This paper proposes a global escape mechanism which can handle unexpected or unwanted conditions changing the default execution of distributed communicational flows, preserving compatibility of the multiparty conversations. Our escape is realised by a collection of asynchronous local exceptions which can be thrown at any stage of the communication and to any subsets of participants in a multiparty session. This flexibility enables to model complex exceptions such as criss-crossing global interactions and fault tolerance for distributed cooperating threads. Guided by multiparty session types, our semantics automatically provides an efficient termination algorithm for global escapes with low complexity of exception messages.

We consider a calculus for multiparty sessions with delegation, enriched with security levels for session participants and data. We propose a type system that guarantees both session safety and a form of access control. Moreover, this type system ensures secure information flow, including controlled forms of declassification. In particular, it prevents information leaks due to the specific control constructs of the calculus, such as session opening, selection, branching and delegation. We illustrate the use of our type system with a number of examples, which reveal an interesting interplay between the constraints of security type systems and those used in session types to ensure properties like communication safety and session fidelity.

Abstract. We consider a calculus for multiparty sessions with delegation, enriched with security levels for session participants and data. We propose a type system that guarantees both session safety and a form of access control. Moreover, this type system ensures secure information flow, including controlled forms of declassification. In particular, the type system prevents leaks that could result from an unrestricted use of the control constructs of the calculus, such as session opening, selection, branching and delegation. We illustrate the use of our type system with a number of examples, which reveal an interesting interplay between the constraints used in security type systems and those used in session types to ensure properties like communication safety and session fidelity.

We suggest an amalgamation of communication based programming (centred on sessions) and object oriented programming, whereby sessions between concurrent threads are amalgamated with methods. In our proposal threads consist of the execution of session bodies on objects and communicate with each other through asynchronously sending/receiving objects on channels. The choice on how to respond to a session request is based on the name of the request and the class of the object receiving the request, the choice on how to continue a session is made on the basis of the class of the object sent/received. Sessions can be delegated to other sessions, although session themselves are not first class objects. We demonstrate our ideas through a core language with generic types, SAM g , and an example. We then formalize a small calculus, Feather SAM g , and prove subject reduction and progress. The latter property is notoriously difficult to achieve in concurrent calculi.

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We consider a calculus for multiparty sessions enriched with security levels for messages. We propose a monitored semantics for this calculus, which blocks the execution of processes as soon as they attempt to leak information. We illustrate the use of this semantics with various examples, and show that the induced safety property is compositional and that it is strictly included between a typability property and a security property proposed for an extended calculus in previous work.

In network applications it is crucial to have a mechanism to guarantee that communications evolve correctly according to the agreed protocol. Session types offer a method for abstracting and validating structured communication sequences (sessions). In this paper we propose union types for refining and enhancing the flexibility of session types in the context of communication centred and object oriented programming. We demonstrate our ideas through an example and a calculus formalising the main issues of the present approach. The type system garantees that, in well-typed executable programs, after a session has started, the values sent and received will be of the appropriate type, and no process can get stuck forever.

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