I was wondering if anyone could tell me where to look for the use or history of C* correspondences. I have heard of `Connes C* correspondence', but cannot find a reference. Any other references would be gratefully received.
Classical correspondences arise when considering subsets of $X\times Y$ which generalise the graph of a function $f:X\to Y$. In noncommutative geometry they are some form of bimodule, just as the functions on the subsets above would be a $C(X)-C(Y)$ bimodule. As such they are used in KK-theory (well, the commuting algebra restrictions can be reduced to this). I am looking more at the historical development or other uses.
I have heard of Connes' preprint but I have never seen it. There this other one by Popa, though.