DATABASES AND THE INTERNET - Fundamentals of Database Management Systems - page 372

TCP/IP and HTTP

PC

Browser

Web
Server

PC

Browser

CGI or API

PC

Browser

Middleware

PC

Browser

“The Internet” ODBC

PC

Browser

Database
Server

PC

Browser

Database

PC

Browser

F IGURE 14.6
Basic software components of the Web to
database connection

Now, using Figure 14.6, let's take a bit more of a detailed look at the same Good
Reading Bookstores scenario, introducing some of the specialized Web software
that we have met. When your browser sends a message to the Web server (and vice
versa), the message follows the rules of the Transmission Control Protocol/Internet
Protocol (TCP/IP), which all Internet traffic (including, e.g., email) must follow,
and the Hypertext Transfer Protocol (HTTP), which is an additional protocol layer
for World Wide Web traffic on the Internet. TCP specifies how the message is
broken up into smaller ''packets'' for transmission. IP deals with the address of the
computer to which the message is being sent. At the Web level, HTTP indicates the
type of browser in the client and other information needed to format Web pages.
But what happens once the message reaches the Web server and, in particular, how
is access to the database accomplished?
In the kind of self-contained computer and database environment illustrated
in Figure 14.1, all of the hardware and software are designed to work together from
beginning to end. The problem to be addressed in the Web database environment is
that there can be different kinds of hardware even merely between the Web server
and the database server, different kinds of application software languages, different
browsers on the client side , and a variety of different kinds of data, not just data in