What is it?
Ajax, (Asynchronous Javascript and
XML), is a set of techniques for creating interactive
web applications that are more responsive to the user.
Instead of reloading whole pages every time the user makes a
change or request, the application exchanges the minimum possible
data with the server, while the application remains available to
the user. Ajax web applications can have the kind of rich user
interfaces usually only available with desktop applications.
Ajax is built on open standards that are available natively in
most browsers, such as Javascript and the XMLHttpRequest
application programming interface, with XHTML or HTML and Cascading
Style Sheets.
In February, Microsoft threw in its lot with
the OpenAjax Alliance, having changed the name
of its Atlas initiative to ASP.net Ajax. It is working with more
than 70 organisations, including Google, Mozilla, Sun
Microsystems and the Eclipse Foundation, to ensure that Ajax
technologies remain open and interoperable.
Where did it originate?
The term Ajax was not coined until 2005, but the key
technologies date back a decade or more.
What's it for?
As Jesse James Garrett, who coined the name Ajax, points out,
HTML was developed to deliver hypertext, not interactive
applications. Ajax acts as an intermediary between the user and the
server, smoothing out the stops and starts that make using a web
application so different to the desktop experience.
Ajax is being used to develop collaborative applications, and
composite applications, or "mashups", which assemble content from
multiple sources and applications.
What makes it special?
The OpenAjax Alliance, says, "Ajax enables rich user experiences
while preserving existing back-end infrastructure. Users benefit
from next-generation applications that have the feel of desktop
applications and provide new capabilities, while IT preserves
existing benefits from web-based application deployment and
continuity with existing HTML-based back-end infrastructure."
However, there are drawbacks:
● The back button will not necessarily return the user to the
unmodified page
● Javascript is implemented differently in different browsers
and is an uneasy fit for Microsoft
● If an author copies a URL to include it as a hypertext anchor
in one of their own pages, that anchor will not lead readers to the
desired view but to the initial state of the page.
How difficult is it to master?
Most web developers will already have prior knowledge of the
basics, such as Javascript, XHTML/HTML, CSS and XML, and there are
many Ajax frameworks to aid development.
What systems does it run on?
Alongside Microsoft and Sun, other members of the OpenAjax
Alliance include Adobe, BEA, IBM, Novell, Oracle, SAP and Zend.
What's coming up?
The OpenAjax Alliance is working on the OpenAjax
Hub, a set of standard Javascript that addresses interoperability
issues that arise when multiple Ajax libraries are used within the
same web page.
Training
There are many free Ajax tutorials on the web. A good starting
point is the
Mozilla developer site.
Tutorials for
Microsoft developers >>
Rates of pay
Salaries for Ajax web developers start at £25,000. Specialist
graphical user interface developers can expect £35,000-plus.
Computer Weekly/SSL salary survey >>
Ajax security: a dynamic approach
>>
Ajax is squeezed as Adobe builds up rival Flex
toolset >>
Microsoft joins Ajax web development alliance
>>
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