## Léo Exibard

### Reykjavik University

I am currently a postdoctoral researcher in the Icelandic Centre of Excellence in Theoretical Computer Science (ICE-TCS) at Reykjavik University, in the Mode(l)s of Verification and Monitorability (MoVeMnt) project, which lies in the area of runtime verification. As the name suggests, it aims at studying monitorability of properties, i.e. whether there exists a program (called a monitor) that checks whether a given property holds by examining the execution of the system under scrutiny at runtime.

Previously, I was working on my PhD thesis under the joint direction of Emmanuel Filiot (at Département d’Informatique, Université Libre de Bruxelles) and Pierre-Alain Reynier (at LIS, Aix-Marseille Université), that I defended last September. I studied extensions of synthesis methods to systems operating with an infinite alphabet, more precisely over Data Words. More details as well as the manuscript, slides and video of the defence are available here.

I am mainly interested in the Verification and Automatic Synthesis of Computer Systems and its theoretical aspects: mathematical models and algorithms to analyse them. This includes, but is not limited to Automata, Logic and Game Theory.

I am also interested in Sociology (I completed in 2017 the first year of a Master of Sociology at the EHESS), specifically in its methodology, on both the qualitative and quantitative aspects, and epistemology. I am particularly curious about its links with Computer Science and Mathematics, and about the epistemological consequences of recent discoveries in Complex Networks theory on the conceptualisation of social dynamics.

### Interests

• Formal Methods
• Runtime Verification
• Automatic Synthesis
• Model-Checking
• Automata
• Logic
• Game Theory

### Education

• First year of Master in General Sociology, 2017

École des Hautes Études en Sciences Sociales

• Master in Computer Science, 2016

Université Paris Diderot (MPRI)

• Bachelor in Computer Science, 2014

École Normale Supérieure de Lyon

# Publications

My publications are also listed on dblp.

### Church Synthesis on Register Automata over Linearly Ordered Data Domains (STACS 2021)

The Church game for register automata over $(\mathbb{N}, \leq)$ is undecidable, but the one-sided game is, for deterministic ones.

### Computability of Data-Word Transductions over Different Data Domains (submitted to the LMCS Special Issue dedicated to FoSSaCS 2020)

We extend the correspondence between computability and continuity over regular functions to the case of data words.

### Synthesis of Data Word Transducers (LMCS Special Issue dedicated to CONCUR 2019)

Register automata are a counterpart of finite automata over data words. Synthesis algorithms can (sometimes) be extended to them.

### On Computability of Data Word Functions Defined by Transducers (FoSSaCS 2020)

We extend the correspondence between computability and continuity over regular functions to the case of data words.

### Synthesis of Data Word Transducers (CONCUR 2019)

Register automata are a counterpart of finite automata over data words. Synthesis algorithms can (sometimes) be extended to them.

### The Complexity of Transducer Synthesis from Multi-Sequential Specifications (MFCS 2018)

Multi-sequential specifications are recognised by unions of sequential transducers. Their synthesis problem is PSpace-complete.

### Two-Way Two-Tape Automata (DLT 2017)

Two-way two-tape automata are devices recognising relations over words. Alternating ones are not closed under complement.

# PhD Thesis

### Automatic Synthesis of Systems with Data

We partly lift synthesis to infinite domains through register automata, targeting register transducers or computable implementations.

# Recent & Upcoming Talks

### Synthesis over Infinite Domains through Machines with Registers @ Journées GT Vérif 2021 (Invited talk)

Synthesis can be lifted to infinite domains through register automata, targeting register transducers implementations.

### History-deterministic Register Automata @ NWPT 2021

History-deterministic register automata form a promising class for synthesis and runtime verification applications.

### On Computability of Data Word Functions Defined by Transducers @ ETAPS 2021

We extend the correspondence between computability and continuity over regular functions to the case of data words.

### On Computability of Data Word Functions Defined by Transducers @ HIGHLIGHTS 2020

We extend the correspondence between computability and continuity over regular functions to the case of data words.

### On Computability of Data Word Functions Defined by Transducers @ MOVEP 2020

We extend the correspondence between computability and continuity over regular functions to the case of data words.

# Teaching

## Université libre de Bruxelles (2019-2020)

• Informatique Fondamentale

Le matériel du cours est disponible en ligne sur l’ Université Virtuelle.

## Université libre de Bruxelles (2018-2019)

• Introduction to Language Theory and Compiling

All the course material is available online at the Université Virtuelle.

## Aix-Marseille Université (2017-2018)

• Algorithmique et Programmation
• Programmation

All the course material is available online on AMETiCE.

## Université libre de Bruxelles (2017-2018)

• Introduction to Language Theory and Compiling

All the course material is available online at the Université Virtuelle.

# Contact

• leoe@ru.is
• School of Computer Science
Reykjavik University
Menntavegur 1
IS-101 Reykjavik