arXiv subjects

Dimitrios Kouzapas

Publications and source records attributed to Dimitrios Kouzapas.

8 recordsLinked to original sources

arXiv2026

Multiparty Session Types for GDPR Purpose Compliance

The General Data Protection Regulation (GDPR) establishes purpose limitation as a fundamental constraint on personal data processing: personal data must be collected, stored, and processed strictly in accordance with explicitly specified purposes. Therefore, systems are required not only to declare the purposes under which personal data are processed, but also to ensure that their runtime behaviour remains aligned with the declared purposes. Yet, in mainstream software engineering practice, purposes are often treated as informal declarations, largely disconnected from system behaviour and, therefore, not amenable to rigorous reasoning about purpose compliance. This gap becomes particularly problematic in distributed systems, where personal data may flow across multiple entities and evolve through complex communication patterns. To address this challenge, recent works propose a more elaborate treatment of purposes based on structured, action-oriented representations of the data-processing interactions involved in their fulfilment. Building on these insights, we introduce a formal, purpose-aware framework grounded in multiparty session types in which purposes are modelled as structured interaction protocols among system entities. Within our framework, system implementations are specified using a process calculus that captures the semantics of distributed interactions and features private data as a first-class entity. Furthermore, we define a type system that verifies compliance between declared purposes and system models, and we establish subject reduction and purpose fidelity results, thereby ensuring that well-typed systems do not deviate from their specified purposes during execution. We demonstrate our approach through a case study involving a healthcare system. Ultimately, our objective is to evolve this formal framework into a software-engineering-oriented approach that unifies purpose modelling and compliance verification within a lifecycle-driven methodology, thus enabling a practically applicable privacy-by-design process.

cs.FL↗

arXiv2025

iCPS-DL: A Description Language for Autonomic Industrial Cyber-Physical Systems

Modern industrial systems require frequent updates to their cyber and physical infrastructures, often demanding considerable reconfiguration effort. This paper introduces the industrial Cyber-Physical Systems Description Language, iCPS-DL, which enables autonomic reconfigurations for industrial Cyber-Physical Systems. The iCPS-DL maps an industrial process using semantics for physical and cyber-physical components, a state estimation model, and agent interactions. A novel aspect is using communication semantics to ensure live interaction among distributed agents. Reasoning on the semantic description facilitates the configuration of the industrial process control loop. A Water Distribution Networks domain case study demonstrates iCPS-DL's application.

eess.SY↗

arXiv2024

A Session Type System for Asynchronous Unreliable Broadcast Communication

Session types are formal specifications of communication protocols, allowing protocol implementations to be verified by typechecking. Up to now, session type disciplines have assumed that the communication medium is reliable, with no loss of messages. However, unreliable broadcast communication is common in a wide class of distributed systems such as ad-hoc and wireless sensor networks. Often such systems have structured communication patterns that should be amenable to analysis by means of session types, but the necessary theory has not previously been developed. We introduce the Unreliable Broadcast Session Calculus, a process calculus with unreliable broadcast communication, and equip it with a session type system that we show is sound. We capture two common operations, broadcast and gather, inhabiting dual session types. Message loss may lead to non-synchronised session endpoints. To further account for unreliability we provide with an autonomous recovery mechanism that does not require acknowledgements from session participants. Our type system ensures soundness, safety, and progress between the synchronised endpoints within a session. We demonstrate the expressiveness of our framework by implementing Paxos, the textbook protocol for reaching consensus in an unreliable, asynchronous network.

cs.LO↗

arXiv2018

Fault Adaptive Routing in Metasurface Controller Networks

HyperSurfaces are a merge of structurally reconfigurable metasurfaces whose electromagnetic properties can be changed via a software interface, using an embedded miniaturized network of controllers, thus enabling novel capabilities in wireless communications. Resource constraints associated with the development of a hardware testbed of this breakthrough technology necessitate network controller architectures different from traditional regular Network-on-Chip architectures. The Manhattan-like topology chosen to realize the controller network in the testbed under development is irregular, with restricted local path selection options, operating in an asynchronous fashion. These characteristics render traditional fault-tolerant routing mechanisms inadequate. In this paper, we present work in progress towards the development of fault-tolerant routing mechanisms for the chosen architecture. We present two XY-based approaches which have been developed aiming to offer reliable data delivery in the presence of faults. The first approach aims to avoid loops while the second one attempts to maximize the success delivery probabilities. Their effectiveness is demonstrated via simulations conducted on a custom developed simulator.

cs.ET↗

arXiv2017

Privacy by typing in the $π$-calculus

In this paper we propose a formal framework for studying privacy in information systems. The proposal follows a two-axes schema where the first axis considers privacy as a taxonomy of rights and the second axis involves the ways an information system stores and manipulates information. We develop a correspondence between the above schema and an associated model of computation. In particular, we propose the \Pcalc, a calculus based on the $π$-calculus with groups extended with constructs for reasoning about private data. The privacy requirements of an information system are captured via a privacy policy language. The correspondence between the privacy model and the \Pcalc semantics is established using a type system for the calculus and a satisfiability definition between types and privacy policies. We deploy a type preservation theorem to show that a system respects a policy and it is safe if the typing of the system satisfies the policy. We illustrate our methodology via analysis of two use cases: a privacy-aware scheme for electronic traffic pricing and a privacy-preserving technique for speed-limit enforcement.

cs.LO↗

arXiv2015

Globally Governed Session Semantics

This paper proposes a bisimulation theory based on multiparty session types where a choreography specification governs the behaviour of session typed processes and their observer. The bisimulation is defined with the observer cooperating with the observed process in order to form complete global session scenarios and usable for proving correctness of optimisations for globally coordinating threads and processes. The induced bisimulation is strictly more fine-grained than the standard session bisimulation. The difference between the governed and standard bisimulations only appears when more than two interleaved multiparty sessions exist. This distinct feature enables to reason real scenarios in the large-scale distributed system where multiple choreographic sessions need to be interleaved. The compositionality of the governed bisimilarity is proved through the soundness and completeness with respect to the governed reduction-based congruence. Finally, its usage is demonstrated by a thread transformation governed under multiple sessions in a real usecase in the large-scale cyberinfrustracture.

cs.LO↗

arXiv2015

Core Higher-Order Session Processes: Tractable Equivalences and Relative Expressiveness

This work proposes tractable bisimulations for the higher-order pi-calculus with session primitives (HOpi) and offers a complete study of the expressivity of its most significant subcalculi. First we develop three typed bisimulations, which are shown to coincide with contextual equivalence. These characterisations demonstrate that observing as inputs only a specific finite set of higher-order values (which inhabit session types) suffices to reason about HOp} processes. Next, we identify HO, a minimal, second-order subcalculus of HOpi in which higher-order applications/abstractions, name-passing, and recursion are absent. We show that HO can encode HOpi extended with higher-order applications and abstractions and that a first-order session pi-calculus can encode HOpi. Both encodings are fully abstract. We also prove that the session pi-calculus with passing of shared names cannot be encoded into HOpi without shared names. We show that HOpi, HO, and pi are equally expressive; the expressivity of HO enables effective reasoning about typed equivalences for higher-order processes.

cs.LO↗

arXiv2014

Session Types for Broadcasting

Up to now session types have been used under the assumptions of point to point communication, to ensure the linearity of session endpoints, and reliable communication, to ensure send/receive duality. In this paper we define a session type theory for broadcast communication semantics that by definition do not assume point to point and reliable communication. Our session framework lies on top of the parametric framework of broadcasting psi-calculi, giving insights on developing session types within a parametric framework. Our session type theory enjoys the properties of soundness and safety. We further believe that the solutions proposed will eventually provide a deeper understanding of how session types principles should be applied in the general case of communication semantics.

cs.PL↗