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An e-commerce site is not necessarily an implementation of the web service paradigm described earlier in this hour; however, it still might use some web-service techniques, especially on the back end. E-commerce is a high-profile example of the way applications and components can be combined together using the tools of the Web.

Vendors and advertisers began to notice early on that the Web is a great way to get people to buy things. It is no secret that many websites look like long, intricate advertisements. Despite the hype, which is enough to make anyone doubt the validity of the design, the fact is that the Web is a convenient and cost-effective way to shop. Rather than sending thousands of catalogs by direct mail, a vendor can simply post the catalog on the Web and let the customers find it through searches and links.

The business of buying over the Web did not really get started until vendors solved the security issues related to sending credit card information over the open Internet. In fact, Internet sales would not even be possible without the secure networking techniques. Most browsers are now capable of opening a secure communications channel with the server. This secure channel makes it impossible for a cyber thief to listen for passwords or credit card information.

A typical web transaction scenario is shown in Figure 20.3. The process is as follows:

  1. A web server provides an online catalog accessible from the Web. A user browses through the product offerings from a remote location across the Internet.
  2. The user decides to buy a product and clicks a Buy This Product link on the web page.
  3. The server and browser establish a secure connection. (See Hour 23, "TCP/IP Security," for more on SSL and other secure communication techniques.) At this point, the browser sometimes displays a message that says something like "You are now entering a secure area...." Different browsers have different methods for indicating a secure connection.
  4. After the connection is established, some form of authentication usually follows. On most transaction sites, the buyer establishes some form of user account with the vendor. This is partly for security reasons and partly for convenience (so the user can track the status of purchases). The user account information also lets the vendor track the behavior of the user and correlate the user's demographic information and purchase history. This logon step requires the web server to contact some form of back end database server—either to establish a new account or to check the credentials for logon to an existing account.
  5. After the user is logged in, the server (or some application working on the server back end) must verify the credit card information and register the transaction with some credit card authority. Often this credit card authority is a commercial service affiliated with the credit card company.
  6. If the transaction is approved, notice of the purchase and mailing information is transmitted to the vendor's fulfillment department, and the transaction application attends to the final details of confirming the purchase with the user and updating the user's account profile.
Figure 20.3

Figure 20.3 A typical web transaction scenario.

Operating system vendors such as Sun and Microsoft offer transaction server applications to assist with the important task of processing orders over the web. Because web transactions are highly specialized, and because they require an interface with existing applications on the vendor's network, application frameworks often provide special tools to assist with the task of constructing a transaction infrastructure.

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