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Database Management Systems/Managing Database

Notes the form to the user. After the user fills in the form, the form is returned to the Web server, and
the information filled in by the user can be used as parameters to a program executing at the
same site as the Web server.
The use of a Web browser to invoke a program at a remote site leads us to the role of databases
on the Web. The invoked program can generate a request to a database system. This capability
allows us to easily place a database on a computer network, and make services that rely upon
database access available over the Web. This leads to a new and rapidly growing source of
concurrent requests to a DBMS, and with thousands of concurrent users routinely accessing
popular Web sites, new levels of scalability and robustness are required.

The diversity of information on the Web, its distributed nature, and the new uses that it is being
put to lead to challenges for DBMSs that go beyond simply improved performance in traditional
functionality. For instance, we require support for queries that are run periodically or
continuously and that access data from several distributed sources. As an example, a user may
want to be notified whenever a new item meeting some criteria (e.g., a Peace Bear Beanie Baby
toy costing less than $15) is offered for sale at one of several Web sites. Given many such user
profiles, how can we efficiently monitor them and notify users promptly as the items they are
interested in become available? As another instance of a new class of problems, the emergence
of the XML standard for describing data leads to challenges in managing and querying XML
data.

14.2 Web Interface to Databases

14.2.1 Server Side Database Communication with CGI

So far in this tutorial we have remained pretty airy. We have learned lots of “database theory”
and “abstract” SQL communication protocols.
But what you probably came to learn was how you could actually put a real-live database on the
web.
Well, to be fair, understanding all that abstract stuff that we have discussed so far is necessary for
you to be able to do what you want to do.

Unfortunately, putting your database on the web turns out to be a pretty complex feat involving
all sorts of technologies. So, there are a bunch of things you needed to learn in order to get the
whole kit-and-caboodle operational.
However don’t worry, in this part, we are going to put it all together and get your data webified.
Nevertheless, before we get into the nitty gritty lets recap a bit and also provide an overview for
what we are going to do in this part.

14.2.2 Chains of Communication

A Web Database follows the client-server database model. A Database Engine sits on some
central computer somewhere and serves data to multiple web-based clients (perhaps lots of
customers using Netscape Navigator).
Because we are dealing with web-based clients however, we must also have a Web Server that
handles requests from web-browsers and then forwards them to the Database. Likewise, the
web server will wait for the database to respond and then pass on that response to the waiting
web browsers. The whole interaction is much simpler as a picture.

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