Article:		Weblogs, Publish-Subscribe, and Web Collections: A REST Analysis
Subject:		Some corrections to claims about PubSub
Date:		2004-12-02 22:07:45
From:		Mike Dierken
Response to: Some corrections to claims about PubSub
1. I apologize for the incorrect metrics of pubsub.com matching rates - I thought I got it right off of your weblog at http://bobwyman.pubsub.com/main/2004/06/hyperbole_numbe.html. (Given 225B/day I still get 2.6M per second). 3. You are right, I didn't realize pubsub.com supported HTTP POST. I would be interested in using this capability, since the mod-pubsub.org system has the ability receive POSTs and to forward messages to clients and desktops. It would be interested to see the two systems hooked up together. 4. Sorry for giving the impression that I thought pubsub.com was not a generalized system - I only meant to describe the data sources currently supported. And I definitely agree that the money is in the applications rather than the technologies. 5. My impression is that most queries are simple enough to express in a URI. More complex ones are the edge case that don't have to follow the one-step creation process. Also, I don't know what user-specific data would be placed in the query that would wind up in the URI, but it definitely would hinder sharing URIs. All in all, I think pubsub.com is a great system and I have the utmost respect for you and your team - keep up the good work of bringing publish/subscribe technologies to the Web.

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• Some corrections to claims about PubSub
  2004-12-03 01:25:09 Bob Wyman [Reply]
  
  Mike,
  1. Yes, you are right. The most we've ever needed to do in production is a few million matches per second. The 3 billion/second number is what we get in testing.

  
  3. re: mod-pubsub support. We used a slightly modified version of our REST support to feed messages to KnowNow LiveServers. I believe the mod-pubsub interfaces are very similar to KnowNow's. The KnowNow/mod-pubsub technology is very useful since it allows us to establish a light-weight, persistent, firewall-piercing connection to the desktop. Our focus is on the matching problem and we're pleased to be able to leverage existing solutions to actually do delivery of messages. Let's talk offline in email about working with mod-pubsub.

  
  5. It would take too long to explain in a comment, however, let me just say that a number of methods for computing "relevance" of matches rely on examining the history of messages that have been delivered to a particular subscription over time as well as on user feedback. Thus, even if two subscriptions have identical queries, they may deliver different results based on when they were created and the user's history of interaction with the results. If we don't provide a binding between a user and a subscription, we will be severely limited in our ability to implement a whole class of improved methods for determining the "relevance" of a matched item. This would not be a good thing. The "single step" solution that you propose works very well with retrospective searches (i.e. what Google, Feedster, etc. do) where the entire result set is available each time the query is re-evaluated. However, this solution is much less useful in a "prospective" system like we implement since in such a system, the result set accumulates over time and we can benefit from user interaction and hinting over time.

  
  bob wyman