It provides the following classification: The third phase, then, that began in 1996 with the protocol of 1988, whose laws are still in force. In the second phase instead, that dates back between 19, there was a distinction between World International Exposition (Universal Expo) that took place every ten years and had a duration of six months, and International Specialised Exposition, that took place every two years and had a duration of six months. The first phase 1931–1980 distinguished: General Expo, that had a duration of until one year with a break of six years (first class) and four years (second class) and Specialised Expo that had a duration of until six months. protocol has distinguished two types of Expo but the terms of this classification underwent some changes in the time and three phases in the history of Expo Classification are recognized. In the convenction of 1928, that came into force in 1931, there is a list of the main characteristics that an universal expo must have. In the Convenction – that is regularly updated – organization criteria and rules are specified that every expo must adopt, as well as the relationships among the member states, and it also points goals that want to obtain.
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Today B.I.E has 154 states and organisms as members. The main organism that arranges the frequency and the organisation of exposition is the B.I.E., Bureau International des Expositions, born 22 November 1928 in Paris by a convenction subscribed by several nations of the world. Their aim is to promote industrial and technological progress world–wide, showing the last scientific and technological innovations that are somehow able to contribute to the creation of better conditions of economic and social global life.
![milan world exposition milan world exposition](https://www.spacesworks.com/wp-content/uploads/2015/06/World_Expo_2015_02.jpg)
World Expo are international exhibitions hosted every five years from a different country in the world.