M Saqalli

B Gérard

C Bielders

P Defourny

Benchmarking humanitarian support: Empirical agent-based modeling of development action types in Nigérien villages

Keywords: farming systems, individual Agent-based model, Niger, development interventions Benchmarking humanitarian support: Empirical agent-based modeling

, which has shown that using an individual Agent-based model (ABM) is a relevant approach to integrate agro-ecological, social and economic characteristics of a system and that family internal rules have strong impacts on village and environment evolutions. Two development project interventions are simulated in a context of no land scarcity: inorganic fertilizers availability for farmers and an inventory credit technique based on millet yields that some villagers may choose to use. Two rationalities are tested, one upon economic values and the second upon the intra-village "reputation" gains. Our results illustrate that a village cannot be considered as a whole and project operators must take in account the precise target population rather than all adult villagers. Project involvements concern only sites where savings for securization or intensification are possible: These proposals need actually some food security and investment capacities that are largely conditioned by family manpower and size. Inorganic fertilizers have little success without any intensification process in a context of good land availability. Inventory credit intervention engages a maximum of 25% of the population in the site with medium agro-ecological conditions. Reputation has little effect on the population behavior and should be considered more as a local wealth estimation factor between villagers. Therefore, one should consider these proposals as a potential support tool for a limited part of the population capable to go beyond the survival level, but not as a global poverty-alleviation panacea.

Introduction

The low impact development operators have had on rural societies in Sahelian Africa for half a century has created a huge research debate within and between scientific disciplines, but also in the development arena [START_REF] Hambally | Mode d'intervention et pratiques paysannes au Niger[END_REF][START_REF] Lavigne-Delville | Impasses cognitives et expertise en sciences sociales : réflexions à propos du développement rural en Afrique[END_REF][START_REF] Mortimore | Farmer adaptation, change and 'crisis' in the Sahel[END_REF]. The debate was widely open after the food crisis1 Niger suffered in 2005 (Médecins Sans Frontières, 2005;[START_REF] Harragin | The Cost of being Poor: Markets, mistrust and malnutrition in southern Niger 2005-2006[END_REF]. In front of this recurrent and desperate failure, the issue is to improve the relevance and the efficiency of development projects [START_REF] Decoudras | L'aide internationale au Niger[END_REF][START_REF] Watkins | Time to stop dumping on the world's poor[END_REF][START_REF] Dollar | The Increasing Selectivity of Foreign Aid, 1984-2003[END_REF]. A proper understanding of the Sahelian village production system is a prerequisite for successful development actions and requires prior recognition of the inherent complexity of this system. Land tenures are various and complex (Le [START_REF] Bris | L'appropriation de la terre en Afrique Noire, Manuel d'analyse, de décision et de gestion foncières[END_REF][START_REF] Lavigne-Delville | Harmonising formal law & customary land rights In French-speaking West Africa[END_REF][START_REF] Mccarthy | Urgence Niger : Payer ou Mourir[END_REF]. Non-separable interactions between the on-farm and off-farm production activities and consumption decisions [START_REF] De Janvry | Progress in the modeling of rural households' behavior under market failures[END_REF], the repartition of the assets between villagers within the village and the family and the multiple purposes of the strategies are some of the socio-economic factors with a direct effect on the success of productionsupporting actions. Actually, many factors may modify the way a development proposal is considered by a village population. Beyond the informal but recurrent local reinterpretation of the rules of the development project itself [START_REF] Laurent | Migration et accès à la terre au Burkina Faso[END_REF][START_REF] Biershenk | Courtiers en développement. Les villages africains en quête de projet[END_REF][START_REF] Laurent | Le big man local ou la «gestion coup d'État» de l'espace public[END_REF], the benefit of a development intervention varies with the type of concerned villagers [START_REF] Lavigne-Delville | Impasses cognitives et expertise en sciences sociales : réflexions à propos du développement rural en Afrique[END_REF][START_REF] Marou | Etude des effets et impacts des initiatives et innovations paysannes améliorant le revenu des ménages dans la zone d'Aguié[END_REF]. As any proposal, a development action should thereby also integrate a "marketing" approach: who are the real focused populations of a development action in a Sahelian village and what factors condition the adoption of a proposal within a population? Because of the size and the type of this actual focused population, what is the extent of the adoption and the real impacts on environment and society of such proposals? Are ABM tools efficient enough for the analysis of such a complexity and what sort of information do they provide that other model types do not? These are the questions that the article considers and analyses. For that purpose, we selected two actions that are emblematic of development strategies in the country:

• Niger having one of the lowest inorganic fertilizer use rates (0.27 kg/ha) (World Bank, 1997), inorganic fertilizers are considered by many development operators as the bottleneck for farming system intensification and income increase in Niger (de [START_REF] De Rouw | Nutrient availability and pearl millet production in Sahelian farming systems based on manuring or fallowing[END_REF][START_REF] Ouédraogo | Intensification de l'agriculture dans le plateau central du Burkina Faso: Une analyse des possibilités à partir des nouvelles technologies[END_REF]. The purpose of these operators is to support farmers to use inorganic fertilizers in food crop fields and vegetable gardens through farmers' organizations, by increasing the availability of inorganic fertilizers at the village-level and the knowledge on their use, with an emphasis on the microdose technology [START_REF] Tahirou | Stages and determinants of fertilizer use in semiarid African agriculture: The Niger experience[END_REF][START_REF] Gérard | Toward farm specific recommendations for the use of mineral fertilizers in Sahelian crop-livestock systems[END_REF], thereby reducing inorganic fertilizers waste and the weed impact [START_REF] Muehlig-Versen | Phosphorus placement on acid arenosols of the West African Sahel[END_REF]. The promoted inorganic fertilizer is Diammonium Phosphate (DAP). Group members can buy inorganic fertilizers at market price. Groups almost entirely consist of either women or men, using inorganic fertilizers for gardens, cash crops or cereal fields. • The second proposal is the warrantage, also named inventory credit. It is a credit technique based on the use of farmers goods set down as a guarantee in a warehouse. This technique is actually applied in Niger under various modalities, depending on the site, the Microfinance Institution (MFI) and the Farmers Association (FA) involved. Usually after harvest, farmers stock a part of the yield in a reliable warehouse as a guarantee for the credit operator. In exchange, this last provides a credit equivalent to 100% of the value of the stock at the time of the deal 2 , with 10% of the initial stock value for the FA as storage and fee costs. The farmer reimburses the credit by buying back the stored millet and sells it on the market at high prices (usually during "soudure" times). The benefit due to price increase during the storage period belongs to the farmer. The objective is to provide better access to financial resources [START_REF] Badamassi | Le warrantage au Niger: Une technique de crédit pour lutter contre la pauvreté rurale? Cas des femmes de l'Union Tonougakay Ni Bonga de Saboudey Carre[END_REF] and for income securization, by compensating millet price fluctuations [START_REF] Pender | Impacts of inventory credit, input supply shops and fertilizer micro-dosing in the dryland of Niger[END_REF].

All the elements of the system to include in the evaluation of this relationship cannot be analyzed in a systematic and/or an experimental manner [START_REF] Ahrweiler | Caffè Nero: the Evaluation of Social Simulation[END_REF], which implies to model the system. As reviewed by [START_REF] Lambin | Are agricultural land-use models able to predict changes in land-use intensity?[END_REF] and [START_REF] Bousquet | Multi-agent simulations and ecosystem management: a review[END_REF], Agent Based Models (ABMs) have been found particularly useful for simulating the multi-disciplinary and multipurpose reality of the rural world. In the present study, the focus is on the project intervention and the population, the target area being south-western Sahelian Niger.

Description of the study sites

The program which supported our research was hosted and managed by a consortium of development and research operators working in Niger and farmers' associations. The institutional position given by our own involvement into a development project helped us to get access to the network of experts in Niger. The operators of the consortium had completed extensive literature and data sets resulting from 20 years of agricultural research and are implementing the two selected development proposals in several sites of the rainfed part of Niger. The three sites represent 3 contrasted situations of the rainfed agro pastoral zone of Niger (Figure 1), , namely Zermou in the region of Zinder, Gabi in the region of Maradi and Fakara in the region of Tillabery. The latter was the main location where we elaborated our social hypotheses, which were then extended to the two other sites with the support of the available literature [START_REF] Luxereau | Changements écologiques et sociaux au Niger[END_REF]Waziri Mato, 2000;Mortimore et al., 2001;[START_REF] Jouve | Typologie des agrosystèmes villageois du département de Maradi (Niger) propositions pour un programme de recherche-développement[END_REF][START_REF] Yamba | Observatoire de Maradi-Mayahi-Dakoro, Rapport de caractérisation[END_REF].

Figure 1. Rainfed Niger and locations of the three study sites These regions are: (i) situated in areas with rainfed agriculture (10% of the territory), (ii) close to a regional urban pole, and (iii) linked to the main farming ethnic groups of the country (Zarma around Niamey, Hausa in Maradi, and Hausa / Hausa-speaking Kanuri in the region of Zinder). The sites we chose in these three regions: (iv) are considered as poorly resources-endowed and (v) are sites of both active scientific research and development support from operators [START_REF] Gérard | Projet Aide à la décision: full proposal for the DGCD[END_REF] working for more than ten years in Niger. Each site covers 45 km per site, an area of about 2000 km². The differences between the sites are summarized in Table 1.

Rainfed millet and sorghum-based agriculture is the main activity in terms of land occupation and manpower requirements in the 15% of the territory where it can be practiced. It is managed in an extensive and anti-risk approach: the rainfed part of the country experiences a low to moderate rainfall between 200 and 800 mm, distributed in one rainy season from June to October, but its main characteristic is its high spatial and temporal intra-annual and inter-annual variability. Soils have a very low fertility as well as a poor water and cation retention capacity [START_REF] Graef | Spatial and temporal rainfall variability in the Sahel and its effects on farmers' management strategies[END_REF]. Manure is the main local fertilizing method, but is not available in quantities large enough to meet demand [START_REF] La Rovere | Livestock roles and agro-environmental sustainability of Sahelian Niger mixed croplivestock systems under intensification[END_REF] while at the same time inorganic fertilizers are still expensive. The population has conquered its own national rural "frontier" in rainfed areas by extending crops and settling new villages [START_REF] Guenguant | Dynamique des populations, disponibilités en terres et adaptation des régimes fonciers: le cas du Niger[END_REF]. This settlement movement is fully complete in the central southwestern part of rainfed Niger (Region of Maradi), as described by Mortimore et al. (2001). It fully continues in the region of Zinder, central southeastern Niger, but seems to slow down in the region of Niamey, western Niger [START_REF] Saqalli | A fast & low-cost indigenous perception based regional mapping methodology in support for rural development: analysis of an experience in Niger[END_REF]. Male farmers are seasonal migrants during the dry season, from October to May, to work usually as small traders [START_REF] Timera | Les migrations des jeunes sahéliens: Affirmation de soi et émancipation[END_REF][START_REF] Rain | Eaters of the dry season: Circular labor migration in the West African Sahel[END_REF]. The money they brought back home is an important source of income for the remaining family members, around 290 € per family per year [START_REF] Reardon | La diversification des revenus au Sahel et ses liens éventuels avec la gestion des ressources naturelles par les agriculteurs[END_REF]Mounkaïla, 2003;[START_REF] Saqalli | Multi acteurs, multi activités: Simulations multi-agents pour la détection des changements dans l'Organisation sociale dans les villages de l'ouest Nigerien[END_REF]. These funds are mainly used to fulfill food requirements that agriculture doesn't cover any more, for male ostentation purposes such as cigarettes or sunglasses and to cover expenses for social and religious ceremonies 3 . Migrants buy small ruminants coming back from migration, thereby saving some money from the requests of the enlarged family, and allowing them to pay the next migration travel expenses, usually just after crop harvest [START_REF] Saqalli | Multi acteurs, multi activités: Simulations multi-agents pour la détection des changements dans l'Organisation sociale dans les villages de l'ouest Nigerien[END_REF]. Dry season vegetable gardening can be practiced only in some villages where wells give access to shallow groundwater in talweg fields. Social access to gardening varies according to the site: it is actually restricted at the Fakara site to married and respectable women with family manpower, by borrowing fields after the millet harvest. This activity provides on average 52,50 € per gardener cultivating per year [START_REF] Saqalli | Multi acteurs, multi activités: Simulations multi-agents pour la détection des changements dans l'Organisation sociale dans les villages de l'ouest Nigerien[END_REF]. Because of better access to markets, larger acreage suitable for irrigation and therefore a better profitability but also a social evolution pushing away women from fields, Gabi has seen a shift in the gardening activity from a female driven traditional mode to a pure male activity. The site of Zermou has seen the same social shift but has access to a very small suitable acreage.

Methodology

The overall approach and assumptions

The overall research methodology followed an iterative process between field investigations, discussions with local experts and modeling. The modeling approach was supported by a two-year field investigation and participatory observation period similar to that described by [START_REF] Bogdan | Introduction to Qualitative Research Methods[END_REF]. This observation period concerned a group of villages and local organizations. Repetitions along interviews and cross-checking between sources were the criteria of validation of these rules. They are then compared to behavior descriptions and rules in the available literature. As for the model rules, the different scenarios were also defined on the basis of field observations, discussions with experts and a literature review. Our strategy is to compare both interventions in terms of impact on the population and under different local environments, based on our hypotheses regarding local villager logics and behavior. As a method combining rather than juxtaposing different disciplines, we do have to formulate numerous hypotheses:

1. The success of a development action is not defined by its very characteristics but results from the villagers perception of this action, whatever its intrinsic quality. The factors and constraints selected for implementation in the model are thus defined on the basis of the villagers perception as the ones which determine the interest in the development actions. This model is therefore individual-based: each villager Agent has its own behavior, depending on its social characteristics and constraints, in order to combine at this very level all the complexity and the specificity of each individual in a village [START_REF] Deffuant | Une démarche expérimentale pour la simulation individucentrée[END_REF], but also to avoid the so-often assumed but rarely clearly defined "household" unit, which is not relevant for sahelian rural situations (Gastellu, 2006;[START_REF] Saqalli | Multi acteurs, multi activités: Simulations multi-agents pour la détection des changements dans l'Organisation sociale dans les villages de l'ouest Nigerien[END_REF].

2. The model is empirical and agent-reactive: villager behaviors and processes are not cognitive and the different small steps of the various activities are implemented as simple as possible to maintain the global consistency of the system. Villagers simply do what they have to do and react over time and as a function of the events without cognitive functions that would require absolute rather than relative parametering of values on social issues. The only cognitive function of villagers concerns our main target: the villager involvement in a development intervention.

3. Considering all the components of a system and simplifying them is more relevant than neglecting some activities by focusing on the one which seems to be the most important [START_REF] Alacs | Complexity and uncertainty in the forecasting of complex social systems[END_REF][START_REF] Amblard | Modélisation et simulations multi-agents: application pour les sciences de l'Homme et de la Société[END_REF]. This model is therefore not based on the binary relationship between a villager and the project but includes the project actions as a component of the pattern of activities of a villager Agent.

Investigation methodology

Assessing the individual-based but family-related organization of a rural village

The agro-ecological part of the model was defined through available literature data (Gérard et al., 2001;Turner and Williams, 2002;La Rovere and Hiernaux, 2005). Millet price and rainfall data as well as the functions relating millet growth to fertility and rainfall came from ICRISAT and ILRI databases.

The social family part of the model was developed through a literature review, transects, interviews and local perception-based regional maps (ZADA) [START_REF] Bonin | Territoire, zonage et modélisation graphique: recherche action et apprentissage[END_REF][START_REF] Caron | Modélisation graphique et chorèmes: la gestion des parcours collectifs à Massaroca (Brésil)[END_REF] described in detail for the Fakara and Zermou by [START_REF] Saqalli | A fast & low-cost indigenous perception based regional mapping methodology in support for rural development: analysis of an experience in Niger[END_REF]. The semi-direct interviews of 126 persons from 4 selected villages focused on the main activity carried out by the interviewed person at the time of the interview. The model was then extended to the two other sites with the support of a ZADA in the site of Zermou, four village Participatory Research Assessments (PRAs) using the methodology and principles of [START_REF] Chambers | Participatory rural appraisal (PRA): Analysis of experience[END_REF] and twenty individual interviews for the Gabi and Zermou sites, as well as a review of the available literature.

Assessing the practical mode of implementation of development actions.

Our long-term field investigation also allows investigating the complex relationship between project and villages and assessing the practical implementation of development actions. We tried to analyse these actions from the operators point of view and the villagers' one, using a participatory observation approach5 . We first used the operators' official documents or documents coming from other operators as a mainframe to confront unofficial expert communications and local situations. The analysis of the development operators practices was done through different cross-checkable methods: (i) 4 to 12 villagers for each study site were re-interviewed on their personal relations with development projects. These persons were selected because of gender and level of responsibility and their will to interact 6 . In the same way, nine elders were interviewed on their perceptions of the history of local development actions; (ii) development actions results are recorded in village-based registers that we collected and compared with head office' records but also with our own village semi-direct interview data; (iii) By staying in villages and remaining as unobtrusive as possible, our everyday presence allowed observing transactions and comments between villagers and development stakeholders with a low level of perturbation and so, to have access to the interface between the project corpus and the village one.

Agent based modeling

The selected ABM platform is CORMAS (Common Resources Management Agent-based System) developed by CIRAD [START_REF] Bousquet | Agent-based modelling, game theory and natural resource management issues[END_REF]. The model was split into an agro-ecological part and a socio-economic part (Figure 2). The modeling methodology, including the parametering functions and related sources for the agroecological and village socio-economic modules is fully described in [START_REF] Saqalli | Multi acteurs, multi activités: Simulations multi-agents pour la détection des changements dans l'Organisation sociale dans les villages de l'ouest Nigerien[END_REF].

Building the village module

Individual agents are defined as equivalent, which means that they have the same attributes: only the values of these attributes vary, defining each agent and its characteristics [START_REF] Verhagen | Multi-agent system as simulation tools for social theory testing[END_REF]. At the model initialization, fifty villager agents are created in the virtual environment. Initial villager agents are from various ages (from 1 to 55 years old), gender, lineages (with a hierarchy from 1 to 4, as a measure of the power of each big kinship group in the village) and land property (between 3 to 5 map cells). After the initialization step, gender and family rank for a villager agent are the most important factors within the village context. They determine the access to all the social and/or economic activities, i.e. marriage, property, food and money redistribution, millet farming and migration for men, gardening for women. Ranks are defined for all child agents but evolve for all adult agents in each family. They are updated at the beginning of each time step, according to newborns, new marriages, reaching adulthood and deaths. The first rank in a family defines the head of the household. However, the family's head does not manage all the multi activity system of the family but only millet farming activities. Other activities (livestock-keeping, migration, gardening, food redistribution) are under the sole responsability of the worker: each villager agent should sustain itself but also its dependents, i.e. all people in the family with a lower rank and directly related to it7 . Families can expand their land properties only if the family annual consumption is higher than the last yield8 . The extension capacity depends on their lineage values, their ratios between the available family manpower 9 and the family size [START_REF] Gavian | Land tenure and allocative Efficiency in Niger[END_REF], and a distance-to-village opportunity cost factor (Loireau-Delabre, 1998). Only married adult males can have access to land ownership. As a strict condition to become by this way a village "citizen", each male adult agent has to marry at least once and up to four times. Earning enough money to afford the dowry is therefore vital for each bachelor. The model has a weekly time step and it is spatialized through a dynamic cellular automata matrix of the model, where each pixel is a parcel of the village territory, introducing the data-derived spatial distribution of soils characteristics (fertility, access to shallow water) of the village territory, the simulated land tenure distribution but also the rainfall spatial variability as observed from the local ICRISAT raingauge network [START_REF] Gérard | ICRISAT agronomic results from the global linear modelization of demonstration tests fields' data[END_REF]. Biophysical and farming processes are defined for each pixel as identified by the villagers and from literature data.

Simulating villagers production activities

Agriculture. Only male adult agents can crop millet fields during rainy seasons in all the three sites and can garden on borrowed fields during dry seasons for Maradi and Zermou sites. For the Fakara site, the latter activity is restricted to female adult agents. The sequence of cropping actions a male adult agent should follow, i.e. sowing, weeding once or twice and harvesting, is conditioned by the diagnosis of available manpower and minimization of expected production losses. Crop growth is governed by the available manpower a villager agent can mobilize to carry out the right cropping action at the right time, defined by rainfall distribution and by the fertility rate at each time step. A parcel's fertility evolves as a function of crop growth, a weeds impact factor and animals manure during dry seasons. Crop yields result from a combination of the crop growth, weeds, fertility and management.

Gardening. For their dry season vegetable gardens, female adult agents follow an equivalent sequence of actions.

Only female adult agents with stepdaughters or with unmarried daughters at least 12 years old can have access to gardening. These can mobilize the available female manpower from then on in a similar fashion than the head of the family for millet farming.

Migration. Only male adult agents more than 16 years old have access to the migration activity. The price for the roundtrip travel is the major constraint for leaving. The date of departure depends on the family rank, i.e. the number of dependent relatives. The weekly gain is a function of the site, season, and number of years of experience. To return home, the migrant should overcome two constraints: (i) for prestige reasons, a male adult agent cannot return to his village without a minimum amount of money, at least the roundtrip ticket for the next migration, i.e. 2* 45.75 €. (ii) Each migrant agent has a certain probability to be racketed by the customs services he meets (Table 1).

Livestock keeping. It is here limited to a saving scheme. Each year, individual gains (crop yields, migration, gardening) can be transformed into livestock, with a depreciation factor. If family yields are good enough, villager agents buy animals after crop harvest, when they have grain to sell; however, it is the time when millet price is the lowest (around 13,75 € per 100 kg bag). When the granary is quite empty, they sell animals to buy millet, but at that period, millet price is high (27,50 € per bag on average). This 50% loss can be considered as a livestock keeping cost. Coming back from migration, the migrants buy small ruminants they feed during the rainy season. At harvest or sometimes before, they are sold to pay the ticket for the next migration. Animal fattening is in this case considered as compensating the 50% loss.

Fertility management and manure: Three fertility restauration processes are considered: The natural regeneration by shrub and weed growth is simulated through a serie of functions of fertility originated from simplification factors issued from d [START_REF] Herbès | Fonctionnement et gestion des écosystèmes forestiers contractés sahéliens[END_REF] and [START_REF] Wesel | Influence of shrubs on soil characteristics and their function in Sahelian agro-ecosystems in semi-arid Niger[END_REF]. The impact of animal manure varies: animals graze at day time their allowed territory (table 2) with no human management. Half of the animal manure is by then spread in grazed areas and the other half in corrals at night (Ayantunde et al., 2000;[START_REF] Ayantunde | Day and night grazing by cattle in the Sahel[END_REF], which allow villagers to spread manure on chosen fields (distance to village, fertility).

Assessing development action types

Action types are gender-specific. Warrantage and fertilizers are proposed to villagers at t=0. For each adult and married villager, choosing to be involved in one of the actions is the only cognitive function: it is based on a gain comparison between the personal experience on annual income with or without using the action type. The gain is based on food and income stock. In case of no experience, all adult villager Agents who manage millet fields or gardens tries the action type for the coming year.

Warrantage.

Inventory credit choices are made after harvest. As a saving choice, the first step is to determine if the agent (i.e. the head of the family or, if absent, the highest ranked adult) has the capacity for saving. It means that we consider that every villager relies on the necessity to keep at least enough millet for half a year for all the family members who rely on him/her: SM fi (t) > CA di (t) / 2 (1) With: di: the number of family members of i relying on i at t; SM fi (t): i family millet stock at t; CA di (t):

annual food consumption of the dependents di; The second step is then a cognitive decision based on personal experience, through a comparison of the mean gain during past years with saving through warrantage and past years with no savings or with saving through livestock: W i (t-1) + X fi (t) > NW i (t-1) + Y fi (t)

(2) With: W i (t-1): the total value of the previous years with warrantage; NWi (t-1): the total value of the previous years without warrantage; If warrantage was used the last year [t-52; t]: X fi (t): the total "gain" of the family of the last year [t-52; t], including the difference in cash of the value of the livestock between t-52 and t. The "gain" is either "reputation" in the reputation scenario or "income" in the economy scenario; Y fi (t) = 0. If warrantage was not used the last year [t-52; t]: X fi (t) = 0; Y fi (t): the total "gain" of the family of the last year [t-52; t], including the difference in cash of the value of the livestock between t-52 and t.

Warrantage is in our case a financial transaction: selling millet through this action type allows buying its own inorganic fertilizers at the same price (majoring a 0.15 € per bag for shelf stocking) than it was sold.

Fertilizers.

Inorganic fertilizer applications is possible throughout the millet cropping season. Only millet field or garden managers can buy fertilizers. The price of the bag of inorganic fertilizers is 50 kFCFA, i.e. 75 €. According to the microdose recommendations [START_REF] Tahirou | Stages and determinants of fertilizer use in semiarid African agriculture: The Niger experience[END_REF], 0.2 bags of inorganic fertilizer are poured on one parcel of 1 ha, meaning that fertilizing one cell in the model cost 10 kFCFA, i.e. 15 €. Gardens need 10 times this value, meaning that, because we consider that one garden is one tenth of a cell, fertilizing a garden also cost 15 €. As a production choice, the first step is to determine if the agent has the financial ability to afford some fertilizers. Setting aside at least enough millet and/or cash for half a year requirements for him/herself and its dependants, the ability depends on whether or not the value of the family's millet and cash stock exceeds the fertilizers needs10 . The capacity is defined as follows: SM fi (t) + SC fi (t) > NF i (t) (3) With: SM fi (t): millet stock of the family i; SC fi (t): cash stock of the family i; NF i (t): inorganic fertilizers needs based on the property which had a better mean production with inorganic fertilizers than without. The second step is also a cognitive decision based on personal experience, through a comparison of the mean gain from past years with and without fertilizers, similar to that used for warrantage. Inorganic fertilizers impact start from their application. They have several effects on millet depending on the crop development (seedling, sowing, maturation and harvest stages). During the maturation stage, there is a risk of 1% per week to lose the harvest in fertilized fields because of the chemical burnt it can occurs (de [START_REF] De Rouw | Improving yields and reducing risks in pearl millet farming in the African Sahel[END_REF][START_REF] Koning | Environmental crisis or 'lie of the land'? The debate on soil degradation in Africa[END_REF].

For each site, thirty simulations were run for a period of sixty years (i.e. two generations) corresponding to 3120 weekly time steps. Simulation outputs were obtained for the entire village, at family level and at gender and age group levels. Village level simulation results are compared to available data, i.e. our macro level field investigation results, literature review and the Niger national census, in order to access the consistency of the model. The two development actions are then compared individually or in combination. Table 2 shows the combination of scenarios and their abbreviations. As the village is founded at t= 0, the first 5 years should not be considered as part of the simulation results as they are strongly affected by the initialization process.

Simulation results

Confidence building

To build some confidence in the model,we compared the simulated production assets from four scenarios with available information for the Fakara site (Table 3). (2002) than La Rovere (2001). As interview results are inherently highly dependent on the interview processes and the questioned issues, the fact that the latter author has mainly focused on livestock management in his work while the two former scholars have worked on villagers assets give us more confidence in the observation of Loireau-Delabre (1998) and [START_REF] Tahirou | Farm level analysis of agricultural technological change: inorganic fertilizer use on dryland in Western Niger[END_REF].

Comparing sites with no development action implementation

Production assets: a structural geographic advantage

Average income evolves at first in a convex curve because of the generation effect: a very high adult per capita ratio during the first 5 to 10 years has positive effects on income (Figure not shown). But the children explosion during the 15 to 30 years period (Figure not shown) force the slope of the income curves of the three sites to become negative. However, the curve amplitude varies depending on the simulated site: Fakara and Gabi show equivalent declining curves, while income at Zermou is continuously significantly lower. Better conditions, both biophysical (rainfall and soil fertility) and economic factors (migration costs) as they are implemented at the Fakara and Gabi allow higher individual incomes, which facilitates the access to marriage for men, reducing therefore the delay for getting children. As the decision to expand fields is conditionned by the food production level and yields are very low at this site, land occupation increases faster at Zermou than at the two other sites. Therefore, the land per capita ratio is higher in this site than the two other sites during the first half of the simulation period. But, as the manpower ratio of Zermou remains quite equivalent to the two other sites, villagers do not benefit from this rapid field expansion as they cannot crop all of it properly. As a consequence, village population growth is equivalent for the Fakara site (585 inhabitants ± 141 inhabitants at the end of the simulation) and Gabi (505 inhabitants ± 131) but is significantly lower for Zermou (321 inhabitants ± 97). The substantial differences between Zermou and the two other sites suggest that the Zermou site has exceeded a threshold resulting from the accumulation of higher constraints.

Activities distribution: site specific specialization

All three activities (agriculture, migration and gardening) grow in volume along the 60 years because of the demographic growth. Income from millet agriculture per villager varies according to the site: Zermou shows a constant decline in the farming income and even a shift in the allocated labor for farming between the 15 th and the 25 th year (i.e. after the very rapid period of field extension in Zermou). The two other sites have similar trends, both strongly affected by a generation effect due to the progressive appropriation of new lands during this period, which does not occurs in Zermou. During at least the first half of the simulation, it seems that the Fakara population is more involved in farming and has higher farming gains than in Gabi. However, this last site is the only one to maintain its farming gains per capita and sees even an increase in the farming labor until it exceeds the Fakara figures between the 35 th and the 45 th year. For the gardening activity, local social and economic rules dramatically change the situation: both hausapopulated sites of Zermou and Gabi restrict gardening to men. However, the Gabi site makes it possible to practice migration and gardening by the same villager at the same time, thanks to the immediate proximity of Nigeria, while this combination is not possible at Zermou. Consequently, the use of the very few gardening places of the site stops quasi totally11 . More land suitable for gardening (Table 1) and access to male manpower in Gabi allow a progressive increase in the gardening gain per villager. But this expansion is lower than in the Fakara, which may have benefited from the gender discrimination between gardening and migration (Table 1). Manpower involvement ratios for the zarma-populated Fakara and in Gabi do therefore concern different populations. For the migration activity, while the three sites show no significant differences in the manpower allocation before the generation peak (year 10 to 2012 ), migration seems to be strongly affected by the access constraints (Table 1): While the lower cost for departure for Gabi allows progressively more people to leave and to bring back home more money than in the Fakara, it seems that the accumulation of disadvantages for the Zermou site (higher departure costs, more risks, poor agriculture gains) limits the extension of this activity at the beginning but the very low gain of agriculture and the impossibility to garden progressively forces people to reallocate their manpower on the sole available activity, i.e. migration.

Inequality and sustainability: producing more for how long and for whom?

One should also analyze the sustainability of the considered systems as some sites show declining figures for production efficency or land occupation ratios. As defined by the model rules, Fakara and Gabi site population extends their cropped land taking account their manpower/population ratios. Land occupancy grows in Gabi by a temporally stable rate of 4,6% per year (Fakara, 2,4% and declining over time). Zermou villagers rapidly conquer their territory although they do not so much involves themselves in farming, because of the far more rapid decline of the fertility of the cropped land. This assertion is compatible with the literature for various zones in Niger, including the Damagaram where Zermou is located, but also other arable places in Niger for the end of the first half and the beginning of the second half of the 20 th century. This conquering behaviour is usually described as a response to manpower scarcity but also as an "investment for the future" at family and village levels (Demont et al., 2006;[START_REF] Bah | An agent-based model to understand the multiple uses of land and resources around drillings in Sahel[END_REF]. Even with lower land ocupation growths in the Gabi and Fakara sites, 60 years of continuous growth eventually led to complete occupation of arable land: it means however that further simulation results concerning sustainability and project action impacts cannot be compared with the present situation, particularly in Gabi where real land occupation has been complete for at least 40 years. After the first cropping years, average yields are not strongly affected by land scarcity. Yields are significantly different between sites as determined by the model inputs and decline slowly from 4 to 5.5 q/ha at t = 10 to 3.5 to 4.5q/ha at t = 60. This resilience cannot be explained by a permanent compensation of the old fields' fertility loss by new fertile inclusions because land is already saturated in Zermou. It means that local farming systems are resilient enough in all the three sites to maintain yields, but with low yield values. It allows the simulated population of the three sites to maintain its food security throughout the simulation period. As people already live in these sites, it gives confidence on the model realism. analyzing the evolution of the ratio between the annual consumption per villager and the income equivalent from the three main activities and the livestock capital, one can notice that if the Gabi site population food ratio even strongly increase, the consumption ratio remains stable for Fakara and slightly declining for Zermou, making them more prone to food shortage crises. The gender income ratio evolution shows the difficulty for women to sustain while having no access to economic activities for the Gabi and the Zermou sites. The Fakara site ratio slightly recovers over time due to female access to garden production gains13 . The Gini coefficients14 established at family and individual levelssuggest another limitation of the systems: inequalities between families and within families grow, meaning that economic discrimination grows along the 60 years of simulation.

Projects implementation: successes and failures

A low success mainly due to a poor saving capacity

The Figure 3 shows the impact of the project interventions on the population and related effects. Both Figure 3.1 and Figure 3.3 show a generation effect which suggests the strong relationship between the capacity for savings and the manpower: it supposes that having a higher manpower per capita ratio allows a household head to save more. However, Figure 3.3 suggests that the saved quantity is strongly linked to the capacity of a site to procure enough excess yield for savings: the Zermou population is unable to create enough production to both feed people and save millet. Therefore, and despite the hope of development operators to implement warrantage all over the country, the success of this intervention should be considered as highly determined by the local capacity for millet production. Inorganic fertilizers use shows strong differences between the three sites : whatever the sites, fertilizer use remains very low, with less than 10% of farmers using it (Figure 3.2) and less than 4% of the total surface (Figure 3.4). Gabi and Fakara populations show similar behavior regarding the inorganic fertilizers use, but at different levels: as far as they maintain a high manpower per capita ratio (between t=5 until t=12 for Fakara and t=20 for Gabi) allowing them to easily clear new fields and to weed cropped fields, farmers are not using inorganic fertilizers15 , suggesting that gains from activities other than farming are used for more promising purposes, such as migration. Thereafter, one can observe that the proportion of population using fertilizer and fertilized land reach a higher value in Fakara than in Gabi due to an initial lower fertility level. In a simulated context of no land saturation, the Gabi population appears less concerned by inorganic fertilizers and on less surfaces. One can then suppose that inorganic fertilizers are not attractive wherever free and fertile land is still easy to acquire. Present-day figures for a full-saturated Gabi site show that ²/ 3 of the farmers actually use Dashed curves for the simulation outputs of the combined actions scenario shows that there is no synergy between the warrantage and inorganic fertilizers use strategy, suggesting that the logics and even the population concerned by the two activities may be distinct. Exploring the characteristics of the population involved in the two proposals helps to identify the most determining characteristics for involvement in projects. As fertilizer and warrantage users at Zermou are too few, the analysis of the involved population concerns only the sites of Gabi and Fakara. Inorganic fertilizers users all had in common a higher manpower per capita ratio at family level but a lower land per capita ratio and a lower livestock per land ratio than the average population. They can be split into two groups (Table 4):

• "Small young disadvantaged but growing families": their average lineage value is low (1.6 vs. 2.8 for the whole population), suggesting that the most interested people are the ones who were disadvantaged in the land access due to social tenure discriminations. Families are small and thereby, manpower and owned land is low. The head of the family is younger than average (35 years-old vs. 43). However, the higher manpower/population ratio allows the family to sustain by diversifying income sources (millet fields, migration and after a few years, livestock sales and gardening. It also allows the use of inorganic fertilizers by succeeding in all the millet cropping cycle steps, particularly the related higher manpower requirement for weeding. Inorganic fertilizer use seems to be a way to compensate the low level of land and livestock manure. This group represents at most of 30% of inorganic fertilizer users around the 15 th year and then declines, eventually disappearing around the 40 th year of the simulation. • "Large old but shrinking families" : the family head is far older than average (61 years-old vs. 43). Because of the non-cooperative family organization [START_REF] Saqalli | Multi acteurs, multi activités: Simulations multi-agents pour la détection des changements dans l'Organisation sociale dans les villages de l'ouest Nigerien[END_REF], elder children leave once they get married, taking with them some parts of the livestock and their manpower. The high income per capita ratio, with a high livestock per capita ratio, allows mobilizing enough funds to compensate for the declining manpower ratio. The size of this group at the start of the simulations is higher by 25% in the scenario combining both warrantage and inorganic fertilizers compared to the scenario with only inorganic fertilizers.

(i) ∆ (ii) ∆ (i) ∆ Family head age - ⇑ ++ ⇑ + ⇑ Lineage -- ⇓ / ⇒ ++ ⇒ Family Size - ⇑ + ⇓ ++ ⇒ Manpower - ⇒ / ⇓ ++ ⇒ Land size - ⇑ ++ ⇒ + ⇑ Livestock -- ⇒ + ⇒ ++ ⇑ Income per capita / ⇒ + ⇒ + ⇑ Livestock per capita - ⇓ - ⇓ ++ ⇑ Land per capita - ⇒ - ⇑ + ⇑ Manpower per capita + ⇑ + ⇓ + ⇒ Manpower per cropped surface / ⇑ - ⇓ ++ ⇒ Livestock per cropped surface - ⇒ - ⇒ + ⇑
(i) --: -25% and less; -: -10 to -25%; /: ±10%; +: 10 to 25%; ++: 25% and more ⇓: -25%; ⇒ ± 25%; ⇑: +25% Anyhow, inorganic fertilizers seem to be interesting only for families in transition: they cannot be used by the poorest as it is too expensive, and the wealthiest can use other and cheaper assets, particularly manpower and livestock in a context where land is still not a constraint. For the two sites, warrantage users are members of a unique group that can be described as "large better-settled families" : their average lineage value is quite high (3.2 vs. 2.8), and the family head is somewhat older than average (48 years-old vs. 43). Families are big and growing, with a higher amount of young adults than average and consequently, manpower and owned land are higher as well. Warrantage seems to be an alternative to livestock as an income saving tool, but only families that are able to maintain a saving capacity get involved.

Discussion and conclusion

One can then estimate that the three sites show different trajectories based on their predefined potentialities: these lasts influence the demographic growth and even more the manpower ratio, but also the involvement in farming activities: Zermou is disadvantaged in the continuous run between family needs and available manpower. Therefore, the question should concern the long-term sustainability of the settlement and colonization process, when the three sites show a decline in income per capita. Social and environmental indicators suggest the sustainability but also the fragility of such systems in the simulated conditions. However, the temporal scale has to be redefined particularly regarding the case of Gabi: the present day situation shows a complete saturation of the available arable land, because of a longer and more intense period of field extension. It means that the fragility suggested by these simulated indicators should be even higher in the real situations. As a matter of fact, the success of both proposals is strongly defined by the local biophysical capacities to sustain village populations. Involvement in warrantage and inorganic fertilizer projects do concern only sites where millet savings for securization or intensification are possible, which is not the case for Zermou. Even so, success in the last two sites is in any case limited, with a greater impact of the warrantage proposal than the fertilizer one. These proposals actually require some investment capacity that few people do have in Fakara and Gabi. This capacity is largely conditioned by each family food requirement in relation to its manpower in a context where land is still available. Only a maximum of 25% of the population engages in a project proposal: warrantage in Fakara, only during periods when enough manpower was available. In the fertile site of Gabi, a land intensification proposal does not have a large success, as long as new fertile land remains available. However, due to the limited temporal scale, simulations do not provide information upon a possible intensification process in a context of land scarcity. Therefore, one should consider these proposals as a potential support tool for a limited part of the population to go beyond the survival level, but not as a poverty-alleviation panacea.

Therefore, this methodology has underlined that:

• Development projects often focus on the costs/advantages of a development proposal, which can be considered as the characteristics of an offer in an economic exchange, assuming that proposing such proposal will generate its own demand. Meanwhile, modeling one society reaction to new economic opportunities, by redefining this demand pattern, i.e. the distribution of assets within families, shows that this demand conditions the "market" size for such proposals.

• Development interventions have various successes according to the household types and to the considered area: future development proposals in Nigerien Sahel should resort to a diverse panel of proposals and never base their future plannings on the assumption that a proposal, whatever its intrinsic quality, will expand all over the country. Unfortunately, this fundraiser-oriented marketing approach is in use in many development-planning programs, often suggesting that a proposal will succeed in a whole country, when data and informations are based on one local experience. This simulation tool, by suggesting the strong impact of local social and biophysical factors and their local variability and distribution, allows advocating for a new marketing approach, focusing on the local and variable population demand.

This work should be understood as a step-by-step construction. As defined from the field observations, some factors were eluded in the modeling process:

• Labor and land markets were not implemented: While land markets are still quasi totally absent in the sites of Zermou and Fakara, they do exist in Gabi, particularly for irrigable places, which is obvious in a context of land saturation that we did not implement. There are still quasi no labor markets in Zermou, but Tahirou & Sanders (2006) and our own observations in Fakara suggest that this activity, while quasi-absent in the 90's [START_REF] Ada | Diagnostic sur le système agraire du Zarmaganda central (Niger)[END_REF][START_REF] Loireau-Delabre | Espaces Ressources Usages: Spatialisation des interactions dynamiques entre les systèmes sociaux et écologiques au Sahel Nigerien, site de Banizoumbou[END_REF]Mounkaïla, 2003), have grown very rapidly. • While literature often defined the Fulani ratio being around 10% of the local population, figures from [START_REF] Barbier | Declining access to Transhumant Areas and sustainability of Agropastoral Systems in the semi-Arid Areas of Niger[END_REF] suggests that they may reach around one third of the total population in the Fakara. As they have a different land and livestock use mode, including their presence on a model may transform outputs and further prospectives. [START_REF] Yamba | Les mutations des systèmes agraires et des modes d'usage des ressources naturelles dans la zone centrale du Niger[END_REF] has noticed a generalization of the divorce institution. Since no data is actually available at the national level, the phenomenon was not modeled but we assume that this factor could have a strong impact as women resort to divorce at least once in a lifetime bringing with them some assets, particularly small livestock. Therefore, this institution can provide more independence to the women-driven local economy and more variability in the accumulation processes at family level [START_REF] Turner | Merging local and regional analyses of land use change: the case of livestock in the Sahel[END_REF].

This model was determined by the initial hypothesis that the present time evolution of any farming system is better understood by integrating the system history and inertia 16 : To start the village simulation from its foundation is more relevant than rebuilding a general tenure or family pattern as "a copy" of an observed situation, because the past social dynamics are also included. Whereas one can find less than 60 year old villages in the Zermou or the Fakara sites, none can be found in the site of Gabi. Therefore, because their dynamics are older than the duration of the simulation period (60 years), some Nigerien areas, as Gabi, cannot be wellsimulated: the simulated outputs may well represent what could have been observed at the time, but do no longer correspond to the present time. If we suppose that the fecundity are quite equivalent for the three sites, it shows that the dynamics in the latter are older and that this difference should be taken in account: the history of the land conquest should be included to understand the present time dynmics of farming systems in Niger.

New phenomena may appear in simulations longer than the 60 years we implemented, as land scarcity will then operate for the different sites. However, pursuing the simulation beyond the 60 years bound may encounter practical simulation limitations as simulation time requirements are exponential. In any case, pursuing simulation by extending the scenario without offering some adaptation processes to the population will obviously show population and environmental crashes in a Malthusian approach. New simulation approaches that include social evolutions may bridge the gap between sociological and agro-economic analyses and thereby open the vision of different futures of these societies.

Figure 2 .

 2 Figure 2. Unified Modeling Language architecture of the SimSahel model

3 .

 3 Yearly average quantity of saved millet per concerned inhabitant inorganic fertilizers. Therefore, simulating present time inorganic fertilizers use would require implementing a full-saturated context in Gabi. Zermou farmers show a different behaviour at the start of simulations, largely due to their particular strategy of fields extension to compensate for their lower yields. The first 25 years shows that, as long as the manpower/population ratio remains favorable and new fields can still be cleared, one observes a growing use of inorganic fertilizers. At the time land is fully occupied, reducing drastically the interest for farming, fertilizer use declines until a quasi-zero level.

Figure 3 .

 3 Figure 3. Comparison between the three sites of simulation output means concerning development action impacts 4.3.2 Two development proposals targeting different groups of populations

Table 1 .

 1 Factors of differentiation between the three sites

			Zermou			Fakara			Gabi
	Location	Zinder Region, Eastern Niger	Tillabery Region, Western Niger	Maradi Region, Central Niger
	Annual rainfall	Mean: 350 mm Variability: [70-525 mm]	Mean: 450 mm Variability: [180-675 mm]	Mean: 550 mm Variability: [275-775 mm]
	Average soil fertility		Poor			Average			Good
	Soil arability proportion	Valley	Plain	Stony hills Valley	Plain	Plateaus	Valley	Plain	Hills
	(%°)	0.1	69.9	30.0	3.9	79.6	16.5	18.1	60.0	21.9
	Initial Agronomic potential *	2	1	0 Transport costs: 5 kFCFA
									Racket risks: 0,5%
	Women activity		Sheep raising		Sheep raising & gardening		Sheep raising
	Men activity	Farming, migration & gardening	Farming & migration	Farming, migration & gardening
	Present time inheritance system 4		Local traditional		Local traditional		Local Muslim

Table 2 .

 2 Combination of scenarios and abbreviations

	Sites	Control	Fertilizers	Warrantage	Warrantage + Fertilizers
	Zermou	ZEC	ZEF	ZEW	ZEFW
	Gabi	GEC	GEF	GEW	GEFW
	Fakara	FEC	FEF	FEW	FEFW

Table 3 .

 3 Comparison between the four Fakara scenario simulation outputs and external available data Data reported by different authors are actually highly variable among each other, particularly regarding herds: livestock ownership simulation outputs fit better with observations of Loireau-Delabre (1998) and Tahirou

	Livestock owned per family

Table 4 .

 4 Indicators and ratio comparison between project user families and the average population

	For the sites of Gabi & Fakara taken	Inorganic fertilizers using population	Warrantage using population
	together
	Family characteristics compared to the
	average population

Choosing between "famine" and "food shortage crisis" to describe what actually happened in

reflects the political position in the development arena 2 It means that the credit value is the yield portion the farmer let in the warehouse, upon the price at the harvest, usually around 0.15 €/ kg.

Based on our interviews, each marriage can cost 1 150 €, shared within the community. In addition, the dowry should be given to the bride's family (a sum equivalent to two bulls, i.e. almost 300 €). Tabaski, the main Muslim feast, where a sheep should be sacrificed, is a time when sheep prices reach 5 to 6 times the usual price (from around 15 kFCFA ~ 22.5 € up to 90 kFCFA ~ 135 €).

The customary so-called traditional mode is considered as favoring one of the male descendents, usually the elder, by giving him almost all the concerned assets, leaving symbolic elements and some small livestock to the others. The local adaptation of the Muslim inheritance system shares the assets between all the male heirs, splitting half of the leg to the brothers of the dead and half to his sons.

The best moment for observation was the time when both social groups were encountering, during meetings, visits and interview times.

It often happens that this depends on their own frustrations, which means that we had to integrate their testimonies in their own political and social context.

It groups all the children but also younger brothers and sisters, and wives for the husbands.

It happens quite often, particularly in the case of Zermou[START_REF] Aquadev | Suivi de la sécurité alimentaire; Région de Zinder : Départements de Mirriah, Tanout et Gouré; Situation octobre 2006[END_REF].

The manpower unit is defined as the Farming Labor Unit.(F.L.U.) For our case and based on our observations, female and male adult manpowers are equivalent (one can even consider that the female manpower is more important locally) and equal to 1. We condition the child manpower capacity on age, i.e. for a child i in the village: Manpower (i) = Age (i) / 20.

We have eliminated the use of livestock as a potential cash source to buy fertilizers, as we never observed anybody selling animals to buy fertilizers in any case. This is consistent with the general assumption that animals should be considered as savings or speculation products by themselves but not as a source for productivity increase investment

The potential acreage for gardening in Zermou is very low compared to the other sites: 0.52% (see Table2)

The generation peak affects migration before farming: migration is allowed for men after 16, even if they are not married, whereas marriage is a prerequisite to become farmers and land "owners". Getting married on the other hand stop the support from their parents for migration, which lower their financial ability to leave.

For the case of Fakara, women manage the gardening activity, which explains the faster redistribution of the income after the generalization of the activity after the year 18, as shown in figure3.6.

For n slices, the coefficient is obtained by the Brown formula (we have chosen n = 5 as used in demographic studies):; Xk: the income of the k slice; Yk: the size of the k slice[START_REF] Dorfman | A Formula for the Gini Coefficient[END_REF].

The initial high values are due to the first trials they manage to get some personal experience with the use of fertilizers.


Germain Lemasson
email: germain.lemasson@univ-ubs.fr

Sylvie Pesty
email: sylvie.pesty@imag.fr

Dominique Duhaut
email: dominique.duhaut@univ-ubs.fr

Increasing communication between a man and a dog

published or not. The documents may come

Increasing communication between a man and a dog

INTRODUCTION

The interaction between man and machine is widely studied and how technology can strengthen the bond between people [START_REF] Judge | Family portals: connecting families through a multifamily media space[END_REF] [START_REF] Judge | Sharing conversation and sharing life: video conferencing in the home[END_REF]. Our team is more interested in the communication between the machine and the animal especially with a dog. And how it can help or improve communication between the dog and his owner. Indeed dogs are loyal companion of humans since 14000 years. Humans and dogs have evolved together [START_REF] Prestrude | Dogs in service to humans[END_REF] [START_REF] Driscoll | From wild animals to domestic pets, an evolutionary view of domestication[END_REF]. Man have first trained dogs in order to help him in is task, hunting dog, shepherd dog. Relatively recently appeared a new type of dog, the service dog. The first ones was trained after WWI for blind soldiers; it is the guide dog that we know today [START_REF] Weiss | Service dog selection tests: Effectiveness for dogs from animal shelters[END_REF].And more recently dogs are trained for assisting person with reduced mobility. These dogs can help people in their daily life; they are also an extraordinary psychological support. The dog is also with the cat the most popular companion animals. He is considered as a member of the family or as a close friend.

In this paper we present our works one how we can communicate with dog through technological equipment.

II. RELATED WORKS

The development of technology for animals is just starting. Several products localization begins to appear on the market. [START_REF] Golbeck | Pet video chat: monitoring and interacting with dogs over distance[END_REF] Golbeck et al conducted a study using a computer to communicate with a dog. Ribeiro et al. [START_REF] Ribeiro | Canine Pose Estimation: A Computing for Public Safety Solution[END_REF] proposed a method to detect the pose of USAR dogs. It uses two 1-axis accelerometer to find the poses of USAR dogs. There method detects the transition between the poses. Results on static activity are really encouraging. [START_REF] Paldanius | Communication technology for human-dog interaction: exploration of dog owners' experiences and expectations[END_REF] Paldanius et al. conducted a study to understand the experiences and expectations of dog owners for communication technology. How they use existing equipment as GPS location. Vernay et al. [START_REF] Vernay | Collaboration hommes, chiens et robots: quels scenarios?[END_REF] have imagined scenario for assistance dog. Our team works with this type of dog and is based these scenario.

III. COMMUNICATION WITH A DOG

A. Context

Our team works in conjunction with the French association Handi'Chien. The Handi'Chien association has trained more than 1,000 dogs in 20 years and getting more and more requests each year. These dogs are trained from birth, and the training lasts two years. The first 6 months of their life, they spend it in a foster family where they socialize and learn basic commands. Then, for 18 months, they are trained in specialized centers where they learn fifty orders. At the end of their training, they are given for free to their new owner. The persons requesting a dog are evaluated to see if they can take care of the dog, they also received a short training on how to act with their dogs. Despite of this preliminary work, some problem may occur. Vernay et al. [START_REF] Vernay | Collaboration hommes, chiens et robots: quels scenarios?[END_REF] exposes the problem and propose solution using technology. We based our work from these scenarios. The first scenario proposes a solution to the problem of the recall that arises when the dog is not in range of sight or of voice. This can happen if the dog has escaped the attention of the owner (pursuit of a cat) or simply if the dog is in pause; it is allowed to move away from its owner. The dog must return to its owner. In the case of a person with a disability, it does not necessarily have the voice power and mobility necessary to regain the dog's attention. In this situation a robotic system can serve as an intermediary between the owner and his dog. This type of situation occurs outdoor in open fields. This means the robotic system must be carried by the dog to communicate with him wherever he goes.

B. Communicating with the dog

Communication is something that is done in both directions. On one hand we have information transmission from the owner to the dog and on the other hand we have information transmission from the dog to the owner.

In order to send information to the dog, we consider 5 channels which are the five senses: view, hearing, smell, touch, taste. We thought of means on how to stimulate each of his sense. Tab. 1 shows some of the means we plan to use.

The order of importance of the senses in dogs is different from the order in humans. The most important sense of the dog is the smell then the hearing and only in third position the view which are our first sense. Dogs communicate between them using smell pheromone. But it's not how we communicate and using this channel is not easy. We can still use it like with some anti-bark collar equipped with spray of lemongrass which is an odor dogs hate. Our best sense, the view in our context is also not the best way to communicate. We can't put a screen in front of the dog and dogs are shortsighted. However dogs are really receptive to pointing, like when you point an object with your finger. It also works with laser pointer so it's a good option. Hearing is our common second best sense we both use it to communicate and dogs understand humans speaking they can memorized 50 orders, plus some name of object. Hearing is definitely the best way to communicate with a dog. So this is the first sense we try to use to communicate with the dog. The other part of the communication is getting information from the dog to the owner. The first information that can be useful for the owner is where is his dog if is not next to him. The dog might be hidden by a corner of a street or in a park he may be one or two hundred meters ahead from him. A second information is how is the environment of the dog. Is there anything that keeps is attention? Other animals or people? A third information is the activity of the dog. What is he doing, is he running or just laying down ? We think these three information allow the owner to know the situation of his dog so he can send new orders or just see if his dog understand the previous one.

Sense

C. Realisation

We develop two prototypes. The first prototype is a harness equiped with speakers connected to a smartphone fasten too the harness Fig. 4. Fig. 5.. The owner of the dog recorded basic order: "seat", "lay down", "to your place" and "good" for the gratification when the dog respect an order. We use recorderd orders and not generatred voice in order to keep good intonations. They are put on the smartphone one the back of the dog. Then the smartphone is connected to two amplified speakers fixed to the harness below the ears of the dog. The vocal orders can be triggered remotly with a second smartphone. The two smartphones run on androids and communicates using the standard Wi-fi Direct which allow us a distance of 50 meters between the two smartphone without too much delay. This prototype use only vocal order however the next one will combine more chanel. We think it's primordial for the system to make physical gratiphication, like vibration or simulated cuddle.

We made a second prototype to detect the activity of the dog. We also use two smartphone for this prototype but this time we use the 3-axis accelerometer and 3-axis gyroscope sensors. The smartphone is placed on the back of the dog. The orientation of the sensors is shown in Fig. 1. Y to the dog's head, X to his right side and Z perpendicular to his back. We choose to start by detecting four basic activities, sitting, laying down, running, walking. Fig. 2. describes the data flowchart of the presented method. Data are collected by the smartphone 1 on the back of the dog then sent to the smartphone 2 in the hand of the owner of the dog which performs the detection. After a first data collection we conclude that the accelerometer z-axis and the gyro z-axis are sufficient to determine our four basic activities. The single z-axis accelerometer can even be sufficient but we chose to add the z-axis gyroscope for more reliability.

Walk Run z-axis accelerometer z-axis gyroscope Tab. 2. Data collected Tab. 2. shows the collected data. The x-axis of the curves is the times in second (3 seconds) and the y-axis is the values returned by the z-axis of the sensors. We clearly see the periodicity of the signal. We use a low pass filter and a FFT (Fast Fourier Transform) [START_REF] Bracewell | The Fourier transform and its applications[END_REF] with a two second window to get the maximum amplitude and the periodicity of the signal. For the sitting and the running the signal are flat. However for the sitting activity, the mean of the signal is less than G the gravitational constant, unlike the 3 others activities where the means are close to G. These data are sent to the smartphone of the owner. We use the method of the nearest neighbor, a supervised learning method. In a fist phase we know the activities corresponding of the data and we label it. At the beginning of the detection phase, the training data are scaled and placed in a 5-dimensional space. Then each received data is scaled and we use the Minkowski distance (generalization of the Euclidean distance) to find its nearest neighbor. The activity is determined by the activity of its nearest neighbor.

For the positioning problem we use the A-GPS service available on the smartphone on the back of the dog and send the position to the smartphone of the owner which displays it. Fig. 3. shows the interface of the owner.

IV. EXPÉRIMENTATIONS AND RESULTS

The aim of the experimentation with the prototype using speakers is to see if the dog will obey to the recorded order if is not in eye contact with is owner. The orders are recorded using the voice of the owner. We put the dog alone in a room where we place webcams to see the reaction of the dog and a pillow that he recognizes as is place. Then we triggered the order. The first order was sit down, at first the reaction of the dog was astonishment, he didn't understand where the voice coming from and searched his owner. We triggered the order two more times and he finally sit. We repeat the experience with the other orders. Each time we must triggered the orders two or three time to be obeyed but he was less and less surprised. These results are really encouraging for our project. Tab. 3. shows the result our experimentation. Errors in the lying position are mainly due to the position of the smartphone on the harness. Indeed, when the dog was lying but lifts high enough his head the harness and the smartphone fell slightly like if the dog was sitting down. The overall percentage of detection on our experiment is 83 %.

V. CONCLUSION

In this paper, we introduce our first ideas on how a system can communicate with a dog. With the experiments done with our prototypes we see that a dog can obey to registered vocal order out without the presence of his master and we can detect remotely the activity of the dog. We are actually working on a new harness which combines multiple stimuli: vibration, voice and physical pressure. This new is in test with he educators and we expect results soon. Another important part of our works will be the design of the software on the side of the user. As indicated by [START_REF] Paldanius | Communication technology for human-dog interaction: exploration of dog owners' experiences and expectations[END_REF], the importance of the user interface is really important. It must be easy to use and meets the expectation of the user. In our case we have two type of user: the dog educators and the disabled people. The interface must be adapted to each type of disease.

Fig. 1 .

 1 Fig. 1. Dog with a smartphone on is back.

Fig. 2 .

 2 Fig. 2. Data flowchart

Fig. 3 .

 3 Fig. 3. Interface of the owner

Fig. 4 .Fig. 5 .

 45 Fig. 4. First dog equiped with HP on harnaess

ACKNOWLEDGMENT

This work is supported by French National Research Agency (ANR-012-BLAN).


Pascal André

Jean-Marie Mottu

Gilles Ardourel

Building Test Harness from Service-based Component Models

Keywords: Test Harness, Model Conformance, Test Tool, MDD

In model-driven development, the correctness of models is essential. Testing as soon as possible reduces the cost of the verification and validation process. Considering separately PIM and PSM reduces the test complexity and helps the evolution of the system model. In order to test models before their final implementation, we propose an approach to guide the tester through the process of designing tests at the model level. We target model testing for Service-based Component Models. The approach produces test harness and provides information on how to bind the services of the components under test and how to insert the relevant data. The tests are then executed by plunging the harness into a technical platform.

Introduction

Testing as early as possible reduces the cost of Verification and Validation (V&V) [START_REF] Shanks | Using ontology to validate conceptual models[END_REF]. In Model-Driven Development (MDD), V&V is improved by directly testing models for correctness [START_REF] Gogolla | Validating uml and ocl models in use by automatic snapshot generation[END_REF]. Testing models helps to focus the effort on the early detection of platform independent errors, which are costly when detected too late. Testing models does not consider implementation specific errors and thus reduces the complexity of testing [START_REF] Born | Model-driven development and testing -a case study[END_REF]. Designing the tests on models ease their adaptation when models are refactored. However, building and running tests on models remain a challenge. We target service-based component models with behaviour, including data and communications. The specification detail level is sufficient enough to enable various kinds of test at the model level. While testing such software components, the encapsulation should be preserved. Therefore, finding where and how providing test data is difficult: variables are accessed through services, which are available from the interface of the component but also from other required services. Designing the test fixture of a service implies a sequence of service calls additionally to the component initialisation. In [START_REF] Gross | Component-based Software Testing With Uml[END_REF], Gross mentioned issues in Component-Based Software (CBS) testing: testing in a new context (i.e. development context one, deployment context ones), lack of access to the internal working of a component. Ghosh et al. [START_REF] Ghosh | Issues in testing distributed component-based systems[END_REF]. also identify several problems: the selection of subsets of components to be tested and the creation of testing components sequences. Our work is concerned with these issues.

We consider the building of test harness for unit and integration testing dedicated to Service-based Component Systems. Test harnesses are used to provide test data, to run the test, to get the verdict (fail or pass). We create test harness from the platform independent model (PIM) of the system under test (SUT) and from test intentions. Those intentions declare which services are tested in which context, with which data. The tester incrementally builds a harness to run the test in an appropriate context, especially without breaking the encapsulation. The tester needs assistance for this task.

In this paper, we propose an approach assisting the test of service-based component models. This approach integrates the tests at the model level and is provided with tools. First, we propose operating at the model level, we modelise the tests at the same abstraction level as the component model. We build test harnesses as component systems made of Components Under Test (CUT) and Test Components (TC), which are created to test. As a consequence, the assembly of test components and regular components can benefit from the development tools associated with the component model. Additionally, test components could be transformed into platform specific models, thus capitalising the early testing effort. Second, we propose a guided process to assist the tester to manage the complexity of the component under test. The test harness is obtained from transformations of the SUT, guided by the test intention, enriched by test components, and assisted by several analyses and heuristics proposing relevant information and ensuring model correctness through verifications. Third, we illustrate the approach on a motivating example, a platoon of vehicles. We have developed a set of prototype tools designed to experiment the proposals. It is implemented in COSTO, the tool support of the Kmelia component model [START_REF] André | Using assertions to enhance the correctness of kmelia components and their assemblies[END_REF].

Testing Service-based Component Model

This section introduces the testing of service-based component model and the challenges to be tackled. It describes our approach on a motivating example.

Service-based Component Model

A component system is an assembly of components which services are bound by assembly links. The interface of a component defines its provided and required services. The interface of a service defines a contract to be satisfied when calling it. The service may communicate, and the assembly links denote communication channels. The set of all the services needed by a service is called its service dependency. The required services can then be bound to provided services. These needs are either satisfied internally by other services of the same component, or specified as required services in the component's interface and satisfied by other components. A composite component encapsulates an assembly. In the example of Figure 1, the component c: Client requires a service provided by the component s : Server, through an assembly link. This assembly is illustrated with the SCA notation [START_REF] Osoa | Service component architecture (sca): Sca assembly model v1.00 specifications[END_REF]. We extended the SCA notation (right part of the legend of Figure 1) to make explicit the dependencies and data useful for testing: (i) typed data define the component state, (ii) services access these variables, (iii) provided services internally depends on required services.

Figure 2 represents a motivating example: a simplified platoon of several vehicles. Each vehicle computes its own state (speed and position ) by considering its current state, its predecessor's state, and also a safety distance between vehicles. Each vehicle is a component providing its speed and position and requiring predecessor's speed and position. Three vehicles are assembled in that example. Each vehicle provides a configuration service conf initiating its state, a service run launching the platoon and requiring the service computeSpeed to calculate new position and speed. The leader is another component controlling its own values according to a position goal.

Testing Components at the Modelling Stage

Conformance testing aims to control that system under test behave correctly according to their specification. With Service-based Components, we test that the behaviour conforms the specification of their interfaces. In the context of Service-Based Component Applications, the test harness is designed by selecting the components under test, replacing their clients and their servers (the first with mocks, the last with test drivers), then providing test data to the test drivers and getting their verdicts [START_REF] Rocha | A method for model based test harness generation for component testing[END_REF]. Test harness should preserve component encapsulation. JUnit classes are an example of test harnesses for Java OO programs.

In MDD, Service-based Component System is modelised with a PIM, and part of its components (the SUT) is tested depending on a test intention. The test intention defines for each test which part of the system is tested (component(s)), with which entry point (a service), in which situation (SUT state), with which request (service call with parameters), expecting which results. At the beginning, the test intention is tester's knowledge, then she has to concretely prepare and run the test to get a verdict from oracles.

Testing such a SUT is not just creating test data and oracles, the difficulty is to consider components in an appropriate context (assembly of components), to run the test data on them, get the output to be checked with the oracles. The building of test harness to fulfil this task is an important work. Moreover, the process of creating a test harness is not trivial for models of components.

We consider several characteristics making the test of component models an original process: (i) Early specifications are often too abstract or incomplete to be executable. In order to test service-based component, we have to execute it in a consistent environment: its dependencies have to be satisfied by compatible services and every operation used in the environment has to be concrete enough or bound to a concrete operation. Furthermore, its environment must be able to run test cases. (ii) In strongly encapsulated components, finding where and how to insert data is challenging: variables are usually only accessible through services and some data is required from external services. (iii) At the model level, tests should be designed as models. Describing test artefacts like mocks and drivers in the component modelling language provides several benefits: it is easy to communicate with designers; tests follow the same validity rules as the model for both consistency and execution, allowing the use of the development tools associated with the component model. (iv) Models are subject to frequent refactoring or even evolutions, which can compromise the applicability of existing tests.

In this work, we are concerned with the building of test harness for servicebased component models. The tester chooses the components and their services she tests (defined with the test intention). She orders the tests. She creates the test data based on existing works considering the specification of component: work of [START_REF] Lei | State based robustness testing for components[END_REF] with state machines, work of [START_REF] Schätz | Integrating component tests to system tests[END_REF] performing LTS behaviours testing, etc. She creates oracles, for instance, based on the contracts usually available defining a service interface. Our approach assists the tester in building the test harness allowing her to run such test data and to apply such oracles.

Assisting the test harness building

The construction process takes as input the System Under Test (SUT) model which is a PIM (Platform Independent Model) and a test intention (Figure 3). It is made of three activities (transformations). The first one builds the test harness as an assembly with the SUT in a Test Specific Model (TSM) at the model level. The second composes the harness with a Platform Description Model (PDM) to get an executable model (code). During the execution, the concrete data providers give the test data needed to run the test, and the concrete assert functions return the verdicts. Designing the oracles and the data sets influences the operational level. This point is out of concern in the rest of the paper.

Test Harness Construction

This section explains how the tester is guided to build a consistent test harness. As noted in [START_REF] Ghosh | Issues in testing distributed component-based systems[END_REF] (and filed under the issue C3), it is sometimes necessary to consider different subsets of the architecture when testing a component, because of the influence (e.g. race conditions) of the other components on the SUT. The test harness is designed by (i) selecting the relevant subset of original components and services to test, (ii) replacing all or parts of their clients (resp. servers) by test drivers (resp. mocks), (iii) providing data sources. The test intention serves as a guideline during the construction process.

As an example, we are intent on testing the conformance of the computeSpeed ( safeDistance : Integer ) : Integer service of the mid component with the following safety property: the distance between two neighbour vehicles is greater than a value safeDistance. The service behaviour depends on (a) the recommended safe distance from the predecessor, (b) the position and speed of the vehicle itself and its predecessor. Coming back to the example of Figure 2, testing the computeSpeed service of mid implies to give a value to the safeDistance parameter, to initialise the values of the pos and speed variables, which are used by the computeSpeed service and to find providers for pilotspeed et pilotpos which are required by computeSpeed. Only one component vehicle is under test here because other ones are not necessary to test the computeSpeed service, but a more complex architecture could have been retained.

The challenge for the tester is to manage the way these data can be provided. They can be provided by the test driver, by the configuration step, or by other components (original components or mock components). Finding the service to be invoked in order to set the component in an acceptable state for the test is not trivial. Our goal is to help the tester to manage this complexity, in order to reduce testing effort. At this stage, assisting the harness building consists in: In the TSM of Figure 4, the vtd test driver is responsible to put the computeSpeed service in an adequate context (providing input data and oracle). The service testcase1 of vtd contains only a computeSpeed call and an oracle evaluation. To fix the computeSpeed requirements, the test designer could (1) ask for mock components (with random values), (2) reuse the first component coming from the SUT (and fulfil the requirements of first ...) or (3) design its own mock. This variability enables several kinds of test and answers to the issue C3 of Ghosh et al. [START_REF] Ghosh | Issues in testing distributed component-based systems[END_REF]. Note that a single integer mock component im1 is used here because it offers a better control of the delivered speed (intdata1) and position (intdata2), but a harness with two independent integer mocks providing a single intdata service would also be possible.

The data of computeSpeed test harness are bound in the following way: (a) the safeDistance parameter is assigned in the call sequence of the test driver, (b) the position and speed (pos and speed variables) of the mid vehicle under test are bound to the conf service of mid, (c) the im1 mock component playing the role of the predecessor is configured to return the position and speed of the predecessor.

Mappings and Transformations

According to the MDD principles, the test will be executed by composing the test harness with the PDM (Figure 3). The test data and test primitives (oracle...) are provided by the PDM test support or implemented by the tester. The PIM may include primitive types and functions (numbers, strings, I/O...) that must also be mapped to the code level. These mappings are predefined in standard libraries or user-defined. High-level TSM primitives are connected to low level (PDM, code) functions, as illustrated by Figure 5. If the mapping is complete and consistent, then the model is executable. The goal of the Mappings and Transformations activity (Figure 3) is to fix this composition. Each service involved in the test must be executable in a consistent environment: its dependencies must be satisfied by compatible services, and every operation used in the environment must be sufficiently concrete or related to a specific operation. Every abstract type should be mapped to a concrete type. At this stage, assisting the harness building consists in (1) detecting missing mappings between the TSM and PDM (Executability), (2) proposing tracks for the missing mappings based on signatures, pre/post conditions... (all the primitive types and functions are mapped to concrete ones, the test data inputs have concrete entry points), (3) generating standard primitive fragments (idle functions, random functions...). The mappings are stored in libraries in order to be reused later and the entries can be duplicated to several PDM. This activity induces an additional cost at model level, but the errors detected are less expensive to solve than those of components and services. Moreover, if the component model is implemented several times targeting several PDM, the tests would be reused and part of the behaviour would have been checked before runtime, as proposed here.

The test process of Figure 3 has been instrumented using the COSTO/Kmelia tool 1 . Kmelia is a wide-spectrum language dedicated to the development of correct components and services [START_REF] André | Using assertions to enhance the correctness of kmelia components and their assemblies[END_REF]. Kmelia includes an abstract language for computations, instead of links to the source code as in related languages like SCA, AADL, Sofa or Fractal. This layer is useful to check models before transforming to PSM. Kmelia is supported by the COSTO tool, a set of Eclipse plugins including an editor, a type checker, several analysis tools.

The test harness construction has been experimented on the platoon example. The goal was to build a harness to test the conformance of the service computeSpeed as introduced in Section 3.

-The test intention is a special Kmelia component, where only the name and description are mandatory. This trick enables to reuse the tool facilities and to consider test design at the model level. -During the process, the building tool (1) starts from a test intention, (2) asks the user to select target system and services (or proposes some if the test intention is detailed), (3) displays the board to match the test intention with the SUT (Figure 6), (4) proposes candidates, (5) checks the correction and testability properties, (6) goes back to step (2) until the TSM is complete, (7) checks the executability properties and proposes candidates (from the libraries) for the missing elements, (8) generates the code.

A web-appendix 2 shows the details of this example. The harness building activities (transformations, decisions, assistance and generation) are implemented and integrated as COSTO functionalities. We developed the PDM framework in Java (7 packages, 50 classes, 540 methods and 3400 LOC). The service instanciation uses Java threads with an ad-hoc communication layer based on buffered synchronous channels (monitors). We keep strong traceability links from the code level to the PIM level for a better feedback on errors and also for animating the specification at the right level (GUI). We add specific support for contract checking (assertions and oracles).

Compared with the Junit practice, the tester could focus on the "business" part and did not need to care with Java details of the implementation. While the specification of the components was available, the tester could not modify them to make the test case more easy to write. He discovers the specification elements on-the-fly when mapping them to the test intention. In [START_REF] Edwards | A framework for practical, automated black-box testing of component-based software[END_REF], Edwards outlines a strategy for automated black-box testing of software components. Components are considered in terms of object-oriented classes, whereas we consider component as entity providing and requiring services.

In [START_REF] Zhang | Test-driven modeling for model-driven development[END_REF], Zhang introduces test-driven modeling to apply the XP test-driven paradigm to an MDD process. Their approach designs test before modelling when we design test after modelling. In [START_REF] Lei | State based robustness testing for components[END_REF], the authors target robustness testing of components using rCOS. Their CUT approach involves functional contracts and a dynamic contract. However, these approaches apply the tests on the target platform when we design them at the model level and apply them on simulation code.

Conclusion

In this paper, we described a method to integrate testing early in an MDD process, by designing test artefacts as models. The test designer is assisted in building component test harnesses from the component model under test and test abstract information through a guided process. The COSTO/Kmelia framework enabled to implement the process activities and to run the tests on the target specific execution platform with a feedback at the model level. The benefits are a shorter test engineering process with early feedback.

In future work, we will study different kinds of oracle contracts in order to find which logics are best fitted to express them in a testable way as well as ensuring a good traceability of the verdict. We will apply mutation analysis on the models rather than on the generated code because such an approach can be integrated in MDD while respecting the hypotheses of the mutation analysis.

Fig. 1 .

 1 Fig. 1. Component and service notation

Fig. 2 .

 2 Fig. 2. Example of a component model of the Platoon system

Fig. 3 .

 3 Fig. 3. Testing process overview

1 .

 1 Detecting missing features between the SUT and the test intention. This detection is achieved by the verification of two properties: (a) Correctness. All the service dependencies are satisfied in the scope of the test harness. No pending or incompatible dependencies remain. (b) Testability. All the formal test data are linked to values in the TSM (variables, parameters, results...). 2. candidates for the missing features: which service can configure data, can handle the test data or can fulfil missing required services? 3. Generating and linking test components (mocks, drivers as mirror services, bindings, abstract functions...).

Fig. 4 .

 4 Fig. 4. A TSM : test harness for the mid component's service computeSpeed (SUT)

Fig. 5 .

 5 Fig. 5. Test harness Concrete data and Function Mapping

Fig. 6 .

 6 Fig. 6. Component and service notation

http://www.lina.sciences.univ-nantes.fr/aelos/projects/kmelia/

http://www.lina.sciences.univ-nantes.fr/aelos/download/ModeVVa_app.pdf