Chapter 6 The World Wide Web

Web Pages Each page is an interactive multimedia publication It can include: text, graphics, music and videos Pages are connected using Hyperlinks Client/ Server Model Pages are built using a markup language (HTML) Homepage: the first page Website: a package of web pages

Web site structures 1) Tree Structure 2) Linear Structure 3) Random Structure

Google Web site

Web Browsers Browser: a Web Client Software Ex. Netscape Navigator, Internet Explorer It contacts the Web Server Plug-Ins: Helper Applications, to add special features to the browsers Display Web pages that created with “HTML” or Programming Languages Active Desktop: Desktop components can be live on the desktop

Internet Explorer

Markup Languages Tags: Instructions that tell the browser how to display and manage a Web document Tags are embedded in the source of the Web page file HTML: The language of the Web Markup Language describes the way that information should be displayed To add HTML tags to an ASCII text document, you can use any text editor

Hypertext In 1960s – Ted Nelson introduced “Hypertext” A concept of connections between Web documents Tim Berners-Lee’s first idea Hyperlinks: an underlined word or a still image that has a target Launch Web pages and Web sites, files and document such as: - Sounds, videos, images, etc…

URLs Uniform Resource Locator Unique identifier for a Web page Web Address URL Parts: 1) Type of transfer protocol “http” 2) Host or Domain Name 3) Directory on the host computer 4) File name “followed by.html” 

Image Maps & Interactive Forms Created by Common Gateway Interface “CGI”: a communication protocol, so the server can communicate with other applications Image Maps: Static Image with hot spots - Image is divided into segments - When you click on a spot, CGI reads the map file to match coordinates of a mouse click with the URL Interactive Form: HTML-based pages that you fill out by providing information - When you fill in information, it will goes to the server - then the server will redirects it to the CGI application “submit” - CGI send the form to another computer program “database”

Host Servers Manages the communications protocols Houses Web pages & server software Use UNIX, Windows or Macintosh Database server – Network Server Web Server: HTTP Server which send information to the client software - The server return an HTML document - Passes requests to run CGI scripts - Send the script to the application via CGI

Web Sites with Databases Easy to search for information Yahoo! Website is linking to a database, we can search for its information by typing keywords Welcome Page: Search dialog Box Bring back a list of all Web sites that contains the keyword CGI is the bridge that links Web sites and databases

Web Sites with Databases Searching steps: 1) Launch a CGI script that sends a search command to the Web server. Ex. 2) Web Server identifies this URL as a trigger, passes it with the search criteria to CGI program 3) CGI script sends the search to the database, then receives the result “HTML documents” 4) CGI passes the result to the Web server to be sent back to the client