence> <xs:element ref="recipient" /> <xs:element ref="order" /> </xs:sequence> <xs:attribute name="orderDate" type="xs:string" /> </xs:complexType>

</xs:element>

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<xs:element name = "recipient">

<xs:complexType> <xs:sequence> <xs:element ref="name" /> <xs:element ref="street" /> <xs:element ref="city" /> <xs:element ref="state" /> <xs:element ref="postalCode" /> </xs:sequence> <xs:attribute name="country" type="xs:string" /> </xs:complexType>

</xs:element>

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<xs:element name = "name" type="xs:string" /> <xs:element name = "street" type="xs:string" /> <xs:element name = "city" type="xs:string" /> <xs:element name = "state" type="xs:string" /> <xs:element name = "postalCode" type="xs:short" />

<xs:element name = "order"> <xs:complexType> <xs:sequence> <xs:element ref="cd" maxOccurs="unbounded"/> </xs:sequence> </xs:complexType> </xs:element>

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<xs:element name="cd"> <xs:complexType> <xs:attribute name="artist" type="xs:string" /> <xs:attribute name="title" type="xs:string" /> </xs:complexType> </xs:element>

</xs:schema>

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D:..\95-733\examples\XSDL\testing>java Validate po.xml

Valid Document is true

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Comments in XSDL

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns="http://www.cds-r-us.com" targetNamespace="http://www.cds-r-us.com" > <xs:annotation> <xs:documentation>This is a comment.

</xs:documentation> </xs:annotation>::

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Element Definitions

• The Element element is used to define an element• The Element element may be empty <xs:element name = "name" type="xs:string" />

• Or, may contain content

<xs:element name="cd"> <xs:complexType> <xs:attribute name="artist" type="xs:string" /> <xs:attribute name="title" type="xs:string" /> </xs:complexType> </xs:element>

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Element Definitions

• The Element element may be empty and contain no other attributes

<xs:element name = "purchaseOrder"/>

• This purchaseOrder element may contain anything (more elements and text)

• DTD <!ELEMENT purchaseOrder ANY>

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Simple Content

• An element may be defined to hold only a number, word or text

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

• DTD <!ELEMENT city (#PCDATA)>

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Complex Content

• The element may contain child elements or attributes <xs:element name="purchaseOrder">

<xs:complexType> <xs:sequence> <xs:element ref="recipient" /> <xs:element ref="order" /> </xs:sequence> <xs:attribute name="orderDate" type="xs:string" /> </xs:complexType>

</xs:element>

An indicator on how these elements are to be combinedsequence =>predefined order

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Place Holder Element Definitions

<element name=“pageBreak”>

<complexType></complexType>

</element>

• No content is permitted

DTD <!ELEMENT pageBreak EMPTY>

<!ATTLIST pageBreak>

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Namespace Issues

• All element definitions belong to a target document-type namespace

• If a prefix is used for schema elements (as we have done above) then we need to specify that prefix on datatypes to distinguish those defined in XSDL from those the author may define.

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

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Occurrence options

• MinOccurs and MaxOccurs

• Default(if not mentioned) MinOccurs = MaxOccurs = “1”

• MinOccurs = “0” element is optional

• MaxOccurs = “unbounded” infinity

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Choices And a New Example

<?xml version="1.0" encoding="utf-8"?> <!-- addr.xsd --><schema xmlns="http://www.w3.org/2001/XMLSchema" xmlns:co="http://www.myCompany.com" targetNamespace="http://www.myCompany.com" > <annotation> <documentation>This is the company address XSDL document.

</documentation> </annotation>

comment

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<element name="addr">

<complexType> <choice> <element ref="co:downtown" /> <element ref="co:uptown" /> </choice> </complexType>

</element>

Downtown or uptown

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<element name = "downtown"> <complexType> <sequence> <element ref="co:street" /> </sequence> </complexType> </element>

<element name = "uptown"> <complexType> <sequence> <element ref="co:street" /> <element ref="co:apt" /> </sequence> </complexType> </element>

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<element name = "street" type="string" /> <element name = "apt" type="integer" /> </schema>

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<?xml version="1.0" encoding="UTF-8"?> <!– addr.xml --><addr xmlns="http://www.myCompany.com" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.myCompany.com address.xsd"> <downtown> <street>Fifth Avenue</street> </downtown> </addr>

java Validate addr.xml

Valid document is true

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Choices

<element name="addr">

<complexType> <choice minOccurs = "0"> <element ref="co:downtown" /> <element ref="co:uptown" /> </choice> </complexType>

</element>

Choose 1 or none

DTD<!ELEMENT addr (downtown |uptown)? >

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Choices

<element name="addr">

<complexType> <choice maxOccurs = “unbounded"> <element ref="co:downtown" /> <element ref="co:uptown" /> </choice> </complexType>

</element>

Choose 1 and then as manyas you like from the same group

DTD<!ELEMENT addr (downtown |uptown)+ >

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Embedded Groups

<sequence>

<element ref = “doc:title”/>

<choice minOccurs=“0” maxOccurs=“unbounded”>

<element ref=“doc:para”/>

<element ref=“doc:list”/>

</choice>

</sequence>

Required

Choose as many as you like includingnone

DTD (title, (para | list)*)

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Mixed Content

<element name=“para”> <complexType mixed=“true”> <choice minOccurs=“0” maxOccurs=“unbounded”? <element ref=“doc:emph” /> <element ref=“doc:name” /> </choice> </complexType></element>

DTD <!ELEMENT para (#PCDATA | emph | name)*>Text is always optional.

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Attributes

• May never contain element tags or sub-elements

• So, attribute type values will always be simple types

• By default, attributes are optional <xs:attribute name="orderDate" type="xs:string" />

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Attributes

• Can be required, prohibited, optional

<xs:attribute name="orderDate" type="xs:string“ use=“required” />

After removing the attribute ….

D:..\95-733\examples\XSDL\testing>java Validate po.xmlReceived notification of a recoverable error.org.xml.sax.SAXParseException: cvc

complex-type.4: Attribute 'orderDate' must appear on element 'purchaseOrder'.Valid Document is false

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Attribute Types

<xs:attribute name="orderDate" type="xs:date“ use=“required” />

Does not validate

<purchaseOrder orderDate="07.23.2001"

Validates

<purchaseOrder orderDate="1955-12-17"