In TACAS 2022 tool demonstration paper "Kmclib: Automated Inference and Verification of Sess... more In TACAS 2022 tool demonstration paper "Kmclib: Automated Inference and Verification of Session Types from OCaml Programs", we introduce kmclib, a practical OCaml library for safe message-passing programming. It enables developers to program and verify arbitrary communication patterns without the need for type annotations or user-operated external tools. The library utilises the meta-programming facilities of OCaml to automatically infer the communication behaviour (i.e the session type) of concurrent programs and verify their compatibility. Well-typed programs, written with kmclib, do not lead to communication errors and cannot get stuck. This artifact is the source code of the library, and includes examples and instructions on how to write and verify concurrent programs with kmclib. The latest version is available at: https://github.com/keigoi/kmclib The enclosing zip files contains: README.txt artifact.md: the instructions to replicate/evaluate our artifact artifact.iso...
We present an inference system for a version of the Pi-calculus in Haskell for the session type p... more We present an inference system for a version of the Pi-calculus in Haskell for the session type proposed by Honda et al. The session type is very useful in checking if the communications are well-behaved. The full session type implementation in Haskell was first presented by Pucella and Tov, which is 'semi-automatic' in that the manual operations for the type representation was necessary. We give an automatic type inference for the session type by using a more abstract representation for the session type based on the 'de Bruijn levels'. We show an example of the session type inference for a simple SMTP client.
We present an inference system for a version of the pi-calculus in Haskell for the session type p... more We present an inference system for a version of the pi-calculus in Haskell for the session type pro-posed by Honda et al. The session type is very useful in checking if the communications are well-behaved. The full session type implementation in Haskell was first presented by Pucella and Tov, which is ‘semi-automatic ’ in that the manual operations for the type representation was necessary. We give an automatic type inference for the session type by using a more abstract representation for the session type based on the ‘de Bruijn levels’. We show an example of the session type inference for a simple SMTP client. 1
IEICE Transactions on Information and Systems, 2012
Distributed applications and services have become pervasive in our society due to the widespread ... more Distributed applications and services have become pervasive in our society due to the widespread use of internet and mobile devices. There are urgent demands to efficiently ensure safety and correctness of such software. A session-type system is a framework to statically check whether communication descriptions conform to certain protocols. They are shown to be effective yet simple enough to fit in harmony with existing programming languages. In the original session type system, the subject reduction property does not hold. This paper establishes a conservative extension of the original session type system with the subject reduction property. Finally, it is also shown that our typing rule properly extends the set of typeable processes.
Theories and tools based on multiparty session types offer correctness guarantees for concurrent ... more Theories and tools based on multiparty session types offer correctness guarantees for concurrent programs that communicate using message-passing. These guarantees usually come at the cost of an intrinsically top-down approach, which requires the communication behaviour of the entire program to be specified as a global type. This paper introduces kmclib: an OCaml library that supports the development of correct message-passing programs without having to write any types. The library utilises the meta-programming facilities of OCaml to automatically infer the session types of concurrent programs and verify their compatibility (k-MC [13]). Well-typed programs, written with kmclib, do not lead to communication errors and cannot get stuck.
In the paper “Multiparty Session Programming with Global Protocol Combinators”, we introduce a li... more In the paper “Multiparty Session Programming with Global Protocol Combinators”, we introduce a library, ocaml-mpst for programming with global combinators – a set of functions for writing and verifying multiparty protocols in OCaml. Local behaviours for all processes in a protocol are inferred at once from a global combinator. Our approach enables fully-static verification and implementation of the whole protocol, from the protocol specification to the process implementations, to happen in the same language. This artifact is the source code of ocaml-mpst, with all the examples and benchmarks discussed in the paper. 2012 ACM Subject Classification Software and its engineering → Concurrent programming structures; Theory of computation → Type structures; Software and its engineering → Functional languages; Software and its engineering → Polymorphism
Whereas ordinary types approximate the results, session types approximate communication among com... more Whereas ordinary types approximate the results, session types approximate communication among computations. As a form of typestate, they describe not only what is communicated now but also what is to be communicated next. Writing session-typed programs in an ordinary programming language such an OCaml requires inordinary cleverness to simulate type-level computations and linear typing – meaning the implementation and the error messages are very hard to understand. One is constantly reminded of template metaprogramming in C++. We present a system exploring a very different approach to session typing: lowering type-level sophistry to ordinary programming, while maintaining the static assurances. Error messages are detailed and customizable, and one can use an ordinary debugger to investigate session-type problems. Our system is a binary-session–typed DSL for service-oriented programming in OCaml, supporting multiple communication channels, internal and external choices, recursion, and...
Electronic Proceedings in Theoretical Computer Science
Multiparty Session Types (MPST) is a typing discipline for communication protocols. It ensures th... more Multiparty Session Types (MPST) is a typing discipline for communication protocols. It ensures the absence of communication errors and deadlocks for well-typed communicating processes. The state-of-the-art implementations of the MPST theory rely on (1) runtime linearity checks to ensure correct usage of communication channels and (2) external domain-specific languages for specifying and verifying multiparty protocols. To overcome these limitations, we propose a library for programming with global combinators-a set of functions for writing and verifying multiparty protocols in OCaml. Local behaviours for all processes in a protocol are inferred at once from a global combinator. We formalise global combinators and prove a sound realisability of global combinators-a well-typed global combinator derives a set of local types, by which typed endpoint programs can ensure type and communication safety. Our approach enables fully-static verification and implementation of the whole protocol, from the protocol specification to the process implementations, to happen in the same language. We compare our implementation to untyped and continuation-passing style implementations, and demonstrate its expressiveness by implementing a plethora of protocols. We show our library can interoperate with existing libraries and services, implementing DNS (Domain Name Service) protocol and the OAuth (Open Authentication) protocol. 2012 ACM Subject Classification Software and its engineering → Concurrent programming structures; Theory of computation → Type structures; Software and its engineering → Functional languages; Software and its engineering → Polymorphism
2019 IEEE International Conference on Big Data and Smart Computing (BigComp), 2019
Session types are a type discipline for eliminating communication errors in concurrent computing.... more Session types are a type discipline for eliminating communication errors in concurrent computing. These types can be thought of as a representation of communication protocols implemented by communicating processes. One application scenario that can be naturally supported by session types is semantics-preserving transformation of processes in response to protocol changes due to optimization, evolution, refactoring, etc. Such transformation can be seen as a particular kind of synchronization problem that has long been studied by the bidirectional transformations (BX) community. This short paper offers a preliminary analysis of the process-type synchronization problem in terms of BX, describing the prospects and challenges.
In TACAS 2022 tool demonstration paper "Kmclib: Automated Inference and Verification of Sess... more In TACAS 2022 tool demonstration paper "Kmclib: Automated Inference and Verification of Session Types from OCaml Programs", we introduce kmclib, a practical OCaml library for safe message-passing programming. It enables developers to program and verify arbitrary communication patterns without the need for type annotations or user-operated external tools. The library utilises the meta-programming facilities of OCaml to automatically infer the communication behaviour (i.e the session type) of concurrent programs and verify their compatibility. Well-typed programs, written with kmclib, do not lead to communication errors and cannot get stuck. This artifact is the source code of the library, and includes examples and instructions on how to write and verify concurrent programs with kmclib. The latest version is available at: https://github.com/keigoi/kmclib The enclosing zip files contains: README.txt artifact.md: the instructions to replicate/evaluate our artifact artifact.iso...
We present an inference system for a version of the Pi-calculus in Haskell for the session type p... more We present an inference system for a version of the Pi-calculus in Haskell for the session type proposed by Honda et al. The session type is very useful in checking if the communications are well-behaved. The full session type implementation in Haskell was first presented by Pucella and Tov, which is 'semi-automatic' in that the manual operations for the type representation was necessary. We give an automatic type inference for the session type by using a more abstract representation for the session type based on the 'de Bruijn levels'. We show an example of the session type inference for a simple SMTP client.
We present an inference system for a version of the pi-calculus in Haskell for the session type p... more We present an inference system for a version of the pi-calculus in Haskell for the session type pro-posed by Honda et al. The session type is very useful in checking if the communications are well-behaved. The full session type implementation in Haskell was first presented by Pucella and Tov, which is ‘semi-automatic ’ in that the manual operations for the type representation was necessary. We give an automatic type inference for the session type by using a more abstract representation for the session type based on the ‘de Bruijn levels’. We show an example of the session type inference for a simple SMTP client. 1
IEICE Transactions on Information and Systems, 2012
Distributed applications and services have become pervasive in our society due to the widespread ... more Distributed applications and services have become pervasive in our society due to the widespread use of internet and mobile devices. There are urgent demands to efficiently ensure safety and correctness of such software. A session-type system is a framework to statically check whether communication descriptions conform to certain protocols. They are shown to be effective yet simple enough to fit in harmony with existing programming languages. In the original session type system, the subject reduction property does not hold. This paper establishes a conservative extension of the original session type system with the subject reduction property. Finally, it is also shown that our typing rule properly extends the set of typeable processes.
Theories and tools based on multiparty session types offer correctness guarantees for concurrent ... more Theories and tools based on multiparty session types offer correctness guarantees for concurrent programs that communicate using message-passing. These guarantees usually come at the cost of an intrinsically top-down approach, which requires the communication behaviour of the entire program to be specified as a global type. This paper introduces kmclib: an OCaml library that supports the development of correct message-passing programs without having to write any types. The library utilises the meta-programming facilities of OCaml to automatically infer the session types of concurrent programs and verify their compatibility (k-MC [13]). Well-typed programs, written with kmclib, do not lead to communication errors and cannot get stuck.
In the paper “Multiparty Session Programming with Global Protocol Combinators”, we introduce a li... more In the paper “Multiparty Session Programming with Global Protocol Combinators”, we introduce a library, ocaml-mpst for programming with global combinators – a set of functions for writing and verifying multiparty protocols in OCaml. Local behaviours for all processes in a protocol are inferred at once from a global combinator. Our approach enables fully-static verification and implementation of the whole protocol, from the protocol specification to the process implementations, to happen in the same language. This artifact is the source code of ocaml-mpst, with all the examples and benchmarks discussed in the paper. 2012 ACM Subject Classification Software and its engineering → Concurrent programming structures; Theory of computation → Type structures; Software and its engineering → Functional languages; Software and its engineering → Polymorphism
Whereas ordinary types approximate the results, session types approximate communication among com... more Whereas ordinary types approximate the results, session types approximate communication among computations. As a form of typestate, they describe not only what is communicated now but also what is to be communicated next. Writing session-typed programs in an ordinary programming language such an OCaml requires inordinary cleverness to simulate type-level computations and linear typing – meaning the implementation and the error messages are very hard to understand. One is constantly reminded of template metaprogramming in C++. We present a system exploring a very different approach to session typing: lowering type-level sophistry to ordinary programming, while maintaining the static assurances. Error messages are detailed and customizable, and one can use an ordinary debugger to investigate session-type problems. Our system is a binary-session–typed DSL for service-oriented programming in OCaml, supporting multiple communication channels, internal and external choices, recursion, and...
Electronic Proceedings in Theoretical Computer Science
Multiparty Session Types (MPST) is a typing discipline for communication protocols. It ensures th... more Multiparty Session Types (MPST) is a typing discipline for communication protocols. It ensures the absence of communication errors and deadlocks for well-typed communicating processes. The state-of-the-art implementations of the MPST theory rely on (1) runtime linearity checks to ensure correct usage of communication channels and (2) external domain-specific languages for specifying and verifying multiparty protocols. To overcome these limitations, we propose a library for programming with global combinators-a set of functions for writing and verifying multiparty protocols in OCaml. Local behaviours for all processes in a protocol are inferred at once from a global combinator. We formalise global combinators and prove a sound realisability of global combinators-a well-typed global combinator derives a set of local types, by which typed endpoint programs can ensure type and communication safety. Our approach enables fully-static verification and implementation of the whole protocol, from the protocol specification to the process implementations, to happen in the same language. We compare our implementation to untyped and continuation-passing style implementations, and demonstrate its expressiveness by implementing a plethora of protocols. We show our library can interoperate with existing libraries and services, implementing DNS (Domain Name Service) protocol and the OAuth (Open Authentication) protocol. 2012 ACM Subject Classification Software and its engineering → Concurrent programming structures; Theory of computation → Type structures; Software and its engineering → Functional languages; Software and its engineering → Polymorphism
2019 IEEE International Conference on Big Data and Smart Computing (BigComp), 2019
Session types are a type discipline for eliminating communication errors in concurrent computing.... more Session types are a type discipline for eliminating communication errors in concurrent computing. These types can be thought of as a representation of communication protocols implemented by communicating processes. One application scenario that can be naturally supported by session types is semantics-preserving transformation of processes in response to protocol changes due to optimization, evolution, refactoring, etc. Such transformation can be seen as a particular kind of synchronization problem that has long been studied by the bidirectional transformations (BX) community. This short paper offers a preliminary analysis of the process-type synchronization problem in terms of BX, describing the prospects and challenges.
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