Since I began writing articles for this magazine I've covered a whole range of systems including web sites, search engines, online marketing applications, intranets and ecommerce systems. In fact, all these system's can be summarised under the title of 'Web Applications'.

What is a Web Application?

In software engineering, a web application, (also referred to as a Web Service), is an application designed to deliver information to users from a web server over the World Wide Web. Web applications are popular due to the ubiquity of the web browser as a client, sometimes called a thin client. The ability to update and maintain web applications without distributing and installing software on potentially thousands of clients is another reason they are popular. Applications like Hotmail, Amazon.com and eBay are well known examples of web applications and there are many other uses for web applications in government, medicine, science and technology - in fact any business.

How does a web app work?

Though many variations are possible, a web application is commonly structured as a three-tiered application. In its most common form, a web browser is the first tier, an engine created using some dynamic web content technology (e.g., CGI, Active Server Pages, PHP or Java servlets) is the middle tier, and a database is the third tier. The web browser sends requests to the middle tier, which services them by making queries and updates against the database and generating a user interface.
What are the advantages of a web application/service?

. Web services provide interoperability between various software applications running on various platforms

. Web services leverage open standards and protocols. Protocols and data formats are text based where possible; making it easy for developers to see and understand what is going on

. By piggybacking on HTTP, web services can work through many common firewall security measures without requiring changes to their filtering rules.

We've built many of these systems for our clients and an example of a web service that we recently developed was for our client 'Workabout Australia' (www.workaboutaustralia.com.au). This member based website, allows members & employer's to log in and view employment opportunities around Australia (including a range of other features). The underlying web application is the member/employer database that records all member information and job availabilities and allows members & employers to update details. In addition the website owners can administer all information throughout the website ed via a web-based administration system.