Conditionals in Algebraic Process Calculi

Conditionals of some form are incorporated in various algebraic process calculi. What is considered to be conditions and how they are evaluated differs from one case to another. This paper gives an overview of the history of conditionals in algebraic process calculi, including the recent elaborate investigation into the potentialities of conditionals in the setting of ACP. The history of conditionals in algebraic process calculi is remarkable. It shows among other things that the potentialities of conditionals in algebraic process calculi have been underestimated for a long time. The paper ends by mentioning some open problems.