JSON and XML

© People Strategists www.peoplestrategists.com Slide 1 of 82
Working with JSON
and XML

In this session, you will learn to:
Handle AJAX requests using jQuery
Identify JSON
Work with JSON
Identify XML
Identify DTD
Validate XML using DTD
Implement PCDATA
Identify and work with namespaces
Objectives

Handling AJAX Requests using jQuery
Can I use AJAX with jQuery
so that I have to write less
code and update parts of a
Web page?

jQuery library provides you with various methods, known as jQuery AJAX
methods, that allow you to make a call to the AJAX code.
These methods allow you to perform various tasks.
Few of these tasks are given in the following list:
Load data from an external file directly into a selected HTML element of you Web
page.
Request data in a specific format, such as text, XML, or JSON.
The following list depicts the jQuery AJAX methods:
load()
get()
post()
ajax()
Handling AJAX Requests using jQuery (Contd.)

The load() method is used to load or fetch data from a Web server into a
selected HTML element.
The syntax to use the load() method is as follows:
$(selector).load(URL[,data][,complete])
In the preceding syntax:
URL: Is used to specify the URL from where you want to load the data. The URL
can be used to refer to any resource, such as text file or html file.
data: Is used to pass an object of a key/value pair along with the request to the
server.
complete: Is used to refer to a callback method that will be executed after the
successful execution of load() method.
The following code snippet depicts how to load content of the file “Test.txt”
into a specific <div> element of an HTML Web page:
$("#div1").load("Test.txt");

The following code snippet depicts how to load content of an element with ID
“para1” inside the file “Test.txt” into a specific <div> element of an HTML Web
page:
$("#div1").load("Test.txt #para1");
There might be situation when retrieving data from a URL resource fails.
In such a scenario, you can use the following code snippet to display the status
of the retrieval:
$("button").click(function(){
$("#div1").load(“Test.txt", function(responseTxt,
statusTxt, xhr){
if(statusTxt == "success")
alert("External content loaded
successfully!");
if(statusTxt == "error")
alert("Error: " + xhr.status + ": " +
xhr.statusText);
});
});

The following code snippet load data from an external source and displays the
AJAX call status:
<html>
<head>
<script
src="https://ajax.googleapis.
com/ajax/libs/jquery/1.11.3/jq
uery.min.js"></script>
<script>
$(document).ready(function(){
$("#div1").load("Test.txt",
function(responseTxt,
statusTxt, xhr){
if(statusTxt == "success")
alert("External Data Retrieved
successfully!");
if(statusTxt == "error")
alert("Error: " +
xhr.status + ": " +
xhr.statusText);});});});
</script>
</head>
<body>
<div id="div1"><h2>The
external content will be
displayed here.</h2></div>
<button>Load External
Data</button>
</body>
</html>
LoadAJAX.htm

The following code depicts the data inside the “Test.txt” file:
The following figures depict the outputs of the code snippet on the preceding
slide.
<h2>Using load() AJAX method in jQuery</h2>
<p id="p1">This is data from external resource.</p>
Test.txt

The get()method is used to load data from a Web server using the HTTP GET
request.
The syntax to use the get()method is as follows:
$(selector).get(url[,data][, callback],[datatype])
server.
callback: Is used to refer to a callback method that will be executed after the
datatype: Is used to specify the type of data, such as text, JSON, or XML, that is
expected in return from the server.

The following code snippet depicts how to use get() method to retrieve data
from a web server:
$.get(“Test.aspx", function(data, status){
alert("Data: " + data + "n Status: " + status);
});
});

The post()method is:
Similar to the get()method.
Used to load data from a Web server using the HTTP POST request.
Used when the requested is large in amount.
Used to send the data in an encrypted format.
The syntax to use the post()method is as follows:
$(selector).post(url[,data][, callback],[datatype])
server.
callback: Is used to refer to a callback method that will be executed after the
datatype: Is used to specify the type of data, such as text, JSON, or XML,
that is expected in return from the server.

The following code snippet depicts how to use post()method to retrieve
data from a web server:
$.post(“LoginPage.aspx",
{
Uname: “User1",
Pass: “password123"
},
function(data, status){
alert("Data: " + data + "nStatus: " + status);
});
});

The ajax()jQuery method:
Can be used to call the AJAX requests.
Helps in partial-page updates.
The syntax to use the ajax()method is as follows:
$(selector).ajax(options)
options: Is an optional parameter that helps in configuring the AJAX calls by
using key/value pairs.

The following table describes few of the important keys that can be specified
as an option.
Option Description
async A boolean value that indicates whether to execute the request asynchronously.
complete A callback function that executes whenever the request finishes.
datatype A string defining the type of data, such as XML, HTML, JSON, or script, that is
expected back from the server.
success A callback function that is executed if the request succeeds.
type A string defining the HTTP method to be used for the request (GET or POST).
URL A required option that refers to the string containing the URL to which the request
is sent.

The following code snippet depicts how to use ajax()method to retrieve
data from a web server:
<html>
<head>
<title>The jQuery
Example</title>
<script
src="https://ajax.googleapis.com
/ajax/libs/jquery/1.11.3/jquery.
min.js"></script>
<script type="text/javascript"
language="javascript">
$(document).ready(function() {
$("#btn").click(function(event){
$.ajax( {
url:'Test.txt',
type:'GET',
success:function(data) {
$('#ContentArea').html(data);}
});});});
</script>
</head>
<body>
<p>Click here to load
Test.txt file:</p>
<div id="ContentArea"
style="background-color:
cyan;">
Content Area
</div>
<input type="button"
id="btn" value="Load Data"/>
</body>
</html>
AJAXMethod.htm

The following code depicts the data inside the “Test.txt” file:
The following figures depict the outputs of the code snippet on the preceding
slide.
<h2>Using ajax() AJAX method in jQuery</h2>
<p id="p1">This is data from external resource.</p>
Test.txt

Identifying JSON
Is there any other easier
and faster way to transfer
data other than XML?

JavaScript Object Notation (JSON):
Is an open standard light-weight format that is used to store and exchange data.
Is an easier and faster alternative to XML.
Is language independent format that uses human readable text to transmit data
objects.
Consists of objects of name/value pairs.
Files have the extension .json.
Syntactically, JSON is similar to the code for creating JavaScript objects.
Due to this similarity, standard JavaScript methods can be used to convert
JSON data into JavaScript objects.
The following code snippet depicts an example of JSON:
{"fName":"Ronald", "lName":"Smith", "Contact":"121 12345"}
Identifying JSON (Contd.)

The following list depicts the similarities between JSON syntax and code for
JavaScript object:
JSON uses name/value pairs to store data.
Commas are used to separate multiple data values.
Objects are enclosed within curly braces.
Square brackets are used to store arrays.
The following code depicts how to create name/value pairs:
"Name":"Value"
JSON keys must be enclosed within double quotes.
JSON Syntax

The following code snippet depicts storing different types of values using JSON
name/value pairs:
A JSON object can include the following types of values:
A numeric value
A string
A boolean value
An array
An object
A null value
JSON Values
"fName": "Jane" Storing string value
"lName": "Doe" Storing string value
"isAlive": true Storing boolean value
"age": 23 Storing integer value
"children": [] Storing an array
"spouse": null Storing null

JSON objects are enclosed within curly braces.
Similar to JavaScript objects, JSON objects can be used to store multiple
name/value pairs.
The following code snippet depicts storing data in a JSON object:
JSON Objects
{
"fName": "Jane",
"lName": "Doe",
"isAlive": true,
"age": 23,
"children": [],
"spouse": null
}

JSON arrays can be created by using square brackets, as shown in the following
code snippet:
Since JSON uses the same syntax as that of JavaScript objects, JSON arrays can
be accessed in the same way as in JavaScript.
JSON Arrays
{
"fName": "Jane",
"lName": "Doe",
"isAlive": true,
"age": 23,
"ContactNumber":[
{"type":"Mobile", "Number":"+9198765" }
{"type":"Office", "Number":"+9124456" }
]
"children": [],
"spouse": null
}

The following figure depicts similarities and dissimilarities between JSON and
XML:
JSON vs. XML
Similarities Dissimilarities
Both are human-readable, that is,
self-describing.
Both represent hierarchical
structure, that is, values within
values.
Both can be accessed and parsed
by almost every programming
language.
Both can be accessed and fetched
with an XMLHttpRequest object.
XML needs an XML parser,
whereas, a standard JavaScript
method can be used to parse
JSON.
There is no need of end tag in
JSON.
JSON is much shorter as
compared to XML.
It is easy to read and write JSON.
JSON can be used with arrays.

The following code snippet depicts a JSON example that defines a student
object containing an array of records of two students:
The following code snippet depicts an XML example that defines a student
object containing records of two students:
JSON vs XML (Contd.)
{"students":[
{"fName":"Jenny", "lName":"Watson"},
{"fName":"Dean", "lName":"Smith"}
]}
<students>
<student>
<fName>Jenny</fName>
<lName>Watson</lName>
</student>
<student>
<fName>Dean</fName>
<lName>Smith</lName>
</student>
</students>

A most common usage of JSON objects is to read/fetch data from a Web server
in JSON format, and display it on an HTML Web page.
To read data from a JSON object, you can use the JSON.parse()method
provided by JavaScript.
The syntax for JSON.parse() method is as follows:
var obj = JSON.parse(text);
The following code snippet depicts how to use the JSON.parse()method:
Reading Data From JSON
var jsonData =
'{"fName": "Jane", "lName": "Doe", "isAlive": true,
"age": 23}';
var contact = JSON.parse(jsonData);
document.write(contact.lName+", "+contact.fName);

The following code snippet depicts how to read data using JSON.parse()
method:
Reading Data From JSON (Contd.)
<html>
<body>
<h2>Reading JSON Object using JavaScript</h2>
<p id="pData"></p>
<script>
var jsonData =
'{"fName": "Jane", "lName": "Doe", "isAlive": true, "age":
23}';
var contact = JSON.parse(jsonData);
document.getElementById("pData").
innerHTML =
contact.fName + "<br>" +
contact.lName + "<br>" +
contact.age;
</script>
</body>
</html>

JavaScript provides you the JSON.stringify()method that allows you to
convert JavaScript value to a JSON string.
The syntax for JSON.stringify()method is as follows:
var obj = JSON.stringify(value);
The following code snippet depicts how to convert JavaScript value into JSON
text/string using the JSON.stringify()method:
Creating JSON Text From JavaScript
var obj = new Object();
obj.fname = "John";
obj.lname = "Doe";
jsonText = JSON.stringify(obj);
document.write(jsonText);
//Output will be {"fname":"John","lname":"Doe"}

The following code snippet depicts how to convert JavaScript value into JSON
text/string using the JSON.stringify()method:
Reading Data From JSON (Contd.)
<html>
<body>
<h2>Reading JSON Object using JavaScript</h2>
<p id="pData"></p>
<script>
var Students = new Array();
Students[0] = "John Doe";
Students[1] = "Jane Smith";
var jsonText = JSON.stringify(Students);
document.getElementById("pData").
innerHTML = jsonText; </script>
</body>
</html>

Introduction to XML
Consider a scenario
where you need to
exchange data in
different formats.

Introduction to XML (Contd.)

XML:
Stands for Extensive Markup Language.
As its name suggests, it has following basic characteristics:
 Extensible: It is an extensible language that allows programmers to define their own
tags.
 Markup: It is based on markup tags similar to HTML tags.
 Language: It is similar language to HTML. In addition, offers more flexibility and power
to programmers to describe data.

XML:
Is a self-describing language.
Is recommended by W3C for information exchange over the Internet.
Tags are not pre-defined, to use it, you need to define your own tags.
Is a software and hardware independent language.
Enables programmers to store data in a well-formed structure.
Transfers data between various heterogeneous systems over the network.

C# Application
Java Application
SQL Server Database DB2 Database Oracle Database
Web Services
XML
The following figure depicts how data is exchanged to heterogeneous
environment using XML:

Some common advantages of XML are:
Extensible: It is an extensible language that allows programmers to define their
own tags based on the specific requirements.
Data Interchange: It allows programmers to store data in textual format that can
be used as a standard to interchange data.
Smart Searches: It allows programmers to specify whether they want to search
information based on text or tags, and returns the information that matches the
search criteria.
Fast Updates: Use of XML allows offers fast update of information, as only text
needs to be updated.
CSS and XSL Support: XML supports CSS (Cascading Style Sheet) and (Extensible
Style Sheet) languages that can be used to apply required formatting of an XML
document.
Data Transformation: As per requirements, data can be stored in the form of text,
object, or data in a database. The stored data can be extracted by the client
application in the required format.
Advantages of XML

Separate Content/Presentation: XML defines the meaning of data. The
representation of data can be controlled with the help of CSS and XSL languages.
New Languages: XML can be also used to develop new languages. Some languages
that are derived from XML are:
 XHTML
 WSDL
 SMIL
 RSS
Advantages of XML (Contd.)

Creating Well-Formed XML
How can I create my own
XML document?

XML is used to represent data in a well-formed structure.
It provides you various components that you can use to define the structure of
data.
Creating Well-formed XML (Contd.)
ComponentsofXML
Processing Instruction
Tags
Elements
Content
Attributes
Entities
Comments

Processing Instruction (PI):
Specifies how an XML document is processed.
Is included in an XML document by adding the following line of code at the
starting of the file:
Creating Well-Formed XML (Contd.)
<?xml version="1.0" encoding="UTF-8"?>

Tags:
Specify the name of information presented in an XML document.
Must have opening (<>) and closing (</>) brackets that encloses the name of the
tag.
For example:
<first_name>Allen</first_name>
Tags Tags

Elements:
Are the basic building blocks of XML.
Are represented with the help of tags.
Are used to describe data in an XML document.
Can contains one or more elements.
That contain child elements are known as root element.
For example:
<name>
<last_name>Thomas</last_name>
</name>
Root Element
Child Elements

Content:
Refers the information represented by the elements.
Can be categories into following types:
 Character Content
 Element Content
 Mixed Content
For example:
Creating Well-Formed XML (Contd.)
<name>
The name of person is:
</name>
Character
Content
Element Content
Element Content

Attributes:
Allow programmers to provide additional information about the elements.
Are created in the form of name-value pair.
For example:
<emp emp_id="001">
</emp>

Entity:
Allows the insertion of special characters in XML documents.
For example, the < entity inserts a literal < character into a document.
Supports the following in-build entities:
 <
 >
 &quote;
 &

Comments:
Are used to explain the purpose of XML markup.
Are not evaluated by the XML parser.
Are enclosed within <!..- -> symbols.
For example:
<emp emp_id="001">
</emp>

<?xml version="1.0" encoding="utf-8"?>
<employee emp_id="001">

<name>
The name of employee is:
<firstname>John</firstname>
<lastname>Smith</lastname>
</name>
</employee>
The following code depicts the output well-formed XML document:

DTD
Stands for Document Type Definition.
Is used to define the structure and the valid elements and attributes of an XML
document.
Verifies the data in an XML document.
Can be used to verify data of a local file or data received over the network.
Can be declared as of the following two types:
Specifying Rules Using DTD
DTD
Declaration
Internal External

Internal DTD Declaration:
Is declared inside the XML file.
Must be enclosed inside the <!DOCTYPE> definition, as:
In the preceding code snippet:
 !DOCTYPE name: Specifies that the name is the root element of this document.
 <!ELEMENT name(first_name, last_name): Specifies that the name element
must has two elements, first_name and last_name.
 <!ELEMENT first_name: Specifies the first_name element to be of type
PCDATA.
 <!ELEMENT last_name: Specifies the last_name element to be of type
PCDATA.
Specifying Rules Using DTD (Contd.)
<?xml version="1.0"?>
<!DOCTYPE name [
<!ELEMENT name (first_name, last_name)>
<!ELEMENT first_name (#PCDATA)>
<!ELEMENT last_name (#PCDATA)>
]>

External DTD Declaration:
Is declared outside the XML file.
References of the DTD file must be included in the <!DOCTYPE> definition.
For example:
Specifying Rules Using DTD (Contd.)
<?xml version="1.0"?>
<!DOCTYPE name SYSTEM
"name.dtd">
<name>
<first_name>John</first_name
>
<first_name>Thomas</first_na
me>
</name>
<!ELEMENT name
(first_name, last_name)>
<!ELEMENT first_name
(#PCDATA)>
<!ELEMENT last_name
(#PCDATA)>
name.dtd name.xml

An XML that has correct syntax is known as a well-formed document.
An XML document that is validated against a DTD is a well-formed as well as a
valid document.
A valid XML document refers to a well-formed (has correct syntax) and follows
all rules specified in a DTD.
A DTD is used to define the structure of an XML document in the form of a list
of valid elements, as shown in the following code snippet:
Creating Valid XML Using DTD
<!DOCTYPE name
[
<!ELEMENT name (first_name, last_name)>
<!ELEMENT first_name(#PCDATA)>
<!ELEMENT last_name(#PCDATA)>
]>
name.dtd

The DTD definition given in the previous slide is interpreted as follows:
!DOCTYPE name defines that the root element of the document is note
!ELEMENT name defines that the note element must contain two elements:
first_name and last_name
!ELEMENT first_name defines the first_name element is to be of type
PCDATA
!ELEMENT last_name defines the last_name element to be of type
PCDATA
When the specified DTD document is referenced in an XML document, the
document must follow the rules specified in DTD.
Creating Valid XML Using DTD (Contd.)

You can declare elements by using the ELEMENT declaration. In a DTD, you can
declare the following type of elements:
Empty Elements
Elements with Parsed Character Data
Elements with any Contents
Elements with Children
Declaring Only One Occurrence of an Element
Declaring Minimum One Occurrence of an Element
Declaring Zero or More Occurrences of an Element
Declaring Zero or One Occurrences of an Element
Declaring either/or Content
Declaring Mixed Content
The general syntax of declaring a DTD is shown in the following syntax:
Element Declaration
<!ELEMENT element-name category>

Empty Elements:
Are declared with the Empty keyword.
Syntax:
Example:
The syntax of declaring an element is shown in the following code snippet:
Element Declaration (Contd.)
<!ELEMENT element-name category>
<!ELEMENT p EMPTY>

Elements with Parsed Character Data:
Are declared with #PCDATA inside parentheses.
Syntax:
Example:
<!ELEMENT element-name (#PCDATA)>
<!ELEMENT from (#PCDATA)>

Elements with any Contents:
Are declared with the ANY keyword inside parentheses.
Can contain any kind of allowed XML data.
Syntax:
Example:
<!ELEMENT element-name ANY>
<!ELEMENT note ANY>

Elements with Children:
Are declared with name of one or more children inside the parentheses.
Syntax:
Example:
<!ELEMENT element-name(child1, child2,...)>
<!ELEMENT name(first_name, middle_name, last_name)>

Only One Occurrence of an Element
Is used to declare an element such that the child element must occur once and
only once inside the root element.
Example:
<!ELEMENT element-name (child-name)>
<!ELEMENT name(full_name)>

Minimum One Occurrence of an Element:
Is declared with the plus (+) sign.
Syntax:
Example:
<!ELEMENT element-name (child-name+)>
<!ELEMENT contacts (mobile_number+)>

Zero or More Occurrences of an Element:
Is declared with the asterisk (*) symbol.
Syntax:
Example:
<!ELEMENT element-name (child-name*)>
<!ELEMENT note (email_id*)>

Zero or One Occurrences of an Element:
Is declared with the question mark (?) symbol.
Syntax:
Example:
<!ELEMENT element-name (child-name?)>
<!ELEMENT note (email_id?)>

Either/or Content:
Is declared with the pipe (|) symbol.
Syntax:
Example:
<!ELEMENT note (child1|child2)>
<!ELEMENT note (email_id|mobie_number)>

PCDATA refers to the parsed character data.
It is generally rep[resents the character data in the form of text that is found
between the start tag and the end tag of an XML element.
The text of PCDATA is parsed by a parser.
The XML parser examines the PCDATD text to find entities and markup.
Tags found inside the PCDATA text are treated as markup.
Entities found inside the PCDATA are explained to their specific meaning.
The PCDATD should not include &, <, or > characters. You can include these
characters by using the &, <, and > entities.
Use of PCDATA

You can declare attributes with an ATTLIST declaration.
To declare an attribute in DTD, you can use the following code snippet:
Example:
XML Example:
Attribute Declaration in DTD
<!ATTLIST element-name attribute-name attribute-type
attribute-value>
<!ATTLIST employee id CDATA "011">
<employee radius="011" />

While declaring an attribute in DTD, you can use one of the following values
for attribute-type.
Attribute Types
Type Description
CDATA Specifies that the value is character type.
(en1|en2|..) Specifies that the value must be from an enumerated list.
ID Specifies that the value is unique ID.
IDREF Specifies that the value is the ID of another element.
NMTOKEN Specifies that the value is a valid XML name.
NMTOKENS Specifies that the value is a list of valid XML names.
ENTITY Specifies that the value is an entity.
ENTITIES Specifies that the value is an list entities.
NOTATION Specifies that the value is the name of notation
xml: Specifies that the value is the pre-defined XML value.

In DTD, you can declare attribute values with one of the following types:
Fixed, Default and Optional Types
Default REQUIRED
IMPLIED FIXED

Attribute with Default Value:
In DTD, you can declare an attribute with a default value.
If no value is specified for that attribute, the default value is automatically
assigned.
For example:
In the preceding example, if the value of radius attribute is not provided, the
default value, 0, is assigned.
Fixed, Default, and Optional Types (Contd.)
DTD Declaration:
<!ELEMENT circle EMPTY>
<!ATTLIST circle radius CDATA "0">
XML Markup:
<circle radius="10" />

Attribute with #REQUIRED Keyword:
Is used to force the users to provide the value of the attribute.
For example:
Fixed, Default and Optional Types (Contd.)
DTD Declaration:
<!ATTLIST employee contact CDATA #REQUIRED>
Valid XML Markup:
<employee contact="897897676" />
Invalid XML Markup:
<employee />

Attribute with #IMPLIED Keyword:
Is used to when the attribute is optional and does not have an default value.
For example:
In the preceding code snippet, the contact attribute is optional. The user is not
forced to provide the value of the attribute.
DTD Declaration:
<!ATTLIST employee contact CDATA #IMPLIED>
Valid XML Markup:
<employee contact="897897676" />
Valid XML Markup:
<employee />

Attribute with #FIXED Keyword:
Is used to provide a fixed value to the attribute. The value cannot be changed in
the XML document.
For example:
DTD Declaration:
<!ATTLIST number base CDATA #FIXED "decimal" >
Valid XML Markup:
<number base="decimal" />
Invalid XML Markup:
<number base="binary" />

Namespaces
What is a namespace in
XML?

A namespace can be considered as a virtual space that is identified by a
Uniform Resource Identifier (URI).
It is represented in the form of a string that uniquely identifies the elements
and attributes from different schemas, as shown in the following figure.
Namespaces (Contd.)
schema1.xsd
www.myschema.com/schema1
Namespace URI

Namespace URI:
Is not a Web URI.
does not locate a resource on the Internet.
Does not actually point to a resource on the Internet.
Is a unique identifier that resolves conflicts between elements having same name.
Declaring a Namespace:
You can declare an namespace with the help of xmlns keyword, as shown in the
following code snippet:
In the preceding code snippet, URI is the namespace name, and prefix is the
alias of the namespace.
Namespaces (Contd.)
xmlns:prefix="URI"

In XML, you can declare namespaces by using the following two methods.
Namespaces (Contd.)
Declaring a
Namespace
Default Explicit

Default Declaration:
Allows programmers to declare a default namespace for a document.
Does not require a prefix name.
For Example:
Namespaces (Contd.)
<schema xmlns="http://myxmlschema.com/XMLSchema">
...
...
</schema>

Explicit Declaration:
Requires the use of a prefix with the xmlns keyword.
Is used to define an XML schema that uses elements and attributes defined in one
or more namespaces.
For Example:
In the preceding code snippet, xsd is the prefix for the namespace URI.
Namespaces (Contd.)
<xsd:schema
xmlns:xsd="http://myxmlschema.com/XMLSchema">
...
...
</schema>

In XML, namespaces are used to avoid conflict between the elements having
same name.
To define the structure of an elements XML schema (XSD) files are used.
An XML document can have the references of multiple schema files.
In this situation, if an element is defined in two or more schemas with the
same name, the conflict of definition may occur.
Why Namespaces?

For example:
Schema 1 contains the Name element that defines the name of a product.
Schema 2 contains the Name element that defines the name of a customer.
Schema 1 and Schema 2 are used in Schema 3.
Now the conflict between the definition of Name element may occur because it is
defined in Schema 1 and Schema 2 both.
To avoid such situations, namespaces are used.
Why Namespaces (Contd.)?
Schema 1 Schema 2Schema 3
Name Name

What are the Advantages of Using XML Schema Over DTD
XML schemas follow a universal standard that made data
communication over the Internet safe.
For example, a date like: "01-07-2015" can be interpreted as 7
January in some countries, whereas in other countries as 1 July.
However, an XML element accepts date in the fixed format "YYYY-
MM-DD" to ensure its correct interpretation.
XML schemas support data types that allow programmers to:
Specify the acceptable content in the document
Ensure the validity of data
Work with databases
Apply restrictions on data
Specify data formats
Convert data from one data type to another

What are the Advantages of Using XML Schema Over (Contd.)
You can define number and order of child elements using XML
schemas, but not with DTDs.
XML schemas support namespaces, whereas DTDs do not support
namespaces.
XML schemas can be also extended, therefore, you can:
Reuse an XML schema in other schemas.
Drive your own data types from the standard types.
Add the reference of multiple schemas in a single XML
document.

In this session, you have learned that:
jQuery library provides you with various methods, known as jQuery AJAX
methods, that allow you to make a call to the AJAX code.
The load() method is used to load or fetch data from a Web server into a
selected HTML element.
The get() method is used to load data from a Web server using the HTTP GET
request.
The post() method is used to load data from a Web server using the HTTP POST
request.
The ajax() jQuery method can be used to call the AJAX requests and helps in
partial-page updates.
JSON is an open standard light-weight format that is used to store and exchange
data.
Syntactically, JSON is similar to the code for creating JavaScript objects.
To read data from a JSON object, you can use the JSON.parse() method
Summary

To read data from a JSON object, you can use the JSON.parse() method
JavaScript provides you the JSON.stringify() method that allows you to
convert JavaScript value to a JSON string.
XML stands for Extensive Markup Language.
XML is a self-describing language.
XML is recommended by W3C for information exchange over the Internet.
XML transfers data between various heterogeneous systems over the network.
DTD can be declared as:
Internal
External
PCDATA refers to the parsed character data.
Summary (Contd.)

A namespace can be considered as a virtual space that is identified by a
Uniform Resource Identifier (URI).
XML schemas follow a universal standard that made data communication over
the Internet safe.
XML schemas support namespaces, whereas DTDs do not support
namespaces.
Summary (Contd.)

JSON and XML

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