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
Belief revision should not produce any effect on formula_10, and the result of revision is formula_94. In the second case, formula_95 is taken a single belief. The fact that formula_9 is false contradicts this belief, which should therefore be removed from the belief base. The result of revision is therefore formula_97 in this case. The problem of using deductively closed knowledge bases is that no distinction is made between pieces of knowledge that are known by themselves and pieces of knowledge that are merely consequences of them. This distinction is instead done by the "foundational" approach to belief revision, which is related