Chinese characters are not alphabetic and only rarely reflect sound changes. The tentative reconstruction of Old Chinese is an endeavor only a few centuries old. As a result, Classical Chinese is not read with a reconstruction of Old Chinese pronunciation; instead, it is always read with the pronunciations of characters categorized and listed in the Phonology Dictionary (韻書; pinyin: "yùnshū", "rhyme book") officially published by the Governments, originally based upon the Middle Chinese pronunciation of Luoyang in the 2nd to 4th centuries. With the progress of time, every dynasty has updated and modified the official Phonology Dictionary. By the time of the Yuan Dynasty and Ming Dynasty, the Phonology Dictionary was based on early Mandarin. But since the Imperial Examination required the composition of Shi genre, in non-Mandarin speaking parts of China such as Zhejiang, Guangdong and Fujian, pronunciation is either based on everyday speech as in Cantonese; or, in some varieties of Chinese (e.g. Southern Min), with a special set of pronunciations used for Classical Chinese or "formal" vocabulary and usage borrowed from Classical Chinese usage. In practice, all varieties of Chinese combine these two extremes. Mandarin and Cantonese, for example, also have words that are pronounced one way in colloquial usage and another way when used in Classical Chinese or in specialized terms coming from Classical Chinese, though the system is not as extensive as that of Southern Min or Wu. (See Literary and colloquial readings of Chinese characters)