694 ITU‐T's Technical Reports and Specifications 2.3 Relationship between open data and smart sustainable cities Smart sustainable cities are innovative efficient, green, safe, and livable place for citizens. Besides the importance of ICT infrastructure and newly emerging innovative technologies, typically including Internet of Things (IoT), cloud computing and so on, soft skills including multi‐source information integration and coordination, real‐time response is even more critical. In the traditional cities, before the informative age, information and data are dispersive and not open to the public. Even where the information belongs to the same owner like government, when they are collected by different agencies there could be problems in coordination and contributing to real‐time response. In SSC, smart application based on open data enable car drivers find the optimal way to avoid traffic jams. City planning with open data in SSC is also an important direction. Cities, especially the metropolis, are divided in regions with different functions. Central business district (CBD) is located in the center of cities surrounded by residential living areas. In some cities, sub‐centers of cities emerge to ease the population and traffic pressure in the center cities. Open data from operation business companies can help to understand the population density and dynamic behaviors in the cities, which can assist city management planning for new area development and district function positioning. 3 The framework of open data 3.1 The principles of overall design Overall design of open data framework follows the following basic principles: Openness Openness is a necessary process for system interconnection and data interaction; that is an important prerequisite to improve the maintenance of the system. From many aspects, openness can be reflected from the design of system architecture, database systems, operating systems, network, etc. It is convenient to adopt modular framework for a third party supplying a cross platform development tool. Alsoit is a continuous process to improve API and services relying on the feedback of the public and government departments. Extensibility One important aspect of designing a framework is making sure the extensibility of the framework has been carefully considered. There is no dispute that data volumes are growing exponentially. Huge amounts of data are generated every hour of every day, and this data comes from an ever‐increasing variety of sources. This requires system design to be considered from two aspects: one is high scalability of hardware; the other is component‐based design of software. Accessibility Accessibility is the degree to which a product, device, service, or the environment is available to as many people as possible. Accessibility can be viewed as the \"ability to access\" and benefit from some system or entity. The design objectives of open data are to strengthen the accessibility, utilization and availability of data. In data publishing and permission management, it is effective to ensure that published data can meet the needs of users, and this requires it based on the maximum degree of data sharing. On the other hand, providing high‐value data sets released, without involving privacy, confidentiality, safety issues, should be based on the needs of each government department and the public. In data presentation, the public can easily get what they need through open data portal.