|By Ted Goddard, Steve Maryka||
|January 16, 2009 05:41 AM EST||
If you Google "AJAX Web 2.0" you'll get over eight million hits, but what technologies will you find in that mix that can truly deliver on the promises of Web 2.0 today? While there's no single definition of Web 2.0, at its heart lays the Internet acting as a platform for social networks, where information can be created and shared in a community of interest. Rich Internet Applications (RIAs) relate to Web 2.0 concepts only in that they enhance the platform by providing a more effective user interface. AJAX relates to Web 2.0 only in that it provides a lightweight approach for developing RIAs that execute through a single ubiquitous interface, the Web browser.
An examination of the interaction models for existing social networking platforms like wikis and blogs reveals that they lack the instantaneous nature of true human interaction. This is an artifact of the synchronous Web model that must be overcome when we consider next-generation platforms envisioned in the Web 2.0 spectrum. Internet-based chat is the most basic example of the near-instantaneous interaction that Web 2.0 demands, but even delivering these basic capabilities in a scalable, lightweight, browser-based mechanism is beyond the scope of most AJAX technologies. In fact, if you sift through those eight million Google hits, you'll find only a handful of open source technologies that address the problems associated with pushing content asynchronously to the user through standard browser mechanisms. We'll provide an overview of those technologies later, but first some basics.
The Basics of Web-based Push
Industry has not standardized on a mechanism or a name for asynchronous data push to the browser. In the AJAX realm the technique goes by a variety of names including AJAX Push, Comet, and Reverse AJAX, but regardless of what you call it, the various approaches share a common characteristic. The only lightweight communication mechanism available to the browser is the HTTP protocol, but HTTP only facilitates standard request/response communication initiated from the browser to the server. To deliver responses asynchronously, it's necessary to invert the HTTP protocol by holding an open request at the server, and fulfilling that request when an update is available. The differences between standard AJAX request processing and the inverted mechanism required for push are illustrated in Figure 1.
To support asynchronous push we need to hold a browser connection open in anticipation of a server-based event that will result in presentation changes in the browser. Intuition suggests that there are issues with this approach and in this case intuition serves us well, since we face connection-related problems at both the browser and the server.
Browser Connection Limit
The problem is amplified in portal environments because legacy portal engines don't support the necessary asynchronous communication path. For push to work in multiple portlets it's not only necessary to share the browser connection, but a single shared server connection is required to marshal asynchronous responses. If portlets are deployed from multiple WARs, there's an additional complication in that the sharing mechanism must coordinate between multiple Web applications and will require some IPC mechanism to do so.
|radixweb 08/13/08 09:21:00 AM EDT|
Hey, Great Post.. Thanks for this..
|MiamiWebDesigner 08/02/08 09:34:25 AM EDT|
Web 2.0 Is Like Pornography
Like so many tech articles posted since Tim O'Reilly coined the term in 2004, this one references "Web 2.0" as if it were something tangible--or at least a concept with clear, concise definition. It is not. In 2006, Web founder Sir Tim Berners-Lee sagely observed that "nobody knows what it means":
In 2007, Michael Wesch put together this video that supposedly "explains what Web 2.0 really is about":
It is a cool video. But the message is all about XML and how it can be used to separate form and content. There was no mention of CSS and XHTML, but no matter. I was writing XML parsers in the '90s, and XHTML/CSS web design pre-dates "Web 2.0" as well. No cigar, Professor Wesch.
And now in 2008, the most honest thing we can say is that "Web 2.0" means whatever the techno-marketeer (ab)using it wants it to mean. Otherwise, why would intelligent people like Isaac O'Bannon still be writing articles asking "What is Web 2.0?":
And, why would McKinsey's just-released best-of-breed report entitled "Building the Web 2.0 Enterprise" ...
... include no attempt at defining the term other than to list the "Web 2.0 Tools" that comprise or enable it? And even there, the chief ingredient is identified only as "Web Services", adding more mystery to the mix as one ethereal term is offered up to explain another.
As originated in an Onstartups.com website design posting...
... "Web 2.0" is like pornography: Nobody has defined it, but you know it when you see it.
Bruce Arnold, Web Designer, Miami Florida
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