XML - Lesson 1

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Learning XML Basics

NIIT eXtensible Markup Language/Lesson 1/Slide 1 of 40

Objectives

In this session, you will learn to:

Identify the limitations of EDI

Identify the need for XML as a standard data

interchange format

Identify the differences between SGML, HTML, and

XML

Identify the role of World Wide Web Consortium

(W3C) in defining XML-related specifications

Create an XML document

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What is Electronic Data Interchange

EDIrefers to the process of exchanging documents in

a standard format between two computer systems.

EDI is often used as a replacement for conventional

business documents such as purchase orders,

requests for quotations, invoices, and shipping

notices.

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How Does EDI Work (Contd.)

The sender of information uses computer files toassemble the data needed for a transaction.

The assembled data is the input to a software modulethat transforms the transaction into the EDI standardformat.

The resulting data file generated by the software

module is transmitted to the receiver via anintermediate channel company known as Value

Added Network (VAN).

This data file is treated as the input at the receiving

end in which a software module translates the datafrom the EDI format into a file that can be understoodby the receivers application system.

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How Does EDI Work (Contd.)

The above process includes a number of security

procedures. Data security is maintained with the help

of user identification numbers and passwords.

The EDI standards also allow a receiver to send an

acknowledgement message to the sender indicating

successful receipt of information.

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Hardware and Software Requirements forImplementing EDI

For implementing EDI, you require EDI software and a

modem (minimum 28.8k baud, 56k baudrecommended).

You need to convey transactions to and from yourtrading partners electronically.

This can be done either using the point-to-pointcommunication method or using a VAN as anintermediary between various trading partners.

In the point-to-point communication method, you use

a telephone line to dial your trading partnerscomputer directly.

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Benefits of EDI

Reduction in data entry errors

Elimination of communication lag time between anagency and a customer

Improved customer service

Minimized costs of transferring information

Reduced order time

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Limitations of EDI

The limitations of EDI are as follows:

Rigid Transaction Set

Fixed Business Rules

High Costs

Slow Pace of Standards Evolution

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Introduction to XML

What is XML

eXtensible Markup Language (XML) is a text-basedmarkup language that enables you to store data in a

structured format by using meaningful tags.

The term "eXtensible" implies that you can extend your

ability to describe a document by defining meaningfultags for your application.

XML is a cross-platform, hardware, and software

independent markup language.

XML can be used to address the problems faced by

EDI.

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Introduction to XML

Advantages of XML over EDI

Some of the advantages of XML over EDI are listedbelow:

Lower Cost

XML does not require a high priced VAN as in the

case of EDI.

Customized Business Rules

XML enables you to store data in a structured

format by allowing you to create customized tags.

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Advantages of XML over EDI (Contd.)

Easy to Interpret

XML documents can be easily interpreted by thetarget systems by using aparser.

Platform Independent

As XML documents are platform independent, a

business unit can have transactions with any other

business unit irrespective of their data storage

platform.

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Difference between SGML, HTML, and XML

A markup language uses tags to indicate how a file

should look when displayed on a Web page.

Some examples of markup languages are Standard

Generalized markup language (SGML) and Hypertext

Markup Language (HTML).

SGML allows documents to describe their owngrammar by specifying the tag set used in the

document and the structural relationship that these tags

represent.

SGML was complex and difficult for developers tomaster.

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Difference between SGML, HTML, and XML

(Contd.)

HTML is based on SGML.

In HTML, a user has to work with a set of predefined

tags that is understood by the browser.

XML is a subset of SGML.

HTML is used for data presentation, whereas XML is

used for data description and definition. Thus, the

purpose of these two markup languages is completely

different.

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Advantages of XML

The advantages provided by XML are as follows:

Domain Specific Vocabulary

Data Interchange

Smart Searches

Granular Updates

User-Selected View of Data

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Introduction to World Wide Web Consortium

W3C is responsible for the development of Webspecifications (recommendations) that describe

communication protocols and the technologies for theWeb.

Role of W3C in defining XML related specifications

W3C has laid down certain rules that need to be

followed by all XML applications. Listed below aresome of these rules:

XML must be directly usable over the Internet.

XML must support a wide variety of applications.

XML must be compatible with SGML.

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Introduction to World Wide Web Consortium

(Contd.)

The number of optional features in XML needs

to be kept to the absolute minimum, ideallyzero.

XML documents must be human-legible and

clear.

XML design must be formal and concise.

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Problem Statement 1.D.1

CyberShoppe requires a centralized repository of data

about the products sold through its e-commerce site.

It has three branches, which maintain data on theirlocal computer systems. Data from all the three

branches must be collated and housed in a

centralized location. This data must be made available

to the Accounts and Sales sections of these branches,regardless of the hardware and software platforms

being used at the branches. The sales personnel also

require access to the data using equipment, such as

palmtops and cellular phones.

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Problem Statement 1.D.1 (Contd.)

The product details of CyberShoppe consist of the

name of the product, a brief description of the product,

the price, and the available quantity on hand. Eachproduct is uniquely identified by a product ID.

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Task List

Identify the method to store data in a device-

independent format.

Identify the structure of the document in which data is

to be stored.

Create an XML document to store data.

View the XML document in a browser.

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Task 1: Identify the method to store data in a

device-independent format.

Result

XML provides a way to store structured data that is

capable of being recognized by different kinds of

devices. In other words, it enables device-

independence.

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Task 2: Identify the structure of the document inwhich data is to be stored.

Before you store data in an XML document, you need

to organize it. An XML document is composed of a number of

components that can be used for representinginformation. These components are:

Processing InstructionAn XML document usually begins with the XML

declaration statement or the ProcessingInstruction (PI).

The PI provides information regarding the wayin which the XML file should be processed.

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Task 2: Identify the structure (Contd.)

The PI statement can be written as:

In the above example, the PI states that version

1.0 is used.

The PI uses the encoding property to specifyinformation about the encoding scheme that is

used to create the XML file.

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Elements

Elements are the basic units that are used to

identify and describe data in XML.

They are the building blocks of an XML

document.

Elements are represented using tags.

An XML document must always have a root

element. All other elements are specified within

the opening and closing tags of the root

element.

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Content

The information that is represented by the

elements of an XML document is referred to as

the content of that element.

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An element can contain any of the following:

Character or Data Content

Elements can contain only textual

information.

Element Content

Elements can contain other elements.

The elements contained in another

element are called child elements.

The containing element is called the

parent element.

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Element Content

A parent element can contain many child

elements.

All the child elements of a parent element

are siblings and are thus related to one

another.Combination

Elements can contain textual information

as well as other elements.

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Attributes

Attributes provide additional information about

the elements for which they are declared.

An attribute consists of a name-value pair.

Elements can have one or more attributes.Attributes or attribute values can be eithermandatory or optional.

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Attributes

While deciding whether to represent information

as an element or an attribute, you can follow theguidelines given below:

If the data must be displayed, you canrepresent it as an element. In general,

element attributes are used for intangible,abstract properties such as ID.

If the data must be updated frequently, it isbetter represented as an element because it

is easier to edit elements than attributes withXML editing tools.

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If the value of a piece of information must be

checked frequently, it may be represented as

an attribute.

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Entities

An entity can be described as a short cut to a

set of information.

It is a name that is associated with a block of

data.

This data can be a chunk of text or a referenceto an external file that contains textual or binary

information.

XML supports the use of three kinds of entities:

internal, general, and parameter entities.

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Internal Entities

An internal entity consists of a name that is

associated with a block of information.

This can be identified easily as it is always

preceded by an ampersand (&) symbol and

terminated with a semicolon.

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Comments

Comments are statements that are used to

explain the code.

When the code is executed, comment entries

are ignored by the parser.

Comments are not essential in an XML file.

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Result

Structure of the XML document to be used for storing

products data:

PRODUCT

PRODUCTNAME

DESCRIPTION

PRICE

QUANTITY

PRODUCTDATA

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Task 3: Create an XML document to store data.

Rules for Creating Well-formed XML Documents

Every start tag must have an end tag.

Empty tags must be closed using a forward slash

(/).

All attribute values must be given in double

quotation marks.

Tags must nest correctly.

XML tags are case-sensitive. They must match

each other in every implementation.

L i XML B i

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Task 4:View the XML document in a browser.

L i XML B i

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Problem Statement 1.P.1

The details of books sold by CyberShoppe need

to be stored at a centralized location. This data

needs to be made available to the variousbranches of CyberShoppe, regardless of the

platforms used at various branches. The book

details consist of the title of the book, the first and

last names of the author of the book and the priceof the book. Each book is uniquely identified by a

book ID.

L i XML B i

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Summary

In this lesson you learned that,

EDI is a standard format used for the exchange of

business data among heterogeneous systems.

XML is a text-based markup language that enables

you to store data in a structured format using

meaningful tags. XML is a method of storing data in a device-

independent format.

HTML and XML are subsets of SGML.

L i XML B i

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Summary (Contd.)

An XML document consists of:

Processing Instructions

Elements

Attributes

Entities Comments

Content

Learning XML Basics

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Summary (Contd.)

The rules that govern the creation of a well-formed

XML document are as follows:

Every start tag must have an end tag.

Empty tags must be closed using a forward slash

(/).

All attribute values must be given in doublequotation marks.

Tags must nest correctly.

XML tags are case-sensitive. They must matcheach other in every implementation.