Complexity and Coupling: Pushmepullyou

by wsampson

As some may know, I have recently been hired at the Mississippi Department of Archives and History. It’s the end of my third week here and it’s been great: great coworkers, interesting materials (I’m working with electronic records in the government section) – and I’ve been able to overhear the back-and-forth on a recently completed project which saw us transitioning from one online catalog to another. It was successful – do not worry.

But for anyone who has worked in IT at all ever, or just had to approach a problematic system and put out the fire may appreciate the elegance of this statement.

Systems that are both tightly coupled and highly complex, Perrow argues in Normal Accidents (1984), are inherently dangerous. Crudely put, high complexity in a system means that if something goes wrong it takes time to work out what has happened and to act appropriately. Tight coupling means that one doesn’t have that time. Moreover, he suggests, a tightly coupled system needs centralised management, but a highly complex system can’t be managed effectively in a centralised way because we simply don’t understand it well enough; therefore its organisation must be decentralised. Systems that combine tight coupling with high complexity are an organisational contradiction, Perrow argues: they are ‘a kind of Pushmepullyou out of the Doctor Dolittle stories (a beast with heads at both ends that wanted to go in both directions at once)’.

That is poetry. From Donald MacKenzie in the London Review of Books (link added). Itself from a post covering Amazon’s April 2011 cloud outage at David Rosenthal’s always-excellent digital preservation blog.

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