Microsoft Word Applied xml a toolkit for Programmers Wiley doc

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Ceponkus, Hoodbhoy - Applied XML - Toolkit for Programmers

Figure 2.11

Figure 2.10:
The problem of integrating databases with the Web.
A lot of this has to do with the way that information is exchanged over the Internet and
the vehicles that we use to traverse the Web (that is, usually the browser). Usually,
information transfers are made using HTTP, the hypertext transfer protocol, which is a
standardized way of transferring information (typically HTML pages) over the Internet (or
an intranet for that matter). Typically, the information transferred is mostly marked-up text
and the markup itself contains pointers to which binary files also need to be transferred
(for example, pictures or sounds). The client (browser) receives the markup and, as it
receives markup, starts making further requests based on the pointers and renders
everything together in the shape of an HTML page.
When making database queries, a database server normally receives a query (usually in
SQL syntax) and gives you back a table that you use to generate a report. If your client
has direct access to the database server, then it’s a fairly mundane process. Typically,
however, you don’t want the user to have direct access to the engine both for security
reasons (and because you normally want to isolate the database logic from the direct
user). Instead, the user has to access a gateway to the database, which both generates
the query and packages/transforms the results of the query into an HTML page, which is
then sent to the client. If you’re thinking in terms of processing overhead (which you
should), then you are quickly realizing that a lot of steps are implicit and take up
significant resources (processor overhead, excess network traffic, and throughput time).
Figure 2.11 illustrates the typical database-to-Web solution.

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Figure 2.11:
Current database-to-Web solutions.
This solution is extremely involved, and there are many ways of doing it. Unfortunately,
very few of those ways are reproducible, and all tax the server intensively. The key is in
the gateway. The gateway has to be able to do the following:
1.
Convert the request from the client (usually posted in HTML or plain text) into a SQL
query.
2.
Send the query to the database and wait for the results.
3.
Receive the results and transform them into an HTML page.
4.
Send the HTML page to the client.
The client’s browser gets a result from the server that is human viewable but cannot be
used to generate further information without taxing the server further. To put it plainly,
you receive dumbed-down data that you can see and that’s it (the bad part of the
WYSIWYG concept is that what you see is
all
you get). You can’t take the information
and do anything else with it, such as sorting, regrouping, calculating, rendering. Also, the
power of your host machine (that is, your PC) is pretty much being wasted. Even though
you have a Pentium III with an infinite amount of RAM, it doesn’t help you a lick if the
server is bogged down by traffic. Table 2.1 lists the limitations of getting HTML pages
served up to you from a database.

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