Page 149 - DLIS408_INFORMATION_TECHNOLOGY-APPLICATIONSL SCIENCES

Information Technology and Application

Notes In contrast, web applications use web documents written in a standard format such as HTML (and
more recently XHTML), which are supported by a variety of web browsers.
Generally, each individual web page is delivered to the client as a static document, but the sequence
of pages can provide an interactive experience, as user input is returned through web form elements
embedded in the page markup. During the session, the web browser interprets and displays the
pages, and acts as the universal client for any web application.

Did u know? In 1999, the “web application” concept was introduced in the Java language in
the Servlet Specification version 2.2. [2.1?].
At that time both JavaScript and XML had already been developed, but Ajax had still not yet been
coined and the XML Http Request object had only been recently introduced on Internet Explorer 5
as an ActiveX object.

In 2005, the term Ajax was coined, and applications like Gmail started to make their client sides
more and more interactive.

Interface

Figure 13.3

Webconverger operating system provides an interface for web applications.
Through Java, JavaScript, DHTML, Flash, Silver light and other technologies, application-specific
methods such as drawing on the screen, playing audio, and access to the keyboard and mouse are
all possible. Many services have worked to combine all of these into a more familiar interface that
adopts the appearance of an operating system. General purpose techniques such as drag and drop
are also supported by these technologies. Web developers often use client-side scripting to add
functionality, especially to create an interactive experience that does not require page reloading.
Recently, technologies have been developed to coordinate client-side scripting with server-side
technologies such as PHP. Ajax, a web development technique using a combination of various
technologies, is an example of technology which creates a more interactive experience.

Structure

Applications are usually broken into logical chunks called “tiers”, where every tier is assigned a
role. Traditional applications consist only of 1 tier, which resides on the client machine, but web
applications lend themselves to a n-tiered approach by nature. Though many variations are possible,
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