DATABASE SYSTEMS AND THE WEB - Database Design and Development: An Essential Guide for IT Professionals - page 591

Close. The server closes the connection.
The simplicity of the protocol mainly comes from its property of being stateless.
What does this mean? As soon as the server closes the connection, nothing is
retained in the server about the transaction. The server does not remember any
prior requests. Once the connection is closed, the memory about the transaction is
completely erased. When you request a document, the server does not know who
you are, whether this is your first request, or whether you are at the website for the
fiftieth time. This property, however, requires very simple logic. There is no need for
elaborate software, and the clients and servers can run lean without holding extra
memory and storage for old requests.
A big challenge in using HTTP is its inability to keep track of the state of your
interaction with the server. The state indicates information about who you are and
about your request or visit. Maintaining state means remembering prior informa-
tion as the user at the client system moves from page to page at the website at the
server system.
Being stateless, HTTP, by itself, cannot apply to database transactions. Database
transactions need the concept of a session during which interactions between the
client and the database can take place. Some schemes are available for maintaining
state information: store it in cookies, encode it in the links, send it in the form of
hidden variables, and store it on the Web server. However, these schemes have
limitations. As you will see later, server functionality must be extended for database
transactions to execute on the Web.
Uniform Resource Locator (URL)
URLs act like addresses to any definable resource on the Internet. They are all-
purpose reference mechanisms for the Internet. URLs are the basis for HTTP and
the Web. They are used to define addresses on the Web where documents or
resources can be found based on their location. Any line from one document to
another is coded in the form of a URL.
A URL is written with a simple syntax consisting of the following parts:
Protocol or scheme. The way or method to exchange data on the Internet (HTTP,
FTP, Telnet, etc.)
Host. The host computer or the server on which the data resource is located
Port. Port number if the requested service is not located at the default port of the
host system
Path. Path name on the host where the resource is to found
A URL, therefore, is a string of characters composed of these components. Here
are a few examples of URLs:
http://wiley.com/author/format.html
ftp://raritanval.edu/documents/dbdesign/syllabus.txt
telnet://iitf.doc.gov