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Type Checking Liveness for Collaborative Processes with Bounded and Unbounded Recursion

Søren DEBOIS, Thomas HILDEBRANDT, Tijs SLAATS, Nobuko YOSHIDA

We present the first session typing system guaranteeing request-response liveness properties for possibly non-terminating communicating processes. The types augment the branch and select types of the standard binary session types with a set of required responses, indicating that whenever a particular label is selected, a set of other labels, its responses, must eventually also be selected. We prove that these extended types are strictly more expressive than standard session types. We provide a type system for a process calculus similar to a subset of collaborative BPMN processes with internal (data-based) and external (event-based) branching, message passing, bounded and unbounded looping. We prove that this type system is sound, i.e., it guarantees request-response liveness for dead-lock free processes. We exemplify the use of the calculus and type system on a concrete example of an infinite state system.

@article{DHSY2016,
  author = {Søren Debois and Thomas Hildebrandt and Tijs Slaats and Nobuko Yoshida},
  title = {{Type Checking Liveness for Collaborative Processes with Bounded and Unbounded Recursion}},
  journal = {LMCS},
  volume = {12},
  issue = {1},
  pages = {1--38},
  year = 2016
}

@article{DHSY2016,
  author = {Søren Debois and Thomas Hildebrandt and Tijs Slaats and Nobuko Yoshida},
  title = {{Type Checking Liveness for Collaborative Processes with Bounded and Unbounded Recursion}},
  journal = {Logical Methods in Computer Science},
  volume = {12},
  issue = {1},
  pages = {1--38},
  doi = "10.2168/LMCS-12(1:1)2016",
  year = 2016
}