Session subtyping is a cornerstone of refinement of communicating processes: A process implementing a session type (i.e., a communication protocol) T can be safely used whenever a process implementing one of its supertypes T ′ is expected, in any context, without introducing deadlocks nor other communication errors. As a consequence, whenever T ≤ T ′ holds, it is safe to replace an implementation of T ′ with an implementation of the subtype T , which may allow for more optimised communication patterns. We present the first formalisation of the precise subtyping relation for asynchronous multiparty sessions. We show that our subtyping relation is sound (i.e., guarantees safe process replacement, as outlined above) and also complete : Any extension of the relation is unsound. To achieve our results, we develop a novel session decomposition technique, from full session types (including internal/external choices) into single input/output session trees (without choices). We cover multiparty sessions with asynchronous interaction, where messages are transmitted via FIFO queues (as in the TCP/IP protocol), and prove that our subtyping is both operationally and denotationally precise. Our session decomposition technique expresses the subtyping relation as a composition of refinement relations between single input/output trees and provides a simple reasoning principle for asynchronous message optimisations.

Session subtyping is a cornerstone of refinement of communicating processes: a process implementing a session type (i.e., a communication protocol) T can be safely used whenever a process implementing one of its supertypes T ′ is expected, in any context, without introducing deadlocks nor other communication errors. As a consequence, whenever T T ′ holds, it is safe to replace an implementation of T ′ with an implementation of the subtype T , which may allow for more optimised communication patterns. We present the first formalisation of the precise subtyping relation for asynchronous multiparty sessions. We show that our subtyping relation is sound (i.e., guarantees safe process replacement, as outlined above) and also complete : any extension of the relation is unsound. To achieve our results, we develop a novel session decomposition technique, from full session types (including internal/external choices) into single input/output session trees (without choices). Previous work studies precise subtyping for binary sessions (with just two participants), or multiparty sessions (with any number of participants) and synchronous interaction. Here, we cover multiparty sessions with asynchronous interaction, where messages are transmitted via FIFO queues (as in the TCP/IP protocol), and prove that our subtyping is both operationally and denotationally precise. In the asynchronous multiparty setting, finding the precise subtyping relation is a highly complex task: this is because, under some conditions, participants can permute the order of their inputs and outputs, by sending some messages earlier or receiving some later, without causing errors; the precise subtyping relation must capture all such valid permutations — and consequently, its formalisation, reasoning and proofs become challenging. Our session decomposition technique overcomes this complexity, expressing the subtyping relation as a composition of refinement relations between single input/output trees, and providing a simple reasoning principle for asynchronous message optimisations.

Web of Linked Data introduces common format and principles for publishing and linking data on the Web. Such a network of linked data is publicly available and easily consumable. This paper introduces a calculus for modelling networks of linked data with encoded privacy preferences. In that calculus, a network is a parallel composition of users, where each user is named and consists of data, representing the user's profile, and a process. Data is a parallel composition of triples with names (resources) as components. Associated with each name and each triple of names are their privacy protection policies, that are represented by queries. A data triple is accessible to a user if the user's data satisfies the query assigned to that triple. The main contribution of this model lies in the type system which together with the introduced query order ensures that static type-checking prevents privacy violations. We say that a network is well behaved if — access to a triple is more restrictive than access to its components and less restrictive than access to the user name it is enclosed with, — each user can completely access their own profile, — each user can update or partly delete profiles that they own (can access the whole profiles), and — each user can update the privacy preference policy of data of another profile that they own or write data to another profile only if the newly obtained profile stays fully accessible to their owner. We prove that any well-typed network is well behaved.

Abstract Protocols in distributed settings usually rely on the interaction of several parties and often identify therolesinvolved in communications. Roles may have a behavioral interpretation, as they do not necessarily correspond to sites or physical devices. Notions ofrole authorizationthus become necessary to consider settings in which, e.g., different sites may be authorized to act on behalf of a single role, or in which one site may be authorized to act on behalf of different roles. This flexibility must be equipped with ways of controlling the roles that the different parties are authorized to represent, including the challenging case in which role authorizations are determined only at runtime. We present a typed framework for the analysis of multiparty interaction with dynamic role authorization and delegation. Building on previous work on conversation types with role assignment, our formal model is based on an extension of the π -calculus in which the basic resources are pairs channel-role, which denote the access right of interacting along a given channel representing the given role. To specify dynamic authorization control, our process model includes (1) a novel scoping construct for authorization domains, and (2) communication primitives for authorizations, which allow to pass around authorizations to act on a given channel. An authorization error then corresponds to an action involving a channel and a role not enclosed by an appropriate authorization scope. We introduce a typing discipline that ensures that processes never reduce to authorization errors, including when parties dynamically acquire authorizations.

This paper deals with partitions of a discrete set S of points in a d-dimensional space, by h parallel hyperplanes. Such partitions are in a direct correspondence with multilinear threshold functions which appear in the theory of neural networks and multivalued logic. The characterization (encoding) problem is studied. We show that a unique characterization (encoding) of such multilinear partitions of S = {0, 1,..., m-1}d is possible within theta(h x d2 x log m) bit rate per encoded partition. The proposed characterization (code) consists of (d + 1) x (h + 1) discrete moments having the order no bigger than 1. The obtained bit rate is evaluated depending on the mutual relations between h, d, and m. The optimality is reached in some cases.