From User-responsive Design: reducing the risk of failure, by C. Thomas Mitchell, "The use and experience of design over time":
"This "soft diagram" represents the qualities of space in the Salon di Palais, in the house the philosopher Ludwig Wittgenstein designed for his sister in 1926. The detail of what this particular diagram represents is less significant than its implications for design. Whereas most plans represent solely physical relationships, in diagrams such as this, Castelli and his students diagram the different environmental qualities that determine how a space is actually [perceived? experienced? over time?]..."