Building Scalable Web Sites

Chapter 1. Introduction

Before we dive into any design or coding work, we need to step back and define our terms. What is it we’re trying to do andhow does it differ from what we’ve done before? If you’ve already built some web applications, you’re welcome to skip aheadto the next chapter (where we’ll start to get a bit nerdier), but if you’re interested in getting some general context thenkeep on reading.

What Is a Web Application?

If you’re reading this book, you probably have a good idea of what a web application is, but it’s worth defining our terms because the label has been routinely misapplied. A web application is neither a web site nor an application in the usual desktop-ian sense. A web application sits somewhere between the two, with elements of both.

While a web site contains pages of data, a web application is comprised of data with a separate delivery mechanism. While web accessibility enthusiasts get excited about the separation of markup and style with CSS, web application designers get excited about real data separation: the data in a web application doesn’t have to have anything to do with markup (although it can contain markup). We store the messages that comprise the discussion component of a web application separately from the markup. When the time comes to display data to the user, we extract the messages from our data store (typically a database) and deliver the data to the user in some format over some medium (typically HTML over HTTP). The important part is ...