1.) In the book ‘A city is not a tree’ the tree in the tittle is not a real tree, it is an abstract structure. He contrasted and distincted this structure with more complex abstract structure. He called the cities have arisen spontaneously; natural cities, and called the cities which created by designers and planners; artificial cities. When we compare it with ancient cities that create living spaces, the modern artificial city-building movement is unsuccessful. But they are both structures of sets. A set is collection of elements belonging each other. For example in the book a drugstore, outside a traffic lights, in the entrance a newsrack. They all work together. This is a unit of the city. These units define the structure. He said in a tree model there is no overlap, but in a more complex tree, semilattice, has overlapping units. For example a tree based on 20 elements has 19 subsets; a semilattice based on 20 elements has 1000 subsets. According to book a tree model doesn’t correspond to social realities. The physical layout of the plans, and the way that suggest a hierarchy of closed social groups ranging from whole city down to family. A village is made up of a number of separate closed groups. But today’s social structure is different. There are no closed groups in modern society. The reality of today’s social structure is overlap, not a tree. In modern life vehicle system and pedestrian system can’t be separated (necessary overlap). He said in the book ‘City must not be a tree. If we make cities which are trees, they will cut our life within to pieces.’
2.) CIAM is an organization of modern architecture. It founded in 1928 by Le Corbusier include 28 groups of architecture. Its aim is spreading the principles of modern movement in every field such as urbanism, industrial design and landscape.Late modernism occurred after the 2nd World War. However it has similarities with postmodernism they are different. Late modernism uses the methods of modernism. The products in late modernism is more abstract than modernism. It is abstract but simple. It against general ideas about art.
3.) Postmodern urbanism is made up of globalization such as increasing human population, frequent intercultural interactions, intersection of local and global knowledge. It started as signs of new forms culture. It is a stage of modernism or a specific period of modernism. Where modern urbanism is identified with linear progress, postmodern urbanism identified with heterogeneity, differences, uniqueness and otherness. According to postmodernist planners it is not able to take under control whole city so we have to focus on design of city and individual’s wishes. It means postmodernist urbans made up by according to the customer’s preference and urbanization style blended with free thought. The postmodern urban examples are: Gordon Cullen’s Concise Landscape, an example of historical eclecticism and City of Spectacle.