Page 252 - Using MIS

220 Chapter 6 The Cloud

Figure 6-9
Sample of Commerce Server
Pages; Product Offer Pages
Source: Reprinted by permission of
zulily. www.zulily.com

discussion, we will use the example of a Web storefront, which is a server on the Web from
which you can buy products.
Suppose you want to buy an item from zulily, a private buyer’s site that sells clothing. To do
so, you go to www.zulily.com and navigate to the product(s) that you want to buy (see Figure 6-9).
When you find something you want, you add it to your shopping cart and keep shopping. At some
point, you check out by supplying credit card data. But what happens when your order data arrives
at the server?

Three-Tier Architecture
Almost all Web applications use the three-tier architecture, which is a design of user comput-
ers and servers that consists of three categories, or tiers, as shown in Figure 6-10. The user tier
consists of computers, phones, and other mobile devices that have browsers that request and
process Web pages. The server tier consists of computers that run Web servers and process
application programs. The database tier consists of computers that run a DBMS that processes
requests to retrieve and store data. Figure 6-10 shows only one computer at the database tier.
Some sites have multicomputer database tiers as well.
When you enter www.zulily.com in your browser, the browser sends a request that travels
over the Internet to a computer in the server tier at the zulily site. In response to your request,
a server-tier computer sends back a Web page, which is a document that is coded in, usually,
html (and, as discussed in Chapter 4, probably includes CSS, JavaScript, and other data).
Web servers are programs that run on a server-tier computer and manage traffic by send-
ing and receiving Web pages to and from clients. A commerce server is an application program
that runs on a server-tier computer. Typical commerce server functions are to obtain product
data from a database, manage the items in a shopping cart, and coordinate the checkout pro-
cess. When a request comes to the server, the Web server examines it and sends it to the proper
program for processing. Thus, the Web server passes e-commerce traffic to the commerce