WWW introduction

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WWW introduction

• Presented by Kresten P. Vester,
• René Brink Jensen and Allan Christensen

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Timeline slide 1
Memex

• Reason Sputnik 1
• Response ARPA
• Advanced Research Projects Agency
• Task finding safeguards against a spacebased
  missile attack

John Lickliders Galactic Network
Leonard Kleinrocks Packet switching theory
Making Computers talk to each other.
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Timeline slide 2
TX-2 connected to Q-32
ARPANET
IMP's Interface Message Processors
ARPANET (1969) In Oct. 1969 2 hosts IMP's where
installed at UCLA and STANFORD. In Dec. 1969 4
Hosts
In Dec 1971 21 Hosts
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Timeline slide 3
Email
Tcp/ip draft Network protocol Network Control
Program
USENET
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Timeline slide 4
"Enquire-Within-Upon-Everything"
Transition to TCP/IP
DNS Naming Service
WWW
First webserver and client
WWW software available for download. CERN
Computer Seminar on WWW. Protocols defined and
revised
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Timeline slide 5
WWW traffic measures 1 of NSF backbone traffic.
NCSA releases working versions of Mosaic
browser Over 200 known HTTP servers
(October) WWW receives IMA award (December)
Berners-Lee director for W3C. Andreessen and
James Clark found Netscape.
Digital Corp. Makes AltaVista available to public
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Access protocols

• TELNET
• Remote login
• SMTP
• Simple mail transfer protocol
• Transferring e-mails
• IRC
• Internet relay chat
• Real-time discussions

• HTTP
• Hypertext transfer protocol
• WWW
• FTP
• File transfer protocol
• NNTP
• Network news transfer protocol
• USENET news

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WWW Advantages

• Simple structure
• Easily understandable
• Creatable with simple text editor
• No high requests on backend
• Defined standards (W3C)
• No dependency on manufacturer
• Expandability (scripts, Java, plug-ins)
• Uniform interface for many types of services
• Links can be established to almost any object
  that can be displayed
• Some existing data can be used without
  modification (e.g. directories)
• Extensible for new multimedia data types
• Platform independent, many clients

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WWW Disadvantages

• Many disadvantages are based on HTML
• XML and related standards solve many
  disadvantages of HTML

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WWW / HTML Disadvantages

• Browser often do not adhere to standard
• Abuse of semantic mark up for layout
• Tags semantically only little meaningful
• No pragmatic mark up (except scripts)
• No new tags creatable
• Only little interaction
• Much junk (hard to find high quality info)
• Links within the document (no separate objects)
• No separation of structure and content
• Difficulty to change protocols, because they are
  widely spread
• No versioning with HTTP (WebDAV closes this gap)

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WWW reasons for success

• Simplicity of structures
• Large availability
• Relatively fast available, easy to use, free, and
  platform independent tools for visualization
• Access to other services (FTP, news, ) with
  uniform interface
• Free search engines WWW as meta information
  systems also for other services
• Increased users influence compared to print media

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Evolution of HTML

• HTML 2.0 first definitive version
• HTML 3 (late 1995) ambitious effort to upgrade
  the features and utility of HTML (never
  completed/implemented)
• Many features were integrated in the next
  "official" version of HTML
• HTML 3.2 next official version
• Support for TABLES, image, heading and other
  element ALIGN attributes
• Missing some of the Netscape/Microsoft
  extensions, such as FRAMEs, EMBED and APPLET.
• HTML 4.01 is the current official standard
• Internationalized documents, support for
  Cascading Style Sheets, extra TABLE, FORM, and
  JavaScript enhancements
• For the future, HTML is being replaced by a new
  language, called XHTML

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HTML -gt XML

• All tag and attribute names must be in lowercase.
  Thus, you can't write ltA HREF"foo.html"gt...lt/Agt
  but must instead write this in lowercase, as
  lta href"foo.html"gt...lt/agt
• "Empty" tags must be written with an extra slash
  at the end. An empty tag is one like ltbrgt or ltimg
  src"foo.html"gt that doesn't have a lt/brgt or
  ltimggt to end it. In XHTML, such tags must be
  written as ltbr /gt, and ltimg src"foo.gif" /gt.
• You can never omit an end tag. With HTML, you
  could sometimes leave off an end tag, as in ltpgt
  ..... paragraph text ltpgt ..... more paragraph
  text With XHTML, you must always put in the end
  tag, so that the preceding must be written as
  ltpgt ..... paragraph text lt/pgtltpgt ..... more
  paragraph text lt/pgt

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HTML -gt XML

• Attributes must always have a value. In HTML you
  can sometimes omit atttibute values, as inlthr
  size"2" noshadegt in XHTML, this would need to
  be written as lthr size"2" noshade"noshade" /gt
  
• Attributes values must always be quoted.. In HTML
  you can sometimes omit the quotes,as in lthr
  size2gt in XHTML, this would need to be written
  as lthr size"2" /gt

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Client side technologies

• Java Applets
• JavaScript
• ActiveX
• VBScript
• CSS
• XSLT
• Plugins ex. Flash, shockwave

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Server side technologies

• ASP
• ASP.NET
• JSP/Servlets
• PHP
• SSI (server side includes)
• CGI

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Lynx
www.msn.dk
msn.dk
ac-data.dk
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IE2
msn.dk
dr.dk
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Netscape 1,0
www.msn.dk
www.dr.dk
dr.dk
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Mozilla
www.msn.dk
msn.dk
dr.dk
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IE6
www.msn.dk
www.dr.dk
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Assignment

• Examine the different versions of HTML and list
  the differences on the mailing list.

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End of presentation

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