## 2 DC Construction under the Demand of Modernization  
### Goals and Ideas of DC  
In his speech of January 1998, US Vice President [PERSON] first proposed the concept of \"digital earth\". [PERSON] suggested that we need a \"digital earth\"--a virtual earth based on earth coordinates embedded with massive geographical data, with multiresolution and three-dimensional visualization [22; 23; 24]. A DC is an important part of \"digital earth\" and a concrete embodiment of \"digital earth\" in cities. [PERSON] et al. (2022) [25] established an optimization model for energy-saving traffic scheduling problems. Based on an energy-saving model, the traffic prediction algorithm and the multilayer virtual topology traffic scheduling algorithm were solved, and the final energy-saving scheduling scheme was obtained. The work played a positive role in reducing the energy consumption of data center network and further provided a reference for the development direction of Internet of Things technology and SC. The development of the \"digital earth\" has gone through three stages, namely digitization, informatization, and intelligence. Digitization is an early stage, but data has not been effectively classified and managed, so it cannot be called information. Information theory refers to the meaningful content of data as information. In the information stage, data can be effectively classified, stored, and managed and becomes an effective resource. [PERSON] et al. [26] suggested that urban information is developing toward intelligence with the emergence and adoption of new connectivity technologiessuch as sensor networks. The evolution and development of human society from \"physical age\" to \"material age\" and then to \"intellectual age\" is the general trend of the continuous upgrading of civilization. When production tools progress from agricultural equipment to industrial equipment, information equipment, and intelligent equipment, society will progress from an agricultural society to an industrial society, information society, and network society. Cities are also changing from agricultural towns, industrial cities, and DCs to SCs. Therefore, SC becomes the inevitable direction of urban progression. [PERSON] and [PERSON] [27] discussed that cities are facing numerous challenges that threaten their long-term sustainability. These challenges can affect cities' economies, businesses, and residents, involving core infrastructures such as transport, water resources, energy, and communications. These challenges must be comprehensively addressed if cities are to build and maintain sustainable urban environments. DC is far more than a highly integrated set of technologies. For cities to evolve, they must utilize and optimize their economic capabilities, physical assets, culture, political will, technology, and business environment [28; 29]. The comparison of operation modes between traditional cities and DC is shown in Figure 1.  
The development of global DC has roughly gone through four stages. The first stage is the construction of the network infrastructure; the second stage is the construction of the municipal government and enterprise internal information system; the third stage is the interconnection between the municipal government and the upstream and downstream enterprises through the internet; and the fourth stage is the formation of network society, network community, and DC. China's DC has gone through more than 20 years since it was proposed in 1999, but the development process is not exactly the same as that of European and American countries [30; 31; 32]. [PERSON] et al. [33] believe that China's DC may have had a number of different stages, from the concept of \"digital earth\" to the establishment and construction of \"the national DC geospatial framework\" and then from the initial purposes such as to achieve paperless office to the future net platform of the digital China geospatial framework.