1. xml-introtoxml

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Introduction to XML

A Universal data format


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Module Introduction

Welcome to the module, Introduction to XML.

The module describes drawbacks of earliermark up languages that led to thedevelopment of XML.

The module also explains the structure andlifecycle of the XML document.

This module covers more on the XML syntaxand the various parts of the XML document.

In this module, you will learn about:1. Introduction to XML2. Exploring XML

3. Working with XML

4. XML Syntax


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#1 - Introduction to XML

Outline the features of markup languages and list theirdrawbacks.

Define and describe XML.

State the benefits and scope of XML.


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Features and Drawback of Markup Languages

Evolution of markup languages:

GML SGML HTML.

Features

SGML ensures to represent the data in its own way.

HTML allows the user to use any text editor

Drawbacks

GML and SGML were not suited for data interchange over theweb.

HTML possesses instructions on how to display the content

rather than the content they encompass.


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Evolution of XML

The Extensible Markup Language (XML) was created in order toaddress the issues raised by earlier markup languages

XML is a W3C recommendation.

XML is a set of rules for defining semantic tags that

Break a document into parts

And identify the different parts of the document.

XML was developed over HTML.


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Features of XML

XML stands for Extensible Markup Language

XML is a markup language much like HTML

XML was designed to describe data

XML tags are not predefined. You must defineyour own tags

XML uses a Document Type Definition (DTD) oran XML Schema to describe the data

XML with a DTD or XML Schema is designed tobe self-descriptive


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XML Markup

XML markup defines the physicaland logical layout of the document.

XML's markup divides a documentinto separate information containers

called elements.

A document consists of oneoutermost element, called rootelement that contains all the otherelements, plus some optionaladministrative information at the top,known as XML declaration.


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Benefits of XML

Data independence: separates the content from its presentation.

Easier to parse: frameworks for data exchange.

Reducing server load: using DOM to manipulate the data.

Easier to create: it is text-based.

Web site content: transforms to HTML using XSLT and CSS.

Remote procedure call: allows distributed computing.

Ecommerce: sends data from one company to another.


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#2 - Exploring XML Lesson Overview

Describe the structure of an XML document.

Explain the lifecycle of an XML document.

State the functions of editors for XML and list the popularlyused editors.

State the functions of parsers for XML and list names ofcommonly used parsers.

State the functions of browsers for XML and list the commonlyused browsers.


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XML Document Structure

XML documents are commonly stored in text files withextension .xml.

The two sections of an XML document are:

Document Prolog

Root Element


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$1- Document Prolog

Help XML parser to get information about the content in the document

Document prolog contains metadata and consists of two parts:

1. XML Declaration Specifies the version of

XML being used

2. Document Type Declaration. Defines entities' or

attributes' values

Checks grammar of markup

Checks vocabulary of markup


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$2 - Root Element

Also called a document element.

It must contain all the other elements and content in thedocument.

An XML element has a start tag and end tag.


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Logical Structure

Gives information about theelements and the order in whichthey are to be included in thedocument.

It shows how a document isconstructed rather than what itcontains.


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Life cycle of an XML document


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XML Editors

The main functions that editors provideare as follows: Add opening and closing tags to the code

Check for validity of XML

Verify XML against a DTD/Schema

Perform series of transforms over adocument

Color the XML syntax

Display the line numbers

Present the content and hide the code

Complete the word

The popularly used editors are:

XMLwriter XML Spy

XML Pro

XMLmind

XMetal


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Parsers

An XML parser/XML processor reads the document and verifies itfor its well-formedness.

After the document is verified, the processor converts thedocument into a tree of elements or a data structure.

Speed and performance are the criteria against which XML parsersare selected.

Commonly used parsers are:

Crimson Oracle XML Parser

JAXP (Java API for XML)

MSXML


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Browsers

After the XML document is read, the parserpasses the data structure to the clientapplication (web browser)

The browser then formats the data and displaysit to the user.

Other programs like database, MIDI program ora spreadsheet program may also receive thedata and present it accordingly.

Commonly used web browsers are as follows: Netscape

Mozilla Internet Explorer

Firefox

Opera


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#3 - Working with XML

Explain the steps towards building an XML

Define what is meant by well-form XML


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Creating an XML document

An XML document has three main components:

Tags (markup) and text (content)

DTD or Schema

Formatting or display specifications

The steps to build an XML document are as follows:

Create an XML document in an editor.

Save the XML document.

Load XML document in a browser.


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Exploring the XML document

The various building blocksof an XML document are:

1. XML Version Declaration

2. Document Type Definition(DTD)

3. Document instance in

which the content is

defined by the mark up


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$1- XML Version Declaration


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$2 - Document Type Definition (DTD)


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$3 - Document instance

< student >

This part defines the content of the XML document called as

mark up.

It describes the purpose and function of each element.


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Meaning in Markup

Markup can be divided into following three parts:

1. Structure1. Describes the form of the document by specifying the

relationship between different elements in thedocument.

2. It emphasizes to specify a single nonempty, root

element that contains other elements and the content

Semantic Describes how each element is specified to the outside

world of the document.

ex. Web browser assigns "paragraph" to the tags

and

Style It specifies how the content of the tag or element is

displayed.


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Well-formed XML document

Well-formedness refers to thestandards that are to be followed bythe XML documents.

Rules:

Minimum of one element is required,

XML tags are case sensitive.

Every start tag should end with endtag.

XML tags should be nested properly.

XML tags should be valid.

Length of markup names

XML attributes should be valid.

XML documents should be verified


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#4- XML Syntax

State and describe the use of comments and processinginstructions in XML.

Classify character data that is written between tags.

Describe entities, DOCTYPE declarations and attributes.


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Comments

Give information about the code

Can appear in the document prolog, DTD or in the textual content.

Not appear inside the tags or attribute values.

Syntax:

-->


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XML Elements

An XML element is everything from(including) the element's start tag to(including) the element's end tag.

An element can contain other elements,

simple text or a mixture of both.Elements can also have attributes.

XML Naming Rules

Names can contain letters, numbers,

and other characters Names must not start with a number or

punctuation character

Names cannot contain spaces


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Processing Instructions

Processing instructions are informationwhich is application specific.

These instructions do not follow XMLrules or internal syntax.

With the help of a parser these

instructions are passed to theapplication.

The main objective of a processinginstruction is to present some specialinstructions to the application.

Syntax


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Classification of character data

An XML document is divided intomarkup and character data.

Character data describes thedocument's actual content with the

white space.

The text in character data is notprocessed by the parser and thusnot treated as a regular text.

The character data can be classifiedinto:

CDATA

PCDATA


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PCDATA (parsed character data)

The data that is parsed by theparser

The PCDATA specifies that theelement has parsed character

data.

It is used in the elementdeclaration.

Escape character like "


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CDATA

The text inside a CDATA section is not parsed by the XMLparser. A text is considered in a CDATA section if it contains '


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Entities

Entities are a construct that are referencedin the document

Every entity consists: name - value.

As the XML document is parsed, it checksfor entity references.

For every entity reference, the parserchecks the memory to replace the entityreference with a text or markup.

Syntax for an entity reference: &;.

All the entities must be declared beforethey are used in the document. An entity can be declared either in a

document prolog or in a DTD.


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Predefined entities


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Entity Categories

Entities are used as shortcutsto refer to the data pages.

The two types of entities are as

follows: General Entity

Parameter Entity


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Entity Categories

General Entity

These are the entities used within the document content.

They refer to the content of a named entity.

References to these entities: &;

Parameter Entity

These types of entities are used only in the DTD.

These type of entities are declared in DTD.

References to these entities: %;


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DOCTYPE declarations

Defines the elements to be used in the document.

To indicate what DTD the document adheres to.

It can be declared either:

In the XML document (internal)

Referenced to the external document (external)


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Example of DOCTYPE declarations - Internal


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Example of DOCTYPE declarations - External

DTD file (note.dtd)

XML file


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Attributes

Additional information about the attributescan be given in the form of attributes.

Attributes are created in the DTD alongwith the elements.

Every attribute within an element is

associated with a name-value pair.

Attributes can be used to distinguishbetween the elements of the same name.

Attributes occur in the start-tags after theelement name.

Attribute values are always enclosed insingle or double quotes.

Attributes are case sensitive and muststart with a letter or underscore


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Thats all for today !

Introduction to XML

Exploring XML

Working with XML

XML Syntax

Thank you all for your attention and patient !

1. xml-introtoxml

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