The development of complex software and hardware systems has increased in recent years. One reason is the continuous development in information and communication technologies sectors that enable a smooth and seamless connection of single components or systems. Another reason is the changed way of life, e.g. urbanization leads to new challenges in city planning to deal with large crowds, high-energy consumption, or big garbage quantities. The future or rather present city planning focuses on the concept of these complex systems (alias smart city). Information technologies interconnect smart city components and enable several smart city sub-systems like smart grid, smart building, supply/waste management, smart traffic, smart government etc. A definition of component functionalities and interfaces is needed to demonstrate their interconnections and information flow. Therefore, alternative techniques can be utilized to specify these both component and system requirements.