ITU‐T's Technical Reports and Specifications 75 Ref. No. Category Definitions/Features Key concept/ Keywords Source 30 Corporate A \"smart sustainable city\" is one in which the seams and structures of the various urban systems are made clear, simple, responsive and even malleable via contemporary technology and design. Citizens are not only engaged and informed in the relationship between their activities, their neighbourhoods, and the wider urban ecosystems, but are actively encouraged to see the city itself as something they can collectively tune in, such that it is efficient, interactive, engaging, adaptive and flexible, as opposed to the inflexible, mono‐functional and monolithic structures of many 20th century cities. Urban system optimization, technology and design, informed citizens, citizen contribution, efficiency, interactive, adaptive, flexible. ARUP (2011) 31 Corporate Infrastructure, operations and people. What makes a city? The answer, of course, is all three. A city is an interconnected system of systems. A dynamic work in progress, with progress as its watchword. A tripod that relies on strong support for and among each of its pillars, to become a smarter city for all. Interconnected systems, progress, infrastructure, operations, and people. IBM (2014)