Palindrome (; "again") and ' (; "way, direction"). Palindromes date back at least to 79 AD, as a palindrome was found as a graffito at Herculaneum, a city buried by ash in that year. This palindrome, called the Sator Square, consists of a sentence written in Latin: "Sator Arepo Tenet Opera Rotas" ("The sower Arepo holds with effort the wheels"). It is remarkable for the fact that the first letters of each word form the first word, the second letters form the second word, and so forth. Hence, it can be arranged into a word square that reads in four different
Principle of least astonishment Principle of least astonishment The principle of least astonishment (POLA) (and variations of ""principle"/"law"/"rule" of least "astonishment"/"surprise"") applies to user interface and software design. A typical formulation of the principle, from 1984, is: "If a necessary feature has a high astonishment factor, it may be necessary to redesign the feature." More generally, the principle means that a component of a system should behave in a way that most users will expect it to behave; the behavior should not astonish or surprise users. A textbook formulation is: "People are part of the system. The design should match the user's experience, expectations,