Re: Development: A Structured Problem Area?

--- Derek Richardson <stuff-YC78yCVKCwA@xxxxxxxxxxxxxxxx> wrote:

> If requirements are fully specified, is the rest of
> the work a "well-structured problem" that can be
> solved by rule-based methods?

Yes, but that just moves the messy unstructured work into writing 
fully-specified requirements. If we had fully-specified requirements -
- a 1:1 scale map of the system -- translating the requirements into 
code would be purely mechanical. The hard part is getting to those 
fully-specified requirements.

The idea that any reasonably intelligent person can write 
requirements and specifications, and that programmers can then 
mechanically translate the specs into code is an old and pernicious 
problem of programming, still believed by many managers and non-
technical people. Programming languages are supposed to be tools for 
unambiguously expressing requirements in a form a computer and (we 
hope) people can understand. Most people don't want to learn 
programming languages, so they write requirements and specifications 
in English or some other ambiguous, informal natural language.

One source of messy emergent behavior comes from the discrepancies 
between the actual requirements and what gets recorded in the specs. 
The customer or user has a need or vision that the requirements only 
partially or imperfectly capture. Another source of messiness comes 
from the programmer translating the requirements from informal 
ambiguous language to formal unambiguous code; the programmer must 
necessarily make assumptions, fill in the blanks, etc. A third source 
of chaos derives from our human inability to understand complex 
systems and predict their behavior.

In 25 years of professional programming I have never seen formal 
requirements or specifications that were worth the time spent on 
them. Having the programmer(s) work directly with the customer/user, 
possibly with a skilled analyst acting as mediator, always (in my 
experience) leads to a better result. Without that interaction 
projects either fail or turn into death marches.

Most people, I think, understand at some level that doctors and 
nurses use experience and intuition more than a set of rules. But 
increasingly even medical professionals are expected to follow 
specific procedures (established by lawyers and insurance companies) 
or risk the consequences. And rule-based diagnostic systems were 
among the first applications of AI. Programmers have never been seen 
by non-programmers as much more than coders mechanically translating 
requirements. Doctors are now increasingly viewed the same way.

Greg Jorgensen
PDXperts LLC - Portland, Oregon USA




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