Inspection, Abstraction and Shipping Containers
On my drive home tonight, a giant “Maersk Sealand” branded truck passed me on the highway. It got me thinking about the innovation of the shipping container, and how introducing a standard size and shape revolutionized the shipping industry and enabled a growing global economy. At least that’s the perspective presented by Mark Levinson in The Box: How the Shipping Container Made the World Smaller and the World Economy Bigger. A synopsis of the story and a sample chapter are available; Wikipedia’s entry on containerization also presents a narrative describing the development and its impacts.
Here’s how impactlab.com describes it:
Indeed, it is hard to imagine how world trade could have grown so fast—quintupling in the last two decades—without the “intermodal shipping container,” to use the technical term. The invention of a standard-size steel box that can be easily moved from a truck to a ship to a railroad car, without ever passing through human hands, cut down on the work and vastly increased the speed of shipping. It represented an entirely new system, not just a new product. The dark side is that these steel containers are by definition black boxes, invisible to casual inspection, and the more of them authorities open for inspection, the more they undermine the smooth functioning of the system.
Although some people like to debate whether the introduction of the shipping container represented an incremental improvement or a breakthrough innovation, I’d like to point out an entirely different aspect of this story: a process improvement step yielded a plethora of benefits because the inspection step was eliminated. Inspection happened naturally the old way, without planning it explicitly; workers had to unpack all the boxes and crates from one truck and load them onto another truck, or a ship. It would be difficult to overlook a nuclear warhead or a few tons of pot.
To make the system work, the concept of what was being transported was abstracted away from the problem, making the shipping container a black box. If all parties are trustworthy and not using the system for a purpose other than what was intended, this is no problem. But once people start using the system for unintended purposes, everything changes.
This reflects what happens in software development as well: you code an application, abstracting away the complex aspects of the problem and attaching unit tests to those nuggets. You don’t have to inspect the code within the nuggets because either you’ve already fully tested them, or you don’t care – and either way, you don’t expect what’s in the nugget to change. Similarly, the shipping industry did not plan that the containers would be used to ship illegal cargo – that wasn’t one of the expectations of what could be within the black box. The lesson (to me)? Degree of abstraction within a system, and the level of inspection of a system, are related. When your expectations of what constitutes your components changes, you need to revisit whether you need inspection (and how much).