Internet Technologies1 XML Schema The main source for these slides is “The XML Companion” by Bradley Other resources:

Internet Technologies 1

XML Schema

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


XML Schema

• “XML Schema” is the official name

• XSDL (XML Schema Definition Language) is the language used to create schema definitions

• Can be used to more tightly constrain a document instance

• Supports namespaces

• Permits type derivation


XSDL Alternatives Include

• DTD’s• RELAX • TREX (James Clark - Tree Regular Expressions

for XML)• RELAX NG (RELAX and TREX combined to

Relax Next Generation)• Schematron (“Rule based” rather than “grammar

based” see www.ascc.net/xml/schematron) Based on XSLT and XPath

http://www.ascc.net/xml/schematron


XSDL - A Simple Purchase Order

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

<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">


<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>


Purchase Order XSDL

<?xml version="1.0" encoding="utf-8"?> <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: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>


<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>


<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>


<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>


Three Major Uses – Same as DTD’s

1. Validation

2. Code Generation

3. Communication


Better than DTD’s

• Good support for namespaces

• Type Checking

• XML Syntax

But Harder than DTD’s


Validate.java// Validate.java using Xerces

import 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;import java.io.*;


import javax.xml.parsers.SAXParser;

import javax.xml.parsers.SAXParserFactory;

import org.xml.sax.helpers.DefaultHandler;

import org.xml.sax.SAXException;

import org.xml.sax.InputSource;

import org.xml.sax.SAXParseException;


public class Validate extends DefaultHandler { public static boolean valid = true;

public void error(SAXParseException exception) { System.out.println("Received notification of a recoverable error." + exception); valid = false; }

public void fatalError(SAXParseException exception) { System.out.println("Received notification of a non-recoverable error."+

exception); valid = false; } public void warning(SAXParseException exception) { System.out.println("Received notification of a warning."+ exception); }

16

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


} catch(org.xml.sax.SAXException e) { System.out.println("Error in parsing " + e); valid = false; } catch(java.io.IOException e) { System.out.println("Error in I/O " + e); System.exit(0); } System.out.println("Valid Document is " + valid); }}


XML Document<?xml version="1.0" encoding="utf-8"?><itemList xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance' xsi:noNamespaceSchemaLocation="itemList.xsd"> <item> <name>pen</name> <quantity>5</quantity> </item> <item> <name>eraser</name> <quantity>7</quantity> </item> <item> <name>stapler</name> <quantity>2</quantity> </item></itemList>


XSDL Grammar itemList.xsd

<?xml version="1.0" encoding="utf-8"?><xsd:schema xmlns:xsd='http://www.w3.org/2001/XMLSchema'>

<xsd:element name="itemList"> <xsd:complexType> <xsd:sequence> <xsd:element ref="item" minOccurs="0" maxOccurs="3"/> </xsd:sequence> </xsd:complexType> </xsd:element>


<xsd:element name="item">

<xsd:complexType>

<xsd:sequence>

<xsd:element ref="name"/>

<xsd:element ref="quantity"/>

</xsd:sequence>

</xsd:complexType>

</xsd:element>

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

<xsd:element name="quantity" type="xsd:short"/>

</xsd:schema>


D:..95-733\examples\XSDL\testing>ant run

Buildfile: build.xml

run:

Running Validate.java on itemList-xsd.xml

Valid Document is true


Purchase again (with Prefixes)

<?xml version="1.0" encoding="UTF-8"?> <myns:purchaseOrder orderDate="07.23.2001" xmlns:myns="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">


<myns:recipient country="USA">

<myns:name>Dennis Scannel</myns:name>

<myns:street>175 Perry Lea Side Road</myns:street>

<myns:city>Waterbury</myns:city>

<myns:state>VT</myns:state>

<myns:postalCode>05675A</myns:postalCode>

</myns:recipient>

Note that there is a problem with this document.


<myns:order>

<myns:cd artist="Brooks Williams" title="Little Lion" />

<myns:cd artist="David Wilcox" title="What you whispered" />

</myns:order>

</myns:purchaseOrder>


XSDL Grammar po.xsd

<?xml version="1.0" encoding="utf-8"?> <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: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>


<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>


<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>


<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>


Running Validate

D:..\examples\XSDL\testing>ant runBuildfile: build.xml

run: Running Validate.java on po.xml Received notification of a recoverable

error.org.xml.sax.SAXParseException: cvc-datatype-valid.1.2.1: '05675A' is not a valid 'integer' value.

Received notification of a recoverable

error.org.xml.sax.SAXParseException: cvc-type.3.1.3: The value '05675A' of element 'myns:postalCode' is not valid.

Valid Document is false


Fix the error and run again

D:\..\XSDL\testing>ant run

Buildfile: build.xml

run:

Running Validate.java on po.xml

Valid Document is true


From W3CXML SchemaPart 2DataTypes


Introduce a Namespace Error

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



<myns:purchaseOrder orderDate="07.23.2001"

xmlns:myns="http://www.cds-r-us.edu"

xmlns:xsi=

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

xsi:schemaLocation="http://www.cds-r-us.com

po.xsd"

>


<myns:recipient country="USA"> <myns:name>Dennis Scannel</myns:name> <myns:street> 175 Perry Lea Side Road </myns:street> <myns:city>Waterbury</myns:city> <myns:state>VT</myns:state> <myns:postalCode>05675</myns:postalCode> </myns:recipient>


<myns:order>

<myns:cd artist="Brooks Williams" title="Little Lion" />

<myns:cd artist="David Wilcox" title="What you whispered" />

</myns:order>

</myns:purchaseOrder>


And run validate

run: Running Validate.java on po.xml

Received notification of a recoverable

error.org.xml.sax.SAXParseException: cvc-elt.1:

Cannot find the declaration of element 'myns:purchaseOrder'.

Valid Document is false


Code Generation

• Run JAXB against the .xsd file

• Code generated will present an API allowing us to process that style of

document


itemList.xsd again

<?xml version="1.0" encoding="utf-8"?><xsd:schema xmlns:xsd='http://www.w3.org/2001/XMLSchema'>

<xsd:element name="itemList"> <xsd:complexType> <xsd:sequence> <xsd:element ref="item" minOccurs="0" maxOccurs="3"/> </xsd:sequence> </xsd:complexType> </xsd:element>


<xsd:element name="item"> <xsd:complexType> <xsd:sequence> <xsd:element ref="name"/> <xsd:element ref="quantity"/> </xsd:sequence> </xsd:complexType></xsd:element>

<xsd:element name="name" type="xsd:string"/> <xsd:element name="quantity" type="xsd:short"/></xsd:schema>


Run xjc

D:..XSDL\testing>xjc itemList.xsd

D:\McCarthy\www\95-733\examples\XSDL\testing>java -jar D:\jwsdp-1.1\jaxb-1.0\lib

\jaxb-xjc.jar itemList.xsd

parsing a schema...compiling a schema...generated\impl\ItemImpl.javagenerated\impl\ItemListImpl.javagenerated\impl\ItemListTypeImpl.javagenerated\impl\ItemTypeImpl.javagenerated\impl\NameImpl.java


generated\impl\QuantityImpl.javagenerated\Item.javagenerated\ItemList.javagenerated\ItemListType.javagenerated\ItemType.javagenerated\Name.javagenerated\ObjectFactory.javagenerated\Quantity.javagenerated\bgm.sergenerated\jaxb.properties

Write Java Code That uses NEW the api


The Ant build script used for these examples is also XML

<?xml version="1.0"?>

<project basedir="." default="compile"> <path id="classpath"> <fileset dir="D:/jwsdp-1.1/saaj-1.1.1/lib" includes="*.jar"/> <fileset dir="D:/jwsdp-1.1/jaxb-1.0/lib" includes="*.jar"/> <fileset dir="d:/jwsdp-1.1/common/lib" includes="*.jar"/>


<fileset dir="D:/jwsdp-1.1/jaxm-1.1.1/lib" includes="*.jar"/> <fileset dir="D:/jwsdp-1.1/bin" includes="*.jar" /> <fileset dir="D:/jwsdp-1.1/jaxp-1.2.2/lib" includes="*.jar"/> <fileset dir="D:/jwsdp-1.1/jaxp-1.2.2/lib/endorsed" includes="*.jar"/> <fileset dir="D:/jwsdp-1.1/jwsdp-shared/lib" includes="*.jar"/> <fileset dir="D:/jwsdp-1.1/jaxr-1.0_03/lib" includes="*.jar"/> <fileset dir="D:/jwsdp-1.1/jakarta-ant-1.5.1/lib" includes="*.jar"/> <fileset dir="D:/j2sdk1.4.1_01/lib" includes="*.jar"/>

<pathelement location="."/> </path>


 <target name="compile">  <echo message="Compiling the java source files..."/> <javac srcdir="." destdir="." debug="on"> <classpath refid="classpath" /> </javac> </target>

<target name="run"> <echo message="Running Validate.java on po.xml"/> <java classname="Validate" fork="fasle"> <arg value="po.xml"/> <classpath refid="classpath" /> </java> </target></project>


More details on XML Schemas


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>::


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>


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>


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)>


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


Place Holder Element Definitions

<element name=“pageBreak”>

<complexType></complexType>

</element>

• No content is permitted

DTD <!ELEMENT pageBreak EMPTY>

<!ATTLIST pageBreak>


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" />


Occurrence options

• MinOccurs and MaxOccurs

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

• MinOccurs = “0” element is optional

• MaxOccurs = “unbounded” infinity


Choices And a New Example

<?xml version="1.0" encoding="utf-8"?> <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


<element name="addr">

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

</element>

Downtown or uptown


<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>


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


<?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


Choices


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

</element>

Choose 1 or none

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


Choices


<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)+ >


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)*)


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.


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" />


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


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"

Documents

Internet Technologies1 XML Schema The main source for these slides is “The XML Companion” by Bradley Other resources: