On Composing Communicating Systems

International audienceCommunication is an essential element of modern software, yet programming and analysing communicating systems are difficult tasks. A reason for this difficulty is the lack of compositional mechanisms that preserve relevant communication properties. This problem has been recently addressed for the well-known model of communicating systems, that is sets of components consisting of finite-state machines capable of exchanging messages. The main idea of this approach is to take two systems, select a participant from each of them, and derive from those participants a pair of coupled gateways connecting the two systems. More precisely, a message directed to one of the gateways is forwarded to the gateway in the other system, which sends it to the other system. It has been shown that, under some suitable compatibility conditions between gateways, this composition mechanism preserves deadlock freedom for asynchronous as well as symmetric synchronous communications (where sender and receiver play the same part in determining which message to exchange). This paper considers the case of asymmetric synchronous communications where senders decide independently which message should be exchanged. We show here that preservation of lock freedom requires sequentiality of gateways, while this is not needed for preservation of either deadlock freedom or strong lock freedom

Explanation before Adoption: Supporting Informed Consent for Complex Machine Learning and IoT Health Platforms

Explaining health technology platforms to non-technical members of the public is an important part of the process of informed consent. Complex technology platforms that deal with safety-critical areas are particularly challenging, often operating within private domains (e.g. health services within the home) and used by individuals with various understandings of hardware, software, and algorithmic design. Through two studies, the first an interview and the second an observational study, we questioned how experts (e.g. those who designed, built, and installed a technology platform) supported provision of informed consent by participants. We identify a wide range of tools, techniques, and adaptations used by experts to explain the complex SPHERE sensor-based home health platform, provide implications for the design of tools to aid explanations, suggest opportunities for interactive explanations, present the range of information needed, and indicate future research possibilities in communicating technology platforms

Specification and Verification of Contract-Based Applications

Nowadays emerging paradigms are being adopted by several companies, where applications are built by assembling loosely-coupled distributed components, called services. Services may belong to possibly mutual distrusted organizations and may have conflicting goals. New methodologies for designing and verifying these applications are necessary for coping with new scenarios in which a service does not adhere with its prescribed behaviour, namely its contract. The thesis tackles this problem by proposing techniques for specifying and verifying distributed applications. The first contribution is an automata-based model checking technique for ensuring both service compliance and security requirements in a composition of services. We further develop the automata-based approach by proposing a novel formal model of contracts based on tailored finite state automata, called contract automata. The proposed model features several notions of contract agreement described from a language-theoretic perspective, for characterising the modalities in which the duties and requirements of services are fulfilled. Contract automata are equipped with different composition operators, to uniformly model both single and composite services, and techniques for synthesising an orchestrator to enforce the properties of agreement. Algorithms for verifying these properties are introduced, based on control theory and linear programming techniques. The formalism assumes the existence of possible malicious components trying to break the overall agreement, and techniques for detecting and banning eventually liable services are described. We study the conditions for dismissing the central orchestrator in order to generate a distributed choreography of services, analysing both closed and open choreographed systems, with synchronous or asynchronous interactions. We relate contract automata with different intutionistic logics for contracts, introduced for solving mutual circular dependencies between the requirements and the obligations of the parties, with either linear or non-linear availability of resources. Finally, a prototypical tool implementing the theory developed in the thesis is presented

Programming Languages with Applications to Biology and Security. Essays Dedicated to Pierpaolo Degano on the Occasion of His 65th Birthday.

This Festschrift volume mainly contains 22 refereed research papers and one extended abstract by close collaborators and friends of Pierpaolo Degano to celebrate him on the occasion of his 65th birthday. The foreword of this volume includes a laudatio that illustrates the distinguished career and the main scientific contributions by Pierpaolo Degano and a portrait of him made by one of his closest friends. The following sections are dedicated to the scientific papers on the main research topics explored by Pierpaolo Degano and still under his investigation, among which formal program semantics, concurrency theory, systems biology and security, and much more