Web Technologies
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Transcript of Web Technologies
What is HTML
• HTML (HyperText Markup Language)
• Language for publications in the World Wide Web, text format for HTTP
• Basic language = English
• Developed 1990 by Berners Lee;
• based very strongly on SGML
SGML: a Brief Introduction
• Standardized General Markup Language
• In 1986, ISO approved an international standard for descriptive markup
• SGML is a metalanguage for defining markup languages
• HTML is one example of an SGML-defined language
History of HTML
• HTML 2.0 is the official standard, which defines those basic functions of HTML, which are meaningfully represented by all Web Browsern.
• HTML 3.2 is the most common used standard, which covers those HTML elements, which are supported to a large extent by nearly all Browser versions (starting from 1996/97).
• HTML 4.0 is a suggestion of the W3-Consortium, which is at least partly supported by newer Browser versions (starting from 1997/98).
• The advancement of HTML starting from 1999/2000 will go into the direction from XHTML.
What is it used for
• Presenting information in LAN / WAN
• Structure your text-based information
• Hyperlinks to reach following texts
• To Put images on your docs
• Basic structure for all web applications, like Guestbooks, Online Stores, Forums, etc …
HTML Standard Tags• TAG: A command inserted in a document that specifies how
the document, or a portion of the document, should be formatted. Tags are used by all format specifications that store documents as text files. This includes SGML and HTML.
• Attribute refers to the properties of the HTML elements• TAG is, which stands within "<...>"• to an opening TAG belongs usually a closing TAG (< font>...
</font>) • Comment tags: <!-- .... -->• There are special tags who not need an end tag, like <br>
HTML Basic Structure<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd"><html><head><title>Title of the page</title></head><body><h1><i>HTML</i> - the language of the
web</h1> </body></html>
Conclusion
• Advantage: HTML is easy to learn• Problems:
– Almost nobody really cares about the standards of w3c, because the „Microsoft Internet Explorer“ (Leading Browser) is very obliging
– As a result the parsers of the non-microsoft browsers can have significant problems in displaying pages correctly
What is XHTML
• EXtensible HyperText Markup Language • Supposed to replace HTML• nearly identically to HTML 4.01• stricter and "more cleanly" version of HTML• HTML 4.01 on XML-Base
History
• Introduced in 26 January 2000 by W3C as the new official standard
• Reason: Problems because of "bad" and "unsuitable" HTML => for search "more cleanly" and "more uniformly" programming
Main characteristics of XHTML
• correct nesting of the tags
• XHTML documents must keep a certain form
• permit no capital letters for the tags
• All elements must be closed: END tag necessarily
Important syntax rules
• Attribute names must be written in small letters
• Attributes must stand in " "• No attributes shortening • The ID attribute replaces the name
attribute• The XHTML DTD defines obligatory
elements.
Conclusion
• XHTML is supposed to make the HTML-Jungle clean, to make the Web-Pages suitable for all browser types.
• Disadvantages:– Web developers have to obey the rules– Errors will not be tolerated
=> More expenditure of time
What is XML
• XML (EXtensible Markup Language)
• Guidance for writing of „Document Type Definitions“ DTD‘s
• XML is more general and uniform than HTML, and simpler than SGML
• SGML - (arcane features) + (new acronym) = XML!
XML - Motivation
• For closing gaps between machine-machine communication ...
• ... applicable in the WWW
• Easy to create
• For humans and machines readable
• To cover as much as possible areas of application
XML - Classification
Structured DataSemi
Structured DataNon
Structured Data
RATIONALDATA BASES
XML FLOW TEXT
Sample Code
<?xml version=„1.0“ encoding=„ISO-8859-1“ ?> <book isbn=„3423085169“> <titel>Sofies Welt</titel> <autor> <name>Gaarder</name> <firstname>Jostein</firstname> </autor> <publisher>DTV</ publisher> <year>1993</year> </book>
End - Conclusion
• HTML– Markup language for the Web– Version and compatibility problems
• XHTML– Tryes to solve this problems
• XML– machine-machine communication