The first time I consciously recognised this type of structure was at the final presentation of a vertical project at the Department of Architecture of the Chinese University of Hong Kong in the spring term of the academic year 1998-99. The proposal of one group consisted of four beams which were shorter than the span of the structure. I had two questions to the students. Do you know if the structure can be extended? Are you interested to find out? They neither knew nor expressed further interest. These anwers triggered my own studies.