A tool for the animation of message interactions between concurrent
processes is presented. Each message interaction, such as a send or
receive, has a corresponding static graphical representation.
The interactions among the processes of an executing distributed
computation are represented by an animated sequence of these
This graphical monitoring tool, called Mona, is part of a distributed
software prototyping environment, called Jade. The Jade environment
supports the implementation of distributed programs written in ADA,
C, Lisp, Prolog, and Simula. The execution of these
multi-lingual programs can be distributed over a loosely coupled
network of Vax/Unix systems and microcomputer workstations.
Preliminary experience using Mona to develop distributed programs is also
reported. In particular, the application of Mona to the debugging of a
distributed implementation of a workstation virtual terminal window
system is described. We also discuss the advantages of graphical monitoring
over more traditional approaches, i.e. textual tracing.