Chapter 7 - World Wide Web -

Hypermedia Access to the Internet

 

7.1 Introduction

 

In the preceding chapters, we have looked at many different ways to interact with the Internet.  This chapter focuses on one of the most exciting aspects of the Internet, the World Wide Web or WWW.  The Web brings it all together.  You can access gopher and ftp sites, and even telnet to other computers, all in a hypertext[1] and hypermedia[2] environment.

 

7.1.1 History

 

The purpose of the Web is to allow a simple, standard for accessing hypermedia documents anywhere on the Internet. The Web is based on a technology called hypertext.  In 1989, scientists at the CERN High-Energy Physics Lab in Switzerland proposed to introduce this technology over the Internet.  The software to allow hypertext access to information on the Internet was introduced in 1991.  One of the first software for navigating the Web was the line-oriented browser www (Fig. 7.1). Graphical and full-screen text browsers have mostly replaced this software today. It wasn't until 1993 that the Web began to see widespread usage.  Two important Web browsers, Mosaic for graphical multimedia and Lynx for full-screen text were developed to allow navigation around the Internet.  Mosaic was developed by the National Center for Supercomputing Applications (NCSA) at the University of Illinois, Urbana-Champaign.  It allows the user to receive hypermedia documents, which include hypertext in addition to images, sounds and movies (Fig. 7.2). Lynx was developed at the University of Kansas and provides an easy hypertext access to the Web (Fig. 7.3).

                                         Welcome to the World‑Wide Web (33/33)

   The features you have by connecting to this telnet server are very primitive compared to the features you have when you run a W3 "client" program on your computer.  If you possibly can, please pick up a client for your platform to reduce the load on this service and experience the web in its  full splendor.

   For more information, select by number:

      A list of available W3 client programs[1]

      Everything about the W3 project[2]

      Places to start exploring[3]

   Have fun!

   ___________________________________

                                                               webmaster@w3.org

1‑3, Up, Quit, or Help:

                                                              Fig. 7.1 - www browser

 

 

7.1.2 Overview - What is the WWW

 

The Web or WWW is a collection of standards and protocols for accessing and transferring information through the Internet. The Web relies heavily on the client/server model that allows users to access information on their computer from computers located throughout the world.  The clients and server computers use primarily three standards or protocols for finding and retrieving information.  These standards are URLs (Uniform Resource Locators), HTTP (Hypertext Transfer Protocol), and HTML (Hypertext Markup Language).  It is these three standards that allow one

 

user to place a document with text, images, sound and video on one computer and another user on another computer to retrieve the hypermedia document.

 

7.2 How the World Wide Web Works

 

7.2.1 Client/Server - Starting Your Web Client

 

The Web or WWW is based on a client/server model.  When you use the Web, you are really using two programs.  Your computer must be running a client program that displays the information on your screen as well as transmitting information you generate.  Your client program interfaces with the server program running on another computer.  The client program transmits the location of the requested document to the server and the server then transmits the document to the client.

 

7.2.2 What are URLs?

 

Uniform Resource Locators or URLs provide the standard for locating documents on the Internet.  They allow for simple addressing of any document on the Internet, whether the document is an HTTP document, an FTP file, a gopher or newsgroup menu or an e-mail address. A typical format for a URL looks like:

 

protocol://server-name:port/path

 

The protocol specifies whether the address is for an HTTP document, an FTP file, etc. The protocol is never capitalized and is always followed by ://.  The server-name is the address of the server and can either be the numeric IP address or the domain name (e.g. www.jaring.my).  The server-name is case-insensitive.  The port number and its semicolon can be omitted and the default port for the protocol will be used.  The path specifies the location of the document on the server.  The case sensitivity is determined by the server, so it is important to use the appropriate capitalization. If no path is specified, it is preferable to include the trailing slash.

 

7.2.3 What is HTTP?

 

            HyperText Transfer Protocol or HTTP is the main protocol used to transmit information around the Web.  The client and server computers communicate with each other using this protocol.  The Web client program sends a request to connect to the server.  Once the connection is established, the client then issues a single request for a particular document from the server.  The server then responds with a status code and the document if it is available.  If the client wants more information from the server, it must reestablish the connection and issue the next request.  This is different from other protocols like ftp and gopher where the server remembers the client's current status. In HTTP, the server will not remember information from a previous connection.

 

            Since the HTTP protocol limits the client to one request per connection, it can take a long time to access an HTML page with many in line graphics.  Each graphic requires a separate connection and request for information.  Many of the new graphical browsers like Netscape overcome this difficulty by opening multiple connections and downloading documents in parallel.

 

7.2.4 What is HTML?

 

Hypertext Markup Language or HTML is a language derived from SGML (Standard Generalized Markup Language).  HTML documents are ASCII text with "markups" or "tags" that determine how the text should be displayed.  These include tags like <strong> </strong> which would cause the bracketed text to be displayed in strong or bold format. Tags like <H1> </H1> are used for first-level headers and are treated differently by the various browsers. HTML also provides the capabilities for including in-line images and hypertext links between documents.  Fig. 7.4 illustrates an

HTML document for the Web page in Fig. 7.3.

7.2.5 Navigating the Web

 

To Navigate or surf or browse or whatever you want to call exploring the WWW, you need a client program like Netscape, Mosaic, Lynx or one of many other browsers.  Once you've started your browser, you will need a URL to start with.  Many of the browsers will start you out at their "home page".  If you do not know where to start, the last section of this chapter has an extensive list of some of the authors' favorite sites. Among these sites are many which list thousands of other sites by category.  One of the best is the Yahoo site at www.yahoo.com (Fig. 7.5).  This is an especially useful site if you are looking for information on a particular topic and the category is listed.  Notice that most of these sites have a hierarchical structure and what you are looking for may be several levels down in the listings.

 

 

If you want to do a broader search of the Internet for information, there are many "Search Engines" available.  A very comprehensive search engine is http://altavista.digital.com. One of the best places to go to find more information about these is http://www.albany.net/allinone/ (Fig. 7.6).  Keep in mind that there are millions of others accessing the Internet daily and searching across the Internet may take some time.

 

7.3 Using Netscape

 

7.3.1 Getting Started

1) Type WIN to run the Windows program

2) Find the Netscape icon and double-click on it:

[This may look different if you are using the later versions of Netscape].

3) You will then see displayed the default home page [Fig.7.7].

[At Highlands, this is the Computer Science Department home page, but often this is Netscape Corp].

4) Any text or graphic in blue is a hypertext link to another page either in this document or somewhere else in the world.  To move to that link, simply press the highlighted text or graphic.

 

5) You should also notice that at the bottom of our Computer Science Dept. home page is a collection of iconic buttons that you can use to link to other important sites at New Mexico Highlands University [Fig. 7.8].

 

6) If you want to link to a site that is not listed, you can enter the Universal Resource Locator (URL) either in the location window at the top of the screen or by clicking on the OPEN button and entering the address [Fig. 7.9].

 

7) URLs have three components. The first part tells Netscape what type of document is being requested. This is the "http://" prefix shown in the address tells you the kind of document being requested {http stands for HyperText Transfer Protocol}. The second part of the URL (e.g. jaring.nmhu.edu) is the Internet address of the "machine" while the last part (e.g. /Class.htm) is the path to the document. The file name usually ends in htm or html which stands for HyperText Markup Language which is a standard that supports formatted hypermedia text. [Note: URLs  are case-sensitive, so you need to be careful when typing in the address]

 

8) When you are finished, select Exit from the File menu at the top to close the Netscape Window.

 

7.3.2 Netscape Bookmarks

 

One of the greatest features of Netscape is the ability to "bookmark" interesting sites so that the user can return to a site without having to write the URL for the site down and then retype it at a later date.  To save a bookmark, simply select Bookmarks from the menu bar and select Add Bookmark from the submenu.

 

To return to a location that has been "bookmarked," select Bookmarks from the menu bar and select the bookmark of the location you wish to link to.  As your list of bookmarks increase, you might want to organize them into categories.  This can be done by using the View submenu of the Bookmarks menu and then select the Item submenu and choose Insert Header from the menu [Fig. 7.10]. This allows you to create a category name.  You can then move the bookmarks into the new category.

 

7.3.4 Other Netscape Menu Options

 

If you have your own personal copy of Netscape, you can also modify your preferences by selecting the Preferences submenu. [DO NOT MODIFY PREFERENCES IF YOU ARE SHARING Netscape IN A LAB ENVIRONMENT]

 

Choosing the Directory Menu from the menu bar provides access to a wide selection of resources, some of which are available from the button bar.  The first option in the Directory Menu takes you to Netscape's Home, which has a lot of interesting information and sites to visit.  The second and third options are What's New and What's Cool which provide more interesting places to visit.

 

If you have a newsreader and software for reading news, you might want to select the next option that provides a nice interface to read newsgroups. The next option Netscape Galleria is another page of interesting sites to visit.

 

If you are looking for someone or something, you will need to check out the next three choices: Internet Directory, Internet Search and Internet White Pages.  Internet Directory provides links to several key sites like Yahoo home directory and the Virtual Tourist homepage.  Internet Search lists a variety of links to search engines like InfoSeek and Lycos.  Internet White Pages contains a list of links for finding individuals on the Internet.

 

If you are developing your own home pages or just curious about how a home page is developed, you need to select View Source from the menu.  What you will see is the HTML document that is nothing more than plain text with html tags inserted to create the effects and links to other documents and images.  Check it out.

 

7.4 Using Internet Explorer

 

Internet Explorer is a Microsoft Product that is free with copies of Windows '95 and Windows NT 4.0.  There are also versions available for Windows 3.1 and Macintosh.

 

7.4.1       Getting Started with Internet Explorer

1) Find the IE icon and double-click on it:

 

2)    You will then see displayed the default home page.

 

3) Any text or graphic in blue is a hypertext link to another page either in this document or somewhere else in the world.  To move to that link, simply press the highlighted text or graphic.

 

4) If you want to link to a site that is not listed, you can enter the Universal Resource Locator (URL) in the location window at the top of the screen.

 

5)    When you are finished, select Exit from the File menu at the top to close the Internet Explorer Window.

 

 

7.6 Using Lynx

 

Lynx is a hypertext browser developed at the University of Kansas [Fig. 7.13].  It does not support graphics but it can be found on a variety of computers including computers that are not able to display graphics.  If your computer does not support graphics or if your connection to the Internet does not permit the transmission of graphical images, then you will need to use a browser like lynx.  You can start lynx by typing lynx.  This will connect you to the University of Kansas lynx server.

 

Highlighted text indicates links to other pages, possibly at other locations.  As you use the cursor arrows to move up and down the page, you will be able to stop at any of the links.  By pressing the Enter key, you will then connect to the link.  If you want to connect to another site, press the G for Go.  Then enter the complete URL for the location that you want to link to.

 

You can also connect to other locations by typing lynx followed by the complete URL when you start.  When you are finished, you can exit lynx by pressing Q.  If you get into trouble with lynx, press h for help.

 

 

 

7.6 Places to Visit on the Web

 

There is a vast and ever-growing collection of interesting and exciting places to visit on the Internet.  By using a web browser, one can access an incredible array of information.  With Netscape, Mosaic and other graphical browsers, one can read text, and view graphics, listen to music and watch videos.  The appendix contains a large collection of interesting sites. But the best way to find interesting places on the Internet is to actually browse it yourself.  The only problem is that this can be very addictive.  Have fun!


[1]Hypertext was first described in 1945 by Vannevar Bush and developed by Ted Nelson in the 1960s.   Hypertext provides connections or associations between different documents or parts of a document.

[2] Hypermedia provides connections or associations between different documents which may include text, audio, images and animation.