# Multiparty Session Types, Beyond Duality (Abstract)

## TL;DR

This paper introduces a novel Multiparty Session Types system that overcomes the limitations of existing duality constraints, enabling more flexible and accurate typing of message-passing protocols involving multiple participants.

## Contribution

It proposes a new MPST typing framework that removes duality restrictions, allowing for broader and more intuitive protocol typing in multiparty interactions.

## Key findings

- Existing MPST restricts protocols due to duality constraints.
- The new system relaxes these constraints, broadening applicability.
- Preliminary analysis shows improved protocol expressiveness.

## Abstract

Multiparty Session Types (MPST) are a well-established typing discipline for message-passing processes interacting on sessions involving two or more participants. Session typing can ensure desirable properties: absence of communication errors and deadlocks, and protocol conformance. However, existing MPST works provide a subject reduction result that is arguably (and sometimes, surprisingly) restrictive: it only holds for typing contexts with strong duality constraints on the interactions between pairs of participants. Consequently, many "intuitively correct" examples cannot be typed and/or cannot be proved type-safe. We illustrate some of these examples, and discuss the reason for these limitations. Then, we outline a novel MPST typing system that removes these restrictions.

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Source: https://tomesphere.com/paper/1704.03097