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In the most web pages and simple web applications, a browser makes
a request from a server for a web page. If any part of the
web page needs to be changed in response to the user's actions,
another request has to be made to the server. This process not
only takes time, but generally produces a more rudimentary
interface.
AJAX technologies are used to make web pages feel more
responsive by exchanging small amounts of data with the
server behind the scenes, so that the entire web page does
not have to be reloaded each time the user requests a change.
This behaviour is designed to increase the web page's
interactivity, speed, and usability.
As well as providing a mechanism for communicating with a server
without a full page reload, AJAX uses the browser's Document Object
Model (DOM) to dynamically update the content of
a web page. Most modern browsers provide support for
dynamic HTML, which allows elements to be re-arranged, added or
removed. Some browsers, like Internet Explorer, include
proprietary extensions like multimedia effects and
filters, which can also be called without reloading a page.
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Internet Explorer users can view a graphing utility that
demonstrates the capabilities of dynamic HTML by clicking on the graph icon.
This demo uses Vector Markup Language (VML) to construct an interactive
histogram. VML is a feature of Internet Explorer 5, which provides
an XML-based exchange, editing, and delivery format for high-quality vector
graphics on the Web.
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AJAX applications do not require Java applets or ActiveX controls
to run, nor do they require the use of the Java Virtual machine. This
means that AJAX web pages are not subject to special security
restrictions, in the same way as a conventional HTML application.
AJAX web pages can be generated using server technologies like
Active Server Pages, which provides a good foundation for most
web-based applications.
Although AJAX web pages do not require the use of compiled components,
there is no reason why they can not be combined in a web
page. AnsaNet have recently developed a Repair and Overhaul system
that integrates these technologies to provide an in-situ explosion of
a manufacturing job down to the level of hours spent of individual operations.
An ActiveX component allows the jobs to be filtered by a wide range of
characteristics using a SQL-based query manager.
See Also
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