The Mechanics of the Web

I would imagine that most of you regularly surf the Web. As a matter of fact, you may have obtained this book online from a site like Amazon.com. In order to do that, you need to use a web browser, such as Internet Explorer, Netscape, or Opera.

Browsers use a basic language called HTML, which stands for Hypertext Markup Language. This is not really a computer language (it does not have loop or decision- making capabilities) but is a way of identifying components of the web page you are looking at.

It is beyond the scope of this book to discuss the mechanics of HTML. If you want to learn more, I strongly recommend the book HTML: A Beginner’s Guide (Second Edition), by Wendy Willard (McGraw-Hill/Osborne, 2002).

What does any of this have to do with Microsoft Access? Let’s look at a potential scenario. When you call up a website, the “www” address you type in is called the URL (Uniform Resource Locator). Your request goes out, through your web connection, over a series of routers that ensure it gets to the right location. Once it arrives at the destination, your request is read by a piece of software called the web server. This server then searches its files for the HTML page you requested, addresses it with your return address, and sends it back to your computer. Your browser receives this HTML packet, unwraps it, reads the code, and displays it on your computer. All of this happens in seconds.

While this seems pretty straightforward, there is one little problem. Let’s change the scenario slightly. Let’s say you go to Amazon.com and get its home page. There is usually a box where you can type in the book, or types of books, you are looking for. This is called a web form. Once you click on the search button, your request is sent back to Amazon.com and the results are returned to you.

Does Amazon.com have HTML pages prebuilt for every possible scenario? That would involve the storage of millions, or tens of millions, of web pages. There is a better solution! Let’s add one step to our original scenario.

Let’s say you used the web form to request books about VBA. When Amazon’s web server receives the request, it passes it to a database server. The database then finds the list of VBA books and returns that list to the web server. The web server then sends the list to a dynamic technology (such as CGI, ASP, ASP.NET, or JSP), which we will discuss shortly, that will write the HTML page (using a template) and pass it back to the web server. The web server then sends the HTML page back to your browser as discussed before.

So, as you can see, the HTML pages are written on-the-fly. Out of several dynamic technologies that perform the function of writing the HTML page, the most common is Active Server Pages (ASP). This comes built into professional versions of Microsoft Windows. Of the other names you may hear, ColdFusion, Java Server Pages (JSP), and PHP, the newest is Microsoft’s ASP.NET. Each of these technologies has pros and cons, but they all do more or less the same thing.

Behind this dynamic technology is a database program to save and retrieve the requested data. Most of the larger sites use database servers such as Oracle or Microsoft SQL Server. However, Microsoft Access is now nicely positioned to serve as the database “backbone” of small- to medium-sized sites (there are no magic numbers as to when it is appropriate).