Introduction to Web Applications (MAJU Fall 2012)

Learning Objective:
To introduce Web Applications in simplist terms and to introduce the key players involved

What are web applications?
Simplist definition:Stored on a server and accessed via A Web Browser

Whats the advantage?
- Code resides at a single place
- Clients need no installation therefore there is no need of high processing and memory capabilities at client end
- Incase new feature needs to be coded then update is required at the server only. In other words maintenance is easy

Why Study Web Application?
- Due to easy maintenance companies donot hestiate to chose web based solutions
- Requires less processing power at the client end
- Can be very easily made available over the internet so that remote users can also use the application

Entities Involved
- Web Browser
- Web Server
- Database Server (optional)

Web Browser: Has the responsibility of displaying the output to the end user

Web Server:
Has the responsibility of processing the request of user and preparinng the response

Database Server:Stores the data that is important to users

To understand the role of each lets take example of restaurant and compare it with Web Applications:
-You give your order to the waiter
-In web application you place request on web browser
-The waiter takes the order to the cook
-The browser sends the request to server
-The cook reads the order and prepares dishes
-The webserver reads the request and prepares response
- To prepare the dishes the cook obtains ingrediants from the server
- To prepare the response server obtains data from Database Server
- The cook gives the prepared dishes to the waiter
- The Server sends the prepared response to the browser
- The Waiter brings the dishes to you
- The browser displays the prepared response to you

Communication Between Browser and Server- The scenario of Browser and Server is more complex than that of Waiter and Cook. Both Waiter and Cook belong to the same restaurant, but browser and server and normally made by different companies
- If browser of each company applies a different set of rules to ensure successfull transit of data to server then developing a server will become a very complex task as server will have to have knowledge of varying rules of each browser
- Similary if server made by each company applies different set of rules to send respone then making browsers will become very difficult
- The solution is to have a standard set of rules that all browsers and servers use. This standard set of rules is known as Hyper text Transfer protocol
- Similary the contents of the response contain a standard language which Hyper text markup language