Commodity. Firmness. Delight.
Years ago, we taught a series of workshops on The Craft of Hypertext, starting from the architectural virtues that Vitruvius sough for a farmhouse: Commodity, Firmness, Delight.
The end is to build well. Well building hath three conditions: firmness, commodity, and delight. (Henry Wotton, trans., 1624)
(I picked up the quotation from a memorable T-shirt, seen at the Columbia's architecture department in the late '70s) Victor Lombardi observes that designers have given the slogan new currency, translated as "usable, useful, desirable". (Latin: "Firmatas, Utilitas, Venustas")