Abstract
Liveness in programming environments generally refers to the ability to modify a running program. Liveness is one form of a more general class of behaviors by a programming environment that provide information to programmers about what they are constructing. This paper gives a brief historical perspective on liveness and proposes an extension of a hierarchy given in 1990, to now account for even more powerful execution-oriented tools for programmers. In addition, while liveness concerns the timeliness of execution feedback, considering a broader array of forms of feedback is helpful both in better understanding liveness and in designing ever more powerful development tools.