Web Designing – 2 (405)

Unit 1: Introduction to XML

Unit-1 : Introduction of XML:

1.1 Characteristic and Use of XML
1.2 XML syntax (Declaration, Tags, elements)
1.3 root element, case sensitivity
1.4 XML document:
1.4.1 Document Prolog Section
1.4.2 Document element section
1.5 XML declaration and rules of declaration.

What is XML?

▪ XML stands for Extensible Markup Language. It is a textual data format which
application used to communicate (send and receive data) with other application.
▪ It is a text-based markup language derived from Standard Generalized Markup Language
(SGML).
▪ It is a markup language it uses tags.
▪ To define and store data in a shareable manner. XML supports information exchange
between computer systems such as websites, databases, and third-party applications.

HTML VS XML
HTML XML
We cand only use pre-defined tags We can use both pre-defined and used
defined tags
Ex.<p><b><br> Ex. <friendlist> <channel><xml>
Not case sensitive case sensitive

Why XML?
In real world xml use for create GUI, Java based web application and increase searching of
your website.
Raj Ram
English,Hindi,Gujarati Chinese,Koren,English
Here, data format English

Application1 Application2
Here, data format may be json,xml,etc
Note: (JavaScript Object Notation) is a data interchange format that uses human-readable
text to store and transmit data.

▪ Data exchange (Platform & language independent)

By: Dr. Ami Desai 1|Page

 Web Designing – 2 (405)

XML allows data to be exchanged between databases, user desktops, and third-party
applications in any platform and any language.
▪ Data structure
XML uses tags to define the structure and meaning of data, such as the beginning and
end of a paragraph or the location of an image.
▪ Data sharing
XML is a flexible way to create information formats and share structured data
electronically.
▪ Data readability
XML is designed to be readable by both humans and machines.
▪ Data customization
XML is highly customizable and can be used to create different content types, such as
web, print, and mobile content.
▪ Web searching
Search engines use XML tags to make searches more accurate. For example, a search
engine can limit search results to pages that contain a specific tag, such as an author's
name.

Uses or Advantages of XML

XML is widely used in the era of web development. It is also used to simplify data storage
and data sharing.

The main features or advantages of XML are given below.

▪ XML separates data from HTML

o If we need to display dynamic data in our HTML document, it will take a lot of work
to edit the HTML each time the data changes.
o With XML, data can be stored in separate XML files. This way we can focus on using
HTML/CSS for display and layout, and be sure that changes in the underlying data
will not require any changes to the HTML.
o With a few lines of JavaScript code, we can read an external XML file and update the
data content of our web page.
▪ XML simplifies data sharing
o In the real world, computer systems and databases contain data in incompatible
formats.
o XML data is stored in plain text format (not in databse). This provides a software-
and hardware-independent way of storing data.

By: Dr. Ami Desai 2|Page

 Web Designing – 2 (405)

o This makes it much easier to create data that can be shared by different applications.

▪ XML simplifies data transport(connect between different application)

o One of the most time-consuming challenges for developers is to exchange data
between incompatible systems over the Internet.
o Exchanging data as XML greatly reduces this complexity, since the data can be read
by different incompatible applications.

▪ XML simplifies Platform change

o XML data is stored in text format. This makes it easier to expand or upgrade to new
operating systems, new applications, or new browsers, without losing data.

▪ XML increases data availability

o Different applications can access our data, not only in HTML pages, but also from
XML data sources.
o With XML, your data can be available to all kinds of "reading machines" (Handheld
computers, voice machines, news feeds, etc.), and make it more available for blind
people, or people with other disabilities.

▪ XML can be used to create new internet languages

o A lot of new Internet languages are created with XML.
o Here are some examples:
✓ XHTML
✓ WSDL(Web Service Description Lang) for describing available web
services
✓ WAP(Wireless Application Protocol) and WML (Wireless Markup
Lang) as markup languages foxr handheld devices
✓ RSS (Really Simple Syndication) languages for news feeds
✓ RDF(Resource Description Framework) and OWL (Web Ontology
Language) for describing resources and ontology
✓ SMIL (Synchronized Multimedia Integration Language) for describing
multimedia for the web

Characteristics of XML
▪ There are three important characteristics of XML that make it useful in a variety of
systems and solutions:
o XML is extensible: XML allows you to create your own self-descriptive tags, or
language, that suits your application.
o XML carries the data, does not present it: XML allows you to store the data
irrespective of how it will be presented. XML page carries data from other data
files.
o XML is a public standard: XML was developed by an organization called the
World Wide Web Consortium (W3C) and is available as an open standard.

By: Dr. Ami Desai 3|Page

 Web Designing – 2 (405)

XML also has some other characteristics:

1. XML is a structured format, which means that we can define exactly how the data is
to be arranged, organized and expressed within the file. When we are given a file, we
can validate that it conforms to a specific structure, prior to importing the data.
2. XML is a described format, which means that within the text file, every item of data
has a name that is both human- and machine-readable as well as being uniquely
identifiable. Ex: <youtube xs:string>
3. XML can easily describe hierarchical data and the relationships between data.
<youtube>
<channel>sony<channel>
<subscriber>1k</subscriber>
</youtube>
4. XML can be validated, which means we can provide a second XML file – an XML
Schema Definition file – that describes exactly how the XML data file should be
structured.

5. XML is a strongly-typed format, which means the schema definition file specifies
the data type of each element. When importing the data, the application can check the
schema definition to identify the data type to import it as.
6. XML is a global format. There is only one way to express a number in an XML file
(with US number formats) and only one way to express a date The most common
types are: xs:string. xs:decimal. xs:integer.
7. XML is a standard format. It also allows different applications to read, write,
understand and validate the same XML files, allowing us to share data between
applications in an extremely strong manner.

Structure of XML
▪ XML document is a well-organized collection of components and associated markup.
▪ An XML document can hold a wide range of information. For instance, a database
having numbers or a mathematical equation etc.
▪ An XML document can have following elements:

XML document has 2 sections:

1) Document Prolog 2) Document Elements

1) Document Prolog: It contains XML & document type declaration. These components
should appear before root of the document and at very first line of the document.it is
optional.

By: Dr. Ami Desai 4|Page

 Web Designing – 2 (405)

1. Declaration: a processing instruction that provides basic information about the

format of an XML document.ex.
<? xml version="1.0" encoding="utf-8"?>
▪ This is the version of XML used in the document. The latest version number can be
fetched from http://w3.org.
Syntax for XML Declaration

<?xml
version="version_number"
encoding="encoding_declaration"
standalone="standalone_status"
?>

E.g. <?xml version = "1.0" encoding = "UTF-8" standalone = "no" ?>

For use external data set standalone=”no”.by default it is “no”

An XML declaration should follow with the following rules −

▪ If the XML declaration is present in the XML, it must be placed as the first line in the
XML document.
▪ If the XML declaration is included, it must contain version number attribute.
▪ The Parameter names and values are case-sensitive.
▪ The names are always in lower case.

By: Dr. Ami Desai 5|Page

 Web Designing – 2 (405)

▪ The order of placing the parameters is important. The correct order is: version,
encoding and standalone.
▪ Either single or double quotes may be used.
▪ The XML declaration has no closing tag i.e. </?xml>

2. Document element
1. Root: XML document must have a root element. A root element can have child
elements and sub-child elements. For example: In the following XML
document, <message> is the root element and <to> , <from> , <subject> and
<text> are child elements.
2. Comments: <!-- My Comment --> but after prolog statement.
3. DocType: Document Type Declaration node can take 2 forms, a reference to an
external file which contains the DTD Schema, or an inline DTD Schema
description.

DTD is the rules to be followed to make the XML file valid.

• It can be standard rules or user defined rules. It may be HTML, math(maths)

,svg(graphics) etc
• DTD can be declared in XML file inside <!DOCTYPE> declaration, or defined in
external file and referenced inside <!DOCTYPE>.
• The purpose of a DTD is to define the structure of an XML document. It defines
the structure with a list of legal elements.

Note: A "well formed" XML document is not the same as a "valid" XML document. But A
"valid" XML document must be well formed. In addition, it must confirm to a
document type definition.

Example :

<!DOCTYPE book[
<!ELEMENT book (title,author,price)>
<!ELEMENT title (#PCDATA)>
<!ELEMENT author (#PCDATA)>
<!ELEMENT price (#PCDATA)> ]>

The DTD above is interpreted like this:

• !DOCTYPE book defines that the root element of the document is book.
• !ELEMENT book defines that the book element must contain the elements: "title,
author, price”
• !ELEMENT title defines the title element to be of type "#PCDATA"

By: Dr. Ami Desai 6|Page

 Web Designing – 2 (405)

• !ELEMENT author defines the author element to be of type "#PCDATA"

• !ELEMENT price defines the price element to be of type "#PCDATA"
Note: PCDATA: Parse able Character Data #PCDATA means that the element contains data
which is display, CDATA: Character Data which is not visible ex: id of any tag.

There are two types of DTDs:

1) Internal / Embedded DTD

2) External DTD

1) Internal / Embedded DTD

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

<!DOCTYPE student [
<!ELEMENT student (id,name,age,addr,email,ph)>
<!ELEMENT id (#PCDATA)>
<!ELEMENT name (#PCDATA)>
<!ELEMENT age (#PCDATA)>
<!ELEMENT addr (#PCDATA)>
<!ELEMENT email (#PCDATA)>
<!ELEMENT ph (#PCDATA)> ]>

<student>
<id>543</id>
<name>Ravi</name>
<age>21</age>
<addr>Guntur</addr>
<email>nsr@gmail.com</email>
<ph>9855555</ph>
<gender>male</gender>
</student>

2) External DTD

<!ELEMENT student (id,name,age,addr,email)>

<!ELEMENT id (#PCDATA)>
<!ELEMENT name (#PCDATA)>
<!ELEMENT age (#PCDATA)>
<!ELEMENT addr (#PCDATA)>
<!ELEMENT email (#PCDATA)>

By: Dr. Ami Desai 7|Page

 Web Designing – 2 (405)

Save the above code as “student.dtd” and prepare “student.xml” as follows... Doctype
define type of file .Here student is name of tag.
SYSTEM: This indicates that the Document Type Definition (DTD) file is specified
externally. The SYSTEM keyword is used to provide the location (a URI or a path) of
the external DTD file.

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

<!DOCTYPE student SYSTEM "student.dtd">

<student>
<id>543</id>
<name>Ravi</name>
<age>21</age>
<addr>Guntur</addr>
<email>nsr@gmail.com</email>
</student>

In the above example we are using <!DOCTYPE student SYSTEM "student.dtd"> which
is used to provide “student.dtd” code in our “student.xml” file.

If the above xml code follows the exact rules defined in DTD then we can conclude
that our xml document is a valid document. Otherwise it is an invalid document.

4. Elements which comprises of element name, value, namespace, comment, CDATA,

entity references.

XML declaration and rules of XML Elements Rules

1. Root: Every XML file must contain a root element that is parent element Ex. <root>
Root Element − An XML document can have only one root element. For example,
following is not a correct XML document, because both the x and y elements occur at
the top level without a root element –

<x>...</x>
<y>...</y>

2. The Following example shows a correctly formed XML document – It should in

paired.
<root>
<x>...</x>

By: Dr. Ami Desai 8|Page

 Web Designing – 2 (405)

<y>...</y>
</root>

3. XML prolog: It is the first line of any xml file.it is optional.

Ex.<?xml version=”1.0” encoding=”UTF-8”?>
4. Tags: all element must have a closing tag.xml tags are case sensitive.
Case Sensitivity − The names of XML-elements are case-sensitive. That means the
name of the start and the end elements need to be exactly in the same case.

5. Attribute:The value must be quoted ex. <name id=”a”> here id is attribute of <name>
element.
6. Comments: <!--- comment text -->
7. An element name can contain any alphanumeric characters. The only punctuation
mark allowed in names are the hyphen (-), under-score (_) and period (.).
8. An element, which is a container, can contain text or elements as seen in the above
example.
Syntax Rules for Tags and Elements

Element Syntax − Each XML-element needs to be closed either with start or with end
elements as shown below −

<element>....</element>
or in simple-cases, just this way −

<element/>
9. Nesting of Elements − An XML-element can contain multiple XML-elements as its
children, but the children elements must not overlap. i.e., an end tag of an element
must have the same name as that of the most recent unmatched start tag.

By: Dr. Ami Desai 9|Page