> The cognitive phenomenon that we describe as "programming plans"
> can occur whether or not there is any "planning" in the software
> development process.
>
> For people wishing to challenge this, it seems to me that the
> only alternatives are:
>
> 1. there is nothing at all inside the programmer's head when he
> or she engages in eXtreme Programming
>
> 2. there is something there, but this mental representation is in
> some form that was not anticipated in the research on
> "programming plans".
>
> 3. the mental representation *is* of pretty much the same type
> described in the research on programming plans, but "programming
> plan" is the wrong word for it.
>
> Anybody want to sign up to any one of these?
Not really, but I would like to point out that there is a somewhat
plausible #4:
4. the plan is in an external memory and the only thing in the head
of the programmer (usually) is (a) indexing knowledge for finding
stuff in that external memory and (b) a collection of local
transformation rules (e.g. refactoring). This is sort of a
combination of #1 and #2, but not ruling out #3.
Before you spew coffee through your nose laughing, it is worth
a closer look. Since Derek brought up the late Herb Simon already, I
feel justified in recalling his rather infamous parable of the ant on
the beach. The idea is that the ant follows a convoluted path with
simple rules because the beach itself is convoluted. But the ant is
really simple, having no internal knowledge of the beach. If you read
Simon really carefully he suggests humans have a two part beach:
internal knowledge and external perceivable structure. They just have
simple mechanisms that crawl along the contours of both. Now the
question is: "*how much* of our beach is internal vs external"? #3
assumes its mostly internal. #4 suggests its more of the external
rather than the internal in many situations, that is, experts have a
very limited internal beach and rely on the external one. How could
this be?
Remember the student who does algebra simply by following memorized
rules rather than by understanding how the algebra *actually* works?
Larkin write a great paper on display-based problem solving in which
she modeled how algebra could be solved by using simple rules to
determine at each point what step to do next. In her model there
is no plan that controls the action---the solver is like an ant
crawling from place to place observing whatever local conditions
are there. The model's "knowledge" of algebra is incredibly slim.
In order to solve problems the model just has a list of rules that
determine local transformations of an external store. Now it seems
like a stretch but it is not hard to imagine that this same sort of
scheme could work in programming, the idea being that programmers get
by much of the time with using local transformation rules and not
really needing to understand how the program *actually* works and is
structured. If you read Jens Rasmussen, then you'll recognize this as
rule-based action rather than knowledge-based action.
Now I'm not as well versed in XP as I'd like, but it seems to me that
we're now eerily close to part of XP's gist. If expert XP programmers
rely on rule-based futzing with refactoring and then use shallow
judgment to evaluate the results (or just test), then one might find
little evidence of plans stuffed in their brains unless, of course, you
are a rather nasty experimental psychologist that forces them to
reconstruct them in an experiment. That is, these programmers could be
much more like rote algebra solvers than knowledgeable solvers. Sure,
Option #3 could be available, but it might be unused except when the
programmer is (probably begrudgingly) forced out of using shallow
comprehension/ shallow reasoning.
Anyway I should get to my point: its possible that psychology has
identified programming plans, and yet its *also simultaneously possible*
that Derek's apparent suspicions are correct that they're not used in
the same way that psychologists may think.
At least, if #4 is a viable alternative to Dr. Blackwell's other
options.
One thing I that hope is clear is that psychologists should maybe
reconsider again the demands placed on their subjects and how that
could evoke different response mechanisms. We may be comfortable now
with the idea of reasoning with schematic knowledge but I don't think
we have a good handle on when it is invoked.
Andrew
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