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Module 15: XML

Java Course

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Module Objective

At the end of this module, participants will be able to: Explain the concept and use of XML

Describe the XML tree structure

Identify and adhere to XML syntax rules

Use XML elements and attributes

Describe how XML documents are validated

Use XML schemas for XML document validation

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XML Overview

XML is a markup language for documents containing structuredinformation

XML is used to describe, store, and transport data

XML is pure information wrapped in user-defined tags

XML was created so that richly structured documents could be

used over the internet

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XML Tree Structure

Elements in XML documents form a logical tree structure

XML tree structure illustrates the hierarchy and locality of the

elements in a XML document

XML tree structure can help in showing which elements are the

descendants and ancestors of each element

** Refer to the Classroom.xml sample code

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XML Tree Structure

Sample code:

Victoria

BrookeFemale

30

MichaelRogers

Male

18

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XML Tree Structure

XML Tree of previous code:

CLASSROOM

TEACHER STUDENT

FirstName

LastName

Gender AgeFirstName

LastName

Gender Age

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XML Syntax Rules

All XML documents should begin with an XML declaration. The XMLdeclaration is a processing instruction that identifies the document asbeing XML.

Example:

There are no predefined tags in XML, users have to make their own

tags

XML documents must have exactly one root element, also known asthe document element.

Basic syntax for XML elements:

Syntax : element value

Examples: Jason

My Favorite Book

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XML Syntax Rules

All XML elements must have a corresponding closing tag

Invalid: some value.

Valid : some value placed here

XML tags are case sensitive

Invalid: 7 Tonner Rice

Valid : 7 Tonner Rice

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XML Syntax Rules

XML elements must be properly nested

Invalid:

Some value here

Some value here

Valid :

Some value here

Another value here

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XML Syntax Rules

XML attribute values must be placed within quotes

Invalid: .

Valid : .

Make use of entity references for special characters

< < Less than symbol

> > Greater than symbol

& & Ampersand

' Apostrophe

" Quotation mark

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XML Elements

Elements are used to classify data in an XML document to makethe data understandable.

Elements can have any name desired and are usually

descriptive of the data they hold.

Elements can contain other elements usually to include more

details.

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XML Elements

Elements can contain attributes which also allow additionalinformation.

Elements are defined by its opening and closing tags.

This sentence is found inside the element -myElement-

Opening tag Closing tagInformation stored in the element

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XML Attributes

XML Attributes provide additional information to the element towhich it belongs.

Attributes are information that is often not part of data but is

used in manipulating the data the element holds.

Attributes are commonly used for identification purposes, in

cases as such there is more than one element of the same type.

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XML Attributes

XML Attribute Sample:

Anna

Sanders

Female

John

dela Cruz

Male

** Refer to the classlist.xml sample code

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Validating XML Documents

Validating of XML documents is done through a DTD (DocumentType Definition) or an XSD (XML Schema Definition)

Different types of XML documents in terms of validity

Broken XML documents

WellFormed XML Documents

Valid XML Documents

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Broken XML documents refer to XML Documents where syntaxrules are violated

Well-formed XML documents refer to XML documents that fully

comply to the syntax rules

Valid XML documents refer to XML documents that are well-

formed and comply to a DTD/XSD

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A DTD defines the structure of an XML document with the list oflegal elements and attributes.

XML Schema Definition (XSD) is the XML-based alternative of

DTDs, having the same purpose of DTDs but more powerful and

extensible.

DTD is the older standard. It is most probable that XSD will

replace DTD for validating XML Documents.

** Refer to the person_DTD.xml sample code

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DTD vs XML Schema (XSD)

XSD is extensible to accept future additions

XSD is more powerful than its predecessor

XSD makes use of XML syntax

XSD supports data types

XSD supports namespaces

** Refer to the person_XSD.xml and person.xsd sample code

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XSD is written similarly to XML as XSD makes use of XMLsyntax, hence most of the rules of XML apply to XSD

XML Schema has data types and namespaces, unlike DTDs

XML Schema data types include

String

Date

Numeric

Many others

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The element is the root element for XSD

Syntax :

The element can have attributes, including the

default namespace to be used

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Attributes of elements are defined within the elements where the

attributes belong

Syntax :

Example :

** Refer to the Samples.xml and XSD_Samples.xsd sample code

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Elements in schemas define the structure and properties ofelements in XML documents

Elements in schemas are divided into two types

Simple Elements

Complex Elements

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Simple elements refer to elements containing only text andcannot contain other elements or attributes

In XML : Michael Angelo

Syntax :

Example :

Simple elements can have default or fixed values

Syntax :

Examples :

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Complex elements refer to elements that can have attributesand can also be one of the following:

Elements that contain only text (with attributes)

Elements that are empty

Elements containing other elements

Elements that contain both text and other elements

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Elements that contain only text but have attributes areconsidered complex elements

XML : Spike

XSD :

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Elements that serve only to contain other elements areconsidered complex elements

XML :

red

4

XSD :

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Elements that contain both text and other elements areconsidered complex elements

XML : Dear Mrs.

Erika Daniels. Your child,

Michael, has done something at school.

Please come to the prinicipals office anytime tomorrow,

2008-08-21.

XSD :

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Indicators control how elements can be used Order Indicators

All

Choice

Sequence

Occurrence Indicators maxOccurs

minOccurs

Group Indicators

Group name

attributeGroup name

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The element allows other elements not specified in theschema, which makes it extensible

Similarly, the element allows other attributes not

specified in the schema within the designated element

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Restrictions set the acceptable values for elements andattributes in XML documents

Some restrictions on values that can be applied are

Set of values

Series of values

Whitespace character

Length Restrictions

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References

W3SchoolsXML Tutorial

http://www.w3schools.com/xml/default.asp

Java SE 6 Documentation, Tutorials, Training, Demos, and

Samples http://java.sun.com/javase/6/docs/index.html

Tizag - XML Tutorial

http://www.tizag.com/xmlTutorial/index.php
http://www.w3schools.com/xml/default.asphttp://java.sun.com/javase/6/docs/index.htmlhttp://www.tizag.com/xmlTutorial/index.phphttp://www.tizag.com/xmlTutorial/index.phphttp://java.sun.com/javase/6/docs/index.htmlhttp://www.w3schools.com/xml/default.asp

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