Nicolas Basset

• PhD
• Research Assistant at University of Oxford

Cyber-physical systems are complex environments that combine physical devices (i.e., sensors and actuators) with a software controller. The ubiquity of these systems and dangers associated with their failure require the implementation of mechanisms to monitor, verify and guarantee their correct behaviour. This paper presents ParetoLib 2.0, a Python...

Adding probabilities to timed automata enables one to carry random simulation of their behaviors and provide answers with statistical guarantees to problems otherwise untractable. Thus, when just a timed language is given, the following natural question arises: What probability should we consider if we have no a priori knowledge except the given la...

We propose a new active learning algorithm for PDFA based on three main aspects: a congruence over states which takes into account next-symbol probability distributions, a quantization that copes with differences in distributions, and an efficient tree-based data structure. Experiments showed significant performance gains with respect to reference...

Cyber-physical systems (CPS) are increasingly becoming driven by data, using multiple types of sensors to capture huge amounts of data. Extraction and characterization of useful information from big streams of data is a challenging problem. Shape expressions facilitate formal specification of rich temporal patterns encountered in time series as wel...

In this work, we introduce a supervised learning framework for inferring temporal logic specifications from labelled patterns in signals, so that the formulae can then be used to correctly detect the same patterns in unlabelled samples. The input patterns that are fed to the training process are labelled by a Boolean signal that captures their occu...

Falsification has garnered much interest recently as a way to validate complex CPS designs with respect to a specification expressed via temporal logics. Using their quantitative semantics, the falsification problem can be formulated as a robustness minimization problem.

This paper presents ParetoLib, a Python library that implements a new method for inferring the Pareto front in multi-criteria optimization problems. The tool can be applied in the parameter synthesis of temporal logic predicates where the influence of parameters is monotone. ParetoLib currently provides support for the parameter synthesis of standa...

This work is concerned with validation of cyber-physical systems (CPS) via sampling of input signal spaces. Such a space is infinite and in general too difficult to treat symbolically, meaning that the only reasonable option is to sample a finite number of input signals and simulate the corresponding system behaviours. It is important to choose a s...

An appealing feature of Signal Temporal Logic (STL) is the existence of efficient monitoring algorithms both for Boolean and real-valued robustness semantics, which are based on computing an aggregate function (conjunction, disjunction, min, or max) over a sliding window. On the other hand, there are properties that can be monitored with the same a...

Various problems about probabilistic and non-probabilistic timed automata (computing probability density, language volume or entropy) can be naturally phrased as iteration of linear operators in Banach spaces. Convergence of such iterations is guaranteed whenever the operator's spectrum has a gap. In this article, for operators used in entropy comp...

The signature of a permutation σ is a word sg(σ) ⊆ {a, d}* whose i th letter is d when σ has a descent (i.e. σ(i) > σ(i + 1)) and is a when σ has an ascent (i.e. σ(i) < σ(i + 1)). Combinatorics of permutations with a prescribed signature is quite well explored. Here we state and address the two problems of counting and randomly generating in the s...

The classical theory of constrained-channel coding deals with the following questions: given two languages representing a source and a channel, is it possible to encode source messages to channel messages, and how to realize encoding and decoding by simple algorithms, most often transducers. The answers to this kind of questions are based on the no...

In order to study precisely the growth of timed languages, we associate to such a language a generating function. These functions (tightly related to volume and entropy of timed languages) satisfy compositionality properties and, for deterministic timed regular languages, can be characterized by integral equations. We provide procedures for closed-...

In previous literature on timed automata, it was noticed that they are in several aspects too precise, which leads sometimes to strange artifacts, mathematical pathologies or unrealistic models. In particular, some timed automata are non-implementable, non-robust, behave badly under discretization, have many Zeno runs etc. In this paper, we propose...

In this paper, we give a characterization based on Nerode's right congru-ence of DWBA which is the subclass of ω-regular languages which are recognized by a deterministic weak Büchi automaton (DWBA). Thanks to that we can define a partial minimization of deterministic Büchi automata (DBA) and explain the DWBA minimization due to Löding [Löd01]. We...