01 - XML - Introduction to XML

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eXtensible Markup LanguageLectu rer : Phan Vo Minh Than g MSc.

eXtensible Markup Language

Foundation, Technologies & Applications

eXtensible Markup Language Phan Vo Minh Thang


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XML is an Acronym standing for:eXtensible Markup Language

XML is fast becoming the new Internet

standard for information exchange. Forcomplex information reuse, XML is the

technology of choice


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XML Lectures Notes Introduction to XML


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< e s o 0 > < ate a > ectu es otes t oduct o to

Why use XML?

It is a universally accepted standard way ofstructuring data (syntax).

It is a W3C recommendation (W3C = World WideWeb Consortium)

The marketplace supports it with a lot of

free/inexpensive tools.

The alternative to using XML is to define your own

proprietary data syntax, and then build your ownproprietary tools to support the proprietary syntax(Not a very appealing idea).


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Alphabet Soup

Whats with all the different markup languages? SGML

HTML XML

XHTML


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A Brief History of XML

First SGML (Standard Generalized Markup Language) The grandfather of all markup languages

An ISO standard for markup of text, Adopted in1986

SGML describes the logical structure of a document, its components,and their relationship to each other, not how the document should beformatted (Separates content from presentation and format)

Conform to a formal model DTD (Data Type Definition)Documents are regarded as having types defined by DTD

Disadvantages of SGML

Comprehensive but very complex and is difficult to learn and apply.SGML tools have traditionally been very expensive.

SGML has been primarily a technology for print publishing

Developed at IBM by Goldfarb, Mosher & Lorie in 1969


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A Brief History of XML (Cont.)

Then HTML, language of Web an simplified applicationof SGML

HTML is a fixed tag set. You cannot add your own tags to HTML.

HTML is designed for display (in Web browser). It is not effectivefor print or other formats.

HTML is static. Its display is fixed, so providing information in

different ways based on user request is difficult. HTML is not structural (with the exception of lists and tables). It's

primarily a linear presentation markup

HTML is not really a standard. Browser vendors have created theirown proprietary codes, which impedes standardization


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Design Goals of XML

XML will be designed for use on the Internet, but shallsupport a wide variety of applications (such as Web-basedpublishing and e-commerce)

XML will be based on and compatible with SGML XML keeps the best of SGML and reduces the complexity

It will be easy to write programs that processes XML

documents XML documents will be easy to create, readable without

specialized tools, and reasonably clear

XML is in ASCII (or text) format

The design of XML will be formal and concise

XML is a precise standard


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HTML has limited structure

Restricted to a fixed set of tags Isnt extensible for specific applications

Presents barriers for Reuse in multiple formats

Interchange between applications or programs Automation or ability to process programmatically


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Revert to using SGML?

SGML overcomes HTMLs drawbacks Information model of freedom and extensibility

Write once, reuse many times

Future-proof, platform-proof

Validation for completeness and correctness

Infinite possibilities for expressing information (infinite tag set)

SGML has its problems:

Its complex and difficult to learn and use

Theres no mainstream browser support

Plus SGML only standardizes structure

Includes no support for styles


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XML to the Rescue

XML was invented in 1997 to enable the delivery of SGMLinformation over the Web

Well-behaved subset of SGML

Stricter rules drive consistency

Enables machine-to-machine communications

SGML --, not HTML ++ Retains the power and flexibility of SGML without the complexity

A World Wide Web Consortium (W3C) standard

Has overwhelming vendor support


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W3C is responsible for the development of Webspecifications (recommendations) that describecommunication 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 allXML applications. Listed below are some 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.

Offical website is at http://www.w3c.org

Introduction to World Wide Web Consortium


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Introduction to World Wide Web Consortium (Contd.)

The number of optional features in XML needs to be keptto the absolute minimum, ideally zero.

XML documents must be human-legible and clear.

XML design must be formal and concise.


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XML Specification

XML 1.0 specification released By W3C consortium on Feb. 10, 1998

As a recommendation - the highest level ofendorsement possible

Cross-platform, vendor neutral standard

Developed by XML Working Group

Many vertical industry initiatives


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XML working group

Consists of 14 companies and organizations Adobe, ArborText, DataChannel, FujiXerox, HP, Inso,

Isogen, Microsoft, Netscape, SoftQuad, Sun

Microsystems, University of Chicago

Along with a W3C representative and James Clark

Yes, Sun and Microsoft can work together!


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XML 1.0 spec has 2 parts

One for XML documents How to use tagged markupto indicate the meaning of

data

One for XML Document Type Definitions (DTDs)

How to indicate the allowable structure for a class of

XML documents

Can constrain the pieces of data that might occur, thehierarchy of data and the number of times each piece

of data might occur


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Summary: XML Advantages

Over SGML Faster download

Supported bymainstream browsers

Standard linking

Standard stylesheet

Over HTML Interchangeable

Reusable Enables automation

Searchable


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What about XHTML?

EXtensible HyperText Markup Language An XML application

Stricter and cleaner version of HTML Almost identical to HTML 4.01

Is aimed to replace HTML

Better support for multimedia, wireless devices

An official W3C Recommendation - January 26, 2000


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Using XHTML

Some dont recommend XHTML because You have all the pain of XML without any of the gain

Markup is still structural and presentational

But, your pages can be validated

And work without a hitch (or youll receive errormessages)

Theres a tool to convert HTML to XHTML

HTMLTidy www.w3.org/People/Raggett/tidy/


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Exercise A

1. Metadata is information about information2. XML is a programming language

3. XML assumes that a document is structuredhierarchically

4. XML is platform and language independent

5. You can use any text editor to create XMLdocuments

6. XHTML lets you define your own tags

TRUE

FALSE

TRUE

TRUE

TRUE

FALSE


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Exercise A (continued)

7. XML content can be in any language of the world8. Internet Explorer 5 and Netscape 6 support XML

9. XML is about adding procedural markup code todocuments

10.XML provides 50% of the capabilities of SGML

11.XML is a good solution to achieve dataindependence

12.A parser checks to see if your markup tags arespelled correctly

TRUE

TRUE

FALSE

FALSE

TRUE

FALSE


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A Look at XML


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A Sample HTML Document

Sample HTML document For pure display, HTML is very effective

Simple code, workable output, clear delineation of content elements

and their nesting by tags

HTML is a good example of a simple markup language

There are start tags and end tags ()

The end tag is differentiated from the start tag by the forward slash

The procedure file shows nesting of the elements of the document

HTML is concerned solely with presentation It does nothing to help you understand what the information is

Need interpret the content, not through the HTML tags


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A Sample HTML Document Illustration


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g g

Tag names have meaning for you and your authors

Names can reflect the content

Tag names have nothing to do with formatting

Formatting can be defined later, when you know the exactpurposes of the document. Nothing in the markup will limit theformats to which you can output

You can have as many or as few tags as you need


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A document includes

Structure

Content

Display (presentation)

HTML: define structure and display

XML: only define structure But it relies on special browsers and/or XSL for displaying it


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XSL

XML

Document

Schema

Language

Documents with

Special Format

(HTML, WML)

Structure

Display

Processing

Conte

nt

XMLPa

rser


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XPath is a querying language for addressingparts of an XML document

XLinkand

XPointer are languages used to linkXML documents to each other

Xlink describes how to associate two or more resources

XPointer describes how to address a resource

SAX (simple API for XML) is a simple Java

interface


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Doc um ent Objec t Model (DOM)

is an application programming interface (API)for HTML and XML documents

Allows for content to be accessed andmanipulated even AFTER it has become part of

an HTML or XML document

Published as a Recommendation by W3C


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XML Browser

View and print XML documents

Microsoft Internet Explorer

XML Editor

Microsoft XML notepad

XML Parser Shield programmers from the XML syntax

IBMs XML for Java

XSL Processor

Transform XML to HTML

LotusXSL


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Characteristics of XML


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Book chapter title -- section summary

When you examine similar information product, structuresare not consistent from product to product

Big problem for reuse

In XML, structure can be defined in a Document TypeDefinition (DTD) or Schema. DTD

Defines all the elements (XML tags) that can be used in adocument.

Defines the relationship of those elements to other elements

Define the hierarchy of elements ("a chapter contains"), theorder of elements, the number of elements

Maintain structural consistency


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XML is a set of rules for creating markup tags

The tag names themselves offer additional detail about theinformation.

The tag names become metadata Attributes can be used to further define metadata

Example

Using attributes identifies the audience for each specific step,option, or even word


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XML makes you look at information in the way of data

XML DTD designers are not interested in the actual datavalues in design. They are concerned with the type ofinformation, the hierarchy of information, and therelationship of the pieces of information

The result is a structural format that can be stored very easily inDB

Each element can become a field of a table


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How to format XML information for presentation?

XSL is a powerful mechanism for both transforming andformatting XML documents

XSL is an XML markup language itself and can

Format content for online display or for paper-based delivery

Add constant text or graphics

Filter content

Sort or reorder text

Three parts of XSL

XPath

XSL transformations

XSL-FO (formatting objects)


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XPath identify and format specific elements in an XML

doc

Can specify and apply specific formatting or transformation toelements, such as a title following a chapter, the first paragraph in

a section, and every other bullet in a list

XSLT

Can manipulate the information to reorder, repeat, filter outinformation, or even add information based on details in the file

Can transform an XML document into another markup language

XSL-FO Provide style sheet capabilities for converting XML to paper-based

format such as PDF

Include page layouts, headers, footers


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Personalization is information that can be manipulated to

serve the needs of a specific user

Personalization can be user defined, or can managed bysoftware, based on a user's login information

Personalization that is managed by software may becontrolled by observing user behavior, and/or combined

with preferences to create a personalized experience With XML, documents can be broken down, stored as

separate physical pieces in a database, and then

assembled in any order to meet user demands


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Phn ni dung tiu

Ni dung bn trong phn thn

ca mt ti liu HTML

pages are predefined

Element

Attribute

Text


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Phn ni dung tiu

Ni dung bn trong phn thn

ca mt element XML

by users

Element

Attribute

Text


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about the products sold through its e-commerce site. It hasthree branches, which maintain data on their localcomputer systems. Data from all the three branches must

be collated and housed in a centralized location. This datamust be made available to the Accounts and Salessections of these branches, regardless of the hardware

and software platforms being used at the branches. Thesales personnel also require access to the data usingequipment, such as palmtops and cellular phones.


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of the product, a brief description of the product, the price,and the available quantity on hand. Each product isuniquely identified by a product ID.


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format.

Identify the structure of the document in which data is tobe stored.

Create an XML document to store data.

View the XML document in a browser.


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XML provides a way to store structured data that iscapable of being recognized by different kinds of devices.In other words, it enables device-independence.


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

components that can be used for representing information.

These components are: Processing Instruction

An XML document usually begins with the XML declaration statement

or the Processing Instruction (PI). The PI provides information regarding the way in which the XML file

should be processed.


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Tagsare used to specify a name for a given piece ofinformation.

Tags usually occur in pairs.

Each pair consists of a start tag and an end tag.

The start tag only contains the name of the tag whilethe end tag includes a forward slash (/) before thename of the tag.


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Elements are the basic units that are used to identifyand 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 andclosing tags of the root element.


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A parent element can contain many child elements.

All the child elements of a parent element are siblings and arethus related to one another.

Combination

Elements can contain textual information as well as otherelements.


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While deciding whether to represent information as an element oran attribute, you can follow the guidelines given below:

If the data must be displayed, you can represent it as an element. In

general, element attributes are used for intangible, abstract propertiessuch as ID.

If the data must be updated frequently, it is better represented as anelement because it is easier to edit elements than attributes with XML

editing tools.

If the value of a piece of information must be checked frequently, itmay be represented as an attribute.


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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 reference to an external filethat contains textual or binary information.

XML supports the use of three kinds of entities: internal, general,and parameter entities.


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An internal entity consists of a name that is associated with a blockof information.

This can be identified easily as it is always preceded by an

ampersand (&) symbol and terminated with a semicolon.


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Structure of the XML document to be used for storingproducts data:

PRODUCTPRODUCT

PRODUCTNAMEPRODUCTNAME

DESCRIPTIONDESCRIPTION

PRICEPRICE

QUANTITYQUANTITY

PRODUCTDATAPRODUCTDATA


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Processing Instructions

Elements

Attributes Entities

Comments

Content


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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 double quotation marks.

Tags must nest correctly.

XML tags are case-sensitive. They must match each other in everyimplementation.


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Special Selected Topic in

Information System Section: Introduction to XML

Number of slides: 100

Updated date: 12/02/2006

Contact: Mr.Phan Vo Minh Thang

([email protected])

01 - XML - Introduction to XML

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