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World Wide Web

WWW

• WWW - World Wide Web is one of the newest client-server based Internet services

• Developed by and for CERN

• Aim- to develop a service that would allow easy access and display documents that were stored anywhere on the internet

• The WWW is a service that makes using the Internet as easy as clicking the mouse

• A number of different client applications read WWW documents
  • E.g graphical based Mosaic, Netscape, terminal based clients such as Lynx.

• WWW can display multimedia files

History of the WWW

• Initiative - a better way to give widely dispersed research groups access to shared information

• End of 1990, researchers at CERN had a text-mode (non graphical) browser and a graphical browser for the Next computer

• During 1991, the WWW was released for general use at CERN

• During 1992, Cern began publicizing the WWW project.

How the Web works?

• Web software is designed around a distributed client-server architecture

• This architecture means that a client program may be running on a completely separate machine from that of the server

• Servers usually operate only when documents are requested, hence putting a minimal amount of workload on the computers they run on

• The language that Web clients and servers use to communicate with each other is called the Hypertext Transfer Protocol (HTTP)

• The Web is composed of thousands of virtual transactions using HTTP taking place per hour throughout the world, creating a web of information flow.

• Future Web servers will include encryption and client authentication abilities

WWW Communications

Client server TCP/IP dialogue

I'd like a connection please
OK, fine
Acknowledging your message "OK, fine"
Here is my HTTP request
Acknowledging your message "Here is my HTTP request"
Here is some more that didn't fit
And the last bit
Acknowledging your message "Here is some more that didn't fit"
Acknowledging your message "And the last bit"
Right, here is your HTML file
And the rest of it
Acknowledging your message "Right, here is your HTML file
Acknowledging your message "And the rest of it
Closing down the connection now
OK then, bye

Navigation

• Home page - loads when your browser starts at home Page
  • All WWW users can set up their home page, that gives links to sites that are frequently used

• Welcome page - front door of your site

• Following links
  • may create new windows

  • may re-use same window

• History list allows back and forward motion

• Bookmark or hotlist saves frequently used URLs

WWW Concepts

Browsers

• To access the WWW, it is necessary to run a WWW browser on your computer

• Browsers are GUI applications
  • take advantage of the graphical capabilities of terminals and computers, allowing different sizes, fonts and formatting for different text types

• Browsers can also give access to documents that contain other media besides text. (e.g sound, pictures)

• X terminal - use a graphics-based browser like the X version of Mosaic

• PC or Macintosh - use the PC or Macintosh version of the Mosaic browser or one of the other WWW browsers

• Browsers can also be set so that the correct application will be started when a document of a particular type is selected

• Some browsers also give you access to other Internet services

• Documents on the WWW are hypertext documents

Hypertext

• Hypertext docuements are not plain text

• Hypertext is text that contains links to other text

• The linked text maybe within the document you are reading or maybe anywhere in the world

• Documents that contain more than just text are called hypermedia documents

HTML

• The standard language the Web used for creating hypermedia documents is the Hypertext Markup Language (HTML)

• HTML is used when writing a document that is to be displayed throughout the WWW

• Web documents are typically written in HTML and are usually named with the suffix ".html"

• HTML is a fairly simple set of commands that describe how a document is structured.

• HTML is widely praised for its ease of use

• An HTML file is a specific type of URL object - namely a file written in the HTML formatting language used by WWW

• Free conversion software is available for translaing documents from many other formats into HTML

• HTML is an SGML document type with fairly generic semantics appropriate for representing information from a wide range of applications

Links

• Links are simple references to other documents

• There are two parts to a link.-
  • one is the reference to the related item

  • the other is the anchor

URL

• Generic naming scheme for specifying global objects

• URL (Uniform Resource Locator) is a standard way of referencing an item, regardless of item type

• A URL is a complete description of an item, containing the location of the item that you want to receive

• A URL is always a single unbroken line with no spaces

• A URL consists of two parts - method of access; and the address

• A URL reference can be set up to be absolute or relative

• Examples of URLs
  • http://www.ehche.ac.uk:80/ehche/ann.html

  • gopher://cent1.lancs.ac.uk:70/00/about

  • mailto:A.Rea@qub.ac.uk

  • news:3jvnls$dot@steel.interlog.com

  • nntp://news.mcc.ac.uk/comp.lang.postscript/02113547

  • ftp://src.doc.ic.ac.uk/pub/

  • ftp://src.doc.ic.ac.uk/pub/

  • telnet://dir.mcc.ac.uk/

HTTP

• HTTP (Hypertext Transfer Protocol) is the proctocol used to retrieve the item

• HTTP allows hypertext documents to be retrieved quickly and simply

• The // indicates that the following is a valid internet host address.

Mosaic

• NCSA created Mosaic as a versatile, multi-platform interface to the Web

• What is mosaic:-
  • Mosaic is a networked information system for wide-area distributed asynchronous collaboration and hypermedia based information discovery and retrieval

• Mosaic suited computers with graphics capability

• Currently versions of Mosaic can run on:-
  • UNIX - based machines such as Sun, Silicon Graphics and DEC workstations

  • IBM-compatibles running Microsoft Windows

  • Macintosh computers.

Features of Mosaic

• A consistent mouse-driven interface

• The ability to display electronic text in a variety of fonts.

• The ability to display hypertext and hypermedia documents.

• The ability to display text in bold, italic, or and layout elements

• Support for sounds

• Support for interactive graphics

• Supports various interactive forms

• The ability to make hypermedia links to and support the following network services: FTP, gopher, telnet, WAIS

• The ability to keep a history of travelled hyperlinks

• The ability to store and retrieve a list of viewed documents for future use

• Support for the current standards of HTTP and HTML

Mosaic for Windows

• Basic requirements:
  • Microsoft Windows version 3.1 or later

  • Mosaic for windows requires at least 4M of free memory and an Intel 80386DX-25 processor

  • The Mosaic for windows configuration requires about 5M of disk space for Mosaic s/w, documentation and Wins32 libraries.

• Network requirements
  • Mosaic requires a direct connection to the Internet, either Ethernet card or a modem connection. Best configuration is with an Ethernet card

• Other software
  • Because Mosaic for Windows comes packaged as a zip file, you will need some s/w to unpack

  • Sound and image software

  • External viewers e.g Ghostview

• The basic Mosaic for Windows s/w is available at:
  • an anonymous FTP site ftp.ncsa.uiuc.edu in the directory /Web/Mosaic/Windows.

  • Additional s/w is available through an anonymous FTP at ftp.ncsa.uiuc.edu in the directory /Web/Windows/Mosaic/viewers

• If you wish to install Mosaic for windows then you will have to install the Windows 32-bit libraries first

Mosaic for Unix

• Need to download the appropriate Mosaic-for-Unix software
  • Mosaic-sun.gz Sun 4, SunOS 4.1.x

  • Mosaic-sun-lresolv.gz Sun 4, SunOS 4.1.x, no DNS

  • Mosaic-solaris23-2.5.Z 2394 Kb

  • Mosaic-solaris24-2.5.Z 2387 Kb

  • Mosaic-sun-2.5.Z 2471 kb

  • Mosaic-sun-lresolv-2.5.Z 2477 Kb

• Network requirements
  • Mosaic requires a direct connection to the Internet, either Ethernet card or a modem connection. An ethernet card is best.

• Other software
  • Because Mosaic comes packaged as a zip file, you will need some s/w to unpack

  • Sound and image software for multimedia displays

  • External viewers to read different file types e.g Ghostview

Installation of Mosaic

• Download the Mosaic s/w (ftp) (source code or pre-compiled binaries)

• Create a directory to hold the Mosaic s/w

• Unzip, untar as appropriate

• Customise Mosaic file (Mosaic.INI) in order to:
  • Make Mosaic recognise Viewers

  • Change caching limit so as to increase the number of documents you wish to be stored in cache

  • Change default page. Default Mosaic home page is http://www.ncsa.uiuc.edu/SDG/Software/Mosaic/NCSAMosaicHome.html

Mosaic Interface

• The title bar contains the usual window function button (control menu box, and maximize and minimize buttons)

• The menu bar gives you access to all the functions you need to use Mosaic

• The URL bar shows the URL of the document

• The document viewing area is where one can see the text of a document and any inline images it may contain

• The status bar serves two functions:-
  • shows the progress of the different files that are being loaded

  • shows the URL of the hyperlink that is under the cursor

• The toolbar gives quick access to some of the most used features in Mosaic

Moving between Documents

• Follow links in documents (colour, words, group of words)

• The URL associated with each link appears when the link is passed over

• Enter URL in URL dialogue box

• Hotlist - store interesting URLs

What you see when loading

• Doing nameserver lookup on: <hostname>

• Connecting to HTTP server (other type of server -gopher, ftp)

• Reading response

• Transferring:<counter> bytes

• Transferring inline images <filename.gif>:<counter> bytes.

• Can set images off

Customizing Mosaic

• Turn off URL, status, tool bar

• Change anchor display

• Change fonts

Multimedia

• Audio - file type WAV, MIDI

• Image - JPEG, GIF, TIFF

• Video - MPEG, AVI, MOV

• Formatted text - PS, RTF, DOC

Local file

Navigation

• Forward and Back buttons

• Use history from Navigation menu

Saving documents

• Use option from File menu, "Save As"

• Use "Load to local disk"

Quick Access

• User-configurable menus (Navigate option "Menu Editor")

• Quicklists - hotlists (selected through the "open URL box, or "menu editor")

• Sharing lists - copy list from MOSAIC.INI file to interested users

• Starting Point hotlist - can delete and modify

Annotations

• Edit MOSAIC.INI to specify the directory where you want annotation to be stored

• Select Annotate option and enter comments

Availability

• Mosaic may be obtained from the National Centre for Supercomputing Applications, 605, E.,Springfield, Champaign, IL 61820.

Netscape

• Netscape is a network navigator that allows retrieval and viewing of WWW multi-media documents

• Netscape is the commercial WWW browser developed by many of the same programmers who brought us NCSA Mosaic

• It is compatible with the NSCA Mosaic research prototype

• Designed to provide the next generation of performance and ease of use

• Access to over 40,000 remote WWW servers

• Because of enhancements in the way graphic files are downloaded, Netscape is significantly faster than NCSA Mosaic

• Do not have to wait until the entire file has been downloaded before you can start scrolling
  • i.e allows simultaneous viewing of documents during loading

• Netscape has better caching facilities

• The downside is increased disk space usage, more memory usage, and increased usage of colour

Features

• Search for specific information

• Netscape is graphical, and runs under:
  • the X Window System

  • networked Macs

  • networked Windows PCs

  • Sun workstations

  • Silicon Graphics workstations (IRIX 5.2 or later)

• Has multiple independent windows

• Superior news group interface - USENET

• Netscape, or Mozilla, is the first major commercial WWW browser

• The Netscape browser is free to students, faculty and staff at educational institutions

• You can find instructions for downloading Netscape at:
  • http://www.indiana.edu/~accessw3/software/elec_dist.html

• Netscape can display most graphics but still may requires "helper" applications to play movies or to listen to sound files

• Netscape is also available via anonymous FTP from the following locations:
  • ftp://ftp.netscape.com/netscape1.1/

  • ftp://ftp2.netscape.com/netscape1.1/

  • http://download1.netscape.com/

  • http://charlotte.med.nyu.edu/InfoPages/Netscape.html

Mozilla

• Directly below the Windows-standard main menu is the toolbar, the location windows and the directory buttons

• Main text window looks like any other

• Status line gives information about items in the rest of the interface as the mouse passes over them

• Netscape caches memory locally so can quickly move from page to page

• Can add book marks using "options" menu

• Can view History using "Go" option from main menu

• Netscape supports the "traditional" Internet protocols as well

• Can customise using "Option" menu and by choosing preferences

• Availability: A test version is in the public domain. Contact Mosaic Communications at info@mcom.com

Cello

• Cello is a multipurpose Internet browser

• It supports WWW, Gopher, FTP, and Usenet News retrievals natively, and other protocols

• Can be used to view hypermedia documents, including inlined images, text, and digital sounds and movies.

• Cello runs under Microsoft Windows on any IBM PC with a 386SX chip or better

• Cello runs best with a direct Ethernet connection to the Net

• Can also been designed for good performance via SLIP (Serial Line Internet Protocol) and PPP (point to point protocol) dial-up connections

• Cello site http://www.law.cornell.edu/cello/cellotop.html

Lynx

• Lynx grew out of efforts to build a campus-wide information system (CWIS) at The University of Kansas

• Lynx clients provide a user-friendly hypertext interface for users on UNIX and VMS platforms

• Lynx allow information providers to publish information located on any platform that can run a Gopher, HTTP, WAIS, FTP, or NNTP (USENET NEWS) server

• Lynx can currently be obtained by anonymous ftp from: ftp2.cc.ukans.edu in the pub/lynx directory