<programming> The program-design version of the law of
diminishing returns. The 80/20 rule says that roughly 80% of
the problem can be solved with 20% of the effort that it would
take to solve the whole problem.
For example, parsing e-mail addresses in "From:" lines in
e-mail messages is notoriously difficult if you follow the RFC
2822 specification. However, about 60% of actual "From:"
lines are in the format "From: Their Name <user@host>", with a
far more constrained idea of what can be in "user" or "host"
than in RFC 2822. Another 25% just add double-quotes around
"Their Name". Matching just those two patterns would thus
cover 85% of "From:" lines, with a tiny portion of the code
required to fully implement RFC2822.
(Adding support for "From: user@host" and "From: user@host
(Their Name) " brings coverage to almost 100%, leaving only
really baroque things that RFC-2822 permits, like "From:
Pete(A wonderful \) chap) <pete(his account)@silly.test(his
host)" or the like.)
It is an eternal question whether too much attention is paid
to the 80/20 rule (leading to systems that are irrevocably
broken for "unusual" cases), or too little (leading to systems
that sacrifice usability in the typical case, just so that
rare cases can work properly).
