XML_Session08

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Extensible Markup Language

Session 8

In this session, you will learn to:

Identify the XML Document Object Model

Validate an XML document against an XML schema using the

Document Object Model

Apply a Style Sheet to an XML document

Objectives


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Session 8

DOM defines the logical structure of documents.

DOM provides an Application Programming Interface (API)

for dynamically accessing and manipulating a document.

The DOM objects have associated methods and properties

to access and manipulate a document.A DOM-enabled parser is required to use the features

provided by DOM.

A DOM-enabled parser:

Parses an XML document to ascertain its validity.

Creates an in-memory representation of the XML document asa tree structure.

Identifying the XML Document Object Model


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Following are the key DOM objects:

Document

Element

Node

NodeListAttr

Text

CDataSection

ParseError

XML DOM Objects and Methods


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Document

Element

Node

NodeListAttr

Text

CDataSection

ParseError

XML DOM Objects and Methods (Contd.)

It is the top-level object that implements all the

basic DOM methods.

It also has methods that support XSLT.

It has methods that can be used to navigate,

query, and modify the content and structure of

an XML document.

Some of the methods provided by this objectare createElement(), createAttribute(),

createComment(), and createTextNode().

Some of the properties provided by this object that

help in manipulating the information contained inthe object are async, childNodes, firstChild,

documentElement, xml, and readyState.


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Document

Element

Node

NodeListAttr

Text

CDataSection

ParseError

It represents all the element nodes in an XML

document.

The attributes associated with the elements are

considered to be the properties of the elementsrather than their child elements.

Some of the methods of this object arealso inherited from the Nodeobject.

Some of the methods provided by this object aregetAttribute(),

getElementsByTagName(),

normalize(),

andremoveAttributeNS().



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Document

Element

Node

NodeListAttr

Text

CDataSection

ParseError

It represents a single node in the XML document

tree structure.

It provides methods to work with child elements.

Some of the methods of this object are

appendChild(newChild),

insertBefore(newNode,refNode),

and removeChild(nodeName).





Session 8


Document

Element

Node

NodeListAttr

Text

CDataSection

ParseError

It provides a list of nodes present in an XMLdocument for manipulation.

This object enables you to iterate through a

collection of nodes.

Some of the method of this object are item()

andnextNode().





Session 8


Document

Element

Node

NodeListAttr

Text

CDataSection

ParseError

It represents an attribute of the Elementobject.

It is also a Node and inherits various attributesand methods of Nodeobject.

An attribute is not considered by the DOM to be

a child node of an element, but rather a property.



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Document

Element

Node

NodeListAttr

Text

CDataSection

ParseError

It represents the text inside an XML element inthe node tree.

The splitText()method is associated withthis object.



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Document

Element

Node

NodeListAttr

Text

CDataSection

ParseError

It represents the CDATA sections in the nodetree.

This node is used to escape the parts of textthat normally would be recognized as markup.



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Document

Element

Node

NodeListAttr

Text

CDataSection

ParseError It returns information about the most recentparse error.

It provides properties to retrieve information,such as the error code, the error text, and theline that caused the error.

Some of the properties of this object areerrorCode, reason, line, and srcText.



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The DOM objects can be used within scripting languages

such as JavaScript and VBScript.

Using DOM objects in scripts allow dynamically applying a

style sheet to an XML document.

The code for using DOM objects for accessing an XMLdocument needs to be used as an HTML page.

XML DOM Objects in Scripts


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DOM:

Used to validate XML documents against XML schemas.

Ensures proper grammar and proper formation of the XML

document.

DOMDocumentobject:

Main object in a DOM.

Represents the top node in every document tree.

Used to load an XML document, parse it, and validate it.

XMLSchemaCacheobject:

Loads the schema document associated with the XMLdocument.

Validating an XML Document Against an XML Schema Using DOM


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Used to hold a collection of schema documents that

specifies the rules to which XML documents must conform.

Following table describes some methods provided by theXMLSchemaCacheobject.

Accessing an XML Document by Using the XMLSchemaCache Object

Method Description

add(namespaceURI,

variable)

This method adds a new schema to the collection and alsoassociates the specified namespaceURIwith the schema.

addCollection(XMLSch

emaCollection

object)

This method adds schemas from other schema collections.

It also ensures that the namespaceURIs of the different

schemas do not clash.

get(namespaceURI) This method returns a node that contains the

element.

namespaceURI(index

number)

This method returns the namespace that is associated with

the schema at the specified index number.

remove(namespaceURI) This method removes a schema from a collection.


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To write a script that validates an XML document against

the schema, you need to follow the given tasks:

1. Create the user interface to accept the name of the XML

document and the XML schema.

2. Write the code to load the XML document.

3. Write the code to add the XML schema in the

XMLSchemaCache object.

4. Write the code to validate the XML document against the

schema.

Validating an XML Document Against the Schema


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Problem Statement:

The head office of CyberShoppe receives data in the form of

XML documents from its branches. In order to ensure the

consistency of data sent by the branches, the head office

maintains the definitions for the structures of documents in

schemas. After receiving data from the branches, the headoffice needs to verify that the data conforms to the schema of

the respective document. For this, the head office needs to

write a script that validates the data stored in an XML

document against a schema. You will initially do the testing forthe product.xmlfile.

Demo: Validating an XML Document


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Is a DOM object that is used to access an XSLT style sheet.

Used to hold a cached style sheet that can then be

dynamically associated with an XML document.

Before a style sheet document can be applied to an XML

document, it is converted into a tree structure by the parser.XSLT tree structure is loaded into the memory of the

computer and used to process the XML document.

The XSLTemplate Object


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Used to apply a style sheet to an XML document and then

process that document.

Applies the given XSLT document to a specific XML

document.

Transforms an XML document by using the XSLT stylesheet.

JavaScript code to create an XSLProcessorobject is as

follows:

var xslprocobj= xsltobj.createProcessor();

The XSLProcessor Object (Contd.)


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Problem Statement:

CyberShoppe sells its products through an e-commerce Web

site. Product details, such as product name, description, price,

and quantity, need to be displayed.

A customer can choose to view the product details either as a

table or as a bulleted list.

Demo: Applying a Style Sheet to an XML Document During Run Time


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Problem Statement:

The following XML document, customer.xmlcontains

customer details:

Harold Johnson56, Regent Road

London

UK

444-425-2355

Create a Web page that accepts the name of the XML file in atext box. When you click the Submit hyperlink, a JavaScript

code should load the XML document and extract theCUSTOMERNAMEelement. The address and phone number

should be changed to 94, McFarlane Avenue and 412-233-

2344, respectively, by using XML DOM objects.

Exercises


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Which of the following methods of the DOMDocumentobject

will you use to create an element node that has a

namespace prefix associated with it?

a. createElement()

b. createTextNode()

c. createNode()

d. createAttribute()

Practice Questions

Answer:

c. createNode()


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You have written a script to load an XML document and

validate it against a schema. Which of the followingproperties of the DOMDocumentobject will you use to

ensure that the script waits till the XML document is loaded

before executing the rest of the code?

a. async

b. readyState

c. documentElement

d. xml

Practice Questions

Answer:

a. async


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Which of the following properties of the IXMLDOMNode

object will you use to return the text associated with a node?

a. nodeName

b. xml

c. nodeType

d. nodeValue

Answer:

d. nodeValue

Practice Questions


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Which of the following properties of theIXMLDOMParseErrorobject will you use to retrieve the

string containing the line that caused an error while parsing

an XML document?

a. srcText

b. linePos

c. reason

d. line

Answer:

a. srcText

Practice Questions


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Which one of the following is an object that represents the

complete XML document map?

a. IXMLDOMNode

b. DOMDocument

c. IXMLDOMNodeList

d. IXMLDOMParseError

Answer:

b. DOMDocument

Practice Questions


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Session 8

In this session, you learned that:

The XMLSchemaCacheobject is used to associate an XML

document with an XSD document.

The XMLSchemaCacheobject is used to hold a collection of

schema documents that specifies the rules to which XML

documents must conform.The XSLTemplateobject is used to access an XSLT style

sheet.

The XSLProcessorobject is used to apply style sheets on a

given XML document.

The XSLProcessorobject is created using thecreateProcessor()method.

The XSLProcessorobject is associated with an XML

document by using the input property of the XSLProcessor

object.

Summary


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The XSLProcessorobject provides the transform()

method to transform an XML document according to the

information provided in an XSLT style sheet.

DOM is an application-programming interface that allows an

application to access the contents of an XML document.

DOM objects allow you to access and manipulate XMLdocuments.

The MSXML parser loads an XML document and creates a

tree structure that represents the various components of the

XML document.

The basic building block of the tree structure is a node. A nodeis a container that holds information about the elements,

attributes, and content stored in an XML document.

Summary (Contd.)


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The Nodeobject represents a node in the XML document

structure. This object provides methods to work with the child

elements.

The NodeListobject allows you to iterate through a collection

of nodes.

The Attrobject represents an attribute of an Elementobject.The Textobject represents the text inside an XML element in

the node tree.

The ParseErrorobject returns information about the most

recent parse error.

Summary (Contd.)

Documents

XML_Session08