Background on the Web

• The Web is a client-server network.

• Pages are stored on Web servers.

• A page is retrieved by the client's browser from a server, and displayed on the client-side.

What about Web Programming?

• Code can be attached to a page, which is executed on the browser (i.e. on the client-side). Java is a client-side programming language.

• Code can be added to a server, so that when a request comes from a browser (e.g. get_page), then the server can execute the program. This is called server-side programming. The most common server-side programming mechanism is CGI, which can utilise many kinds of languages (e.g. C, Perl, Prolog).

Client-side or Server-side Programming?

Each approach has advantages and disadvantages.

Advantages of Client-side Programming (e.g. with Java):

• Code is downloaded and executed locally. There are no network overheads caused by its execution.
• Code can utilise features of the browser (e.g. its history list).

Disadvantages:

• Security (someone else's code is running on your machine).
• Not suitable for all applications, such as databases, where there needs to be centrally stored information.

Advantages of Server-side Programming (e.g. with CGI and C):

• The server can monitor users (e.g. it can collect usage statistics).
• The server can control users (e,g, it can stop certain users from accessing information).
• It is suitable for applications with centralised information (e.g. databases).
• In general, it is easier to write server-side programs than client-side ones.

Disadvantages:

• The server must do all the processing for each client request, and so it can become a bottleneck.
• Server-side programs typically have less sophisticated user interfaces than client-side programs.

Back to the Main Lab Page