How to make Biological Systems Compute: Simply Observe Them

We survey work on the paradigm called computing by ob- serving. This is a formal model of the way many biochemical experiments are conducted, where an external observer pro- tocols the evolution of a system in a test tube or some other limited environment. So this observer, which is not acting on the input, produces the output. In this the paradigm con- trasts strongly to many formal models of bio-computation that follow the classical input/output paradigm from com- puter science. In the presentation we put a special focus on the identif- cation of key features that make systems especially suitable for serving as the basis of a computer in the computing by observing architecture. It turns out that context-sensitivity can be simulated well by simpler mechanisms, while un- boundedly reusable workspace plays a key role.