duck typing

from The Free On-line Dictionary of Computing (8 July 2008)
duck typing

   <programming> A term coined by Dave Thomas for a kind of
   {dynamic typing} typical of some programming languages, such
   as {Smalltalk}, {Ruby} or {Visual FoxPro}, where a
   {variable}'s {run-time} value determines the operations that
   can be performed on it.

   The term comes from the "duck test": if it walks like a duck
   and quacks like a duck, it must be a duck.

   Duck typing considers the {methods} to which a value responds
   and the {attributes} it posesses rather than its relationship
   to a type hierarchy.  This encourages greater {polymorphism}
   because types are enforced as late as possible.

   
(http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-talk/100511).

   (2006-09-13)