ITWALES.COM - Section 1 - Introduction to the WWW and HTML

Section 1 - Introduction to the WWW and HTML

Contents:

Introduction to the WWW and HTML

The Web Model

Introduction to the WWW and HTML

The World Wide Web (WWW) enables the distribution and access digital data easily and inexpensively.
Web sites have been developed for:

Online company brochures

Customer and member support

E-commerce sites (electronic trading via the Web)

Online training

Project management and communication

"Everyone" is now buying / downloading the latest web tools and madly learning to build pages.
The Web is a collection of documents written in HTML stored on servers. These web / HTML pages can be linked with hypertext links.

The Web Model

Preparing useful well designed web resources requires an in-depth understanding of how the tools that deliver these resources work.
Internet is a courier service for sending digital information from one computer to another, consisting of 4 concepts:

Universal Resource Locators (URLs)
This is the means by which Internet resources are addressed on the WWW. Your web browser needs to be instructed where it is going to fetch the requested document from. So if you want to specify a resource on the Internet you need to specify its URL.
URLs are a naming scheme for specifying how and where to find any Internet server resource.

The URL references
the important file: webcourses.zip

in the directory: /pub/web/

on the http server: www.educationalcourses.net

In this URL: http://www.educationalcourses.net/pub/web/webcourses.zip

WWW hypertext documents use URLs to reference or point to other hypertext resources . So you can create a web page and link it to any other pages on the web if you have that URL .

Hypertext Mark-up Language (HTML)
HTML is the mark-up language with which the WWW hypertext documents are written. HTML is what allows you to create hypertext links, fill-in forms, email links, formatted text and image in your web pages.
HTML contains commands (called TAGS) to mark text headings, paragraphs and enables the inclusion of images and forms. HTML enables you to format documents for distribution via the internet .
HTML allows a user to click on highlighted text and access a new document / image from a computer thousands of miles away by hypertext links, using URLs to request another internet resource, for example another web page.

Hypertext Transfer Protocol (HTTP)

HTTP servers (web servers) are designed to specifically distribute Web / HTML documents. It is an Internet communications protocol (language) designed for the rapid distribution for hypertext documents from servers to browsers and vice versa.
A web browser is a client program , running on the user's computer which sends a message requesting a service to a server program running on another machine (HTTP server) on the Internet.
The server responds by sending a message back to the client. The HTTP protocol is designed expressly for hypertext document delivery .

Server-Side Resource Processing

This lets a user with a Web browser interact with resources on an HTTP server .
Server side support enables the client to get information generated by other programs running on the server, and take information from the client and pass to programs on the server for further processing.
The interaction between the server and gateway programs is governed by the common gateway interface (CGI). We will look at this in more detail later in the course.

Figure 1: The Web Model. A user uses the browser or client program to display an HTML document. The URL specifies the location of the server on the Internet, HTTP is the protocol used to transport the HTML document which is displayed using the client web browser application.
The browser (client application) interprets URLs to determine where a resource is and which protocol (http, ftp, gopher) to use to access it, and can communicate over the Internet using these protocols to access desired resources.
The most important protocol is HTTP, most servers on the Web use the HTTP protocol and are called HTTP servers, or Web servers.
Using a Web server's CGI or Common Gateway Interface, users can access other resources on the Web server machine, particularly databases.

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