One of the most popular articles I've ever written was on Amazon.com Web services. The article was written for the Macromedia Developer Center and is located at www.macromedia.com/devnet/coldfusion/articles/wsamazon.html.

This article is a bit dated. A few days before it was published, Amazon.com released version 1 of their SOAP Web services. In this issue on exchanging data, I thought it'd be great to write an article on version 4 of Amazon.com's SOAP interface, released in September. They are now called "Amazon.com E-Commerce Services."

After two days of much frustration, I was unable to successfully invoke the SOAP Web services from ColdFusion or BlueDragon; I kept getting semantic errors when compiling the WSDL. However, you can still use Amazon.com Web services without SOAP, using REST instead, which is a SOAP alternative. In this article, I'll introduce you to Web services and show you everything you need to know to implement Amazon.com's E-commerce services on your site.

Web Service Definitions
Before delving into Amazon.com specifics, I want to make sure we're all on the same page when it comes to terminology. If you're already familiar with Web services, you can probably skip this section. If you are new, or want a reminder primer, read on.

Most of the time when you hear someone talk about Web services, they're talking about SOAP. SOAP stands for Simple Object Access Protocol, an XML dialect that is used to define how Web services can communicate with the programming language calling it. Not all Web services are SOAP, though. A Web service is defined as any program run over a network by another program. If you've ever used cfhttp to process a credit card transaction through a gateway provider, you've used a non-SOAP-based Web service. These types of requests are sometimes called REST requests. REST stands for Representational State Transfer. Instead of passing an XML-based SOAP request, REST is done by using a variety of URL parameters to specify which methods to invoke and which values to pass in. More information on REST can be found at www.ics.uci.edu/%7Efielding/pubs/dissertation/rest_arch_style.htm.

The next definition is the WSDL, the Web Services Definition Language. It defines the functionality of a SOAP Web service. WSDL is another XML variant. The WSDL will tell you the operations you can perform against the Web service and what you would expect to get in return for that service. In many cases, you'll be provided with English documentation (such as a Word doc, PDF, or HTML) for the Web services and won't have to read the WSDL manually. If you think of a Web service as a CFC, the WSDL will define the names of methods, the input parameters to those methods, and the type of data that is returned from those methods. If you create a Web service in ColdFusion, the WSDL is generated automatically for you, just by appending "?wsdl" to the URL. In ColdFusion, you'll need to know the location of the WSDL is to create a Web service object.

There are two other definitions that you can use when speaking about Web services. The first is to publish a Web service. When you publish a Web service, you're making it available for people to use. If the Web service is public, such as Google or Amazon's Web services, anyone can use it. If the Web service is private, you may only be providing access to clients, customers, or other departments in your company. The act of publishing is merely telling someone the URL and providing the documentation on how to use the Web service.

On the other side of the coin, Web services are consumed. To consume a Web service means that you are using a Web service. It's as simple as that. Amazon.com published their Web services by making them public. As the one using the Web service, we are consuming them. Publish always seemed like a logical name for making Web services available, but it took me a while to get used to "consuming" them.

Getting Started with Amazon.com Web Services
Why would you want to use Amazon.com Web services? Perhaps you're an associate and want to bump up your potential for income by allowing people to search the full Amazon catalog. Perhaps you're a merchant who is selling a product through the Amazon.com store. The Amazon.com e-commerce services offer many features, including:

• Product Searches: If you take away its product catalog, there isn't much to the Amazon.com Web site. You have the full array of search options available through the Web service interface that you do via the Amazon.com Web site. After a search, you can always get full details on an individual product.
• Product Images: Image data is returned as part of the search.
• Customer Reviews: You have full access to the customer reviews for any given product.
• Wish List Searches: You can search wish lists by name, e-mail address, city, or state using the Web service interface.
• Remote Shopping Cart: You can now have your users add items to their Amazon.com shopping cart without leaving your own site.

Deconstructing the Amazon.com URL
You're ready to perform your search. The first step is to construct your URL. The URL starts with the location http://webservices.amazon.com/onca/xml. It is the query string parameters that provide us with the search results:

• Service: The service parameter accepts the value of AWSECommerceService to access Amazon.com E-commerce services. It is required.
• SubscriptionId: The subscriptionID was provided to you when you signed up for the developer program. This is also a required parameter.
• Operation: The operation parameter describes what operation you are trying to perform. There are 18 different actions that you can perform. In this article I'll show you ItemSearch and ItemLookup. You can also look up seller info, perform similarity searches, add information to the user's Amazon.com shopping cart, or look up public customer information (such as reviews or wishlists). This is required.
• AssociateTag: If you are an Amazon.com associate, put your associate tag here to ensures that you keep getting the kickbacks when people buy something based on your referral. This is optional.
• ResponseGroup: The responsegroup parameter is used to define the type of information that is sent back to you
• Operation Parameters: The operation parameters are a set of parameters required for each operation. You might think of this as similar to the way that cffile works. You use a different set of parameters to upload a file than you do to copy a file, move a file, and so on. Other tags, such as cfobject and cfloop, operate in a similar manner.