Marc-Antoine Georges

Julien Diard

Laurent Girin

Jean-Luc Schwartz

Thomas Hueber

REPEAT AFTER ME: SELF-SUPERVISED LEARNING OF ACOUSTIC-TO-ARTICULATORY MAPPING BY VOCAL IMITATION

Keywords: Speech production, computational models, articulatory synthesis, representation learning

We propose a computational model of speech production combining a pre-trained neural articulatory synthesizer able to reproduce complex speech stimuli from a limited set of interpretable articulatory parameters, a DNN-based internal forward model predicting the sensory consequences of articulatory commands, and an internal inverse model based on a recurrent neural network recovering articulatory commands from the acoustic speech input. Both forward and inverse models are jointly trained in a self-supervised way from raw acoustic-only speech data from different speakers. The imitation simulations are evaluated objectively and subjectively and display quite encouraging performances.

INTRODUCTION

Speech production involves the activation of a complex system for uttering sounds from articulatory gestures. Learning to control such a complex system is a real challenge, considering the many underlying problems such as the large number of degrees of freedom of the vocal tract, the highly nonlinear relationship between articulatory configurations and sounds, the variability and complexity of the acoustical realizations available in the learning process and, most of all, the lack of corresponding articulatory information (apart from visual information on the facial movements of the interlocutor, if available). Therefore, from a statistical modeling point of view, learning the acoustic-to-articulatory relationship can be seen as a weakly supervised process.

This hard problem has generated computational developments in basically three directions: (i) articulatory synthesizers enabling to generate vocal tract shapes and speech sounds from a restricted set of interpretable parameters [START_REF] Maeda | Compensatory articulation during speech: Evidence from the analysis and synthesis of vocal-tract shapes using an articulatory model[END_REF][START_REF] Birkholz | Model-based reproduction of articulatory trajectories for consonant-vowel sequences[END_REF][START_REF] Birkholz | Construction And Control Of A Three-Dimensional Vocal Tract Model[END_REF]; (ii) statistical learning techniques modeling the articulatory-toacoustic forward (e.g. [START_REF] Hueber | Speaker-Adaptive Acoustic-Articulatory Inversion Using Cascaded Gaussian Mixture Regression[END_REF]) or inverse mapping (e.g. [START_REF] Bocquelet | Robust articulatory speech synthesis using deep neural networks for BCI applications[END_REF]) from in-vivo articulatory recordings; and (iii) speech motor control This work was funded by the Multidisciplinary Institute in Artificial Intelligence MIAI@Grenoble-Alpes (ANR-19-P3IA-0003).

architectures mimicking how the human brain exploits internal sensory and motor representations in speech production. These architectures usually associate internal forward and inverse models [START_REF] Miall | Forward models for physiological motor control[END_REF], respectively in charge of the articulatoryto-acoustic prediction and acoustic-to-motor-command inference (e.g. [START_REF] Frank | A neural theory of speech acquisition and production[END_REF][START_REF] Parrell | The facts model of speech motor control: Fusing state estimation and task-based control[END_REF][START_REF] Parrell | Current models of speech motor control: a control-theoretic overview of architectures and properties[END_REF]). However, most of these models are tuned and tested on very simple data, such as vowels, simple syllables or synthetic data generated by the articulatory model itself (e.g. [START_REF] Patri | Optimal speech motor control and token-to-token variability: a Bayesian modeling approach[END_REF][START_REF] Kröger | Towards a neurocomputational model of speech production and perception[END_REF][START_REF] Laurent | The complementary roles of auditory and motor information evaluated in a Bayesian perceptuo-motor model of speech perception[END_REF][START_REF] Bailly | Learning to speak. Sensori-motor control of speech movements[END_REF][START_REF] Moulin-Frier | Self-organization of early vocal development in infants and machines: The role of intrinsic motivation[END_REF][START_REF] Kristina Philippsen | Learning how to speak: Imitation-based refinement of syllable production in an articulatoryacoustic model[END_REF][START_REF] Chen | Modeling sensorimotor adaptation in speech through alterations to forward and inverse models[END_REF]).

Another recent line of research focused on self-supervised learning of speech representations from large unlabeled audio datasets (e.g. [START_REF] Chung | An Unsupervised Autoregressive Model for Speech Representation Learning[END_REF]). These representations enable to train generative spoken language models that can be used to reproduce and extend a set of input audio stimuli [START_REF] Polyak | Speech Resynthesis from Discrete Disentangled Self-Supervised Representations[END_REF]. A number of recent developments in this field occurred in the framework of the "zero-resource challenge" [START_REF] Dunbar | The Zero Resource Speech Challenge 2019: TTS Without T[END_REF]. However, the developed systems do not incorporate knowledge about the speech production process. Therefore, although they are powerful and efficient for generating speech sounds, they cannot provide much light on the underlying mechanisms involved in speech production.

The present paper provides some progress at the crossroads between these two lines of research. We propose a fully neural architecture combining (i) a pre-trained articulatory synthesizer (i.e., the plant) combining a deep neural network (DNN) based articulatory-to-acoustic mapping with the LPCNet neural vocoder [START_REF] Valin | LPCNet: Improving neural speech synthesis through linear prediction[END_REF] and able to reproduce complex speech stimuli from a limited set of interpretable articulatory parameters [START_REF] Georges | Towards an articulatory-driven neural vocoder for speech synthesis[END_REF][START_REF] Georges | Learning Robust Speech Representation with an Articulatory-Regularized Variational Autoencoder[END_REF], (ii) a DNN-based internal forward model predicting the sensory consequences of articulatory commands, and (iii) an internal inverse model based on a recurrent neural network (RNN) recovering articulatory commands from the acoustic speech input. Both the forward and inverse models are jointly trained in a self-supervised way from raw acoustic-only speech data from different speakers. To that purpose, we investigate the "accommodation" algorithm proposed in [START_REF] Laurent | The complementary roles of auditory and motor information evaluated in a Bayesian perceptuo-motor model of speech perception[END_REF], enabling the model to progressively shift from a random exploratory phase typical of infant babbling to a tuning phase in which the forward-inverse system converges to allow to efficiently imitate the sounds of a given speaker.

MATERIAL AND METHODS

Overview

The proposed model is illustrated in Fig. 1. We briefly explain its expected behavior and set the mathematical notations. Let us denote s an acoustic speech stimulus which is encoded into a sequence of D s -dimensional feature vectors such as s = [s 1 , • • • , s T ] (where T is the sequence length). The internal inverse model g estimates at each timestep t a set of ulatory parameters represented by the D a -dimensional vector a t = g(s t ). At each timestep t, the internal forward model f estimates the sensory (acoustic) consequence s t = f (a t ) of the articulatory input a t . Simultaneously, the articulatory synthesizer φ (i.e., the plant) simulates the physical process of speech production and generates the acoustic feature vector s t = φ(a t ). The precise nature of the acoustic (s t , s t and s t ) and articulatory features (a t ) will be detailed in Section 2.2.

Here, g, f and φ are DNNs. When trained to reproduce an input audio speech stimulus (i.e., minimizing the discrepancy between s t and s t at each timestep), this model learns a forward and inverse articulatory-to-acoustic mapping in a self-supervised manner. The following sections describe the three components in more details, as well as the accommodation learning algorithm used to jointly train the internal models from audio-only speech stimuli.

Neural articulatory synthesizer

In the present study, we use the neural articulatory synthesizer originally proposed and described in [START_REF] Georges | Towards an articulatory-driven neural vocoder for speech synthesis[END_REF] (and recently used in [START_REF] Georges | Learning Robust Speech Representation with an Articulatory-Regularized Variational Autoencoder[END_REF]). We recall here the key features of this synthesizer.

First, it was built from an articulatory-acoustic dataset containing recordings of 1,108 items (vowels, vowel-consonantvowel sequences, short words and sentences) pronounced by a male French speaker (hereafter the reference speaker RS). The movements of the tongue, jaw and lips during speech production were recorded at 100 Hz using 2D electromagnetic articulography (EMA), synchronously with the speech sound. An articulatory model accounting for the different degrees of freedom of the vocal tract was then built from the raw EMA coordinates using the guided-PCA method proposed in [START_REF] Maeda | Compensatory articulation during speech: Evidence from the analysis and synthesis of vocal-tract shapes using an articulatory model[END_REF]. Using this model, EMA coordinates were then converted into a limited number of interpretable articulatory parameters: Jaw Height (JH), Tongue Body (TB), Tongue Dorsum (TD), Tongue Tip (TT), Lip Protusion (LP), and Lip Height (LH). In parallel, the short-term spectral content of the acoustic speech signal (initially recorded at 16 kHz) is encoded into a vector of 18 Bark-scale cepstral coefficients, which is the acoustic feature vector s t (the analysis is processed with a window size of 20 ms and a hop size of 10 ms, ensuring the synchronization of the acoustic and articulatory feature vectors).

The articulatory-acoustic relationships for speaker RS were then approximated by a feedforward DNN (4 fullyconnected hidden layers of 256 neurons each, with an hyperbolic tangent activation function, batch normalization and dropout (p = 0.25) used in each layer, trained on 80% of the dataset with the Adam optimizer and mini-batches of 8 observations, the remaining 20% being used for early-stopping). At synthesis time, a synthetic speech waveform can be obtained using the LPCNet neural vocoder, conditioned on the speech spectrum estimated from the articulatory parameters, and combined with source features (i.e., f 0 and harmonicity parameters in LPCNet).

Importantly, this neural articulatory synthesizer is used here as a pre-trained module. When used within the proposed architecture, its parameters are not updated contrary to the inverse and forward models g and f , which are described in the next section.

Implementation of the forward and inverse models

The forward model f (converting an articulatory feature vector a t into an acoustic feature vector s t ) is implemented with the same architecture as that of the articulatory synthesizer (4 fully-connected hidden layers of 256 neurons each, trained with the same settings as those reported in Section 2.2).

The inverse model g in charge of recovering the articulatory parameters that must be sent to the plant φ to reproduce the input speech stimuli is implemented with an RNN. This choice is motivated by the one-to-many nature of the acousticto-articulatory mapping, which may be partially tackled by considering contextual information. Therefore, we use 2 layers of 32 long short-term memory (LSTM) cells (with dropout p = 0.25), stacked with a linear (time-distributed) layer, for converting a sequence of T acoustic feature vectors s

= [s 1 , • • • , s T ] into a sequence of T articulatory feature vectors a = [a 1 , • • • , a T ].

Accommodation learning

Accomodation learning is defined here as a learning process, during which an agent tries to imitate external sound stimuli by generating articulatory commands, and gathers observations about the correspondence between target sounds and attempted articulations on one hand, attempted articulations and real sounds generated by these articulations on the other hand. Starting from a random initialization, the procedure used to jointly train the forward and inverse models can be summarized as follows: (i) given a sequence of acoustic observations s (in practice, a mini-batch of K sequences with K = 8 in our implementation), estimate a = g(s) (inverse model), s with s t = f (a t ) (forward model) and s with s t = φ(a t ) (articulatory synthesizer) (ii) update the forward model f using backpropagation to minimize the discrepancy between s and s (in practice, the mean squared error is used as the loss function), and (iii) update the inverse model g to minimize the discrepancy between s and s, while keeping the forward model unchanged. This is achieved by freezing the parameters (i.e., the weights and biases) of the forward model during the backpropagation of the prediction error from the last layer of the forward model to the first layer of the inverse model).

When starting the accomodation learning, no prior knowledge is present in the inverse and forward models. Therefore, the inversion step yields unadapted productions, which amounts to randomly explore the articulatory space. However, applying such random gestures as inputs to φ provides "ground-truth" acoustic consequences, allowing f to locally learn the articulatory-to-acoustic mapping. Over time, learning progresses and focuses on relevant regions of the articulatory space, with an improvement of the forward model leading to a better inversion, improvement of the inverse model and of the articulatory gesture selection, and finally, of the imitation task.

SIMULATIONS

Datasets

Model training and evaluation were conducted on 3 audioonly datasets. The first one is derived from the audio recordings of the reference speaker (RS) used to train the articulatory synthesizer (see Section 2.2). In that case, the model perceives (and tries to repeat) its own "voice." The two other audio datasets were built by recording two other male speakers (hereafter S1 and S2) uttering the same set of speech utterances.

For each of the 3 speakers considered in this study (RS, S1, S2), 80% of the items in the dataset were selected randomly and used for training while the remaining 20% were used for test. Among the training items, 20% of them were used for validation (early stopping). For each speaker, we repeated the simulation 3 times. The experimental results are reported and discussed in the following sections.

Learning dynamics

Fig. 2 displays the typical evolution of the RMSE values for the forward and inverse models (that is, between s and s for the forward model f and between s and s for the inverse model g) along the model training for one simulation. Learning is rapid, though less smooth for f than for g, since it is trained on the productions inferred by the constantly evolving inverse model, causing instabilities. RMSE at convergence is quite low for f since it is progressively tested on specific regions of the articulatory-acoustic space where it is particularly well trained and accurate.

Fig. 3 further evaluates the accuracy of the forward model at the beginning and at the end of the learning phase. For this aim, we first gathered the whole set of articulatory feature vectors generated by the model when processing the test set at the end of the learning process. These vectors were then randomly modified with an offset and fed into the forward model and the articulatory synthesizer. We then computed the difference between the resulting outputs. The right plot of Fig. 3 displays this difference sorted by the distance between the articulatory feature vector selected by the model and its randomly offset version. The left plot of the figure displays the same process on the forward model at the beginning of the learning phase (Epoch 1). The results show that at learning onset, the forward model is consistently bad at inferring acoustic outcomes. In contrast, after learning, the forward model is accurate for articulatory feature vectors close to the ones the inverse model has selected, while accuracy decreases further away from these selected vectors. This shows that the accommodation learning algorithm only learns the forward model in small, useful portions of the articulatory space.

Evaluation of imitation performance

The models were then tested on the quality of the phonemic content of the produced speech signal, with both an objective evaluation by an HMM-based phonetic decoder and a subjective evaluation by human listeners.

A phonetic decoder based on a set of 39 3-state left-toright HMMs was first trained on the audio dataset of speaker RS, using the same items and acoustic features as those used to train the forward and inverse models (training was done using the HTK toolkit and a standard procedure). Then, at each learning epoch, the test set outputs of the 9 simulations were fed into the HMM system providing correctness scores at the phonetic level, which are displayed on Fig. 4. These scores have similar learning dynamics as those of RMSE values of the forward and inverse learning models in Fig. 2. Correctness reaches values around 70% for the imitation of RS, and lower values, around 60%, for the two other speakers. This is not surprising considering that the content of the phonetic utterances produced by speakers S1 and S2 differ from the productions by speaker RS, which provided the basis for the HMM training. Still, the global quality of the produced utterances at the end of the training stage is rather satisfactory. 1 To better evaluate the quality of the imitation test set for each imitated speaker, we extracted from the test corpus a set of isolated oral vowels /i y u e ø o a/ and a set of non-nasal consonants /b d g p t k f v s z S Z/ in a VCV context, with V one of the three vowels /i a u/. This set of stimuli, separately produced by each of the three speakers, was presented to the model for imitation, carefully ensuring that the corresponding model had not been trained on the stimulus to imitate. The resulting 18-Bark band spectrum was converted into sound by using the LPCNet vocoder with the source parameters from the original sound to imitate. The set of synthesized stimuli for each of the three imitated speakers was presented to 20 listeners in an online test in the Prolific platform, with a forced choice response. The average correct scores for consonants are around 60% (58 % for RS, 62 % for both S1 and S2). For vowels, they vary from 94% from speaker RS to lower scores, respectively 54% and 72% for S1 and S2. lower scores for speakers S1 and S2 are probably due to some inconsistency between vowel targets among the target speakers, confusions arising typically between close vowels in the formant space (e.g., /y/ vs. /e/).

CONCLUSION AND PERSPECTIVES

The presented simulations show that it is indeed possible to train in a weakly supervised way a sensory-motor model to jointly learn a forward and an inverse model from speech samples provided by different speakers. The end-to-end neuronal architecture presented and evaluated in the present paper provides powerful ways of adapting sensory-motor architectures to the real speech world. Still there is much room for improvement of the proposed architecture, particularly concerning its ability to better define the speech task in terms of phonetic and linguistic goals rather than strict imitation of acoustic patterns. The next step in these developments will hence consist in introducing linguistic units in the definition of representations and loss functions.

Fig. 1 .

 1 Fig. 1. Overview of the proposed model of speech production.

Fig. 2 .

 2 Fig.2. RMSE evolution for the forward (in orange) and inverse (in blue) models (y-axis) as a function of the number of epochs (x-axis), for a simulation in which RS imitates S1.

Fig. 3 .

 3 Fig. 3. Accuracy of the forward model (y-axis) as a function of the distance between an articulatory input and the articulatory set selected at the last epoch (x-axis). Left: at learning onset; Right: at the end of learning.

  The

1

  Productions associated to these simulations are available at https:// georges.ma/p/imitative-model.

Fig. 4 .

 4 Fig. 4. Evolution of the correctness (in percent, y-axis) of the HMM-based phonetic decoding of the model productions as a function of the number of model training epochs (x-axis). Each of the 9 curves represents a different simulation trained to reproduce one dataset.


D Pellier
email: damien.pellier@imag.fr

H Fiorino

M Grand

A Albore

R Bailon-Ruiz
email: rafael.bailonruiz@onera.fr

HDDL 2.1: Towards Defining an HTN Formalism with Time

Real world applications of planning, like in industry and robotics, require modelling rich and diverse scenarios. Their resolution usually requires coordinated and concurrent action executions. In several cases, such planning problems are naturally decomposed in a hierarchical way and expressed by a Hierarchical Task Network (HTN) formalism. The PDDL language used to specify planning domains has evolved to cover the different planning paradigms. However, formulating real and complex scenarios where numerical and temporal constraints concur in defining a solution is still a challenge. Our proposition aims at filling the gap between existing planning languages and operational needs. To do so, we propose to extend HDDL taking inspiration from PDDL 2.1 and ANML to express temporal and numerical expressions. This paper opens discussions on the semantics and the syntax needed to extend HDDL, and illustrate these needs with the modelling of an Earth Observing Satellite planning problem.

Introduction

The Hierarchical Task Network (HTN) formalism [START_REF] Erol | HTN planning: Complexity and expressivity[END_REF] is used to express a wide variety of planning problems in many real-world applications, e.g., in task allocation for robot fleets [START_REF] Milot | Solving Hierarchical Auctions with HTN Planning[END_REF], video games [START_REF] Menif | SHPE: HTN Planning for Video Games[END_REF] or industrial contexts such as software deployment [START_REF] Georgievski | Cloud ready applications composed via HTN planning[END_REF]. Real world applications of planning, like in industry and robotics, require modelling rich and diverse scenarios. In several cases, such planning problems are naturally decomposed in a hierarchical way, and they contain both numerical and temporal constraints defining the sub-tasks decomposition, and agents synchronisation on collaborative tasks. In fact, concurrency between the actions, and agents coordination in HTN problems are needed to find solutions for nontrivial tasks in complex scenarios.

Over the last years, much progress has been made in the field of hierarchical planning [START_REF] Bercher | A survey on hierarchical planning -one abstract idea, many concrete realizations[END_REF]. Novel systems based on the traditional, search-based techniques have been introduced (Bit-Monnot, [START_REF] Bit-Monnot | Delete-free reachability analysis for temporal and hierarchical planning[END_REF][START_REF] Ramoul | Grounding of HTN planning domain[END_REF][START_REF] Shivashankar | Incorporating domain-independent planning heuristics in hierarchical planning[END_REF][START_REF] Bercher | An admissible HTN planning heuristic[END_REF][START_REF] Höller | On guiding search in HTN planning with classical planning heuristics[END_REF]Höller et al., , 2020b;;[START_REF] Höller | Landmark generation in HTN planning[END_REF], but also new techniques like the translation to STRIPS/ADL [START_REF] Alford | Translating htns to PDDL: A small amount of domain knowledge can go a long way[END_REF][START_REF] Alford | Hierarchical planning: Relating task and goal decomposition with task sharing[END_REF][START_REF] Behnke | Making Translations to Classical Planning Competitive with Other HTN Planners[END_REF], or revisited approaches like the translation to propositional logic (Behnke, Höller, andBiundo, 2018, 2019;[START_REF] Schreiber | Tree-REX: SAT-based tree exploration for efficient and high-quality HTN planning[END_REF][START_REF] Schreiber | Lilotane: A lifted SAT-based approach to hierarchical planning[END_REF][START_REF] Behnke | Block Compression and Invariant Pruning for SAT-based Totally-Ordered HTN Planning[END_REF].

Despite these advances, not all these systems use the same formalism to represent hierarchical task decomposition. This makes difficult to compare the different approaches and to promote HTN planning techniques, even if some formalism are more adopted than others. For these reasons, an extension of the PDDL (Planning Domain Description Language) [START_REF] Mcdermott | PDDL -The Planning Domain Definition Language[END_REF], used in the International Planning Competitions (IPC), has been proposed. This extension (Höller et al., 2020a), called HDDL (Hierarchical Planning Domain Description Language), is based on PDDL 2.1 [START_REF] Fox | PDDL2.1: An extension to PDDL for expressing temporal planning domains[END_REF] and is the result of several discussions within the planning community (Behnke et al., 2019) to fill the need of a standard language for the first Hierarchical Planning track of IPC 2020. In this first version, it was decided that, considering the efforts to develop the language and related tools, none of the temporal and numerical features of PDDL would be included. The objective of this paper is to initiate and organise the discussion on the temporal extension of HDDL, to propose some starting ideas and tools.

Our motivation is grounded on compelling needs to devise applications involving autonomous systems, i.e. agents, which must be coordinated to fulfil hierarchical tasks containing both numerical and temporal constraints. As a matter of fact, action concurrency and agent coordination are needed in HTN problems to find solutions for nontrivial tasks in complex scenarios, like collaborative robotic missions [START_REF] Weser | Htn robot planning in partially observable dynamic environments[END_REF]. Starting from a real satellite application example, we propose two extensions for HDDL including elements of PDDL 2.1 and ANML to express temporal and numerical expressions. This is intended to initiate discussions within HTN community on establishing a standard -HDDL 2.1 -aimed at filling the gaps between existing hierarchical-temporal planning approaches. To that end, we make this preliminary extension of HDDL an open source project with a publicly available repository.

The rest of the paper is organised as follows. Section 1 and section 2 propose two extensions of HDDL 1.0 syntax to deal with time, numeric and constraints in method declaration. Section 3 illustrates HDDL 2.1 with a real world ex-ample of an Earth Observing Satellite (EOS) mission. Section 4 presents the related works, and Section 5 discusses the main features of the proposed language. The full syntax of our HDDL dialect is presented in the appendix.

Durative methods

To deal with time in HDDL, we propose to add the concept of durative method. Like methods in HDDL 1.0, durative methods have parameters, the abstract task they decompose, and the resulting task network, and, like durative actions, they can have duration constraints and a condition that has to hold to apply the decomposition. Note that, unlike durative actions, duration constraints may be not mandatory. By default the duration of a method is the sum of all the durations of the primitive tasks that compose it. However, it can be interesting to specify temporal constraints on the execution of the decomposition such as, for example, whatever decomposition is chosen, the duration of the primitive tasks must not exceed a given value, or that a subtask must last less than another subtask. We propose to allow these durative constraints only if the requirement :durative-inequalities is set. This is the same requirement as for PDDL.

Method Duration Constraints

We propose to add optional constraints to restrict the allowed value for the duration of the method or the sub-tasks that compose it. Therefore, it could be necessary to be able to refer explicitly to the duration of a subtask and not only to the duration of the method with the variable ?duration. We propose the following syntax for the method duration constraints based on PDDL syntax.

<method-duration-constraint> ::= :duration-inequalities (and <method-simple-duration-constraint>+) <method-duration-constraint> ::= () <method-duration-constraint> ::= <simple-method-duration-constraint> <simple-method-duration-constraint>::= (<binary-comp> <duration> <td-value>) <simple-method-duration-constraint>::= (at <time-specifier> <simple-method-duration-constraint>) <duration> :: = ?duration <duration> :: = <task-duration> <td-value> ::= <d-value> <td-value> ::= <task-duration> <task-duration> :: = (duration <task-id>)

Method Condition

We propose to used the same syntax as PDDL temporal precondition of the durative method (see <da-gd> rule in appendix).

Method Ordering Constraints

To deal with time, it is necessary to generalise the ordering constraints defined in the task network of the method. Task network declaration stays unchanged from HDDL 1.0. We just propose to declare the ordering constraints via the task ids decorated with time specifiers. Time specifiers allow to specify as in a point algebra if the ordering constraints are about the start time or the end time of the task. We propose to use the same time specifiers as in PDDL: start to define the start time of a task, and end to define the end time of a task. Note that we propose to extend also the list of operators available to express ordering constraints between tasks. It has been extended to define any constraints on the start or end of a sub-task of a method, and allows to express all Allen's intervals [START_REF] Allen | An interval-based representation of temporal knowledge[END_REF]) between these subtasks. (<d-task> <time-task-id> <time-task-id>) 21 <d-task> ::= < 22 <d-task> ::= :durative-action >= 23 <d-task> ::= :durative-action <= 24 <d-task> ::= :durative-action > 25 <d-task> ::= :durative-action = 26 <time-task-id> ::= (<time-specifier> <task-id>) 27 <time-specifier> ::= start 28 <time-specifier> ::= end HTN Method Constraints and Semantics HDDL 1.0 only accepts equality constraints or inequality on method parameters in the task network. We propose to add constraints based on the syntax of the constraints used on state trajectory constraints defined in PDDL 3.0 [START_REF] Gerevini | Plan constraints and preferences in PDDL3 -the language of the fifth International Planning Competition[END_REF], and that were first introduced by [START_REF] Erol | HTN planning: Complexity and expressivity[END_REF]. These constraints allow to express logical constraints on the decomposition of the method in addition to the ordering constraints. In particular, it is possible to show that the preconditions of the durative methods can be rewritten with these constraints without losing the generality of the form of these constraints. We propose to use a new requirements for these constraints: :method-constraints. <constraint-def> ::= :method-constraints (hold-between <task-id> <task-id> <gd>) <constraint-def> ::= :method-constraints (hold-during <task-id> <task-id> <gd>) <constraint-def> ::= :method-constraints (at end <effect>) <constraint-def> ::= :method-constraints (at start <gd>) <constraint-def> ::= :method-constraints (always <gd>) <constraint-def> ::= :method-constraints (at-most-once <gd>) <constraint-def> ::= :method-constraints (sometime <gd>) <constraint-def> ::= :method-constraints (sometime-before <task-id> <gd>) <constraint-def> ::= :method-constraints (sometime-after <task-id> <gd>)

The semantics of these constraints can be defined as in [START_REF] Gerevini | Plan constraints and preferences in PDDL3 -the language of the fifth International Planning Competition[END_REF]. Given a task network w (i.e. a tuple (T, ≺), where T is a set of tasks and ≺⊆ T × T is a strict partial order on the tasks), and a state s 0 , that is the state prior to the execution of w, and π a decomposition of N into atomic subtasks; π generates the finite temporal trajectory:

(s 0 , t 0 ), (s 1 , t 1 ), . . . , (s n , t n )
This trajectory is valid if it satisfies all the constraints of tn. Let then φ and ψ be two goal description formulae over the predicates of the planning problem. We note [t s , t e ]T the interval of execution of a task T . Given these intervals, where t s is the start time and t e is the end time, a series of times ordering constraints are defined in an interpretation such as:

Constraint hold-before expresses the properties that must be satisfied in the state before the execution of a specific subtask. It generalises the notion of preconditions used in classical planning to task networks (φ is a goal description and |= is the satisfiability relation as defined in [START_REF] Gerevini | Plan constraints and preferences in PDDL3 -the language of the fifth International Planning Competition[END_REF].

(s 0 , t 0 ), (s 1 , t 1 ), . . . , (s n , t n ) |= (hold-before [t s , t e ]T φ) iff s ts |= φ
Constraint hold-after expresses the properties of the world that must be satisfied after the execution of a specific task.

(s 0 , t 0 ), (s 1 , t 1 ), . . . , (s n , t n ) |= (hold-after [t s , t e ]T φ) iff s te |= φ
Constraints at start and at end are generalisations of hold-before and hold-after constraints. They express that a specified expression must be satisfied before or after every subtask of a task network. Both constraints should be added to be compatible with PDDL version 3.1 and to simplify the expression of constraints between subtasks. These two constraints can easily be rewrit-ten in hold-before and hold-after constraints.

(s 0 , t 0 ), (s 1 , t 1 ), . . . , (s n , t n ) |= (at end φ) iff s n |= φ (s 0 , t 0 ), (s 1 , t 1 ), . . . , (s n , t n ) |= (at start φ) iff s 0 |= φ
Constraint hold-between indicates that some properties must always remain true between the end of the execution of a task, and until the begin of the execution of another task. This type of constraint makes it possible to express the notion of causal link used in Plan Space Planning.

(s 0 , t 0 ), . . . , (s i , t i ), . . . , (s n , t n ) |= (hold-between [t 1 s , t 1 e ]T 1 [t 2 s , t 2 e ]T 2 φ) iff ∀t i : t 1 e ≤ t i ≤ t 2 s such as s i |= φ
Constraint hold-during is quite similar. However, it does not cover the same interval. For hold-during, some properties must always remain true during the execution of a task until the end of the execution of another task. This constraint is not strictly necessary, but is necessary to be compatible with PDDL version 3.1. It can be rewritten in terms of constraints hold-before, hold-between and hold-after. It allows to specify temporal "envelops".

(s 0 , t 0 ), . . . , (s i , t i ), . . . , (s n , t n ) |= (hold-during [t 1 s , t 1 e ]T 1 [t 2 s , t 2 e ]T 2 φ) iff ∀t i : t 1 s ≤ t i ≤ t 2
e such as s i |= φ Constraint always expresses that some properties must be satisfied whatever the decomposition of the task network is.

(s 0 , t 0 ), . . . , (s i , t i ), . . . , (s n , t n ) |= (always φ) iff ∀t i :

t 0 ≤ t i ≤ t n s i |= φ
Constraint sometime say that some properties must be verified sometime in the trajectory produced by the decomposition of the task network.

(s 0 , t 0 ), . . . , (s i , t i ), . . . , (s n , t n ) |= (sometime φ) iff ∃t i : t 0 ≤ t i ≤ t n such as s i |= φ

Constraint sometime-before says that some properties must be verified sometime before the begin of the execution of a specific subtask of the task network.

(s 0 , t 0 ), . . Such timed constraints are an important aspect of the semantics we discuss here. Other aspects are left out for space reasons, but are open questions that deserve to be discussed for a timed HDDL standard, namely the treatment of empty methods and actions, the way time-constraints and durations are dealt with by method's decompositions.

A satellite example

Our reflection on HTN planning with time are based on a commercial optical Earth Observing Satellite (EOS) study case, which delimits our requirements for this new language, namely durative actions and durative methods, method preconditions, numeric preconditions, and timed ordering constraints.

We present thereafter this real use case of an EOS with the mission of observing areas on the surface of the planet and embedding the capacity of producing and executing autonomous plans. This example is shaped on the International Planning Competition hierarchical satellite domain (Schattenberg, 2020), and is intended to illustrate the temporal features, as well as the orderings and the hierarchical constraints of the proposed language extension. New generations of commercial EOSs guarantee better performances by embedding a certain degree of autonomy on-board [START_REF] Pralet | An Autonomous Mission Controller for Earth Observing Satellites[END_REF]). An automated planner is expected to produce new observation mission plans whenever environment changes or new requests are sent from ground control. Because observation tasks depend on the environment -which is not known in advancethis is a planning problem and not just a scheduling matter [START_REF] Rodriguez-Moreno | An AI Planning-based Tool for Scheduling Satellite Nominal Operations[END_REF].

Description of the domain

The EOS mission goal is to fulfil a set of Acquisition Requests of images of the Earth surface. Requests can be single images, which can be obtained by powering on sensors, and pointing at the sites of interest. The different modalities of fulfilling those requests require the extension of the satellite domain to a temporal model.

Considering the structure of the requests that must be completed, the action specifications have a duration to reflect the warming up of certain instruments and the time to modify the attitude of the satellite. Figure 1 shows the calibrate action having a duration specific to the used instrument and defined in the problem initial state. The action has conditions that, if set at start are equivalent to the Classical planning PDDL preconditions. In a similar way, effects set to happen at end are applied at the end of the action duration, similarly to classical planning effects. The satellite is agile, that is, it can rotate forwards and backwards in addition to left and right with respect to its track. This capability is used to point towards sites that represent the direction of an acquisition request. However this is only possible during a short period of time [t start , t end ] in which the location is visible. The observable timespan of each site of interest is specified in the initial situation with timed initial literals like in PDDL 2.2 [START_REF] Hoffmann | The deterministic part of ipc-4: An overview[END_REF], e.g. The take-image preconditions depend then on the site visibility (Figure 3). This action has conditions that should hold at start like in Fig. 1, but also throughout the action execution, noted with over all; hence it should be a durative-action, with a duration (here set to a constant value).

Pointing to sites is performed by the turn to task. turn to can be decomposed in two ways, one of which is less precise (the overall quality of the images will be reduced) but quicker to execute. These two durative-methods differ mainly in the duration constraints, reflecting the different pointing times. This choice, only possible on-board, corrects over-confident plans regarding transition times that otherwise would have caused the acquisition to fail. The planning problem can be designed to optimise image quality, but also accept lower quality images when time is short. On the modelling side, the distinction between the two methods is done on the basis of the duration interval.

Methods (pre)conditions can be a way, like method durations, to filter, or to anticipate, the decomposition of the :ordered-subtasks (and (point_to ?ta_s ?ta_d ?ta_d_prev) (take_image ?ta_s ?ta_d ?ta_i ?ta_m) (decrease_overall_quality ?ti_s) )

:constraints (and (not (= ?ta_d ?ta_d_prev))) )

Figure 4: turn precise and turn approx methods use duration inequalities to reflect the duration time, which is bounded by the duration of the durative-action point to. The duration of point to is bounded by the relative position of the two sites to observe. subtasks. A simple way to use them, is to set them to the precondition of the first subtask, when the ordering of the tasks is known. In a more expressive way, in the following example (Figure 5), the durative-method constraints fix an order between the subtasks task0 and task1 when the duration of the latter is lower than the calibration time of the instrument (line 8) by imposing that the effect of instrument activation holds before task1 (line 19). Similarly, we allow to constrain subtask durations, which is a powerful feature aimed at providing a finer control on the method decomposition, e.g. by using (< (duration task1) (duration task0)) in the temporal constraints of Figure 5 example. Figure 5: method observe uses a duration inequality and a constraint over literals to constrain an ordering. Similarly, a decomposition can be constrained at method-level.

Related work

Durative actions with intermediate effects have received some criticisms in the past [START_REF] Smith | The case for durative actions: A commentary on PDDL2. 1[END_REF], in particular the fact that they fail in guaranteeing that preconditions/conditions hold over specified intervals, and that effects can take place at arbitrary time points within the action. Even if it is true that forcing all effects to take place at the start and end points of actions, as in PDDL2.1 and as we intend to do, imposes constraints on how activity can be modelled, it does not represent any constraint on expressiveness [START_REF] Fox | An investigation into the expressive power of PDDL2. 1[END_REF]. While PDDL2.1 is not the most convenient language for durative actions with intermediate effects, HDDL supports them with ease as they can be naturally divided into sub-actions. Here, the extension to durative methods is simple, considering a method duration is the max of the duration of its decompositions.

In 2008, a first attempt to standardise a hierarchical and temporal language was proposed. This language, called ANML (Action Notation Modeling Language) [START_REF] Smith | The ANML language[END_REF], is an effort to provide a high level, convenient, and succinct alternative to existing languages. ANML is based on the notions of action and state, uses a variable/value representation, supports temporal constraints, and provides simple and convenient idioms to ex-press the most common forms of action conditions and effects. However, few planners adopt the ANML formalism as input, e.g., FAPE [START_REF] Dvorák | Planning and Acting with Temporal and Hierarchical Decomposition Models[END_REF] or EUROPA [START_REF] Barreiro | EUROPA: A platform for AI planning, scheduling, constraint programming, and optimization[END_REF]. The main drawback of ANML is that it is not as widespread as the PDDL family of languages, which are more familiar to the planning community. Therefore, extending HDDL -that is based on PDDL-to deal with temporal and numerical problems seems to be a better approach to standardise and structure the planning community.

Several temporal hierarchical and numeric planners have already been presented in the literature. One of the first is TimeLine [START_REF] Yaman | Timeline: An HTN Planner that can Reason about Time[END_REF]. This planner is an extension of the well known and widely used HTN planner SHOP2 [START_REF] Nau | SHOP2: An HTN Planning System[END_REF]. It supports actions with durative effects. Task decompositions are described as methods that have preconditions, subtasks, and time constraints (with inequalities) between subtasks. Another temporal extension of SHOP2 was proposed by [START_REF] Goldman | Durative planning in HTNs[END_REF]. This provides a way to encode PDDL durative actions in a HTN formalism compatible with the SHOP2 planner. The same year, [START_REF] Castillo | Temporal Enhancements of an HTN Planner[END_REF] published a new hierarchical temporal planner called SIADEX. It exploits partial order relations to obtain parallel plans, using PDDL durative actions based on Simple Temporal Networks. The formalism used by SIADEX, although based on PDDL, is specific to it and has not been taken over by other planners.

Discussion

With the assistance of an EOS planning problem inspired from an IPC benchmark and grounded on a real application, we have illustrated the main features that HDDL 2.1 aimed at describing hierarchical temporal domains should integrate. The generation of EOS mission plans is highly combinatorial as multiple activity types -instrument operation, payload data download and maintenance -are to be planned under strict resource and time constraints. In order to reflect the temporal constraints present in satellite operations, we have adopted a problem formulation that includes elements of temporal planning, besides the usual HDDL 1.0 formulation for expressing hierarchical planning problems (Höller et al., 2020a).

This effort aims at ferrying HTN planning towards domains close to real world applications, where the temporal elements like concurrent actions, coordination, and a hierarchical distribution of tasks are prominent.

The lack of a unified language featuring both temporal and numerical constraints in the continuity of the works done on PDDL is, in our view, an obstacle and a need to address. The automated planning community has produced in the past several approaches for modelling complex planning problems including temporal aspects and a hierarchical decomposition of tasks, but the variety of language solutions is also a hindrance for having common tools and solvers.

ANML [START_REF] Smith | The ANML language[END_REF] has an expressivity close to what we seek here. In ANML effects that happen at time intervals during an action duration can be specified. This can also be represented in HDDL 2.1 by using constraints semantics and dividing actions with intermediate effects into separate durative actions. FAPE proposes benchmarks where ordering constraints are delayed. 1 For instance in ANML it is possible to specify that an action must happen at least some amount of time after the end of a previous action. With the proposed syntax and semantics, such expressivity can be reached by using auxiliary tasks that decompose in a durative primitive task (of the desired duration) with no effects.

Time sampling represents another open question for this extension of HDDL with time. Basically, two approaches exist. Sampling can be either constant -when time is divided into regular-spaced discrete steps-or with variable time steps instantiated when effects and preconditions are applied. The latter can benefit from the Simple Temporal Problem formalism to model the temporal aspects of the plan and to include timed initial effects, and Interval Temporal Logics can be used to define truth of formulas relative to time intervals, rather than time points [START_REF] Bresolin | Interval temporal logics over strongly discrete linear orders: Expressiveness and complexity[END_REF].

Joined with the suggested HDDL 2.1 language grammar, we propose a parser and an illustrative benchmark part of the PDDL4J librairie [START_REF] Pellier | Pddl4j: a planning domain description library for java[END_REF]) available online 2 . Future works include, as first step, an open discussion on the semantics and the syntax. To that end, we publish the current preliminary version of HDDL 2.1 as an open source project publicly available on a repository: link will be provided in the final version of the paper. More work lies ahead to provide the planning community with the tools it needs to deal with hierarchical temporal planning problems. As for instance developing a plan validator for HDDL 2.1.

To be fully compatible with PDDL 3.0 features, the language HDDL 2.1 needs to include axioms and preferences, besides the associated parsing, and validating tools. Benchmarks in HDDL 2.1 are also something we plan to provide as challenges for future solvers and the International Planning Competition (IPC). To provide a rich variety of HTN temporal instances, we plan to decompose hierarchically the already existing benchmarks of the temporal IPC track or to translate existing ANML domains from the FAPE distribution [START_REF] Dvorák | Planning and Acting with Temporal and Hierarchical Decomposition Models[END_REF]. Such collection of planning domains can be the kernel of a future IPC for HDDL 2.1 solvers.

  <durative-method-def> ::= :durative-method <name> :parameters (<typed list (variable)>) :task (<task-symbol> <term> * ) [:duration <method-duration-constraint>] :duration-inequalities [:condition <da-gd>] :method-preconditions <tasknetwork-def>)

  18 <ordering-defs> ::= () | <ordering-def> | (and <ordering-def>+) 19 <ordering-def> ::= (<d-task> <task-id> <task-id>) 20 <ordering-def> ::= :durative-action

Figure 1 :

 1 Figure 1: The calibrate action has a duration depending on the instrument calibration time

Figure 2 :

 2 Figure 2: Timed initial literals for site observability

Figure 3 :

 3 Figure3: take image conditions depend on site observability.

  . , (s i , t i ), . . . , (s n , t n ) |= (sometime-before [t s , t e ]T φ) iff ∃t i : t 0 ≤ t i ≤ t n such as s i |= φ and t i ≤ t sConstraint sometime-after says that some properties must be verified sometime after the end of the execution of a specific subtask of the task network.Constraint at-most-once indicates that some properties must be satisfied at most once in the trajectory produced by the decomposition of the task network.(s 0 , t 0 ), . . . , (s n , t n ) |= (at-most-once φ) iff ∀t i : t 0 ≤ t i ≤ t n if s i |= φ then ∃t j : t j ≥ t i such as ∀t k : t i ≤ t k ≤ t j such as s k |= φ and ∀t k : t k > t j such as s k |= ¬φ

(s 0 , t 0 ), . . . , (s i , t i ), . . . , (s n , t n ) |= (sometime-after [t s , t e ]T φ) iff ∃t i : t 0 ≤ t i ≤ t n such as s i |= φ and t i ≥ t e

<constraint-defs> ::= () | <constraint-def> | (and <constraint-def>+)

<constraint-def> ::= (not (= <term> <term>)) | (= <term> <term>)

<constraint-def> ::= :method-constraints (hold-before <task-id> <gd>)

<constraint-def> ::= :method-constraints (hold-after <task-id> <gd>)

Appendix: Full Proposal of Syntax for HDDL 2.1

This proposed syntax for HDDL2.1.alpha takes its roots in HDDL (Höller et al., 2020a). From that initial definitions, we here describe its proposed extension.

Domain Description

The domain definition has been extended to durative actions (line 84) and durative methods (line 42). The definition of the basic domain elements is nearly unchanged. Function declaration are now possible.

Methods constraints are extended based on the syntax of the constraints used on state trajectory constraints defined in PDDL 3.0. (hold-before <task-id> <gd>) 71 <constraint-def> ::= :method-constraints (hold-after <task-id> <gd>) 72 <constraint-def> ::= :method-constraints (hold-between <task-id> <task-id> <gd>) 73 <constraint-def> ::= :method-constraints (hold-during <task-id> <task-id> <gd>) 74 <constraint-def> ::= :method-constraints (at end <effect>) 75 <constraint-def> ::= :method-constraints (at start <gd>) 76 <constraint-def> ::= :method-constraints (always <gd>) 77 <constraint-def> ::= :method-constraints (at-most-once <gd>) 78 <constraint-def> ::= :method-constraints (sometime <gd>) 79 <constraint-def> ::= :method-constraints (sometime-before <task-id> <gd>) 80 <constraint-def> ::= :method-constraints (sometime-after <task-id> <gd>)

The original action definitions defined in PDDL remains unchanged. As in PDDL, duration constraints with the :duration-inequalities requirement allow to express duration inequalities. The definition of the duration constraints for durative actions does not change. Now, we propose to use timed goal description defined in PDDL 2.1 for durative action precondition and durative method condition.

<da-gd> ::= <timed-gd> <da-gd> ::= (and <da-gd> * ) <da-gd> ::= :universal-preconditions (forall <typed-list (variable)>) <da-gd>) <timed-gd> ::= (at <time-specifier> <gd>) <timed-gd> ::= (over <interval> <gd>) <interval> ::= all Symmetrically, we allow the used the used of temporal effect as in PDDL 2.1. The temporal and numeric definitions of effects are as follows:

<da-effect> ::= (and <da-effect> * ) <da-effect> ::= <timed-effect> <da-effect> ::= :conditional-effects (forall (<typed list (variable)>) <da-effect>) <da-effect> ::= :conditional-effects (when <da-gd> <timed-effect>) <timed-effect> ::= (at <time-specifier> <cond-effect>) <timed-effect> ::= :numeric-fluents (at <time-specifier> <f-assign-da>) <timed-effect> ::= :continuous-effects+:numeric-fluents (<assign-op-t> <f-head> <f-exp-t>) <f-assign-da> ::= (<assign-op> <f-head> < f-exp-da>) <f-exp-da> ::= (<binary-op> <f-exp-da> < f-exp-da>) <f-exp-da> ::= (<multi-op> <f-exp-da> < f-exp-da>+) <f-exp-da> ::= (-<f-exp-da>) <f-exp-da> ::= :duration-inequalities ?duration <f-exp-da> ::= <f-exp> <assign-op-t> ::= increase <assign-op-t> ::= decrease <f-exp-t> ::= ( * <f-exp> #t) <f-exp-t> ::= ( * #t <f-exp>) <f-exp-t> ::= #t

Problem Description

The problem definition includes as additional element the initial task network (line 179) as in HDDL 1.0. But now, we propose to define in the initial state of the problem initial function values and initial time literals. It is also possible to define metric specs on solution plans. We have chosen here not to allow the definition of preferences. But preferences could be added in a next extension of the language. Likewise we have also chosen not to allow the definition of constraints on plans although it is possible in PDDL. We believe that it is preferable to add constraints on plans by adding logical constraints associated with task networks. This allows for a more unified language.

Temporal and Numeric HDDL Requirements

The overall definition includes all the following requirement flags as in HDDL 1.0: • :hierarchy requires the applied system to support HTN planning, so this can be seen as the basic requirement for the language defined here. • :method-preconditions requires the applied system to support method preconditions or condition when define in durative methods.

But now, the following requirement flags are also compatible with HDDL 2.1:

:durative-actions requires the applied system to support durative actions and temporal ordering constraints in method definitions.

:duration-inequalities requires the applied system to support duration inequalities in durative actions declarations. Implies :durative-actions.

:timed-initial-literals requires the applied system to support initial state with literals that become true at a specified time point. Implies :durative-actions.

:numeric-fluent requires the applied system to support numeric fluents in preconditions and effects of actions and methods.

:continuous-effects requires the applied system to support continuous action effects.

We add the following requirement flag:

:method-constraints requires to specify constraints on method task decomposition.


Eric Bertin
email: ebertin@chu-reims.fr

Eric Pr

Bertin

Titre : Pour une approche tridimensionnelle de l'éducation à l'alimentation Title : For a three-dimensional approach to nutrition education

Keywords: comportement alimentaire, attitudes envers l'alimentation, intervention nutritionnelle, éducation sensorielle, information en santé eating behavior, attitudes towards food, nutrition intervention, sensory education, health information

Face au constat que la communication habituellement utilisée pour promouvoir une alimentation équilibrée tend à accentuer les inégalités sociales de santé, de nouvelles approches éducatives ont été développées au cours des dernières années pour tenter de freiner l'épidémie d'obésité dans les populations défavorisées sur le plan socio-culturel. Parmi ces différentes approches, celles ciblant notamment la sensorialité alimentaire et l'éducation alimentaire ont montré leur intérêt mais restent largement minoritaires face aux discours normatifs voire injonctifs qui sont encore le principal vecteur d'éducation à l'alimentation. Cet article est une synthèse des différentes composantes/approches éducatives à l'alimentation à privilégier dans la prévention des pathologies nutritionnelles. Il propose in fine une approche éducative tridimensionnelle intégrant, au-delà de la dimension « nutritionnelle » habituelle, deux autres dimensions de l'alimentation : « psycho-sensorielle et comportementale » et « socio-environnementale ».

Cette proposition est destinée à élargir l'éducation à l'alimentation dans un mouvement intégratif des différents courants de pensée sur le sujet, et à favoriser une plus grande acceptabilité des messages éducatifs concernant l'alimentation par les populations les plus déficitaires en termes de compétences psycho-sociales.

Introduction

La prévention des pathologies nutritionnelles, et notamment de l'obésité, s'est très longtemps polarisée sur la dimension nutritionnelle, c'est à dire l'impact des nutriments sur la santé, via une approche quantitative (ex : 5 fruits et légumes par jour). Si cette dimension éducative biomédicale est indispensable pour soutenir une alimentation adaptée aux besoins nutritionnels de la population générale, le fait de la promouvoir de façon isolée s'est révélé être peu productif en termes de changements de comportements, notamment dans les populations socialement défavorisées où la prévalence de l'obésité n'a cessé d'augmenter au cours des dernières années, accroissant d'autant les inégalités sociales de santé (1-3). Selon S. Lahlou, le modèle naïf de détermination des comportements alimentaires, dans lequel celui-ci résulte de la volonté consciente du sujet, est responsable de l'échec de nombreux régimes alimentaires et de campagnes de santé publique [START_REF] Lahlou | Peut-on changer les comportements alimentaires ?[END_REF].

Les messages cognitifs (transmission de connaissances) ne suffisent de fait pas à modifier les comportements alimentaires individuels [START_REF] Masullo | Obe śite , goûts et consommation. Inte ǵration des normes d'alimentation et appartenance sociale[END_REF][START_REF] Spronk | Relationship between nutrition knowledge and dietary intake[END_REF] qui se sont inscrits au fur et à mesure de la vie des personnes par des interactions avec l'environnement, amalgamant à l'alimentation diverses dimensions symboliques, notamment celle de compenser des privations ou insatisfactions [START_REF] Bertin | Comportement alimentaire et obésité : place de la symbolique alimentaire[END_REF][START_REF] Fielding-Singh | A Taste of Inequality: Food's Symbolic Value across the Socioeconomic Spectrum[END_REF], voire une revanche sociale [START_REF] Corbeau | Évolution des modes de vie et des trajectoires sociales d'obésité chez les jeunes enfants[END_REF]. Les personnes qui reçoivent ces messages, tout particulièrement quand elles n'ont pas les moyens financiers ou les habiletés culinaires nécessaires pour s'approprier les aliments conseillés, se trouvent ainsi confrontées à un écart manifeste entre ce qu'elles pensent devoir faire et ce qu'elles effectuent en réalité, ce qui induit un phénomène de dissonance cognitive [START_REF] Vaidis | La théorie de la dissonance cognitive : une théorie âgée d'un demi-siècle[END_REF]. Celle-ci explique vraisemblablement la sous-déclaration des ingesta -favorisée par la restriction cognitive -chez les sujets en excès pondéral [START_REF] Vansant | The assessment of dietary habits in obese women: influence of eating behavior patterns[END_REF], et pourrait faire intervenir un phénomène d'effacement mnésique actif mais inconscient [START_REF] Kouchaki | Memories of unethical actions become obfuscated over time[END_REF][START_REF] Anderson | Neural mechanisms of motivated forgetting[END_REF].

De plus, l'alimentation étant un élément de socialisation et d'appartenance communautaire très marqué, celle-ci ne peut être modifiée sans la motivation des personnes concernées. Le changement d'alimentation doit donc être porteur de sens pour devenir le projet de la personne, et lui être accessible (c.a.d. ne pas générer trop de difficultés quant à sa réalisation) tant dans son instauration que sa pérennisation [START_REF] Ryan | Facilitating health behavior change and its maintenance: interventions based on self-determination[END_REF][START_REF] Bandura | Auto-efficacité. Le sentiment d'efficacité personnelle[END_REF]. Ainsi, certaines recommandations incitant à consommer des repas cuisinés « maison » plutôt que des plats tout faits, peuvent être particulièrement difficiles à mettre en oeuvre, notamment dans les familles où les deux parents ont une activité professionnelle [START_REF] Marquis | Comportements, préoccupations et priorités liés à l'utilisation du temps entourant les repas familiaux au Québec[END_REF].

Sortir de l'injonction des messages normatifs

Les messages injonctifs (il faut ...) destinés à la modification des comportements d'achats et des profils de consommation alimentaires, se sont révélés être contre-productifs [START_REF]Inégalités sociales de santé en lien avec l'alimentation et l'activité physique[END_REF][START_REF] Decosta | Changing children's eating behaviour -A review of experimental research[END_REF]. Ils génèrent en effet des résistances aux changements via le sentiment de privation de liberté qu'ils véhiculent [START_REF] Ryan | Facilitating health behavior change and its maintenance: interventions based on self-determination[END_REF], et/ou induisent de la culpabilité et un sentiment de stigmatisation chez les personnes en difficulté financière [START_REF] Ramel | Se nourrir lorsqu'on est pauvre. Analyse et ressenti de personnes en situation de précarité ?[END_REF]. Ainsi, les messages sanitaires diffusés lors des publicités alimentaires sont perçus de façon différente selon les catégories socioéconomiques : les ouvriers sont 2,5 fois plus nombreux a ̀ les trouver culpabilisants et 5 fois plus a ̀ les conside ŕer comme anxioge ǹes que les cadres supe ŕieurs [START_REF] Delamaire | Facteurs socio-e ćonomiques et perception des campagnes de communication du PNNS. Journe é du Pôle alimentation Parisien[END_REF][START_REF] Waysfeld | Résistances psychologiques à l'amaigrissement[END_REF]. Chez l'enfant qui refuse de consommer un aliment, le recours à des arguments « santé » contribuerait à générer une association entre message santé et dégoût [START_REF] Wardle | An experimental investigation of the influence of health information on children's taste preferences[END_REF]. Le modèle éducatif alimentaire parental est également déterminant : plus celui-ci représente une relation d'emprise sur l'enfant, moins bonne est sa capacité d'autorégulation vis à vis de l'alimentation [START_REF] Jansen | Do not eat the red food!: Prohibition of snacks leads to their relatively higher consumption in children[END_REF] ; à l'inverse, une absence totale de guidance, n'incitant pas l'enfant à goûter les aliments nouveaux, semble générer une déstructuration des prises alimentaires et une moindre diversité alimentaire [START_REF] Rigal | Links between maternal feeding practices and children's eating difficulties. Validation of French tools[END_REF]. Ce point est d'autant plus crucial lors de la période de néophobie alimentaire développementale du jeune enfant [START_REF] Nicklaus | A prospective study of food variety seeking in childhood, adolescence and early adult life[END_REF].

Selon le rapport de l'IGAS de 2016 [START_REF] Batz | Evaluation du programme national nutrition santé 2011-2015 et 2016 (PNNS 3) et du plan obésité 2010-2013[END_REF], l'approche utilisée jusqu'ici par le Programme National Nutrition Santé serait trop hygiéniste, trop moralisatrice, en décalage complet avec l'alimentation plaisir, l'identité culturelle française assimilant l'alimentation, la gastronomie et la convivialité à l'art de bien vivre... Les travaux issus de la psychologie cognitive montrent d'ailleurs que les messages explicites dans les interventions de santé publique sont peu efficaces [START_REF] Marty | Comparison of implicit and explicit attitudes towards food between normal-and overweight French children[END_REF], peuvent avoir un effet boomerang [START_REF] Werle | The boomerang effect of mandatory sanitary messages to prevent obesity[END_REF] et sont susceptibles d'accroître les inégalités sociales de santé [START_REF] Mcgill | Are interventions to promote healthy eating equally effective for all? Systematic review of socioeconomic inequalities in impact[END_REF].

L'exposition à un message « santé » non attentivement perçu lors d'une publicité pour aliment « plaisir » le rend en effet moins négatif et conduit à une désinhibition vis à vis de sa consommation, soit un effet contraire à celui attendu [START_REF] Chambaron | Impact of olfactory and auditory priming on the attraction to foods with high energy density[END_REF]. Ce phénomène est d'autant plus marqué chez le sujet en excès pondéral en raison d'un niveau de biais attentionnel élevé vis à vis de la nourriture [START_REF] Yokum | Attentional Bias to Food Images Associated With Elevated Weight and Future Weight Gain: An fMRI Study[END_REF]. Il est intéressant de noter sur ce point que des approches spécifiques sont testées depuis quelques années avec plus ou moins de succès pour atténuer les biais attentionnels favorisés par les publicités pour les aliments « appétissants » [START_REF] Kemps | Longevity of attentional bias modification effects for food cues in overweight and obese individuals[END_REF][START_REF] Kemps | Can attentional bias modification inoculate people to withstand exposure to real-world food cues[END_REF].

Ne pas censurer le plaisir alimentaire et promouvoir la sensorialité alimentaire

Le plaisir alimentaire est souvent absent des actions de promotion de la santé, sans doute parce qu'il est associé à la « gourmandise » qui, dans l'imaginaire collectif, expose au risque de surconsommation alimentaire. Pourtant, il existe une relation inverse entre plaisir alimentaire et taille des portions alimentaires (retrouvée dans deux populations différentes : aux Etats-Unis et au Québec) [START_REF] Cornil | Plaisir épicurien, plaisir viscéral, et préférence de tailles de portions alimentaires[END_REF]. Les enfants qui associent l'alimentation au plaisir font des choix de meilleure qualité nutritionnelle que les enfants qui associent l'alimentation à la santé [START_REF] Marty | Do hedonic-versus nutrition-based attitudes toward food predict food choices? a cross-sectional study of 6-to 11-year-olds[END_REF]. Selon les auteurs de cette étude, une promotion de la santé centrée sur le plaisir de manger favoriserait dans le même temps la promotion de la consommation d'aliments « bons pour la santé » chez l'enfant et l'adulte [START_REF] Marty | Learned pleasure from eating: an opportunity to promote healthy eating in children?[END_REF][START_REF] Vaillancourt | Promoting Healthy Eating in Adults: An Evaluation of Pleasure-Oriented versus Health-Oriented Messages[END_REF]. D'autres études ciblant la sensorialité alimentaire sont en faveur de cette assertion. Ainsi, une plus grande attention portée à la sensorialité alimentaire au cours d'un repas génère une diminution de la consommation des aliments ingérés au cours de ce repas [START_REF] Arch | Enjoying food without caloric cost: The impact of brief mindfulness on laboratory eating outcomes[END_REF] et peut également limiter les prises alimentaires au décours [START_REF] Higgs | Focusing on food during lunch enhances lunch memory and decreases later snack intake[END_REF][START_REF] Robinson | Eating 'attentively' reduces later energy consumption in overweight and obese females[END_REF]. La demande de représentation multi-sensorielle (imaginer le goût, l'odeur et la texture) d'aliments plaisants à des enfants scolarisés en maternelle avant leur goûter génère une diminution significative des portions consommées lors de cette prise alimentaire [START_REF] Cornil | Pleasure as a substitute for size : How multisensory imagery can make people happier with smaller food portions[END_REF]. Les mêmes effets sont constatés avec des adultes. Par contre, quand la demande de mentalisation avant l'ingestion concerne les effets potentiels sur la santé et le poids, il existe également une diminution des portions consommées au repas suivant, mais via une restriction cognitive au détriment de la satisfaction des sujets [START_REF] Cornil | Pleasure as a substitute for size : How multisensory imagery can make people happier with smaller food portions[END_REF]. Or, il est maintenant bien établi que la restriction cognitive favorise une plus grande consommation d'aliments lors d'une exposition à des stimuli alimentaires externes [START_REF] Rogers | Breakdown of dietary restraint following mere exposure to food stimuli: interrelationships between restraint, hunger, salivation, and food intake[END_REF][START_REF] Fedoroff | The effect of pre-exposure to food cues on the eating behavior of restrained and unrestrained eaters[END_REF], notamment chez les sujets présentant un excès de poids [START_REF] Herman | External cues in the control of food intake in humans: the sensory-normative distinction[END_REF].

Par conséquent, la valorisation de la sensorialité alimentaire, en préservant le plaisir de manger et en soutenant l'écoute de soi, contribue à favoriser une meilleure régulation des apports alimentaires. Il faut par ailleurs souligner que le fait d'aborder la dimension du plaisir alimentaire lors de la promotion des aliments « sains » est un moyen de renforcer l'efficacité des messages de promotion de la santé [START_REF] Jacquier | Improving the effectiveness of nutritional information policies: assessment of unconscious pleasure mechanisms involved in food-choice decisions[END_REF]. Chez l'enfant, l'éducation sensorielle, basée sur la découverte des diverses perceptions sensorielles procurées par les aliments, apparait être une approche particulièrement intéressante, puisqu'elle permet à la fois d'aborder les diverses perceptions générées par l'acte 1 alimentaire (et de les exprimer au-delà du bon/pas bon), et d'identifier la dimension symbolique de bien être associée à certains aliments. Elle constitue également un élément de socialisation dans la mesure où elle favorise la prise de conscience des différences culturelles d'habitudes alimentaires tout en partageant des aliments avec d'autres [START_REF] Godin | Entre plaisir et contrôle : L'équilibre comme fondement de la normativité et de l'action dans l'alimentation contemporaine[END_REF]. Cette approche éducative a été initialement développée dans les années 1970 sous le vocable « classes du goût » par l'oenologue et philosophe Jacques Puisais, puis a été relayée en France par l'association nationale d'éducation au goût des jeunes (ANEGJ) à la suite des résultats obtenus dans le cadre du programme de recherche EDUSENS [START_REF] Reverdy | Effect of sensory education on willingness to taste novel food in children[END_REF]. L'intégration des classes du goût dans les écoles primaires est soutenue financièrement depuis 2010 par le ministère français de l'alimentation, de l'agriculture et de la forêt.

Une étude québécoise récente montre que le fait de concilier plaisir alimentaire et éducation nutritionnelle est tout aussi pertinent chez l'adulte [START_REF] Landry | Is eating pleasure compatible with healthy eating? A qualitative study on Quebecers' perceptions[END_REF]. [START_REF] Corbeau | L'indispensable plaisir alimentaire in Nourrir de plaisir : Régression, transgression, transmission ?[END_REF]. La dynamique de l'éducation alimentaire intégrant le plaisir, valorise aussi la dimension ludique de l'apprentissage [START_REF] Bihan | L'intérêt de l'éducation alimentaire » in L'alimentation à découvert[END_REF].

Aider à mieux gérer la relation à l'alimentation

1) par la prise de conscience des éléments permettant d'ajuster les apports alimentaires sur les besoins du corps La balance énergétique est physiologiquement équilibrée de façon inconsciente par l'hypothalamus qui génère les signaux intéroceptifs alimentaires de faim et de rassasiement.

Lorsque ces signaux sont respectés, on parle d'alimentation intuitive qui est associée à un niveau d'IMC plus bas que par une régulation cognitive de l'alimentation [START_REF] Madden | Eating in response to hunger and satiety signals is related to BMI in a nationwide sample of 1601 mid-age New Zealand women[END_REF][START_REF] Camilleri | Intuitive eating is inversely associated with body weight status in the general population-based NutriNet-Santé study[END_REF]. Chez le sujet en excès pondéral, le recentrage de la régulation des apports alimentaires sur ces signaux semble produire des effets intéressants [START_REF] Schaefer | A review of interventions that promote eating by internal cues[END_REF].

La sensation de faim est le signal nous informant sur le besoin de nourrir notre corps. Elle est en général la traduction de contractions de la paroi de l'estomac. Le rassasiement devrait théoriquement être le signal d'arrêt du repas. Il correspond au moment d'extinction du signal de faim et non à l'apparition d'un nouveau signal au niveau de l'estomac.

Selon Herman et Polivy, la population générale a une faible conscience de ce que sont les sensations de faim et de satiété (état acquis après le rassasiement), excepté dans leurs niveaux extrêmes [START_REF] Herman | Normative influences on food intake[END_REF]. Dans l'étude NutriNet-Santé destinée à étudier le comportement alimentaire de la population française, il ressort que 24% des sujets s'arrêtent de manger quand ils éprouvent une sensation de tension, pesanteur ou douleur gastrique, et que ces sujets prennent 2 fois plus de poids que ceux qui s'arrêtent de manger avant de ressentir ces sensations [START_REF] Bertin | Sémiologie du comportement alimentaire en phase prandiale et excès pondéral -les résultats de l'étude Nutrinet-Santé[END_REF].

L'identification du moment du rassasiement peut en outre être perturbée par une vitesse d'ingestion des aliments trop rapide (due à un défaut de mastication ...) qui peut ainsi entraîner une prise alimentaire excessive au cours des repas [START_REF] Robinson | Eating 'attentively' reduces later energy consumption in overweight and obese females[END_REF], d'autant plus qu'elle contribue conjointement à diminuer la sensorialité alimentaire (moindre interaction avec les récepteurs gustatifs). Une vitesse d'ingestion élevée est souvent acquise par mimétisme familial (56) ou quand le temps du repas est raccourci par des contraintes environnementales diverses (telles qu'un manque de place dans les cantines).

Une diminution de la vitesse d'ingestion alimentaire (VIA) entraîne une diminution spontanée des ingesta [START_REF] Smit | Does prolonged chewing reduce food intake? Fletcherism revisited[END_REF]. L'auto-évaluation subjective de l'alimentation (par échelle analogique) est un moyen aisé et suffisamment fiable d'évaluation de la VIA permettant à chacun(e) de s'évaluer (entre 1, la moins rapide et 10, la plus rapide) ; la tachyphagie se définissant par une VIA ≥ 7 sur 10 (58). D'autre part, la restriction cognitive, notamment quand elle est la conséquence de régimes restrictifs destinés à contrôler son poids déconnecte le sujet de ses signaux alimentaires internes, ce qui nécessite parfois un long travail de rééducation pour les restaurer [START_REF] Gravel | Sensory-based nutrition pilot intervention for women[END_REF]. De plus, les mères en restriction cognitive respectent moins les signaux alimentaires de leur enfant [START_REF] Tylka | Maternal intuitive eating as a moderator of the association between concern about child weight and restrictive child feeding[END_REF]. La forte augmentation de la restriction cognitive en France, comme en témoigne l'évolution de la prévalence de la maigreur chez les adolescentes de 11 à 14 ans entre 2006 et 1 2016 (4,3% à 19,6%) selon l'étude ESTEBAN [START_REF] Verdot Ch | Corpulence des enfants et des adultes en France métropolitaine en 2015. Résultats de l'étude Esteban et évolution depuis[END_REF], est à cet égard particulièrement préoccupante.

Face à ces constats, il nous apparait donc particulièrement utile de renseigner la population sur les éléments suivants concernant leur comportement alimentaire : 1) le rôle des signaux intéroceptifs de faim et de rassasiement (en les explicitant et en incitant à y être attentifs) ; 2) les risques de la restriction cognitive et des injonctions alimentaires telles que l'obligation de finir son assiette ; 3) l'importance de prendre le temps de manger tranquillement lors des repas en étant à l'écoute de ses sensations (comme lors d'une dégustation). Cette approche dénommée alimentation en pleine conscience est de plus en plus utilisée dans la prise en charge des personnes atteintes d'excès pondéral. Elle recommande par ailleurs de ne pas manger devant un écran de façon à éviter des biais attentionnels, et profiter de cet espace pour échanger avec ses proches.

Il est intéressant de constater que cet apprentissage peut être rapidement effectif chez des jeunes enfants dans le cadre de programmes scolaires spécifiques [START_REF] Johnson | Improving preschoolers' self-regulation of energy intake[END_REF].

2) par la prise de conscience des éléments favorisant une alimentation « émotionnelle » Le recours à l'alimentation pour gérer les états de tension psychique (stress), les émotions (colère...) et les angoisses (de séparation…), est fréquent, notamment chez les sujets atteints d'obésité [START_REF] Hemmingsson | A new model of the role of psychological and emotional distress in promoting obesity: conceptual review with implications for treatment and prevention[END_REF]. Cette « alimentation émotionnelle » se manifeste le plus souvent sous la forme d'une impulsivité alimentaire (correspondant sémiologiquement à des compulsions ou accès de boulimie). Elle s'explique à la fois par le fait que l'alimentation active les circuits neuronaux impliqués dans le système de récompense (64) et par les symboliques psychoaffectives véhiculées par l'alimentation [START_REF] Bertin | Comportement alimentaire et obésité : place de la symbolique alimentaire[END_REF].

Les personnes qui présentent une alimentation émotionnelle ont une tendance spontanée à minimiser ce comportement défensif, voire à ne pas faire le lien avec leur prise de poids [START_REF] Bartholome | A comparison of the accuracy of self-reported intake with measured intake of a laboratory overeating episode in overweight and obese women with and without binge eating disorder[END_REF].

Il apparait donc nécessaire d'éclairer plus avant les populations sur cette utilisation de l'alimentation à des fins de « soulagement », de façon à ce qu'elles puissent mettre en place d'autres modalités de résolution et/ou en parler plus facilement à leur médecin traitant. D'autre part, la prise de conscience de ses émotions (et sensations corporelles correspondantes) et des capacités de gestion de celles-ci mériterait d'être abordée plus globalement car les signaux intéroceptifs alimentaires sont soumis à de multiples influences au cours du développement de l'enfant [START_REF] Harshaw | Alimentary Epigenetics: A Developmental Psychobiological Systems View of the Perception of Hunger, Thirst and Satiety[END_REF]. Le refoulement des émotions génère en effet un déficit global d'intéroceptivité limitant l'identification des signaux alimentaires, et est un facteur favorisant non seulement l'impulsivité alimentaire mais aussi les autres manifestations d'impulsivité sous la forme de comportements agressifs ou addictifs [START_REF] Bertin | La relation au corps, un e ĺe ḿent complexe et multiple a ̀ conside ŕer dans l'obe śite[END_REF]. Il est intéressant de noter à cet égard l'émergence du concept d'addiction alimentaire au cours des dernières années [START_REF] Brunault | Food Addiction in Bariatric Surgery Candidates: Prevalence and Risk Factors[END_REF].

Le stress est également un facteur favorisant la prise de poids, qu'il soit d'ordre professionnel ou familial [START_REF] Geiker | Does stress influence sleep patterns, food intake, weight gain, abdominal obesity and weight loss interventions and vice versa ?[END_REF]. Son identification, les pistes pour en diminuer l'intensité, à défaut de pouvoir agir sur le(s) déterminant(s), sont des éléments faisant partie intégrante des compétences psycho-sociales à acquérir par la population générale dans le champ de l'éducation pour la santé [START_REF] Who/Oms | division santé mentale et prévention des conduites addictives. Life skills education in schools[END_REF].

Il est également important d'informer la population sur l'importance de disposer d'un temps de sommeil suffisant pour se maintenir en bonne santé. En effet, une durée de sommeil courte (< 6h) favorise l'obésité, via l'induction d'un état de stress métabolique et des modifications hormonales agissant sur les prises alimentaires [START_REF] Knutson | Associations between sleep loss and increased risk of obesity and diabetes[END_REF][START_REF] Chaput | Lack of sleep as a contributor to obesity in adolescents: impacts on eating and activity behaviors[END_REF]. D'autres dimensions, que l'on pourrait intégrer sous le vocable « écologie personnelle », seraient également à soutenir : avoir un espace pour soi, investir des activités de loisir (« hobbies ») favorisant l'épanouissement de la personne ; apprendre à s'affirmer / à mettre des limites à l'autre et à exprimer ses besoins / être bienveillant et tolérant envers soi, renforcer son estime de soi quand nécessaire… Parmi celles-ci, la capacité à s'affirmer (et à mettre des limites à l'autre) est une ressource nécessaire pour se différencier des habitudes culturelles environnementales en termes de consommation alimentaire.

Ces éléments contribuent à élargir le concept de promotion de la santé aux dimensions de l'empowerment et du bien-être, comme préconisé par la charte d'Ottawa, constituant ainsi un levier intéressant en faveur d'une prise en soins de soi [START_REF] Deschamps | Une « relecture » de la charte d'Ottawa[END_REF].

Renforcer les interactions sociales à travers l'éducation « alimentaire »

L'être humain a besoin de s'autonomiser tout en restant en relation avec ses semblables. L'alimentation étant un fait social total [START_REF] Mauss | Essai sur le don[END_REF], elle est un excellent vecteur de socialisation tant en ce qui concerne sa production, que sa préparation et sa consommation.

La consommation d'un nouvel aliment est par ailleurs favorisée par le partage de cet aliment avec des personnes familières qui l'apprécient [START_REF] Birch | Effects of peer models food choices and eating behaviors on preschoolers food preferences[END_REF][START_REF] Hendy | Effectiveness of teacher modeling to encourage food acceptance in preschool children[END_REF].

Dans un contexte de suspicion généralisée des consommateurs quant à la qualité de l'alimentation, réintroduire de l'Humain via des rencontres avec les producteurs locaux (agriculteurs, éleveurs, boulangers…) venant parler avec passion de leur métier et de leurs savoirs faire, est sans doute une réponse intéressante pour, non seulement revaloriser des producteurs (agriculteurs et éleveurs) en désarroi face à l'agribashing actuel, mais aussi contribuer à démystifier des peurs irrationnelles et éviter des orientations alimentaires parfois délétères.

L'éducation alimentaire est une approche favorisant la connaissance des aliments (de leur production à leur consommation) et des métiers correspondants, qui peut s'inscrire assez facilement, de par sa transversalité, dans différents enseignements disciplinaires au cours des cursus scolaires. Elle concerne également les savoir-faire alimentaires implicites et explicites, et contribue ainsi à mettre en lumière les différences culturelles concernant la sélection et la préparation (pratiques culinaires) de l'alimentation [START_REF] Augor | Cuisiner ensemble : ethnographie de trois ateliers cuisine[END_REF]. Elle permet ainsi d'aborder de façon globale la dimension socio-culturelle de l'alimentation et d'appréhender les différences de modes de vie sans stigmatiser les individus ni les groupes auxquels ils appartiennent [START_REF]Colloque IFN du 9 décembre 2008 : Eduquer les mangeurs : de l'éducation nutritionnelle à l'éducation alimentaire[END_REF].

Cette pratique éducative a ainsi l'avantage de favoriser une meilleure compréhension de l'influence de l'environnement sur les orientations alimentaires, et de favoriser une réflexion sur les difficultés à changer ses conduites/comportements acquis même lorsqu'ils ne sont pas promoteurs de santé.

Les ateliers « cuisine » qui se sont fortement développés au cours des dernières années dans les centres socio-éducatifs sont également un fort vecteur de partage culturel, de valorisation personnelle et de créativité, et favorisent le sentiment d'intégration sociale des plus défavorisés [START_REF] Augor | Cuisiner ensemble : ethnographie de trois ateliers cuisine[END_REF][START_REF] Lepeltier | L'empowerment dans les « ateliers cuisine » : entre enjeux et pratique[END_REF], chez lesquels l'impact potentiel des outils numériques d'aide au développement des compétences culinaires est très limité [START_REF] Régnier | Les outils numériques pour réduire la fracture alimentaire ? : Étude sociologique de deux dispositifs à destination des catégories modestes[END_REF]. D'après notre expérience, il est assez aisé d'intégrer une part d'éducation nutritionnelle (comme par exemple la diversité alimentaire et les repères de consommation) dans les ateliers culinaires. Cependant, la finalité des ateliers doit rester centrée sur la découverte et l'échange, et l'animateur doit adopter une posture suscitant la curiosité et s'appuyant sur les savoirs et la créativité des participants, sans idée de normativité pour ne pas altérer leur motivation [START_REF] Lepeltier | L'empowerment dans les « ateliers cuisine » : entre enjeux et pratique[END_REF].

L'atelier culinaire représente surtout une excellente opportunité de réflexion sur les signaux alimentaires internes (la sensation de faim, et la distinction entre faim et envie de manger).

Une dégustation en pleine conscience de l'aliment élaboré au cours d'un atelier culinaire met en lumière l'intérêt de le consommer tranquillement, et contribue également à favoriser la prise de conscience de ses dimensions symboliques (en amenant les participants à se poser la question de ce qui fait qu'ils apprécient ou pas cet aliment, de ce qu'il évoque pour eux…).

Cette combinaison d'approche éducative constitue ainsi une opportunité de renforcer le sentiment d'efficacité personnelle, dont l'optimisation est un facteur de réduction des inégalités sociales de santé [START_REF] Meyer | L'auto-efficacité : quelle contribution aux modèles de prédiction de l'exposition aux risques et de la préservation de la santé[END_REF].

Synthèse/conclusion

Sans remettre en cause l'utilité d'avoir des informations sur les normes permettant à chacun de se situer quant aux moyens de conserver une bonne santé physique, les données de la littérature montrent que les messages « normatifs » sont vécus comme stigmatisant par les personnes les plus concernées, et s'avèrent contre-productifs en termes de changements de modes de vie. Il est donc nécessaire d'utiliser d'autres approches plus respectueuses de l'individu, et ne générant pas le sentiment de perte du plaisir de manger, car l'Homme a une aversion naturelle pour la perte [START_REF] Bergeron | Le biais comportementaliste[END_REF].

Soutenir le développement des compétences des personnes vulnérables sans les enfermer dans des normes devrait être le fil conducteur des actions de promotion de la santé [START_REF] Jourdan | De l'utilité de clarifier les référents théoriques de l'éducation pour la santé[END_REF]. Le changement est ainsi plus aisé quand il contribue au renforcement des compétences, fait appel à la créativité de la personne, et est valorisé par l'entourage.

A partir de ces différentes assertions et des arguments présentés précédemment, pour favoriser une optimisation des pratiques de terrain au sein des différents espaces éducatifs, nous proposons de décliner la promotion de la santé par l'alimentation en ces 3 dimensions 1 complémentaires (donc potentiellement synergiques) :

1) dimension « nutritionnelle » : elle permet de répondre aux besoins nutritionnels de la population, et est actuellement encore largement majoritaire voire exclusive dans le paysage éducatif (que ce soit via le PNNS, les professionnels de santé ou les professeurs des écoles) ; Elle est en phase avec l'approche bio-psycho-sociale proposée récemment par Catherine G. et Alan Russell, qui mettent en exergue l'importance d'associer les composantes psychosociales de l'alimentation à sa composante biologique dans la prévention de l'obésité [START_REF] Russell | Biological and Psychosocial Processes in the Development of Children's Appetitive Traits: Insights from Developmental Theory and Research[END_REF].

Elle est également cohérente avec la position de Magali Volery (spécialiste suisse de la prévention des troubles du comportement alimentaire) qui énonce l'intérêt d'agir sur les émotions et la connaissance de soi dans la prévention de l'obésité [START_REF] Volery | avenir : intégrer la prévention des troubles du comportement alimentaire dans la prévention de l'obésité[END_REF]. L'équipe de la Maison de la Nutrition -Justine Pierrard, Thomas d'Amico, Caroline Leclerc et Aline Bonneaux -associée à cet article est salariée de cette structure associative (loi 1901) de promotion de la santé (https://www.maison-nutrition.fr) et a développé avec Eric Bertin (président bénévole de la Maison de la Nutrition) le concept d'approche tridimensionnelle de l'éducation à l'alimentation présenté dans cet article.

  Jean-Pierre Corbeau, anthropologue et sociologue de l'alimentation, avait bien saisi l'importance de cette approche éducative puisqu'il énonçait dans un ouvrage sur le sujet : « Le plaisir ne conduit pas forcément à l'excès, il est conciliable avec la santé […]. Il faut quitter la simple perspective d'une information, d'une recommandation, d'une obligation nutritionnelle qui "déconstruisent" le repas, le mets, l'aliment et "éduquent" les jeunes mangeurs et les autres à la suspicion […]. Nous devons revaloriser le plaisir, l'inscrire dans une éducation alimentaire qui réhabilite l'aliment […], qui favorise la verbalisation d'un goût jubilatoire qui participe à la régulation de nos pratiques

2 )

 2 dimension « psycho-sensorielle et comportementale » : elle inclue la sensorialité alimentaire (composante hédonique de l'alimentation et ses fondements), la prise de conscience de la relation entre émotions et alimentation, et les éléments favorisant une bonne régulation de l'alimentation sur les signaux internes (faim et rassasiement). Celle-ci se décline habituellement sous la forme d'une éducation sensorielle ; 3) dimension « socio-environnementale » : elle concerne la dimension relationnelle de l'alimentation et le sentiment d'appartenance à un groupe (famille, communauté) généré par les diverses pratiques alimentaires. C'est cette dimension qui attribue inconsciemment une valeur symbolique affective et/ou relationnelle à certains aliments (comme par exemple celle associée à « la petite madeleine » pour l'écrivain Marcel Proust). Les ateliers cuisine, qui représentent une composante de l'éducation alimentaire (cf. chapitre précédent) en sont l'illustration la plus courante. Cette approche éducative élargie a fait la preuve de son applicabilité par sa mise en oeuvre depuis plus de 5 ans (2014) à travers les diverses actions éducatives de la Maison de la Nutrition en Champagne-Ardenne (https://www.maison-nutrition.fr), avec le soutien de l'Agence Régionale de Santé du Grand-Est.

  Dans un autre article publié en 2018, Lucile Marty et al. ont suggéré 3 dimensions inhérentes à celle du plaisir alimentaire pouvant être utilisées pour la prévention de l'obésité chez l'enfant (36): la dimension sensorielle, la dimension interpersonnelle (définie comme les représentations et symboles associés à l'acte de manger) et la dimension psychosociale (la composante sociale de celle-ci étant définie par l'acte de manger ensemble). Cette déclinaison 1 Liens d'intérêt:


Nadir Guendouz

Camille Viatte

Martin Van Damme

Lieven Clarisse

Pierre-François Coheur

Cristelle Cailteau-Fischbach

Cathy Clerbaux

Evaluation of ammonia concentrations derived from IASI using a ground-based instrument (mini-DOAS) over two different areas (urban and rural) in France

Introduction Method

Comparison IASI vs. mini-DOAS

The

Mini-DOAS in Paris

The average NH 3 concentration between January 2020 and September 2021 is 2.09 +/-0.02 μg.m -3 .

During springtime (March to May 2020 and 2021), the average NH 3 concentration is 3.84 +/-0.05 μg.m -3 . Higher concentrations in spring are due to the transport of NH 3 from the surrounding regions during fertilizer spreading periods [START_REF] Viatte | Atmospheric Ammonia Variability and Link with Particulate Matter Formation: A Case Study over the Paris Area[END_REF] .

NH 3 concentrations averaged in springtime 2020 are 1.32 times higher than in 2021 in Paris. Meteorological conditions (precipitation) could explain this difference.

Mini-DOAS comparison Paris vs. Grignon

NH3 concentrations measured in September-October 2021 in Grignon is 2.55 times higher than the average NH3 concentrations measured in Paris during the same period in 2020.

The proximity of the Grignon farm to the mini-DOAS measurements at this rural area most likely explains this difference.

• Using 2 years of continuous NH 3 measurements derived from the mini-DOAS in Paris, seasonal variability of NH 3 concentrations is assessed. Higher concentrations are found during springtime due to spreading practices in the surrounding regions.

• NH 3 concentrations in the rural area of Grignon is found to be more than 2 times higher than in the urban region of Paris.

• This first evaluation of IASI measurements by the mini-DOAS show similar results with better agreement in a 100 km and 30 km area in Paris and Grignon, respectively.

• The agreement between IASI and the mini-DOAS is higher in spring (R = 0.72) when both instruments monitor NH 3 concentrations coming from the northeast.

• The mini-DOAS dataset will be used in the future to contribute further to the evaluation of the IASI NH 3 product over relevant sources.

Comparison in Paris and Grignon

To assess the representativeness of the mini-DOAS NH 3 observations, we have compared both data using different spatial criteria for IASI measurements (600, 100, 50, 30, and 10 km radius circle around Paris).

In Paris, the best agreement between the mini-DOAS and IASI is found to be at 100 km whereas in Grignon, is found to be at 30 km. Possible reasons for this difference might be:

1 Ammonia (NH 3 ) is an atmospheric pollutant mainly emitted by the agricultural sector [START_REF] Fowler | The Global Nitrogen Cycle in the Twenty-First Century[END_REF] . Increasing availability of such reactive nitrogen species causes major impacts on the environment (species extinctions 2 , impact on the ecosystem [START_REF] Fowler | The Global Nitrogen Cycle in the Twenty-First Century[END_REF][START_REF] Rockström | Planetary Boundaries: Exploring the Safe Operating Space for Humanity[END_REF] , public health [START_REF] Lelieveld | The Contribution of Outdoor Air Pollution Sources to Premature Mortality on a Global Scale[END_REF] and climate change [START_REF] Myhre | Radiative Forcing of the Direct Aerosol Effect from AeroCom Phase II Simulations[END_REF] ).

Due to the difficulty of measuring NH 3 in ambient air [START_REF] Bobrutzki | Field inter-comparison of eleven atmospheric ammonia measurement techniques[END_REF] , along with the very large variability of NH 3 concentrations in space and time, there are too few systematic and representative ground-based measurements around the world [START_REF] Nair | Quantification of Atmospheric Ammonia Concentrations: A Review of Its Measurement and Modeling[END_REF] .

Objective

In this context, we used a state-of-art ground-based instrument (mini-DOAS) to evaluate NH 3 concentrations derived from IASI (Infrared Atmospheric Sounding Interferometer), within two different regions : urban (Paris) and rural (Grignon).

Seasonal comparison Mini-DOAS vs. IASI in Paris

Overall, the agreement between IASI (100 km around Paris) and the mini-DOAS is relatively good (R = 0.69).

This agreement depends on the season. In spring, the mini-DOAS and IASI show the best agreement (R=0.72) and higher NH 3 concentrations.

Pollution roses

The IASI and mini-DOAS pollution roses reveal similar pattern with high NH 3 concentrations coming from the northeast.

This confirms that the mini-DOAS observations footprint is at the scale of the parisian region.

  mini-DOAS is a ground-based open-path instrument based on the Differential Optical Absorption Spectroscopy technique (DOAS), which measures NH 3 concentrations in the UV-Visible between 200-230 nm every 10 seconds 8 . It was installed within the QUALAIR facility (Paris city-center) since December 2019. In this work, mini-DOAS observations performed in Paris (January 2020 -September 2021) and at Grignon (September 2021 -October 2021) are presented. Comparison of the mini-DOAS hourly NH 3 concentrations coincident to the IASI morning measurements (Metop B and C) is discussed.

  ) The altitude of the mini-DOAS instrument (40 m at Paris vs. 0 m at Grignon) impacts the representativeness of its observations 2) Local emissions from agricultural sources (farm) at the rural site of Grignon drive NH 3 variability

Figure 2 :

 2 Figure 2 : Mini-DOAS in Paris (left) and in Grignon (right)

Figure 6 :Figure 3 :Figure 1 :Figure 4 :Figure 5 :

 63145 Figure 6 : Pollution roses of NH 3 in Paris derived from the mini-DOAS (left) and IASI (right) instruments