Tuesday, December 23, 2008

Pub-sub

We often casually describe event driven architectural patterns as being "pub/sub". This is, of course, an over simplification and misses the point.

The key is to think of this kind of architecture is subscription driven or subscription dominated. This has been brought home. big time, in the social networking frameworks (like Twitter). People who post on Twitter essentially say whatever comes into their heads. We follow individuals or groups because, on balance, we get more out of following them than not. However, we will need to filter. For example, there are Twitterers who post about the industries that I am interested in, the beer they like to drink, their cooking interests, their children, their other hobbies,.....

I typically don't want to see all of that, but the poster shouldn't be deterred and stop. The poster's responsibility is to post. The listener's responsibility is to filter the dull stuff - or the stuff that is dull to the specific listener. That is often hard because the signal to noise ratio for any specific listener will be different than the signal to noise ratio for any other.

The4 same is true in any kind of event dominated system - human or otherwise. The listener is in a position to make decisions about what it is interested in, what it may respond to. The "teller" must continue to deliver the narrative.