Another similar project
Status: Alpha
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mattj
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There is another similar project like OpenQueue and xmlBlaster, which has a lot
a really cool features like subscribing against a list of keywords instead of just a
queue name.
It is named Elvin. It is free for non commercial use, so it is not really free :-(
It is available on http://elvin.dstc.edu.au/
Luc
I met a couple of the Elvin developers at WISEN '98 (Workshop on Internet Scale Event Notification). They definitely have some interesting ideas, such as content-based subscriptions (which you mentioned), and "quenching", where clients essentially tell the server what they _don't_ want to see, to reduce fanout of messages. These ideas can really boost performance within the problem space Elvin addresses.
The Elvin space seems to be more about the current states of objects, instant messaging, a file was just changed, etc. In other words, "this is happening now." As I understand it, there is no provision for persistent messages, nor for transactional messaging.
Which is fine, because an architecture for instant messaging between ten million simultaneous users (such as ICQ, not exactly Elvin) is going to be different than an architecture for a dozen computers to reliably queue up messages for each other. That was one conclusion many people reached at WISEN; it would be nice if one protocol/solution could be leveraged for ALL the possible notification applications, but for now the instant messaging apps and the queuing apps really have different needs, and neither group can really compromise on their needs.
(p.s. - This is a great link you posted (to Elvin), thanks! It reminds me that I want to send mail to all the attendees of WISEN and let them know about OpenQueue's new site.)