Meriem Riahi

Faouzi Moussa
email: moussa<maddouri@ensi.rnrt.tn>

Christophe Kolski
email: kolski@univ-valenciennes.fr

Mohamed Moalla

Use of interpreted petri nets for human-machine dialogue specification in process control

Keywords: User Interface (UI), Human-Machine System (HMS), Formal specification, Interpreted Petri Nets, Dialogue modelling

This paper studies an approach for designing graphical Interfaces for process control. This approach is based on a formal modelling of the Human-Machine System behaviour. This modelling allows the deduction of the user requirements and then, the identification of the interface objects. The formal aspect permits the validation of the generated specifications before proceeding to the automatic generation of the interface. A formalism using Interpreted Petri Nets is here proposed for modelling the Human-Machine dialogue.

Introduction

With the considerable evolution of computer sciences and the important use of software designed to control automation's applications with high degree of security, the role of the User interface (UI) becomes preponderant. Many researchers were tended towards design and development of UI. Within these researches, several models and approaches were defined. Many tools for interface generation were also proposed. Our works can be divided into two main points : (i) the choice of a rigorous formal tool adequate to the application's context ; (ii) the perfection of a design approach for graphical user interfaces. This paper starts with a brief critical synthesis of related works on these two points. Then, it describes the proposed approach for UI design, focusing on the modelling of human-machine dialogue.

Related Work

Researches, nowadays, are oriented more and more to formal approaches. In fact, only formal techniques allow the designers to describe the external behaviour of any system without considering the implementation context. These techniques permit also the validation of specifications before proceeding to the effective UI generation. They are recommended specially for complex and critical systems such as industrial processes [START_REF] Turner | Using formal description techniques : An introduction to ESTELLE, LOTOS and SDL[END_REF]. So, it is very interesting to use a formal technique for specifying UI for process control. But, which technique must we choose?

In literature, we can find several formal specification languages based on different theories: universal algebra, typed logic, theory of sets (Z, VDM, B) or automatons theory (state transition diagrams, Petri Nets,…). Each of these families, has a predilection domain (data processing, real time, protocol management,…), a community of researches and users and a number of variants or disciplines [START_REF] Monin | Comprendre les méthodes formelles : panorama et outils logiques, edition masson[END_REF].

Particularly, in the field of human computer interaction, some formal methods were proposed by different researchers. The state transition diagrams were proposed since the 60's, for modelling the screens chaining [START_REF] Parnas | On the use of transition diagrams in the design of user interface for an interactive computer system[END_REF]. State transition diagrams were then proposed by Jacob for direct manipulation interfaces [START_REF] Jacob | A state transition diagram language for visual programming[END_REF]. They were followed by Petri Nets [START_REF] Williem | Extending Petri Nets for specifying Man-Machine dialogues[END_REF] [START_REF] Mahfoudhi | TOOD : Une méthodologie de description orientée objet des tâches utilisateur pour la spécification et la conception des IHM : : Application au contrôle du trafic aérien[END_REF], to which we can associate the ICO formalism [START_REF] Palanque | Spécifications formelles et systèmes interactifs : vers des systèmes fiables et utilisables[END_REF], then, temporal logic and LOTOS [START_REF] Paterno | On the use of Lotos to describe graphical interaction[END_REF], the Z formalism [START_REF] Harrison | formal methods in human computer interaction, Harrison & Thimbelby[END_REF], the LUSTRE language [START_REF] D'ausbourg | Deriving a formal model of interactive system from its UIL description in order to verify and to test its behaviour[END_REF] and recently B method [START_REF] Ait-Ameur | A uniform Approach for specification and design of interactive systems : the method B, DSV-IS'98[END_REF].

What one can reproach , mainly, to techniques like Z, lotos, or Lustre, is the difficulty that exists in reading and manipulating their notations. This limit is removed with graphical techniques like state charts and Petri nets. The latter (technique of Petri Nets ) seems to be particularly adapted (suitable) for modelling the dynamic aspect of human-machine dialogue in the particular context of process control. Petri nets are expressive for event's aspect, synchronism and parallelism, as much pertinent criterias for constraints of interactive graphical interfaces. Moreover, Petri nets have been already used for human machine dialogue modelling [9] [14] or human task description [START_REF] Mahfoudhi | TOOD : Une méthodologie de description orientée objet des tâches utilisateur pour la spécification et la conception des IHM : : Application au contrôle du trafic aérien[END_REF]. They are, here, proposed for modelling human-machine system (HMS) behaviour and interface objects, as explained further.

For methodological viewpoint, we can notice that most of the approaches proposed in literature, apprehend only one aspect of the interface design problem. Considering, especially, the researchers focusing on using Petri Nets, some observations should be notified :

-Palanque propose to model the interactive application's interface using the ICO formalism (Interactive Cooperative Objects) [START_REF] Palanque | Spécifications formelles et systèmes interactifs : vers des systèmes fiables et utilisables[END_REF]. This provides a formal specification of the UI and its behaviour which allows a functional analysis and a possibility of the specification's validation. But, his approach is based on an object oriented method. This method doesn't explicit the principle of interactive objects' identification. He leaves that to the common sense of the designer.

-With the TOOD method [START_REF] Mahfoudhi | TOOD : Une méthodologie de description orientée objet des tâches utilisateur pour la spécification et la conception des IHM : : Application au contrôle du trafic aérien[END_REF], Mahfoudhi propose a design approach based on an hierarchical decomposition of the HMS in tasks modelled using Petri Nets. This allows the identification of user requirements. An object design method of the UI is then proposed. But, there is many problems, not yet resolved, to which the designer is faced for automatic generation of the interface.

-No one, of the authors, take into consideration, the dysfunctionning modes in their HMS analysis. Nevertheless, it is a crucial aspect for the critical systems.

-Concerning the particular industrial applications, the Ergo-Conceptor system [START_REF] Monin | Comprendre les méthodes formelles : panorama et outils logiques, edition masson[END_REF] presents an ergonomic approach for the interface design allowing an automatic interface generation. However, in this approach, there is no indication to how identify the user requirements. It allows only a static interface generation. It didn't consider the dynamic aspect of the interactive objects and the human machine dialogue.

In view of these limitations, our objective is to propose a most possible completed design approach for automatic interface generation for process control. A synthetic presentation of this approach, is first, advanced in this paper. Then, we focus on the formalisation of the human-machine dialogue using Petri nets.

Proposed approach

In the proposed approach, we try to benefit from the advantages of different previous works. We aim, especially, to satisfy these points :

-analyse different functioning contexts (normal and abnormal functioning) as well as the operator's tasks, -identify the user requirements from this analysis, -automate the deduction of interface objects, -benefit from formal techniques to specify the interface, the objects and their behaviours, -use guidelines for objects' presentation, -verify the specifications before automatic generation.

The proposed approach is made up of six steps (figure1). First, a step of process analysis is needed. It provides a document containing the process data and the different technical and functional constraints. Then, a second analysis of the hole HMS in terms of the process, its command system and the operator's tasks, is carried out. The dynamic aspect of the HMS is modelled using Petri nets. The third step concerns the identification of the user requirements in terms of interface objects from previous analysis. The interface specification is then ensured. We benefit, afterwards, from the formal technique used to verify the generated specifications. The last step of this approach is dedicated for the automatic interface generation.

The principle of HMS analysis and user requirements deduction is explained in [START_REF] Riahi | Vers une spécification formelle des interfaces homme-machine basée sur l'utilisation des réseaux de Petri[END_REF]. This paper focus on the human machine dialogue specification from the HMS's behaviour modelling using Petri nets.

To be lucid, we develop this point, in the sections below, through an industrial pedagogical example. This example is now presented.

Presentation of the example

As first application, we have chosen a simple industrial process which consist on manufacturing metallic products. The process is controlled by an operator in the control room. It consists on : (1) producing the metallic sheets, then (2) covering these sheets with a chemical solution. This solution is obtained by mixing two products C and D. To prepare the product C, we have to mix two other solutions A and B, having variable temperatures and flows (tA, tB, fA and fB). The result C must be at fixed temperature and flow (TC and FC). The operator's task consists, then, in controlling the mixer functioning and intervene when a dysfunctionning appear to restore the normal functioning state of the system.

The step 2 of the proposed approach consists in applying the SADT method to decompose the HMS and identify the appropriate elementary sub-systems. Four sub-systems can be identified in this example: (1) a first sub-system for preparing the different components (metallic sheets, products A, B and D), ( 2) a second sub-system for preparing the mixture C (the mixer), (3) a third sub-system is needed for preparing the chemical solution and (4) the last is for covering the sheets with the chemical solution. We choose to study the second sub-system (the mixer).We suppose, then, that an analysis using the classical and complementary methods (FMEA and FAT) has been carried. This analysis identify two possible panes: (1) deviation of the temperature or the flow of the product C, and (2) the overflow of the storage tank.

Thus, we deduce, principally, three states of this system : a normal functioning state, a dysfunctionning state relative to the deviation of the temperature or the flow of the product C, and a second dysfunctionning state relative to the overflow of the storage tank.

We suppose also, that an operator task analysis was carried out. This analysis identify three essential operators' tasks relative of the three states: a supervision task in normal functioning, a correction task consisting in adjusting temperature and flow of the product C, manipulating different parameters of the system (tA, tB, fA and fB), and an other correction task relevant to the second pane. It consists to empty the storage tank.

We consider, principally, the two latter tasks and we suppose that a task analysis was carried out. This allows the identification of the actions procedures. The arguments of these procedures define the variables which should be manipulated by the operator. They will constitute, afterwards, the user requirements.

This preliminary analysis of the HMS aims to identify the different functioning states of the system and possible interventions of human operator. The purpose is to specify adequate interfaces for the system control. The HMS behaviour is, then, modelled using Petri nets. The principle of this modelling is exposed below.

Modelling the HMS behaviour

The specification of the dialogue component of the UI is the most delicate part in the specification task. In fact, the human-machine dialogue modelling require the detailed description of all of the possible and acceptable states of the interactive application according to possible evolutions [START_REF] Palanque | Spécifications formelles et systèmes interactifs : vers des systèmes fiables et utilisables[END_REF].

In order to succeed this task, we propose within this approach to start by modelling the HMS behaviour using Interpreted Petri Nets [START_REF] David | Du GRAFCET aux Réseaux de Petri[END_REF]. The places represent the HMS states. The evolutions between these states are modelled by the transitions. The Petri net in figure 2, illustrate the modelling of the tank sub-system. The place P1 models the normal functioning state. The places P2 and P3 model respectively the two dysfunctioning states. P4 and P5 model the valuation states after the operator's actions. These states imply nothing at the interface. That's why, they are considered as non observable places and will be ignored in the step of deducting the user requirements. T1 and T2 model the system state changing from the normal functioning state to the alarm states, under the passing conditions c1 and c2. T3 and T4 model the operator's interventions for regulating the system. These transitions aren't really passed unless the operator finish his actions. A3 and A4 are the action procedures associated to these transitions modelling the execution of the operator's tasks. T5, T6, T7 and T8 model the state evolution after the operator's intervention.

Our objective is to identify from the HMS analysis, the appropriate interface objects in first time, then models the human-machine dialogue. The idea is to associate to each state, the appropriate informational variables and to each transition, the necessary command variables. These variables identify the user requirements and then interface objects. This is explained in [START_REF] Riahi | Vers une spécification formelle des interfaces homme-machine basée sur l'utilisation des réseaux de Petri[END_REF].

Two kinds of graphical objects will be considered : informational objects will be associated to the places of HMS model, representing the system's state ; command objects will eventually be associated to the transitions modelling the operator's tasks.

When a transition becomes passable, the action objects associated to this transition will become activated according to the conditions expressed in the action procedures. They will be disactivated after passing the transition. The informational objects associated to the places of the Petri Net, are displayed when a token is put.

Specification of the human-machine dialogue

Once, graphical objects have been identified, the next step consists in specifying this interface in terms of presentation and dialogue. For interface presentation, we propose to benefit from the researches carried out since the eighties, by some researchers [START_REF] Kolski | Two examples of "Tools for working with guidelines" for process control field : Synop and ERGO-CONCEPTOR[END_REF] concerning knowledge-based approaches for automatic evaluation and design of UI used in process control. In fact, there are many ergonomic rules available literature. For instance, Gilmore and al. ( 1989), inspired by their works with the U.S. Nuclear Regulatory Commission (USNRC), have written a handbook of guidelines for user-computer interface design in process control. These guidelines were organised into four categories, namely, (1) video displays, (2) control and input devices, (3) control/display integration, (4) workplace layout and environmental factors. Each guideline was presented in a structured format. Hundreds of guidelines adapted to this particular field (process control) were listed in the handbook.

Several model-based tools for the interface development are described in the literature. The Ergo-Conceptor system, one of these tools, is oriented towards process control interactive applications. So, following the principle of Ergo-Conceptor, our system will be able to decide on the appropriate displays to associate to each sub-system. For that, it will takes into consideration, on the first hand, the characteristics of each sub-system (the list of its functioning states, the user requirements associated to each state,...) and on the other hand, specific formalised guidelines stored in its knowledge bases.

Once, the different graphical displays are identified, we have to specify the presentation and the dialogue associated to each of them. Interface objects are identified according to the user requirements deduced in step 2 of our approach. Their presentations will, also, be chosen according to a knowledge based system, dealing with guidelines, in order to ensure an ergonomic quality. At this level of abstraction, guidelines are more frequent and it is easier to formalise them and to automate their inference.

We focus, here, on the specification of dialogue component. In fact, having the model of HMS behaviour, it is necessary to define the behaviour of the different graphical objects of the interface, in order to model the human-machine dialogue. In fact, each object has an intrinsic behaviour according to the services it offers. So, we have to model the different evolutions of its states in relation to the interface. This evolution (activation/desactivation and display/ mask) is related to the system's evolution. Thus, as the ICO model [START_REF] Palanque | Spécifications formelles et systèmes interactifs : vers des systèmes fiables et utilisables[END_REF], we propose to define for each graphical object a control structure. This structure determine the services the object offers and its different possible states. This structure is described by an Interpreted Petri nets like those proposed for HMS behaviour.

Considering the two kinds of graphical objects identified (informational and command objects), we propose two generic control structure (figure 3). The first concerns informational objects. These objects have principally two states : displayed and masked. The control structure of such object will have two particular transitions. The actions associated to these transitions will ensure the display and the mask of the object. The second type of control structure concerns command objects. A command object has three principle states : masked, displayed/disactivated and displayed/activated. So, four particular transitions are proposed in this structure. One for the display of the object, a second for its mask. The two others are for the activation and desactivation of this object. The principle of dialogue modelling is described by these three points :

1-from initial marking of the HMS model, display all informational objects associated to the marked places. 2-When a transition becomes passable, all command objects associated to it will be displayed/ disactivated. These objects will be activated and disactivated according to the evolution of operator's actions.

3-At the end of the execution of operator's task, all the command objects will be masked. The displays will be refreshed according to rule 1.

An operator task is a combination of actions executed sequentially, in parallel manner or alternatively. This is identified by the task analysis elaborated previously. This can precise the order of the activation and desactivation of command objects. In fact, a transition in HMS model, associated to an operator task, is a 'macro-transition'. It resumes a Petri net which is composed principally of a 'macro-place' and two transitions : 'beginning task' and 'ending task'. The command objects will be displayed and masked respectively on passing these transitions. The 'macro-place' is a Petri net modelling the synchronism and concurrency of the execution of different actions of the task (figure 4).

With such decomposition, and on passing the transition 'beginning task', events for displaying in disactivated state, all command objects associated to this task are generated. Then, these objects are activated and disactivated on passing the transitions 'beginning action' and 'ending action'. These objects are masked on passing the transition 'ending task'.

Ending task

Beginning task

Beginning task

Beginning action1

Ending action1

Beginning action2

Beginning task

Beginning action i

Ending action i

Beginning task

Beginning action i

Ending action i

The macro-transition Task

Case of sequential actions Case of alternative actions

Case of parallel actions

Figure 4 : Decomposition of the "macro-transition" task

The global dialogue is determined by different Petri nets proposed here : Petri net modelling the HMS behaviour and different Petri nets corresponding to the control structures of different graphical objects. The communications between all these nets is insured by production of internal events. The idea is to consider the orders of masking, displaying, activating and disactivating the interface objects as events generated when a token is put on a place or when a transition is passed. The events will, therefore, be produced by the net modelling HMS behaviour. The principle of generating these events is described by these points : 1-the put of a token on a place generate events for displaying informational objects associated. 2-Passing a transition 'beginning task' produce the generation of events for displaying command objects disactivated. 3-Passing a transition 'beginning action' produce the generation of events for activating command objects needed for this action. 4-Passing a transition 'ending action' produce the generation of events for disactivating relative command objects. 5-Passing a transition 'beginning task' generate events for masking all informational and command objects.

Figure 5 illustrates this with the tank sub-system. It contains a Petri net modelling the HMS and 2 Petri nets modelling the behaviour of informational objects, "curve", associated to the informational variables TC and FC. Two other Petri nets represent the control structure of command objects, "command button", associated to the command variables fA and fB. The communication is expressed in this figure by arrows in dotted lines :

express the generation of events for displaying the interface objects, express the generation of events for activating command objects, and express the generation of events for masking informational objects or disactivating command objects.

The communication process between different Petri nets avoid the construction of a global net and the addition of places and transitions.

Conclusion

We have focused in this paper on one of the more difficult steps of any global methodology for UI design : the modelling of human-machine dialogue. We have explained, through an industrial application, the principle of modelling the human-machine dialogue using Petri nets. The next step of this approach concerns the verification of UI specifications before proceeding to the generation its self. We are concentrating, now, on this aspect. We are studying the verification of the Petri nets correctness with the proposed extensions.

Figure 1 :

 1 Figure 1: Methodological framework of the proposed approach

Figure 2 :

 2 Figure 2 : Dynamic modelling of the sub-system "Mixer"

Figure 3 :

 3 Figure 3 : Control structure of Interface objects

Figure 5 :

 5 Figure 5 : Communication process between different Petri Nets


Saaxewer B Diop
email: diop1@llnl.gov

Nicolas Bonod

Marine Chorel

Éric Lavastre

Nadja Roquin

Lilian Heymans

Pierre Brianceau

Laurent Gallais

Laurent Lamaignère
email: laurent.lamaignere@cea.fr

Influence of the multilayer dielectric design on the laser damage resistance of pulse-compression gratings

Keywords: Compression-gratings, Laser-induced damage, high-power laser

Multilayer dielectric (MLD) gratings provide high diffraction efficiency and a high damage threshold. They represent the main solution to compressing a high-power laser beam. However, the laser resistance of MLD gratings limits the power of such facilities. The community devoted a lot of resources to increasing the damage threshold of those components. Today, it is well known that the etching profile plays a key role in the electric field distribution and consequently the laser resistance. In this paper, we focused our optimization on the multilayer dielectric stack to increase the laser-induced damage threshold (LIDT). We numerically and experimentally demonstrated the impact of the MLD stack on the electric field distribution and the LIDT. We manufactured two sets of three samples with identical etching profiles. The calculated electric field intensities were in good agreement with the measured LIDTs. These results demonstrated how to further optimize grating designs through the dielectric stack.

INTRODUCTION

Multilayer dielectric (MLD) pulse compression gratings, due to their high laser-induced damage threshold and high diffraction efficiency, are of particular interest for high-power laser facilities. Svakhin et al. demonstrated first the feasibility of diffraction gratings made with dielectric materials. [START_REF] Svakhin | Diffraction gratings with high optical strength for laser resonators[END_REF] A few months later, Perry et al. demonstrated the improvement of the laser-induced damage threshold (LIDT) of MLD gratings compared to metallic gratings for similar ranges of diffraction efficiencies. [START_REF] Perry | Highefficiency multilayer dielectric diffraction gratings[END_REF] Since the development of the chirped pulse amplification (CPA) technique, [START_REF] Strickland | Compression of amplified chirped optical pulses[END_REF] laser facilities have reached a new level of power. However, the peak power remains limited by laser-induced damage to components located at the end of the laser chain and generally on pulse compression gratings. A lot of studies have been carried out to improve the LIDT of MLD gratings by optimizing the design, manufacturing, and cleaning processes. [START_REF] Xie | Rectangular multilayer dielectric gratings with broadband high diffraction efficiency and enhanced laser damage resistance[END_REF][START_REF] Nguyen | Improvement of laser damage resistance and diffraction efficiency of multilayer dielectric diffraction gratings by hf etchback linewidth tailoring[END_REF][START_REF] Ashe | Optimizing a cleaning process for multilayer dielectric (mld) diffraction gratings[END_REF][START_REF] Britten | Multilayer dielectric gratings for petawatt-class laser systems[END_REF] The efforts were mainly devoted to the etching profile. Néauport et al. demonstrated the significant impact of the etching profile on the electric field intensity (EFI) and the laser resistance. [START_REF] Neauport | Effect of electric field on laser induced damage threshold of multilayer dielectric gratings[END_REF] In particular, for a given period and condition of illumination, small duty cycles must be favored since they allow to strongly decrease the EFI inside the pillars. [START_REF] Bonod | Optical performance and laser induced damage threshold improvement of diffraction gratings used as compressors in ultra high intensity lasers[END_REF] The influence of the dielectric stack on the electric field distribution was investigated to optimize the laser resistance of pulse compression gratings at the PETawatt Aquitaine Laser (PETAL) by fixing the etching parameters. The optimization relies on the reduction of the electric field intensity (EFI). Chorel et al. demonstrated an important improvement in the LIDT of the PETAL dielectric mirrors by modifying the layer thicknesses. [START_REF] Chorel | Robust optimization of the laser induced damage threshold of dielectric mirrors for high power lasers[END_REF] First, from a given MLD stack used for a previous PETAL grating, we defined the etching profile to maximize the diffraction efficiency. Then, we reduced the EFI by modifying the thickness of several upper layers. The electric field distribution and the diffraction efficiency were calculated numerically. Three designs were manufactured to perform laser damage tests to assess the numerical results. From these three designs, we defined a second etching profile by only reducing the duty cycle in order to consolidate our approach. In the end, two sets of three samples with identical etching profiles were manufactured.

NUMERICAL MODEL

Pulse compression gratings of the PETAL facility operate in reflection, in s-polarization with an angle of incidence of 77.2°at a centered wavelength of 1053 nm. To calculate the performance of a grating design, we used a numerical model developed to calculate the diffraction efficiency and the electric field distribution. The model is based on the differential method with fast Fourier factorization and the S-algorithm to solve Maxwell's equations. [START_REF] Neviere | Light Propagation in Periodic Media: Differential Theory and Design[END_REF][START_REF] Popov | Factorization of products of discontinuous functions applied to fourier-bessel basis[END_REF][START_REF] Li | Note on the s-matrix propagation algorithm[END_REF][START_REF] Bonod | Diffraction gratings: from principles to applications in high-intensity lasers[END_REF] The model allows different input parameters to be incremented over a defined range and step, such as etching parameters or layer thicknesses. The model explores all possible combinations using the brute force method and calculates the grating performance of each design. We paid special attention to the supply of samples when designing the gratings. The manufacturing capabilities and constraints of the suppliers have been taken into account. To limit deviations between each design, we considered a single etching profile.

Protocol of optimization

First, we started with a given MLD stack used for previous PETAL gratings. The starting design was [Borofloat / (LH) 10 L / Air], where L and H represent the SiO 2 and HfO 2 layers, respectively. The refractive indexes of SiO 2 and HfO 2 materials are taken to be equal to 1.430 and 1.826, respectively. The etching profile was defined in the top layer with a trapezoidal shape (see Fig. 1). The duty cycle and the slope angle were set to values with the lowest probability of deviation due to the fabrication process at 0.44 and 88°respectively. The period is fixed by the PETAL compressor specification at 562 nm. We do not consider a residual thickness under the pillars, which is a source of potential deviations. We maximized the diffraction efficiency by exploring different values of the etching depth over a range between 400 nm and 800 nm, with a step of 10 nm. The results show that a depth of 590 nm leads to a diffraction efficiency greater than 98% (see Fig. 2). Next, we modified the MLD stack to reduce the EFI. We perform a parametric optimization as a function of the 7 upper layers, which correspond to the 14 th to the 20 th in Fig. 1. The variation range of each layer is equal to 100 nm, with an incremental step of 10 nm. The model explored 10 7 combinations. Designs with a diffraction efficiency greater than 92% were selected.

Numerical results

Figure 3. Representation of the performances in terms of EFI and diffraction efficiency of the 14000 designs selected from the computational model. Only designs with a diffraction efficiency greater than 92% were selected. Each design is represented by a square plotted in terms of the EFI and diffraction efficiency associated with the design. The green dots represent the 3 designs selected for the fabrication of the samples.

Figure 3 represents the distribution of the 14,000 solutions selected that exhibit a diffraction efficiency in the -1st order higher than 92%. They are represented as a function of the EFI and diffraction efficiency. In the narrow 92%-93% efficiency range, we observed that gratings show discrepancies in EFI values up to 13%. It clearly shows the impact of the MLD stack on the EFI values. We selected three designs to manufacture samples (see Fig. 3): design 1 represents the design with the lowest EFI value; design 3 represents the design with the highest EFI value and a similar diffraction efficiency to design 1; and design 2 represents the third point of comparison and a trade-off between EFI and diffraction efficiency. The top layer thicknesses of each design are detailed in Tab.1 Figure 4 shows the electric field distribution and the variation of the layer thicknesses between each design. The highest EFI value is localized for the three designs on the upper right side of the pillars for an incident beam coming from the left at an incidence of +77.2°.

PROCESS OF FABRICATION

The process of manufacturing the three samples is detailed in Fig. 5. First, the MLD stack was deposited through an e-beam evaporation process on borofloat substrates with a diameter of 200 mm. The supplier responsible for the etching process used UV optical lithography, which is usually used for etching semiconductors. Therefore, a second step was implemented to make the samples compatible with the microelectronics machines. These instruments work with detectors in the visible range. However, the substrate and the dielectric stack are transparent in this wavelength range. A layer of Ti was deposited on the back side of the substrate to opacify it and thus make it detectable by the instruments. A layer of SiN was also deposited to ensure the lift-off of the plates from the sample holder after electrostatic clamping. Then, a back anti-reflective coating (BARC) and a layer of photosensitive resin coating (PRC) were deposited on the dielectric stack with 49 nm and 570 nm of thickness, respectively. The ARC layer aims to reduce reflections at the recording wavelength of the etching pattern, i.e., 248 nm. A binary amplitude mask placed on the optical path of the laser allows for the printing of the etching profile in the PRC. The system can print the pattern over a zone of 22 mm 2 . 5×5 cm 2 centered on the substrate were illuminated by an alternation of expose and non-expose areas to avoid issues of overlapping and pillar alignment during the scanning. Dry etching was performed to etch the top SiO 2 layer. A plasma composed of N 2 O 2 and C 4 F 8 reacted with the solid SiO 2 . The etching depth depends on the reaction time, and during tests, the HfO 2 layer underneath the etching was difficult to identify compared to the SiO 2 layer. To remedy this issue, we have chosen to keep a residual thickness of 30 nm under the pillars. At the same time, we decided to add a second etching profile by increasing the insolation time in order to reduce the duty cycle, i.e., the thickness of the pillars. We applied the second etching profile to half of each sample. In this case, each sample was etched twice (see Fig. 6) In the end, we obtained, on the same sample, two gratings with the same multilayer dielectric design. Finally, a cleaning process allows for the removal of all the reaction residues, especially the PRC and the ARC. Due to the scanning scheme, the etching forms a checkerboard of etched and unetched areas. Figure 7 shows an SEM observation of the final etching. The DC featured by the manufactured grating, estimated at roughly 0.51, slightly differs from the DC used to perform the numerical designs and simulations (DC = 0.44). We found a DC of approximately 0.41 for the second design. We calculated the new performance of each design. We considered possible deviations of the etching parameters over a range of 30 nm (4°for the slope angle) and a step of 5 nm (1°). The results are presented in Tab. 2 and Tab.3 and with average values. The uncertainties correspond to the standard deviation.

LASER DAMAGE TESTS

Laser damage tests were performed on the dedicated optical set-up called DERIC at the French Atomic Commission (CEA-CESTA), described in Ref. [START_REF] Diop | Influence of the multilayer dielectric mirror design on the laser damage growth in the sub-picosecond regime[END_REF] A commercial Amplitude laser source provides a beam centered at 1053 nm with a pulse duration of 800 fs. The output energy is around 2 mJ with a repetition rate of 10 Hz. A 60 cm focal lens focuses the beam to obtain, at the focal plane, a Gaussian beam of diameter 160 µm at 1/e. We performed 1-on-1 damage tests on each sample to determine the laser-induced damage threshold (LIDT). 16 Tests were carried out at 77.2°of incidence (the operating incident angle of the gratings), and 5 shots per fluence were set.

Results are shown in Tab. 2 and 3. In regard to the initial etching profile, it has been demonstrated that design 1 with the lowest EFI max value corresponds to the design with the highest LIDT, whereas design 3 with the highest EFI max value corresponds to the design with the lowest LIDT. Let us point out that the differences in LIDTs are equivalent to the differences in EFIs between each design.

Table 2. 1-on-1 tests results and calculated features of manufactured designs for the first etching profile (DC = 0.51).

Designs

EFI max Taking design 1 as a reference value, an increase of approximately 5% and 12% in EFI was calculated for designs 2 and 3, respectively. Regarding the laser resistance, a decrease of 5% and 13%, for designs 2 and 3 was measured compared to design 1, respectively. The experimental results are therefore coherent with the theoretical results. In addition, the calculation of the theoretical intrinsic damage threshold (LIDT int = EF I max × LIDT ) reveals very close results between designs 1 and 2, but a deviation with design 3. This deviation may be the consequence of manufacturing errors inducing a variation of the EFI max . The intrinsic LIDTs are very close and highlight a final etching profile close to the profile defined in numerical simulations. Regarding the second etching profile, the results are different. We found again that the design with the lowest LIDT is the best design in terms of LIDT. However, the discrepancies between each design are not the ones expected. Even if they are higher than we calculated, these results demonstrate the manufacturing deviation of the etching profile. In addition, the calculation of the intrinsic LIDT merges to the same conclusion with three different values. We assume that the second etching profile is not uniform across all the samples. By fixing the etching profile, we demonstrated an improvement in the LIDT through an optimization of the MLD design. Scanning electron microscopy (SEM) observations (see Fig. 8) of the damage sites provide evidence that a portion of the pillars were ablated during the irradiation (see Fig. 8(c)) while the MLD stack seems to be unaffected. This result, common for both etching profiles, is concordant with the numerical simulations that predict a maximum of the EFI on the nanostructured pillars. [START_REF] Hocquet | The role of electric field polarization of the incident laser beam in the short pulse damage mechanism of pulse compression gratings[END_REF]

EF I 1 EF I i LIDT (J/cm 2 ) LIDT 1 LIDT i LIDT int (J/cm 2 )

CONCLUSION

To conclude, we investigated the influence of the MLD stack on the electric field distribution of compression gratings. The objective was to reduce the EFI by adjusting the thickness of the upper layers. First, we started with a given MLD stack design and defined the etching profile which maximizes the diffraction efficiency. In a second step, we performed a parametrical optimization of the EFI as a function of the thicknesses of the 7 top layers of the multilayer for a specific and constant etching profile. We selected designs with diffraction efficiencies greater than 92%. We obtained designs with similar diffraction efficiencies but with discrepancies in terms of EFI up to 13%. During the manufacturing process, we added a second etching profile to each sample by reducing the duty cycle. Two etching profiles were etched on the same multilayer dielectric design. In the end, we obtain two sets of three grating designs. For the first etching profile, the experimental results followed the numerical predictions of the EFI, and we found an equivalent deviation of the laser damage threshold from the EFI values. These results clearly demonstrate the impact of the MLD stack on the electric field distribution of a grating and consequently the laser damage threshold. For the second etching profile, the LIDT discrepancies between each design are not in good agreement with the calculated EFIs. We assume that the etching profile was not uniform across each sample. However, we still found the designs in the expected order in terms of laser damage resistance.

Manufacturing constraints limit the optimization of the etching profile, which is the most sensitive part of grating manufacturing. Production errors in the etching can impact the performance of the grating, as we demonstrated for the second etching profile. With this approach, it is possible to define a supplier-optimized etching profile and then optimize the LIDT of the grating through the MLD design. The next step of this work will be to find a protocol to optimize the MLD stack and the etching profile at the same time.

Figure 1 .

 1 Figure 1. Schema of a multilayer dielectric grating design. The profile is etched with a grating period d. The pillars have a trapezoidal shape with depth h and a slope angle α. The thickness DC at mid-height of the pillars corresponds to the Duty Cycle (DC = 1 -c 1/2 d )

Figure 2 .

 2 Figure 2. Evolution of the diffraction at -1 and 0 order as a function of the etch depth.

Figure 4 .

 4 Figure 4. Representation of the electric field distribution in the pillars and the top layers of the selected designs 1, 2, 3. Design 1 represents the design with the lowest EFI value; design 3 represents the design with the highest EFI value and a similar diffraction efficiency to design 1; design 2 represents the third point of comparison and a trade-off between EFI and diffraction efficiency. Calculations are performed by considering a plane wave illuminating the grating from the top (superstrate) with an angle of incidence of +77.2°. The maximum EFI value is displayed for each design and the arrow points to the location.

Figure 5 .

 5 Figure 5. Representation of the grating sample process flow. First, the MLD stack is deposited on the borofloat substrate. Then, SiN and Ti layers are deposited on the backside of the substrate to opacify the samples. An anti-reflective and a photosensitive resin coatings are deposited on the MLD stack. Optical lithography records the pattern in the resin, which is then etched to obtain the final structure.

Figure 6 .

 6 Figure 6. Representation and photography of the final samples.

Figure 7 .

 7 Figure 7. Representation and photography of the final samples. Scanning Electron Microscopy (SEM) of the final etching profiles with a duty cycle of (a) 0.51 and (b) 0.41.

Figure 8 .

 8 Figure 8. (a)SEM observations of a laser damage site of 1-on-1 test. The laser shot was performed at high fluence, greater than the LIDT. (b) and (c) represent the same damage sites at higher resolution.

Table 1 .

 1 Top layer thicknesses of the three selected designs.

	Layers Design 1 (nm) Design 2 (nm) Design 3 (nm)
	14	190	210	230
	15	200	280	240
	16	210	160	200
	17	130	240	250
	18	220	230	270
	19	180	250	285
	20	120	100

Table 3 .

 3 1-on-1 tests results and calculated features of manufactured designs for the second etching profile (DC = 0.41).

	1	1.70 ± 0.13	/	3.67 ± 0.01	/	6.23
	2	1.78 ± 0.09 +5%	3.49 ± 0.09	-5%	6.21
	3	1.91 ± 0.08 +12%	3.19 ± 0.01	-13%	6.09
	Designs	EFI max	EF I 1 EF I i	LIDT (J/cm 2 )	LIDT 1 LIDT i	LIDT int (J/cm 2 )
	1	1.33 ± 0.03	/	3.77 ± 0.04	/	5.01
	2	1.41 ± 0.09 +6%	3.42 ± 0.02	-9%	4.82
	3	1.51 ± 0.12 +14%	3.04 ± 0.02	-19%	4.59

ACKNOWLEDGMENTS

We would like to thank the Optical Manufacturing Shop group led by Amy Rigatti of the Laboratory for Laser Energetics for supplying the coating samples and for their interest in developing these dielectric stacks.


Roger Eston

Jeremy Coquart

Kevin Lamb

Gaynor Parfitt

Misperception: No Evidence to Dismiss RPE as Regulator of Moderate-Intensity Exercise

published or not. The documents may come   L'archive ouverte pluridisciplinaire

Misperception: No evidence to dismiss RPE as regulator of moderate-intensity exercise

Shaykevich et al. [START_REF] Shaykevich | Auditory feedback improves heart rate moderation during moderate intensity exercise[END_REF] demonstrate the efficacy of auditory feedback anchored at 75% of age predicted maximal heart rate (HRmax) to regulate intensity (claimed as 'moderate') during several 20-min bouts of cycling. Their technical approach is novel, but 76% HRmax is the upper limit of moderate intensity, so given the large error in age-predicted HRmax, it is unlikely that their exercise bandwidth was 'moderate' for all participants. This is not our major concern, but it reveals one among other inaccuracies: The most serious include training, interpretation and inferences relating to the rating of perceived exertion (RPE).

Their rationale discusses the use of RPE (which they describe as 'rate') to control intensity. They rely heavily on a single study to support their conclusion that this method is effective only at intensities above 80% HRmax. However, in that study [START_REF] Smutok | Exercise intensity: subjective regulation by perceived exertion[END_REF] the slopes and intercepts of individual regression lines of speed generated from several 5-min RPE production trials and RPEs estimated from a prior progressive exercise trial (T1) were identical (Fig. 1,ref 8). The differences in HR at the lower RPEs between T1 and the randomized RPE production trials were most likely attributable to a combination of protocol (progressive T1 versus randomised RPE production) and differences in gait (walking versus running) which were not controlled.

Studies normally include some training in RPE prior to use, which typically involves memory recall and/or experiential anchoring. In the present study, there was no such training. Participants' first exposure to RPE was on completion of the initial testing session, when a pre-recorded message 'invited subjects to complete an RPE response'. Instructions on the RPE scale are not provided. Also, the cited 6-20 RPE scale is a momentary scale, validated for use during exercise. The timing of the perceptual response (i.e., post versus during) affects the value reported (4).

Despite the rationale described, an RPE-regulated paradigm was not applied in their study. It is therefore disconcerting that the authors should dismiss the efficacy of RPE to regulate moderate intensity exercise on the basis of their data, when no such evidence is presented! Many studies show that RPE is a valid means of reproducing a range of intensities (by physiological variables, power or speed) below and above 80% HRmax in healthy [START_REF] Ceci | Self-monitored exercise at three different RPE intensities in treadmill vs field running[END_REF][START_REF] Smutok | Exercise intensity: subjective regulation by perceived exertion[END_REF]; disabled (3) and clinical populations (1), including short (e.g., 3-5 min, 5,8) and longer duration exercise (e.g., 20-30 min, 1,3,6), to name a few.

In our view, the similar RPEs between trials do not suggest that '...RPE alone may not be a sufficiently effective cue to ensure repeatability of effort intensity'. On the contrary, and given the issues raised, their results suggest that RPE is actually quite reliable as it most likely reflected RPE during the last moments of exercise when HR was 'in zone'.

In summary, Shaykevich et al. [START_REF] Shaykevich | Auditory feedback improves heart rate moderation during moderate intensity exercise[END_REF] did not train participants in the use of RPE and did not use RPE to regulate intensity. They therefore provide no evidence to support their assertion that RPE 'cannot be used to regulate moderate intensity exercise.'


Arnaud Brossard
email: brossard.arno@orange.fr

Mourad Abed
email: mourad.abed@univ-valenciennes.fr

Christophe Kolski
email: christophe.kolski@univ-valenciennes.fr

Guillaume Uster
email: guillaume.uster@inrets.fr

User modelling: the consideration of the experience of time during journeys in public transportation

Keywords: H.1.2 [User/Machine systems]: Human Factors H.5.2 [User Interfaces]: User-centered Design Design, Human Factors Model Driven Engineering, Interactive Applications, User Model

With the generalization of mobile computing devices, everyone can access to a large amount of information anytime and anywhere; the difficulty for the user is to access to the relevant information. This is more accurate in the public transportation field where during their trip users want to reach information on their move. But they also wish to access a whole range of services adapted to their needs. However, these are different for each traveller and evolve during the trip through the so-called experience of time during journeys specific to each individual. Unfortunately, tools or methods to manage these changes do not exist currently. The purpose of this paper is to suggest, by using a model driven approach, to take into account the activity of the travellers; that is to say the experience of time during journeys.

INTRODUCTION

With the generalization of mobile devices, everyone can access to a large amount of information anytime and anywhere; the difficulty being to access the right information at the right time. This is more important in the public transportation field where users need to reach information on mobility throughout their trip [START_REF] Viatic | Mobilité: Web site[END_REF]. Also, it is essential to allow interactive applications to adapt themselves to the users. This requires a personalization of information and services [START_REF] Vesanen | What is Personalization: A Literature Review and Framework[END_REF] but also by taking into account the specificities of the business domain allowing to center the analysis on human needs [START_REF] Cooper | About Face 3: The Essentials of Interaction Design[END_REF]. In the public transportation field, it is only since a few years that researchers are on the problems of the use of time during journeys [START_REF] Flam | A qualitative perspective on travel time experience[END_REF]. To our knowledge, this point has never been taken into account within a modeling method. Finding a solution to these problems is not sufficient. Indeed, as applications are more and more complex, it is also necessary to create reusable models. It is what Model Driven Engineering (MDE) [START_REF] Omg | [END_REF] proposes. But, today, it is only used in a limited way in the field of interactive applications [START_REF] Pérez-Medina | A Survey of Model Engineering Tools for User Interface Design[END_REF] although its interest has been often highlighted [START_REF] Stahl | Model-Driven Software Development[END_REF]. In this article, we propose a method allowing us to manage, within an MDE approach, the so-called experience of times during journeys concept.

APPLICATIONS MODELIZATION AND HUMAN-COMPUTER INTERACTIONS 2.1 Modeling of interactive applications

Today, in modelization, the new emergent paradigm seems to be the MDE approach [START_REF] Stahl | Model-Driven Software Development[END_REF] [START_REF] Schmidt | Model-Driven Engineering[END_REF]. Its objective is to allow the creation of applications based on conceptual models or on an assembly of existing conceptual models; each model managing well defined business problems. The transition from conceptual models to applications is done through a succession of model transformations based on a Model Driven Architecture approach (MDA) [START_REF] Omg | [END_REF]. In our work, we have studied this approach from the Human-Computer Interaction (HCI) point of view. Concerning application modeling, few researches, proposing a true MDA approach, exists [START_REF] Vanderdonckt | A MDA-Compliant Environment for Developing User Interfaces of Information Systems[END_REF] although its interest was often highlighted [START_REF] Sottet | Towards model driven Engineering of plastic user interfaces[END_REF]. In this article, based on a modeling method described in [START_REF] Brossard | PERCOMOM : Une méthode de modélisation des applications interactives personnalisées appliquée à l'information voyageur dans le domaine des transports collectifs[END_REF][START_REF] Brossard | Modélisation conceptuelle des IHM : Une approche globale s'appuyant sur les processus métier[END_REF], we will show how it is possible to integrate the experience of time during journeys concept in an MDA approach.

User modeling in interactive applications

To provide users with relevant information and services, it is necessary to be able to identify and characterize them. This generally requires the use of user profiles containing two types of information [START_REF] Razmerita | User Model and User Modeling in Knowledge Management Systems: An Ontology-based Approach[END_REF]: (1) explicit information provided by the users, (2) implicit information, collected by the system. But, to adapt the applications to the users, it is necessary to change the way of conceiving applications by adopting an approach of interactions centered on the users and on their goals [START_REF] Cooper | About Face 3: The Essentials of Interaction Design[END_REF]. It is also necessary to find new ways of interacting with them in order to allow faster adaptations. One of the possible solutions consists in recognizing the emotions of the user [START_REF] Cowie | Emotion recognition in human-computer interaction[END_REF]. Today, if some research provides answers to these problems, few of them deal with problems specific to the public transportation.

The experience of time during journeys

In public transportation, time during journeys is often regarded as a waste of time [START_REF] Lyons | The gift of travel time[END_REF] during which activities are carried out by travelers only to kill time [START_REF] Lyons | Travel time use in the information age[END_REF]. However, a study [START_REF] Marzloff | Le temps des puces[END_REF] showed that the time in transport was perceived as wasted time for less than 40% of travelers. On this basis, some researches have tried to differentiate the act of moving from the activities carried out [START_REF] Mokhtarian | How derived is the demand for travel? Some conceptual and measurement considerations[END_REF]. Thus, a first categorization of these activities [START_REF] Flam | A qualitative perspective on travel time experience[END_REF] proposes to classify them in three groups: (1) Productive activities, (2) Activities of relaxation and transition, (3) Social activities.

Another possible categorization, based on an anthropological and sociological study carried out during the Viatic.Mobilité project [START_REF] Viatic | Mobilité: Web site[END_REF][21] (see §4), has defined four groups distributed on two axes: a vertical axis for the level of concentration and a horizontal axis for the level of openness to the others (cf. Figure 1). These groups are: [START_REF] Viatic | Mobilité: Web site[END_REF] The beaver who has a productive activity; (2) The owl who is lost, who is looking for information; (3) The peacock who is showing of, who communicates with others; (4) The marmot who sleeps, who drowses, who looks at the landscape.

Figure 1. User categories identified in Viatic.Mobilité [21]

We have used this last categorization in order to take into account the experience of times during journeys concept (ETDJ).

ADAPTATION TO THE CONTEXT OF USE FOR INTERACTIVE APPLICATIONS

A new approach of the needs analysis

In well-known software engineering methods (RUP, SADT…), during the analysis phase, the organization of the tasks defines only the organization of the business tasks and considers the user only in a marginal or global way. That is why we propose to enrich the analysis phase (cf. Figure 2). This enrichment will consist, once all the business tasks are identified, to gather them in business processes; i.e. in sets of tasks allowing to achieve a business goal. Then, they should be distributed in the various ETDJ categories. Then, if necessary, each process is adapted to the various ETDJ categories.

After the application is deployed, it is important to plan a loop phase to validate the choices done during the analysis phase through ground surveys. In the case of a variation, it will be necessary to reconsider the analysis phase and to adapt the distribution of the business processes in the various categories and/or to modify the adaptation to the categories. So the distribution of the business processes in each category and their adaptation must be a multi-field work (engineering and social sciences). This is one of the major challenges of our approach.

Identification of the ETDJ category

General principle

A problem with the ETDJ concept lies is that we need, at every moment, to know the category in which the traveler is. And, today, we do not have, to our knowledge, sensors or models that allow knowing surely the ETDJ category at every moment.

Within our work, we defined a basic technique for identifying the ETDJ category according to the "localization" of the user in the application. It is done from the knowledge of the business process used and of the context in which this one is used. Thus, in the application, the launch of each business process is always associated with specific level of ETDJ categories (see §3.2.2). For the moment, since we limit ourselves to applications of WIMP type (Windows, Icon, Menu, Pointing device), we propose to use the menus as the elements allowing to make this distribution. Once the category is identified, it is stored in the user profile allowing using it like a property of the explicit profile of the user.

Level of confidence and use of history log

For limiting incorrect changes, we propose to define, for each business process and for the associate ETDJ categories, a level of confidence. This level could have a value between 0 (certainly not) and 1 (surely). To determine the levels of confidence, we propose to proceed with a three steps process added to the needs analysis of §3. But the level of confidence is not enough to determine if the ETDJ category should be changed or not. In fact, we must know also from which category the user is coming from and what he/she was doing before. This is done through the use of a history log where each change of business process is logged with the associate levels of confidence for each ETDJ category. Then, for each ETDJ category, a general level of confidence is determined by: ∑ The current ETDJ category is defined as the category with the higher general level of confidence. The problem is that, if the data contained inside the history log has no time limit, the system will become less and less efficient. As determined by the sociological and anthropological study carried out during Viatic.Mobilité [21], the change of an ETDJ category could be determined as been sure after 7 minutes. If no change of business process is done during this time limit, only the information on the ETDJ categories of the last business process are keeped in the history log.

CASE STUDY

Our work has been done within the scope of the Viatic.Mobilité 1 project. The purpose of this project was to create a set of services to assist the travelers before, during and after their mobility in public transports, by using different information supports.

Access to adapted services

In Viatic.Mobilité [START_REF] Viatic | Mobilité: Web site[END_REF], users access information through a portal.

To determine the categories of each group of services, the needs approach presented in §3.1 has been used during the conception of the portal. This has been done through the creation of a workgroup with transport experts, sociologists and traveler's representatives. This conducted to the creation of a simplified portal with five services groups: Communication, Transport Information, General Information, Leisure, Work. For each services group, the needs analysis conducted to the definition of the levels of confidence showed in table 1. (2) The definition of the levels of confidence is more experimental than scientific as, for the moment, we was unable to define rules for validating them. (3) The validation through ground surveys is not easy as the pollsters and analysts could have a different perception of the ETDJ categories.

But it gives us also some good results as: [START_REF] Viatic | Mobilité: Web site[END_REF] The change of the EDTJ category is done in accordance with the direct observation during ground surveys. [START_REF] Vesanen | What is Personalization: A Literature Review and Framework[END_REF] The incorrect determination of the current ETDJ category of the user inside the application is limited.

In fact, the main problem of the approach resides in the fact that it is not possible to determine an ETDJ category when the traveler does not use the application.

Adaptation of business processes

To illustrate the case of the adaptation of a business process to the ETDJ category, we will present a business process allowing the display of information associated with the next journey of the user. The needs analysis results in the identification of two 1 The project was realized by a consortium of industrial companies (Archimed, Atos Wordline, Canal TP, Digiport, Infodio, IP4U, Transport Terrestres Promotion, Visionor, What time is it?, Worldspace, W@Lan, ) and research centers (Iemn, Inrets, Lagis, Lamih); coordination: Inrets.

different adaptations for the business process. The first one, which is related to the Beaver category, will allow binding the display of information on displacement with the information contained in the professional diary of the user. The second one, which is common to all the other categories, will display only information associated with the journey itself. The access to this process could be done by using a button or an option in a menu. From there, a business process could be launched which would use a selection criterion to display a group of elements of interactions called "UIGroupNextJourneyPro" if the user belongs to the Beaver category and display another group of interaction elements "UIGroupNextJourneyGen" for the other categories. Figure 3 shows an extract of the business process model associated.

Extension to other business domains

Regarding our approach, one of the main question is whether it is expandable on other business domains than transportation. In fact the problem here is to determine the categories which could be associated with the experience of time of the user in other business domains. As they will probably not be the same for each business domain, the question will be to know how to link each business domain together. It is a very critical question as a user could use different applications from different business domains.

One of the solutions could be to create semantic links between categories of the different business domains. As it will not always be easy to make direct links between two categories, we propose to use a weighting, between 0 and 1, on each semantic link which will allow to define a semantic distance between each categories. Table 2 shows an example of this type of relations. For time reasons, we have not been able to validate, this approach. But, for the sociologists and anthropologists working with us in the Viatic.Mobilité project, it has been considered as a good approach as it is quite simple to understand, handle and manage.

Discussion

As suggested in the previous examples, our approach allows managing the ETDJ at different levels in interactive applications:

(1) Like an element allowing to distribute and to define the content of the business processes; (2) Like a selection criterion, in a direct way or through a business rule.

These examples allow us to see the main advantages of our approach: (1) The possibility to create applications which are more reactive to user needs by introducing the notion of ETDJ;

(2) To manage the ETDJ categories in a smooth way through the use confidence levels which limit the risk of false selection; (3) The possibility to extend the concept to other business domains.

But, these two examples allow us also to see the current limits of the approach: (1) The importance of the preliminary phase of analysis to distribute and adapt the business processes which rely on a multi-disciplinary approach difficult to set up; (2) The difficulty of knowing, with certitude, the ETDJ category of the user; changes of category being carried out only through interactions done by the users. (3) Lastly, there are problems in the characterization of the ETDJ categories and their number.

Within our work, we used four categories, but in other works only three can be found [START_REF] Schmidt | Model-Driven Engineering[END_REF] and there is no proof that one would not have to use more than four categories. At the level of the ETDJ categories characterization, which defines with the criteria identifying to which category the user belongs to, the difficulty lies in the definition of sufficiently discriminating criteria to avoid any ambiguity when choosing an ETDJ category. But, it is also dependant on the ways of life and thus can evolve during time and in space (different user cultures); the question being then of knowing how to take into account these evolutions.

CONCLUSION

Taking into account the user in applications becomes more and more an important general criterion. many works studied various derived concepts about: (1) user profile, (2) information personalization, (3) time consideration (user point of view).

But, to our knowledge, there is very few works which tried to bring conceptual and practical responses to the problem of the taking into account of the attitude of the travelers during their journeys in public transport. More exactly, no works have tried to manage into conceptual models the so-called experience of time during journeys concept. Within the Viatic.Mobilité project, through the use of results from a sociological and anthropological ground study and with the help of the industrial partners involved in the project, we bring a first answer to the problem. Thus, we propose to add new steps to the analysis phase of user needs, which is a precondition to any application development, so that this one takes into account the so-called experience of time during journeys. Then, we propose, trough a MDA approach, solutions to take into account it within the conceptual models of the application. Lastly, we propose a solution to identify the category of experience of time during journeys according to the business processes used within the application. If our work leaves many questions without answers, it represents a new step concerning personalized application development in public transportation.

Figure 2 .

 2 Figure 2. Specific analysis process associated to ETDJ

  1: (1) Determination of the initial confidence levels during the initial definition of user needs. (2) Analyze of the results of the ground survey. (3) Adaptation of the levels of confidence if necessary and loop back on the second step.

Figure 3 .

 3 Figure 3. Extract of the business process associated to the display of information on the next journey of the user (notation based on BPMN [22])

Table 1 . Levels of confidence on ETDJ category for each services group of the Viatic.Mobilité simplified Portal

 1

	Service group	Beaver	Owl	Peacock Marmot
	Communication	0.4	0.3	0.8	0.1
	Transport information	0.5	0.7	0.2	0.3
	General information	0.5	0.4	0.2	0.3
	Leisure	0.1	0.2	0.4	0.8
	Work	0.9	0.1	0.1	0.1
	During the Viatic.Mobilité project, for limited time reasons, only
	some experiments with users have been carried out. This does not
	allow us to have a definitive conclusion on the approach but this
	give us three main limitations: (1) The semantic characterization
	of each ETDJ category was not easy as each participant inside the
	workgroup used during the needs analysis has a different
	perception of it.

Table 2 . Generic example of a semantic link between categories of experience of time for two business domains ETDJ Category Beaver Owl Peacock Marmot

 2

	Experience of	Category A	0.1	0.8	0.3	0.6
	time categories	Category B	1.0	0.0	0.1	0.1
	for business	Category C	0.4	0.2	0.7	0.3
	domain X	Category D	0.5	0.6	0.1	0.4

ACKNOWLEDGMENTS

This research work was partially supported by the "Ministère de l'Education Nationale, de la Recherche et de la Technologie", the CISIT, the "Région Nord Pas-de-Calais", the FEDER, the Agence Nationale de la Recherche (Viatic.Mobilité) and the PREDIT through the PREDIM (MouverPerso).