Friday, August 31, 2007

Limits to abstraction

Suze Woolf put me on to Grady Booch’s Handbook of Software Architecture, which aims to codify the architecture of a large collection of interesting software-intensive systems, presenting them in a manner that exposes their essential patterns, and that permits comparisons across domains and architectural styles.

Booch mentions in passing on the Welcome page that “abstraction is the primary way we as humans deal with complexity”. I don’t know if that’s true; it sounds plausible. It’s definitely true that software developers deal with complexity this way, creating a ladder of increasingly succinct languages that are ever further away from the nitty gritty of the machine. While there are huge benefits in productivity, there’s also a price to pay; as Scott Rosenberg puts it in Dreaming in Code, “It's not that [developers] wouldn't welcome taking another step up the abstraction ladder; but they fear that no matter how high they climb on that ladder, they will always have to run up and down it more than they'd like--and the taller it becomes, the longer the trip.”

The notion of “limits to abstraction” is another useful way to frame the hard intangibles problem.

These limits may be structural (abstraction may fail because of the properties of a problem, or the abstraction) or cognitive (it may fail because the thinker’s mind cannot process it). In The Law of Leaky Abstractions (2002), Joel Spolsky wrote (giving lots of great examples) “All non-trivial abstractions, to some degree, are leaky. Abstractions fail. Sometimes a little, sometimes a lot. There's leakage. Things go wrong. It happens all over the place when you have abstractions. . . . One reason the law of leaky abstractions is problematic is that it means that abstractions do not really simplify our lives as much as they were meant to.”

There’s more for me to do here, digging into the literature on abstraction. Kit Fine’s book, The Limits of Abstraction (2002) could be useful, though it’s very technical – but at least there have been lots of reviews.

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