Lecture 4 - Adding XTHML for the Web

XML For Dummies
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slideshares.blogspot.com

Book Author : Lucinda Dykes & Ed Tittle
Lecture 4 : Adding XTHML for the Web

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Contents
1. HTML, XML, and XHTML

2. Comparing XML and HTML

3. XHTML Makes the Move to XML Syntax

4. Convert a document from HTML to XHTML

5. The Role of DOCTYPE Declarations

4.1. HTML, XML, and
XHTML
 HTML, XHTML, and XML represent
stages in the development of markup
languages.

◦ HTML, designed to display content in
Web browsers, came first.

◦ XML, intended for data exchange, came
next.

◦ XHTML — which uses the markup tags of
HTML and the strict syntax of XML.

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4.1.1 What HTML does

best
 HTML makes our Web world look
pretty.
◦ Such as a personal site that you create
for your family.
 Most Web sites use straight HTML to
display data

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1.2 The limits of
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HTML
 HTML was enlisted to perform some pretty specify tasks.
◦ Allow tight control over document display.
◦ Provide the flexibility to describe different, specific types of
information and data.
◦ Convey information from a variety of media and in a
various formats.
◦ Define complex linking relationships between document.
◦ Publish a single set of information cross a variety of media.
 Two overarching problems prevent Web designers from
achieving this control with HTML:
◦ HTML lacks fine controls.
 Not include mechanisms for the control.
 …
◦ Display vary.
 Problems with browsers that users view web pages (IE,
Firefox…)
 …

4.2. Comparing XML and
HTMLHTML are not the same kind of markup
XML and
language.
 But XML and HTML both derive from the same
parent SGML.
◦ So they must be similar, right ?
 HTML and XML both use tags and attributes.
 XML and HTML look similar.
 HTML defines basic text elements and includes
defaults (and more explicit controls) for how text
may be displayed in a browser window
 XML tells us only what each element means.
 XML says nothing about how elements should or
must be displayed — XML separates content and
the presentation of that content.

4.2.1 Using XML to describe
data
 XML is not limited to any fixed set of tags or
element types.
◦ You can define your own sets of elements
and even your own attributes that you
may then Document
HTML use within your documents.
XML Document

<Cover>
<html> <Abstract>
 This book is about the foundations of the
Blah blah blah blah blah blah blah blah blah blah Extensible Markup Language (XML)
blah blah blah blah blah (XML) and how to use it for your own applications.
blobbity blobbity blobitty blah blah blah blah. blah </Abstract>
blah blah <AuthorInfo>
 The authors are <Author>Lucinda
 Dykes</Author> and
Blah blah blah Lucinda Dykes blah Ed Tittel. <Author>Ed Tittel</Author>.
 </AuthorInfo>
</html> </Cover>

4. 2.2 The benefits of using
HTML
 It’s quick, easy, and cheap.

 HTML is way easier than the alternative.

 Anyone can create an HTML document by
using a text editor and a little knowledge.

◦ Even if you don’t know HTML, you can use an
HTML editor — a What You See Is What You
Get-style (that is, WYSIWYG-style) editor
such as FrontPage or Dreamweaver — to
produce readable Web pages in minutes.

4.2.3 The benefits of
using XML
XML seems to be brimming with benefits.
◦ Unlimited element
◦ Structured data
◦ Data exchange
◦ XML complements HTML
◦ XML documents are well formed
◦ Self-describing
◦ Search engines
◦ Updates
◦ User-selected view of data
 Intelligent XML-based pages that contain human-
readable data offer exciting potential for users.
 A Web designer/developer reaps several benefits
from XML as well.
 The benefits of XML are endless.

4. 3. XHTML Makes the Move to
XML Syntax
 XHTML is the successor to HTML 4.01; in effect,
it’s the final version of HTML.
 XHTML is a clever reformulation of HTML 4 as an
application of XML 1.0.
 Why do we like XHTML?
◦ XHTML documents can be viewed, edited, and validated
using XML tools.
◦ Well-formed XHTML documents mean better-structured
documents.
◦ XHTML documents can be delivered using different
Internet media types and output devices.
◦ Using valid XHTML gives you the best chance of having
your document displayed the way you intend.

4. 3.1 Making the switch
 Making the switch from HTML to XHTML means
mastering the rules of XHTML — in particular, XML
syntax and structure.
 You have only a few major rules to get under your
belt, but you have to follow them if you want to
create a valid XHTML document. 
◦ Every tag in an XHTML document must be closed.
◦ Empty elements (elements without content, such as a br
tag) must be correctly formatted with a closing slash.
◦ All tags must be nested correctly — the tag you open last
must be the tag you close first
◦ All XHTML tags must be written using only lowercase.
◦ All attribute values must be put in quotation marks.
 An acceptable XML document must be well
formed.

4. 3.2 Every element must be
closed
 That all nonempty elements (that is,
those that contain actual text) must
have a start tag and an end tag.
 In the case of HTML

Is the same as
text text text text text text
 Doing without an end tag just doesn’t
fly in XHTML.
◦ You have to add closing paragraph tags
where they belong if you want the
resulting lines to work right.

4. 3.3 Empty elements must be
formatted correctly
 All nonempty XML elements must use
both a start tag and an end tag to be
correct.
 An empty element is a singleton tag
(also called an empty tag) that hangs
around by itself.
◦ Empty tags in HTML include the , <hr>,
<hr>and <img> tags.

◦ The
<hr /> hr element looks like this in HTML:

◦ In XHTML, it looks like this:

4. 3.4 Tags must be properly
nested
 The rules of XHTML syntax say that
tags must be nested in the correct
order.
 The rule is always to close first what
you opened last, working your way
Ill formed
from the inside to the outside tags.
This book was written by Dan Brown.

Well-formed

This book was written by Dan Brown.

4.3.5 Case makes a
difference
 HTML is not case sensitive; XHTML is.
◦ When you use HTML, it doesn’t matter what case
you use for elements and attributes.
◦ For example, for the opening body tag, you can
use <BODY>, <body>, or even <Body> they all
work fine.
 XHTML, on the other hand, is a bit more
finicky about case.
◦ All XHTML elements and attribute names must
be in lowercase or your page won’t validate.
◦ Use any case for the value of an attribute

4. 3.6 Attribute values are in
quotation marks
 In XHTML, all attribute values must be in quotation marks.
◦ The following markup works just fine on an HTML page:

◦ You have to add quotation marks around the attribute value
<tr align=right>
to create valid XHTML.

<tr align=”right”> highlights the major rules for XHTML syntax and
 Table 4-1
shows how markup looks in HTML and XHTML.

4. 4. Converting a document
from HTML to XHTML

4. 5. The Role of DOCTYPE
Declarations
 The DOCTYPE declaration serves several
purposes:
◦ It allows your page to be validated as
XHTML.
◦ It tells the browser which version of which
markup language you used to create the
page and references the specific DTD for
that language.
◦ It enables your page to be displayed
properly in Web-standards-compliant
browsers.
 You have three different DOCTYPES to choose
among for an XHTML 1.0 document: strict,
transitional, and frames.

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4.6 Summary
 Understanding the limitations of HTML

 Comparing HTML with XML

 Getting the best of both worlds:
XHTML

 Converting HTML to XHTML

Lecture 4 - Adding XTHML for the Web

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