E-Commerce systems, no matter how fancy or how simple, involve three basic functions:

• Displaying a product catalog
• Allowing customers to browse through the product catalog
• Allowing customers to buy items from the product catalog

What do you do when you visit an online merchant? You look through their product catalog to see what they have for sale. Let's say you find something that you like and would like to buy, you'd add the item into your shopping cart and then eventually complete the order by supplying payment information.

Here is a simple diagram to illustrate the process:

1. John Doe visits the MyMarket website and access the product catalog
2. The server generates the product catalog by reading the items from the database
3. John browses the catalog and adds items into his shopping cart
4. The server updates John's shopping cart with the items he has selected
5. John goes to the checkout to complete his order
6. The server generates his order summary by calculating the price of the order
7. John verifies the order, then supplies his credit card number for validation
8. The server talks to a payment authorization service to validate the credit card
9. The payment is authorized and the result is sent back to the server
10. If all goes well, and John's transaction is saved into the database and John waits for the socks

That's the big picture of the entire process. For now it may be a little confusing, but as we go through each of the steps everything will make more sense. We will begin by creating the product catalog, and the maintenance scripts that will us to manage it.