Posted by & filed under Structure.

The parable of the two watchmakers was introduced by Nobel Prize winner Herbert Simon to describe the complex relationship of subsystems and their larger wholes.

There once were two watchmakers, named Hora and Tempus, who made very fine watches. The phones in their workshops rang frequently and new customers were constantly calling them. However, Hora prospered while Tempus became poorer and poorer. In the end, Tempus lost his shop. What was the reason behind this?

The watches consisted of about 1000 parts each. The watches that Tempus made were designed such that, when he had to put down a partly assembled watch, it immediately fell into pieces and had to be reassembled from the basic elements. Hora had designed his watches so that he could put together sub-assemblies of about ten components each, and each sub-assembly could be put down without falling apart. Ten of these sub-assemblies could be put together to make a larger sub-assembly, and ten of the larger sub-assemblies constituted the whole watch.

I am reasonably sure that most software people reading this little parable would be inclined to nod. For sure, modularity is and always has been a hugely desirable trait in our attempts at software development and design.

In fact, though, I would suggest that the overwhelming majority of software projects today follow the example of Tempus, who lost his shop, rather than Hora. Why?

Because, mostly, we only pay attention to aspects of modularity and component-ness at two levels of granularity: low-level code (classes, methods) at one end of the spectrum, and unit of deployment (jar, dll) at the other. Everything in between we tend to treat as a largely amorphous blob comprising hundreds or even thousands of interacting entities. Even in those case where we do have meaningful abstractions/layers between the low-level code and and the unit of deployment, these are generally invisible and unmeasured. In this context it is hardly surprising that they will tend to degrade over time.

Simon’s parable was one of the key drivers behind Koestler’s theory of holons and holarchy. I will follow up on this – and its (to my mind) huge relevance to software thinking today – in a future post.

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