Beginning Web Development, Silverlight, and ASP.NET AJAX

CHAPTER 11 ■ AJAX APPLICATIONS AND EMPOWERING THE WEB USER EXPERIENCE 255
user actions, providing a dynamic environment that reduces postbacks and page
refreshes.
Another increment to this came with Microsoft’s Remote Scripting technology, which
took this to the next level, providing a browser plug-in that could communicate with a
server over sockets and expose the data that it received to JavaScript. This plug-in was a
Java applet and was released with Internet Explorer 4.
After this, an ActiveX control that provided a dependency-free plug-in was produced
by Microsoft. This object, called XMLHttpRequest, came with Internet Explorer 5. The first
major application to use this functionality was the web-based version of Microsoft’s popular
Outlook e-mail program, Outlook Web Access. The e-mail scenario is perfect for
asynchronous web page updates—when a new e-mail comes in, you would like it to
appear in your inbox without a complete page refresh, just like it does in your desktop
application.
This XMLHttpRequest ActiveX control is the heart of Ajax. Oddly enough, although it
was released to the wild in 2000, it didn’t really pick up until nearly five years later.
There are a number of possible reasons for this, including browser support—initially,
XMLHttpRequest was Internet Explorer–only. Another reason was likely the availability of
broadband. Increasing broadband penetration over that five-year period lead to a greater
demand for richer web applications and more incentive for web sites to provide richer
experiences.
The first Ajax application that I used was Google Maps—with mapping being the perfect
sweet spot for consumer-oriented rich applications. Consider your workflow when
using a mapping application—you enter an address and receive a map showing the area
around your address. You then likely want to inspect the area around that address, for
example, to plot routes to that address. Before Ajax was used, you would pan around
the map using North, South, East, and West buttons. The Ajax implementation used
XMLHttpRequest to download the surrounding areas of the map in the background while
you were inspecting the map. You would then drag the mouse around the map, and they
would appear. Of course, if you dragged quickly, the tiles may not have been in place yet,
and you would get a blank map while they downloaded—but the experience was still
vastly superior to full page refreshes.
The improvement in the user experience and the reduced amount of bandwidth that
needed to be served to provide it created an irresistible new design pattern for web sites
and experiences, and it wasn’t long before use of XMLHttpRequest became commonplace.
At the same time, the concept of Web 2.0 was emerging. This concept, invented by
Tim O’Reilly, described the next phase of the Web, built around services that allowed
users, not just web developers, to be contributors of information. Effective collaboration
from novice users requires an enhanced experience, and Ajax was there to provide it. As
such, in developer terms, Ajax is pretty synonymous with Web 2.0. In the next section,
we’ll take a look at getting started with Ajax programming and some of the neat things
that you can do with it!