MobilityReadingGroup

π-calculus, Session Types research at Imperial College

Talks & Presentations

Recent invited talks and presentations from our group.

More recent
Session Types and Linear Logic and Lightweight Applications of Session Types in Java
PPVL Research Seminar, Department of Computer Science, UCL, March 2017

Session types is a well-established typing discipline for message passing concurrency, originally developed in the pi-calculus and later studied in functional and object-oriented settings. The first part of this talk is a tutorial on session types and its connections to linear logic. A recent interpretation of propositions as session types for intuitionistic linear logic has been given by Caires and Pfenning, viewing proofs as processes and proof reduction as inter-process communication. We discuss how several generalisations and extensions of this interpretation arguably form a basis for a logical foundation that captures several interesting features of message-passing concurrent computation. Specifically, we will detail how the basic interpretation can be extended to richer typed settings such as polymorphism and dependent type theories, and how to account for a notion of typed process equivalence that gives meaning to both proof conversions and type isomorphisms. We will then briefly introduce the key concepts and intuitions behind multiparty session types (MPST).

The second part of this talk will demonstrate Scribble, a toolchain based on MPST, and applications in Java by using MPST to generate protocol-specific APIs for implementing distributed endpoints. This practical approach builds on the linear understanding of session types as a hybrid form of session safety: the interaction structure of an endpoint is captured via static Java typing, complemented by lightweight run-time checks on linear usage of channels. Examples include Scribble specifications and Java implementations of interoperable clients/servers for standard protocols such as HTTP and SMTP, and Web service choreographies. Finally, we demonstrate a recent extension of MPST with explicit connection actions, that allow sessions with dynamic and optional participants.

Date 7 Mar 2017
Speakers
Let It Recover: Multiparty Protocol-Induced Recovery
Computer Science Seminar Series, University of Camerino, Italy

In this talk, first we summarise the recent activities on session types in Imperial College London http://mrg.doc.ic.ac.uk/.

Then we talk about a new recovery strategy in Erlang based on Multiparty session types, which was presented in 26th ACM International Conference on Compiler Construction (CC’17).

Fault-tolerant communication systems rely on recovery strategies which are often error-prone (e.g. a programmer manually specifies recovery strategies) or inefficient (e.g. the whole system is restarted from the beginning). In this talk, we will present an algorithm to efficiently compute a safe global state from which a system of interacting processes should be recovered. We statically analyse the communication flow of a program, given as a multiparty protocol, to extract the causal dependencies between processes and to localise failures. We formalise our recovery algorithm and prove its safety. A recovered communication system is free from deadlocks, orphan messages and reception errors. Our recovery algorithm incurs less communication cost (only affected processes are notified) and overall execution time (only required states are repeated). On top of our analysis, we design and implement a runtime framework in Erlang where failed processes and their dependencies are soundly restarted from a computed safe state. We evaluate our recovery framework on message-passing benchmarks and a use case for crawling web pages. The experimental results indicate our framework outperforms a built-in static recovery strategy in Erlang when a part of the protocol can be safely recovered.

Date 22 Feb 2017
Speakers
Multiparty Session Types and their Applications
Université Pierre et Marie Curie Paris 6, Dec 2016

We give a summary of our recent research developments on multiparty session types for verifying distributed, parallel and concurrent programs, and our collaborations with industry partners. We shall first outline the multiparty session types and then explain how we started collaborations with industry to develop a protocol description language called Scribble. We then talk about the recent developments in Scribble, the runtime session monitoring framework used in Ocean Observatories Initiative and network protocol verifications. We also demonstrate how our multiparty session synthesis theory is applied to Zero Deviation Life Cycle project with Cognizant; and static deadlock analysis for Google’s Go language.

Date 14 Dec 2016
Speakers
Compositionality and Session Types
Compositionality workshop, Simon's Institute for the Theory of Computing, University of California, Berkeley, Dec 2016

I shall talk about a difficulty to extend session types to be compositional in several contexts: multiparty session types, communicating automata and Linear Logic. I also talk about several solutions – some of them are motivated by practical applications of the session types.

Date 5 Dec 2016
Speakers
Building Graphical Choreographies From Communicating Machines: Principles and Applications
Seminaire Preuves, programmes et systèmes, University Paris-Diderot / IRIF, Nov 2016

Graphical choreographies, or global graphs, are general multiparty session specifications featuring expressive constructs such as forking, merging, and joining for representing application-level protocols. Global graphs can be directly translated into modelling notations such as BPMN and UML. In the first part of the talk, I will first present an algorithm whereby a global graph can be constructed from asynchronous interactions represented by communicating finite-state machines (CFSMs); and a sound characterisation of a subset of safe CFSMs from which global graphs can be constructed. In the second part, I will outline a few recent applications of this work to communicating timed automata and the Go programming language.

Date 29 Nov 2016
Speakers
Session Types and their Open Problems
COST Action BETTY final meeting, NOVA University of Lisbon, Portugal
Date 6 Oct 2016
Speakers
μServices and Scribble, a.k.a. Scribble @ ThoughtWorks
COST Action BETTY final meeting, NOVA University of Lisbon, Portugal

BETTY final project meeting keynote

Date 6 Oct 2016
Speakers
Multiparty Session Types and their Applications to Concurrent and Distributed Systems
Papers We Love Conference / Strange Loop 2016 preconference, St. Louis, MO, Sept 15-17, 2016

Nobuko Yoshida’s talk will present a summary of recent papers on multiparty session types for verifying distributed, parallel and concurrent programs, illustrating how theoretical work is grounded on collaborations with industry partners. This research led to the development of the protocol description language Scribble and other work such as static deadlock analysis in Go.

PWLConf 2016

Date 15 Sep 2016
Speakers
Building Graphical Choreographies From Communicating Machines: Principles and Applications
Computer Science Colloquium, University of Southern Denmark, Aug 2016

Graphical choreographies, or global graphs, are general multiparty session specifications featuring expressive constructs such as forking, merging, and joining for representing application-level protocols. Global graphs can be directly translated into modelling notations such as BPMN and UML. In the first part of the talk, I will first present an algorithm whereby a global graph can be constructed from asynchronous interactions represented by communicating finite-state machines (CFSMs); and a sound characterisation of a subset of safe CFSMs from which global graphs can be constructed. In the second part, I will outline a few recent applications of this work to communicating timed automata and the Go programming language.

Date 18 Aug 2016
Speakers
Static Deadlock Detection for Go
GolangUK 2016, 17-19 Aug 2016

Go’s concurrency features differ from mainstream programming languages in that they are based on the high-level and formal model of CSP (or process calculi) by Tony Hoare in 1978. Over the years, a large body of research work was developed for understanding concurrency based on process calculi, but rarely applied directly in programming languages. I will talk about a static analyser we developed for detecting deadlocks in Go, inspired by a research area which gives “types” to process calculi. In a nutshell, the tool infers “types” for communication between goroutines from Go source code, then construct a bird’s eye view of all communication (also called choreography or global graph) possible at runtime, through which deadlocks and communication problems are discovered.

This talk will focus on the work-in-progress aspects of the tool. No knowledge of CSP/process calculi are needed but some understanding of concurrency in Go and static analysis concepts are expected.

Date 17 Aug 2016 - 19 Aug 2016
Speakers
Synthesis of Multiparty Session Types
Nagoya University, Jul 2016

Multiparty session types are a type system that can ensure the safety and liveness of distributed peers via the global specification of their interactions. To construct a global specification from a set of distributed uncontrolled behaviours, this talk explores the problem of fully characterising multiparty session types in terms of communicating automata. We equip global and local session types with labelled transition systems (LTSs) that faithfully represent asynchronous communications through unbounded buffered channels. Using the equivalence between the two LTSs, we identify a class of communicating automata that exactly correspond to the projected local types. We exhibit an algorithm to synthesise a global type from a collection of communicating automata. The key property of our findings is the notion of multiparty compatibility which non-trivially extends the duality condition for binary session types.

At the end of the talk, I also show a couple of applications of the synthesis theory of multiparty session types.

Date 27 Jul 2016
Speakers
Synthesis of Multiparty Session Types
National Institute of Informatics (NII), July 2016

Multiparty session types are a type system that can ensure the safety and liveness of distributed peers via the global specification of their interactions. To construct a global specification from a set of distributed uncontrolled behaviours, this talk explores the problem of fully characterising multiparty session types in terms of communicating automata. We equip global and local session types with labelled transition systems (LTSs) that faithfully represent asynchronous communications through unbounded buffered channels. Using the equivalence between the two LTSs, we identify a class of communicating automata that exactly correspond to the projected local types. We exhibit an algorithm to synthesise a global type from a collection of communicating automata. The key property of our findings is the notion of multiparty compatibility which non-trivially extends the duality condition for binary session types.

At the end of the talk, I also show a couple of applications of the synthesis theory of multiparty session types.

Date 19 Jul 2016
Speakers
Multiparty Session Types and their Applications
NJ Programming Languages and Systems Seminar, University of Pennsylvania, May 2016

We give a summary of our recent research developments on multiparty session types for verifying distributed, parallel and concurrent programs, and our collaborations with industry partners. We shall first outline the multiparty session types and then explain how we started collaborations with industry to develop a protocol description language called Scribble. We then talk about the recent developments in Scribble, the runtime session monitoring framework used in Ocean Observatories Initiative and network protocol verifications. We also demonstrate how our multiparty session synthesis theory is applied to Zero Deviation Life Cycle project with Cognizant; and static deadlock analysis for Google’s Go language.

Date 16 May 2016
Speakers
Multiparty Session Types and their Applications
Departmental Seminar, School of Computer Science, The University of Manchester, May 2016

We give a summary of our recent research developments on multiparty session types for verifying distributed, parallel and concurrent programs, and our collaborations with industry partners. We shall first introduce the multiparty session types and then explain how we started collaborations with industry to develop a protocol description language called Scribble. We then talk about the recent developments in Scribble, the runtime session monitoring framework used in Ocean Observatories Initiative and network protocol verifications. We also demonstrate how our multiparty session synthesis theory is applied to Zero Deviation Life Cycle project in Cognizant; and static deadlock analysis for Google’s Go language.

Date 4 May 2016
Speakers
Multiparty Session Types and their Applications
Computer Science Seminar Series, Computer Science Division, School of Science and Technology, University of Camerino, Italy, April 2016

We give a summary of our recent research developments on multiparty session types for verifying distributed, parallel and concurrent programs, and our collaborations with industry partners. We shall first introduce the multiparty session types and then explain how we started collaborations with industry to develop a protocol description language called Scribble. We then talk about the recent developments in Scribble, the runtime session monitoring framework used in Ocean Observatories Initiative and network protocol verifications. We also demonstrate how our multiparty session synthesis theory is applied to Zero Deviation Life Cycle project in Cognizant; and static deadlock analysis for Google’s Go language.

Date 29 Apr 2016
Speakers
Phil & Session Types / Session Types & Linear Logic
WadlerFest - In celebration of Philip Wadler's 60th birthday, Informatics Forum, Edinburgh, Apr 2016
Date 11 Apr 2016 - 12 Apr 2016
Speakers
The Upscale project: Actors and sessions
Celebration Event for Frank de Boer's 60th Birthday, Eindhoven Univesity of Technology, The Netherlands
Date 3 Apr 2016
Speakers
An overview of multiparty session types
Language Based Verification Tools for Functional Programs (Dagstuhl Seminar 16131), Schloss Dagstuhl, Germany, April 2016
Date 28 Mar 2016 - 1 Apr 2016
Speakers
Multiparty Session Types And Their Applications
Center for Mathematics and Statistics, University of Novi Sad, Serbia, March 2016

We give a summary of our recent research developments on multiparty session types for verifying distributed and concurrent programs, including our collaborations with industry partners and NSF-funded project (Ocean Observatories Initiatives). The OOI provides an ultra large-scale cyberinfrustracture (OOI CI) for 25-30 years of sustained ocean measurements to study climate variability, ocean circulation and ecosystem dynamics. We shall first talk how Robin Milner, Kohei Honda and Yoshida started collaborations with industry to develop a web service protocol description language called Scribble and discovered the theory of multiparty session types through the collaborations with Red Hat. We then talk about applications of Scribble to the runtime session monitoring framework used in the OOI and Scala verification. We also summarise more recent results and applications using Multiparty Session Types.

Date 4 Mar 2016
Speakers
Verify me if you can: Supervisors, Actors and Session Types
UPMARC Seminars, Uppsala University, Feb 2016

Actor coordination armoured with a suitable protocol description language has been a pressing problem in the actors community. We study the applicability of multiparty session type protocols for verification of actor programs. We incorporate sessions to actors by introducing minimum additions to the model such as the notion of actor roles and protocol mailboxes. The framework uses Scribble, which is a protocol description language based on multiparty session types. Our programming model supports actor-like syntax and runtime verification mechanism guaranteeing communication safety of the participating entities. The usage of multiple roles allows safe cooperative interconcurrency in a single actor. We present the design of our session actor library in Python, which is evaluate by implementing twelve use cases from an actor benchmark suit. Benchmarks demonstrate that the runtime checks induce negligible overhead. We also present a recent work incorporating the session actors model into Erlang, where session types are used for faster error recovery on top of Erlang supervision trees.

Date 19 Feb 2016
Speakers
Session types and their applications
Lecture at 'Journées Francophones des Langages Applicatifs', JFLA 2016, Saint-Malo, France, January 2016
Date 27 Jan 2016 - 30 Jan 2016
Speakers
Multiparty Session Types and their Applications
PLAS Group Seminar at University of Kent, December 2015

We give a summary of our recent research developments on multiparty session types for verifying distributed, parallel and concurrent programs, and our collaborations with industry partners. We shall first talk how the session types were discovered from the theory of the pi-calculus, and how we started collaborations with industry to develop a protocol description language called Scribble. We then talk about the recent developments in Scribble, the runtime session monitoring framework used in Ocean Observatories Initiative and network protocol verifications with demos. We also talk how our synthesis theory is applied to Zero Deviation Life Cycle project with Cognizant. Finally we show how multiparty session types are used to generate safe MPI code.

Date 11 Dec 2015
Speakers
Multiparty Session Types and their Applications
Distinguished Seminar Series, School of Computing and Communications, Lancaster University, December 2015

We give a summary of our recent research developments on multiparty session types for verifying distributed and concurrent programs, and our collaborations with industry partners and a major, long-term, NSF-funded project (Ocean Observatories Initiatives) to provide an ultra large-scale cyberinfrustracture (OOI CI) for 25-30 years of sustained ocean measurements to study climate variability, ocean circulation and ecosystem dynamics. We shall first talk how Robin Milner, Kohei Honda and Yoshida started collaborations with industry to develop a web service protocol description language called Scribble and discovered the theory of multiparty session types through the collaborations. We then talk about the recent developments in Scribble and the runtime session monitoring framework used in the OOI CI. Finally we summarise our recent other results on Multiparty Session Types.

Date 2 Dec 2015
Speakers
Multiparty Asynchronous Session Types and their Applications
15th International School on Formal Methods for the Design of Computer, Communication and Software Systems: Multicore Programming, Bertinoro, Italy, June 2015
Date 18 Jun 2015
Speakers
From Communicating Machines to Graphical Choreographies
Logic and Semantics Seminar, University of Cambridge, May 2015

Graphical choreographies, or global graphs, are general multiparty session specifications featuring expressive constructs such as forking, merging, and joining for representing application-level protocols. Global graphs can be directly translated into modelling notations such as BPMN and UML . In this talk, I will present (i) an algorithm whereby a global graph can be constructed from asynchronous interactions represented by communicating finite-state machines (CFSMs); and (ii) a sound and complete characterisation of a subset of safe CFS Ms from which global graphs can be constructed.

Date 22 May 2015
Speakers
Earlier