A Chart Semantics for the Pi-Calculus

Johannes Borgström, Andrew D. Gordon, Andrew Phillips

Research output: Contribution to journalArticlepeer-review

Abstract

We present a graphical semantics for the pi-calculus, that is easier to visualize and better suited to expressing causality and temporal properties than conventional relational semantics. A pi-chart is a finite directed acyclic graph recording a computation in the pi-calculus. Each node represents a process, and each edge either represents a computation step, or a message-passing interaction. Pi-charts enjoy a natural pictorial representation, akin to message sequence charts, in which vertical edges represent control flow and horizontal edges represent data flow based on message passing. A pi-chart represents a single computation starting from its top (the nodes with no ancestors) to its bottom (the nodes with no descendants). Unlike conventional reductions or transitions, the edges in a pi-chart induce ancestry and other causal relations on processes. We give both compositional and operational definitions of pi-charts, and illustrate the additional expressivity afforded by the chart semantics via a series of examples.
Original languageEnglish
Pages (from-to)3-29
Number of pages27
JournalElectronic Notes in Theoretical Computer Science
Volume194
Issue number2
DOIs
Publication statusPublished - 2008

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