The Roman architecture critic Vitruvius advanced the notion that well-designed buildings were those which exhibited firmness, commodity, and delight. The same might be said of good software. Firmness: A program should not have any bugs that inhibit its function. Commodity: A program should be suitable for the purposes for which it was intended. Delight: The experience of using the program should be pleasurable one. Here we have the beginnings of a theory of design for software.
Bringing Design to Software - Ch. 1 Kapor
Feb 2012