<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).
Compare: KISS Principle
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