Intro to E-Commerce

The fundamental concepts of e-commerce are easy enough to grasp, and these days most e-commerce sites follow normative standards and conventions. There are three basic components: the storefront, the shopping cart, and the checkout.

The Storefront
When someone is shopping on the web, they want to browse products on a site to see what's available. Usually, products use categorization to make it easy for users to find the sort of products they're looking for.

For example, a shoe store typically has top-level categories such as Men's and Women's. A shoe store might also have one or more levels of sub-categories of each top-level category. For example, the Men's category might have sub-categories such as Boots, Sandals, Dress Shoes, Sneakers etc.

It is not uncommon for a particular product to fall into more than one category. For example, a casual hiking boot may fall under both Hiking and Casual.

Now for a small tangent on the topic of categorization: A modern twist on the idea of categorization is tagging. Many sites, especially "Web 2.0" sites, now offer tags in addition to, or as a replacement for, categories. Tags are just keywords that are associated with a particular product. Often, but not always, tags are user-generated, meaning that users of a site can add whatever keyword they want to a particular product. If users can collaboratively add tags to a product or asset, then the site offers what is known as a folksonomy.

Managing the storefront of an e-commerce site is a matter of organizing products, and managing inventory. How you organize the storefront, and how you categorize your products, are important concepts to work out in the information architecture phase of an e-commerce project, since the methods of navigation and categorization that you choose will affect every aspect of the site architecture.

In terms of development, a storefront would have separate database tables for categories, products, and the association of products to categories.

A typical categories table might have fields for id, title, parent_category_id, and created. A products table would typically have fields for id, title, description, num_available, price, thumbnail_image_path, large_image_path, and created. An association table could have fields for id, product_id, category_id, created, thereby allowing for a many to many relationship between products and categories by thereby having a separate row for each category a particular product belongs to.

The Shopping Cart
Shopping carts are an essential part of any e-commerce site. They take the metaphor of the physical shopping basket, and transpose it into online media. At its most fundamental, a shopping cart is tool for maintaining state and remembering which products a user has selected for purchase so that they can buy them all together as a batch without having to re-enter their billing and shipping info for each one individually.

As you can probably imagine, most shopping carts are simply tables in a database that have fields for user_id, product_id, and quantity (as well as the id and created fields, of course). That way, the database table simply has a row for every product in the user's cart. To get the contents of the cart, you make a query on the table for all rows that match a given user_id.

Payment Processing
The checkout and payment processing parts of an e-commerce site are the most complicated. You need to securely process a transaction on a user's credit card. This entire process should take place on a secure server where all communication between the client and server is encrypted. Also, in order to process credit cards online, you need to have what is known as a merchant account with a bank. To charge cards over the phone, in a store, or online, merchants need these special accounts with a bank.

Assuming you have a merchant account (or are using a payment service that does), the first step in processing payment online is to send the data from a user's shopping cart to a script that then calculates the total fee owed, as well as an taxes and surcharges. Once the user enter's his/her credit card, billing, and shipping info, you perform a transaction on their credit card by first authorizing it with the issuing credit card company.

If the credit card authorization passes, you must process the order with the credit card company by charging their card, remove the items from the user's shopping cart, and make sure your site's product inventory is up-to-date now that you have sold off a few items. Once everything is finished, you show a confirmation screen to the user with an order receipt. Often, the site will automatically send an email to the user (assuming they entered an email address) with the order receipt in it.

One rule of thumb to follow if you are running your own store is never to store sensitive information like credit card numbers in your database. Unless you have a budget to hire a decent security expert, your site can (and very well may) be hacked, and you do not want to be liable for the damages that would result from someone getting a hold on your clients' credit card numbers.

Due to the complication of doing all these steps yourself, most online merchants opt to use a third-party payment processing service that provides security and handles all the dirty work of charging a card for them.