Principle of Least Astonishment

POLA or POLS (surprise) states that, when two elements of an interface conflict or are ambiguous, the behaviour should be that which will least surprise the user. DWIM is a similar initialism for "Do What I Mean", where code does something (usually very subtly) different from what the programmer originally intended. Occam's razor is another related principle attributed to the 14-th Century English logician and Franciscan friar William of Ockham. The principle states that the explanation of any phenomenon should make as few assumptions as possible, eliminating, or "shaving off", those that make no difference in the observable predictions of the theory.