Onion: A Graphical Language for Process Algebra

There are a number of graphical languages for process algebras to specify distributed mobile real-time systems: Ambient calculus, KELL for MA, Bigraph for π-calculus, etc. However there are some limitations in representation of large and complex such systems in these languages, since only the most immediately available actions of processes are graphically represented. Further the temporal properties are represented numerically, not graphically. In order to overcome the limitations, this paper proposes a new graphical language, Onion, to represent visually all the actions of each process in the process. In Onion, the timed actions of each process are represented graphically by circularly layered leaves, like those of real onion, and their interactions and movements as edges among the leaves. Further the temporal properties of the actions are visually and quantitatively represented in a separate graph. Onion makes the understanding of the systems visually quantitative between the in-the-large and the in-the-small perspectives of the systems. Onion can be considered one of the most integrated graphical languages for process algebras.