eighty-twenty rule

eighty-twenty rule
80/20 rule

   <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}

   (2003-11-17)