Conceptual Integrity

In The Mythical Man Month, Fred Brooks emphasizes the importance of conceptual integrity in design. Our deep view of programming suggests some practical ways to achieve conceptual integrity.

First, we know the importance of mental maps. If every member of the team shares a mutually-agreed mental map of the system being constructed, then it is possible for everyone's' contribution to be in the spirit of the overall design. If they don't, then it isn't, because a style guide detailed enough to allow someone to get everything right without knowing what they are doing would be much harder for the architect to write than the system itself would be.

Secondly, we have a picture of the programmer optimizing a series of design choices to produce a minimal solution and control complexity. So we need to look at the kinds of constructs the programmers cook with, and ensure that they are shared. Such a project style guide indicates a coherent collection of variable naming conventions, error-handling strategies, example idioms for using the subsystems' APIs, even the comment style. One might say that by controlling the shape of the bricks, the architect can constrain the shape of the house while leaving flexibility in the hands of the designer. The structure of the code then ensures that the code between the canonical examples is predictable and elegant. So code examples in style guides control structure, and structure controls code. Here we see another echo of the Knight's Fork - if we use the right structure, we can bring necessary and sufficient syntax into play and write minimal text. Conversely, the more twisted the stuff gets, the more of it you get, to be twisted up.

A final benefit of conceptual integrity that is very valuable to the professional programmer is very practical. Imagine you are on a roll. You've seen the way to divide up your functionality, you've got a really elegant way of catching all the odd ways the OS can signal failure, you're halfway through coding up all the cases, and you need a new variable name. Your head locks up, overloaded by a triviality! The exponential benefits of getting focused and staying that way are as great as the exponential benefits of minimizing the code size, so every silly distraction you can get rid of is worth it. On sites where everyone stops work every ten minutes to argue about administration, the benefits of real focus can never emerge anyway, but where external conditions have been sorted out, having a style guide to let you pretty much derive this kind of stuff on the fly can dramatically improve effective productivity.