BYTE.com > Tangled in the Threads > 2001 > December
The Event-Driven Internet
By Jon Udell
December 3, 2001
(The Event-Driven Internet
: Page 1 of 1 )
What Worked for the GUI Should Work for the Internet, Too
In the web services paradigm, software speaks when spoken to. With
publish/subscribe, software speaks when it has something to say.
When it comes to defining the emerging next-generation Internet, we are all
blind men groping an elephant. Back in July, in a column called Kenamea's Application
Network, I highlighted some of the agreed-upon features of the beast.
These included peer autonomy, reliable and transacted communication layered
over HTTP, network-global (versus per-application) access control, and a
publish-and-subscribe event notification scheme.
Recently, I talked with the folks at KnowNow, whose technology touches many of
these same bases. Event notification has been a longstanding research interest
of KnowNow's founders, Rohit Khare and Adam Rifkin, so it's not surprising
that pub/sub is a central feature of their system.
Like Kenamea, the KnowNow system arranges for a persistent HTTP connection to
the browser, and routes network events to JavaScript handlers in order to
create real-time effects. A simple example, adapted from one of the KnowNow
samples, shows how the notification can work. Here's the setup:
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The KnowNow event router (downloadable from KnowNow) is running on a
machine, and listening on port 8000.
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The router's kn_apps folder has an application subfolder — let's say
it's called Dommy — with an index.html page. On that page, there can
be one or more event-enabled DOM elements.
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The index.html page refers to some JavaScript that does the event enabling —
that is, it wires the DOM elements to the event router.
Given this setup, here are the effects:
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