http://www.informatik.uni-marburg.de/~pgiarrusso/papers/pldi14-ilc-2014-02-05.pdf http://www.informatik.uni-marburg.de/~pgiarrusso/papers/pldi... defines one fo

http://www.informatik.uni-marburg.de/~pgiarrusso/papers/pldi14-ilc-2014-02-05.pdf http://www.informatik.uni-marburg.de/~pgiarrusso/papers/pldi... defines one for programs as something that "maps changes in the program’s input directly to changes in the program’s output, without reexecuting the original program."