arXiv subjects

Ivan Prokić

Publications and source records attributed to Ivan Prokić.

4 recordsLinked to original sources

arXiv2026

On Asynchronous Multiparty Session Types for Federated Learning

This paper improves the session typing theory to support the modelling and verification of processes that implement federated learning protocols. To this end, we build upon the asynchronous ``bottom-up'' session typing approach by adding support for input/output operations directed towards multiple participants at the same time. We further enhance the flexibility of our typing discipline and allow for safe process replacements by introducing a session subtyping relation tailored for this setting. We formally prove safety, deadlock-freedom, liveness, and session fidelity properties for our session typing system. Moreover, we highlight the nuances of our session typing system, which (compared to previous work) reveals interesting interplays and trade-offs between safety, liveness, and the flexibility of the subtyping relation.

cs.LO↗

arXiv2023

Correct orchestration of Federated Learning generic algorithms: formalisation and verification in CSP

Federated learning (FL) is a machine learning setting where clients keep the training data decentralised and collaboratively train a model either under the coordination of a central server (centralised FL) or in a peer-to-peer network (decentralised FL). Correct orchestration is one of the main challenges. In this paper, we formally verify the correctness of two generic FL algorithms, a centralised and a decentralised one, using the CSP process calculus and the PAT model checker. The CSP models consist of CSP processes corresponding to generic FL algorithm instances. PAT automatically proves the correctness of the two generic FL algorithms by proving their deadlock freeness (safety property) and successful termination (liveness property). The CSP models are constructed bottom-up by hand as a faithful representation of the real Python code and is automatically checked top-down by PAT.

cs.DC↗

arXiv2020

Precise Subtyping for Asynchronous Multiparty Sessions

This paper presents 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) 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.

cs.LO↗

arXiv2019

The Cpi-calculus: a Model for Confidential Name Passing

Sharing confidential information in distributed systems is a necessity in many applications, however, it opens the problem of controlling information sharing even among trusted parties. In this paper, we present a formal model in which dissemination of information is disabled at the level of the syntax in a direct way. We introduce a subcalculus of the pi-calculus in which channels are considered as confidential information. The only difference with respect to the pi-calculus is that channels once received cannot be forwarded later on. By means of examples, we give an initial idea of how some privacy notions already studied in the past, such as group creation and name hiding, can be represented without any additional language constructs. We also present an encoding of the (sum-free) pi-calculus in our calculus.

cs.PL↗