Biomedical Engineering Reference
In-Depth Information
originally referred to as Personal Home Page/Forms Interpreter (PHP/FI), is less established than
CGI, it is considerably more powerful as a database interface. For example, unlike other scripting
languages for Web page development, PHP offers excellent connectivity to most of the common
databases, including Oracle, Sybase, MySQL, ODBC and many others. Java is also a server-side
language that shares many of the database interface features of CGI and PHP. In addition, like PHP,
Java uses a language that loosely resembles C.
CGI, PHP, and Java are all dependent on the server hardware for performance, and don't make
additional demands for space or execution time on the workstations that are accessing data. This is
in contrast with JavaScript, which has little to do with Java. JavaScript runs on the client side of the
interface and, as such, can be malicious because of JavaScript viruses. JavaScript, while providing
interactivity to Web pages, is much less useful as a database query tool compared to CGI, PHP, or
Java.
Regardless of the language used to extract data from a database, the data have to be displayed on
the user's monitor in an appropriate, understandable, and attractive way. This component of the user
interface is most easily handled with a separate style sheet that defines the characteristics for the
display device. In this paradigm, data to be displayed are first extracted from the database and
coded in XML, a markup language for the Web that classifies content, but doesn't define how it
should be displayed. A separate style sheet, in the form of an Extensible Stylesheet Language (XSL)
document, specifies how the data are to be displayed in the user's browser.
Using the XML/XSL approach, modifying the manner in which data are displayed can be done without
changing the XML Document, and involves simply modifying the relevant style sheet. Similarly, if the
data change, only the XML document need be changed, not the style sheet. For example, consider
the differences in how wireless content appears in HTML, XML, and XSL for the following database
report.
Genetic History
: The patient's
mother
is
carrier
for
BCG1
.
In standard HTML, which combines data and formatting instructions, the source code could appear
as:
<HTML>
<BOLD> Genetic History: </BOLD>
The patient's
<I> mother </I>
is a
<I> carrier </I>
for
<I> BCG1 </I>.
</HTML>
Notice that <BOLD> and </BOLD> are the HTML instructions to display in boldface type whatever
comes between these two tags. Similarly <I> and </I> are the instructions to italicize the type
between these two commands. By decoupling content from format instructions, changes in content
can be made without the need to modify the formatting instructions given in the style sheets. Here's
an example (formatted for clarity), using XML to categorize the data and XSL source code to describe
