Conceptual blending
From Fake Guns and Stone Lions: Conceptual Blending and Privative Adjectives, by Seana Coulson and Gilles Fauconnier:
Imagine two college students are [sic!] up late studying for an exam. Suddenly, one crumples up a piece of paper and heaves it at the wastepaper basket. As the two begin to shoot the “ball” at the “basket,” the game of trashcan basketball is born. Because it involves the integration of knowledge structures from different domains [emphasis mine], trashcan basketball can be seen as the product of conceptual blending. In conceptual blending, frames from established domains (known as inputs) are combined to yield a hybrid frame (a blend or blended model) that contains partial structures from each of its inputs, as well as unique representational structure of its own [emphasis mine]. For example, in trashcan basketball, the input domains are trash disposal and (conventional) basketball, and the resultant blend incorporates a bit of both domains to yield a novel concept.
Very relevant for the system metaphor in Extreme Programming, as well as for constrained universes of expression.