Didier Sebastien
email: didier.sebastien@univ-reunion.fr

Olivier Sebastien
email: olivier.sebastien@univ-reunion.fr

Noël Conruyt
email: noel.conruyt@univ-reunion.fr

Mamy-Haja Rakotobe
email: mamy-haja.rakotobe@univ-reunion.fr

Evaluation of Information in Biodiversity Information Systems: A model to capitalize on experts and amateurs

Keywords: biodiversity information system, data evaluation, modeling, crowd-sourcing

For observation of coastal and ocean ecosystems, the acquisition and processing of scientific data in databases have led to the proliferation of specialized Information Systems, as it is the case for monitoring biodiversity. Given the various data that they contain, these Biodiversity Information Systems (BIS) provide complex applications focused on the needs of domain experts, but are often closed to amateur's field contributions. However, such a new open and interoperable Biodiversity Information Service could attract more and more hobbyists whose skills would be useful to integrate, in order to share, improve and keep information up to date with people. A part of the solution could be to render service to amateurs by tagging the quality of their contributions, in order to clearly indicate the origin and quality of provided information. This paper presents a Scientific Information Evaluation (SIE) model instantiated as a Web Service (WS), which is a contribution to the enhancement of BIS for Citizen Science. Crowdsourcing and evaluation by peers in communities of practice enhance this BIS because the WS is managed by adding qualitative metadata (certificates) on the regular primary data found in cards, as a global evaluation and a conversation thread. This WS module has been tested in the frame of the NEXTIC project at University of Reunion Island for data acquisition of the Herbarium of Reunion Island. It reveals the central role of such a module for the community to gain confidence about the BIS. It is to be ported to the marine domain.

INTRODUCTION

The important loss of world biodiversity has led Eco-Informatics experts [F. [START_REF] Recknagel | Ecological informatics: Current scope and future directions[END_REF] to develop specific Environmental Management Information Systems (EMIS) called Biodiversity Information Systems (BIS). The objective is to help communities of practice in Biology (thematic experts, also called systematicians) who work on species monitoring in their everyday tasks: produce inventories of specimens, model, describe, classify and identify them, obtain a better visibility on biodiversity studies, plan coordinated actions between institutions and communicate their results. They focus on the management of taxa and specimens [S. J. [START_REF] Mayo | Alpha e-taxonomy: responses from the systematics community to the biodiversity crisis[END_REF]. In this context, Web Services (WS) are more and more used to manage virtual biodiversity [K. D. Fook, A. M. V. [START_REF] Fook | Web Service for Cooperation in Biodiversity Modeling[END_REF], leading to the modeling of Biodiversity Information Services for interoperability of these data [N. [START_REF] Conruyt | Moving from Biodiversity Information Systems to Biodiversity Information Services, Information and Communication Technologies for Biodiversity and Agriculture[END_REF]. Such Web services can be found in portals such as EOL (www.eol.org/), GBIF (www.gbif.org), ALA (www.ala.org.au). Nevertheless, the quality and completeness of these data cannot be guaranteed in BIS, because this content needs continuous updates and validation from experts. For some years, amateurs were not allowed to contribute to the system by adding their own data in order to share them with the scientific community. Today, due to biodiversity crisis and lack of specialists, the biodiversity field attracts a parallel community of non-specialists that gathers important sets of data. These data were generally rejected only because experts did not provide them. Nevertheless, crowdsourcing has arisen with the advent of Citizen Science [J.C. [START_REF] Tweddle | Guide to citizen science: developing, implementing and evaluating citizen science to study biodiversity and the environment in the UK[END_REF] and Web 2.0. Indeed, there is a social demand that cannot be eluded for engaging citizens in the knowledge construction about the richness of the environment and their territories [A. [START_REF] Cosquer | Observations of everyday biodiversity: a new perspective for conservation?[END_REF]. Conservation in the context of biodiversity loss needs the acquisition of qualitative data from every skilled and motivated amateur. To gain from these public and opened data, it would be useful to let amateurs have a controlled access on the BIS for them to participate to this endeavor. A solution to acquire such qualitative information is to support a scientific data validation policy, which is often made by an administrator in BIS. However, because the quantity of data expert-administrators have to validate is colossal, they cannot afford to treat amateurs' resources. In this new context, we propose a Scientific Information Evaluation (SIE) model. To introduce our contribution, we will first detail our model through its prerequisites and general process, then we will present an example of implementation realized in the frame of the Nextic research project.

GENERAL MODEL

Context and prerequisites

Our model relies on modular information systems' architectures and more specifically Biodiversity IS, like MABIS developed in a precedent work [D. [START_REF] Sebastien | Biodiversity Information Systems evolution: The MABIS model to gather several communities on an adaptable environment[END_REF]. MABIS stands for Modular Architecture for Biodiversity Information System. This stratified model relies on several Web applications that are components interconnected together by webservices. Fig. 1 presents the four layers used by the different users. The first layer manages the main entities of the IS through simple online application defined as modules. The second one introduces meta-modules for data management. The third layer is composed by softwares, i.e. installed applications, dedicated to information analyze and knowledge treatment. The fourth, and last layer, allows the diffusion and the valorization of the information contained in the BIS. In this frame, the evaluation system of information can be integrated through a module of the second layer interconnected with the different modules of the first layer, for the management of main entities.

In order to ease the use of each module is available under three functioning modes (Fig. 2). Main mode allows users to work directly in the environment of the Web application dedicated to the management of the entity he is focusing on. The deported mode is used to provide popup windows and inclusions offering synthetic graphical information's and functionalities from a module in another one used in main mode. The remote mode means that the Web application is used through its webservices, in order to fully integrate its data and functionalities in another module's GUI. Thus, the Scientific Information Evaluation (SIE) module should be able to provide its services through different functioning modes. Now that the context of the SIE and its prerequisites have been defined, we introduce its general model in the following part.

Model

Our aim is not to provide a methodology to analyze data, for instance by error elimination [K. R. [START_REF] Popper | All life is problem solving[END_REF], but to set up a workflow that induces the community to evaluate, comment and follow the enhancement of a card until it reaches the best acknowledgement level. The module offers several ways to authenticate the scientific aspects of data, to share the evaluation's work, to simplify the communication between experts, and to ease the identification of the evaluation's state by end-users who can be the general public or decision makers. The enhancement process is presented in Fig. 3. When a card describing an entity is created every user have the possibility to evaluate it. In order to focus the attention of the community on a new card or on a deeply modified entry, the authors have the possibility to emit a request for an evaluation. The evaluation consists in two aspects: a level of certification conveying the achievement's degree of the card for the evaluator, and a thread of comments allowing a discussion/debate among the community of users. Theses elements further the enhancement of the card that can be evaluated and commented again, through a virtuous circle, until it reaches the best certificate.

Contrary to most validation processes that result in a binary answer (validated/not validated), evaluations result in certificates associated to a precise time. Each certificate corresponds to a level of trustworthiness that gives a more precise idea of the data acquisition condition. The certificates can be considered as a succession of steps toward the validation level. It is represented as a simple and easy to read icon that sums up the state of the card. Fig. 4 presents an example of representation that can be used for the different certificates, from the "not evaluated" state to the "validated at present time" state.

In order to reduce the work of data evaluation by experts, two participative evaluation systems are offered. The authoritative certification represents the evaluation of the current version of the entity's card made by identified specialists of the thematic on the BIS. Depending on their recognized specialization in a discipline, a limited set of experts acquire from the administrator the possibility to deliver certificates that represent their approval to the data. This ability to deliver up to a defined level of certification is entityspecific, and for the taxa, taxa-specific. So the SIE stores a list of privileges that can be associated to profiles of users registered in the directory. This evaluation is presented as an icon showing the lowest certificate delivered by the expert of the highest level about the card. The algorithm is chosen to be the less permissive, in order to ensure that the quality of selected data is, at least, equal of the displayed certificate. The community certification is the evaluation of the card made by all identified users on the BIS. Because everyone can participate and deliver the certificate they consider deserved, this evaluation is less secured and specialized than the precedent one; however, a certificate coming under an important participation of users gives a good basis of evaluation if experts have no time to consider the card. An icon that shows the average level of certification given by voters also sums up this notation based on folksonomy [START_REF] Vander Wal | Folksonomy[END_REF]. Thus, the algorithm tend to offset the inexperience of the amateurs by considering that the multiplicity of evaluations will reflect a result close to the effective state of the card.

Authoritative and community certifications are displayed side by side as this last one can reflect an appreciation about the last changes on the card. They can be used as criteria, in a combined way or not, to sort and research data. Thus, it is easy to work only with, for instance, data defined as relevant by experts.

In order to smooth the connections between the different elements in the workflow, information (certificates and comments thread) can be inserted under several forms through the functioning modes of the SIE module. Thus, it is relevant to provide directly in a module dedicated to a type of entity the main information and functionalities, like the certificates, the possibility to add a comment, an alert to focus the attention of the community and request an evaluation, a way to post an evaluation, the history of certificates and the thread of comments Fig. 5 sums up this list as a set of banners. The SIE's main mode (Fig. 6) is gathers all detailed information about the evaluation of entities. It allows to:

-present general metadata and statistics about entities evaluation on the BIS (most discussed cards, most heterogeneous evaluation per module, etc.).

-list all evaluations' requests and focus on those concerning the authenticated user.

-show the logged-in user his own evaluation requests, delivered certificates, discussions' threads (new messages since last connection), and the current evolution of his cards.

-manage the sharing of privileges concerning the authorized level of certification.

The remote mode of the SIE is of course not related to a specific representation, but can Fig. 6. SIE main mode model Fig. 5. Banners for deported information of the SIE often be used in other modules, for instance to sort entities by certification level in other Web applications' main mode. This general model could be extended, under specific conditions, from biodiversity IS to other types of IS.

Managing users interactions

The goal of this section is to deal with the way to involve non-specialists to use a system that rely on scientific content. Indeed, experts and amateurs do not share the same background in term of information classification, vocabulary or even rigor. That is why two levels of use are identified: the casual one, targeted to general users and the expert one. Let us focus first on their similarities and then on their specific aspects relying on the following table describing the main points that separate those groups.

Common points of users interaction levels are rather related to the human-computer interface than the BIS-related activities. Indeed it consists in providing support to create and edit content online on one hand and to enable file upload for further sharing. Those activities rely on mechanisms that are nowadays trivial because they are already in use on popular Web 2.0 services such as Youtube (video sharing), Flickr (picture sharing) or Wikipedia. Basically, interface usability can be assessed thanks to criteria, like Nielsen's ones [START_REF] Nielsen | Usability inspection methods, Conference companion on Human factors in computing systems[END_REF]. As far as mobile devices are concerned, dedicated recommendations are proposed by main Operating System builders as Google for the Android environment (https://developer.android.com/design/index.html) to achieve the same goal. Thus, BIS general operations are not so different to the ones accomplished in other application, provided users have the minimal required level of understanding the device. Specific points of the interface are related to the activities that are not shared by experts and amateurs. Actually, the latter should not be aware of the features made available to the former, as they may not be accessible enough for them. That is why screen layout is to be set slightly differently according to user profile. The main point that guide interaction design is the objective of the service. Tasks listed on the interface show a restricted set of tools for non-specialists. This can be viewed as a "write-only" function, to upload a new case. The full set of features appears only to researchers. Practically, scientists have access to the ontology modules and can edit links between content. Of course, they are to solve the cases brought by the general users. These interactions can be seen as "read-write".

IMPLEMENTATION

In order to experiment our model of Scientific Information Evaluation, we implemented it in the frame of a research project: NEXTIC. This project is dedicated to the valorization of natural collections. As NEXTIC relies on MABIS architecture, the SIE model has been instantiated in the form of a module gathering two modes: main and deported. We worked with a designer and optimized the ergonomics of the graphic user interface (GUI) in order to turn several texts into icons representing information and functionalities. Fig. 7 presents the appearance of the deported mode dedicated to the SIE inserted in other modules GUI.

The main mode of the module is a web application centralizing the workflow for all entities of all types (Fig. 8). It also helps the administrators and the community by presenting statistics and pinpointing major differences between authoritative and community evaluations. The SIE has been connected to one module of the BIS, dedicated to the management of multimedia files. Preliminary results confirm that allowing amateurs on the BIS should enhance the growth of the users community.

CONCLUSION AND PERSPECTIVES

In this paper, we introduced a model of scientific information evaluation in Biodiversity Information Systems. This model is based on two kinds of certifications and a workflow to frame the exchanges of users. The main idea is to ease the communication between the community members in order to collect a maximum of contributions and advices about the card describing entities. By opening the system to amateurs, and supporting two kinds of certifications to be able to sort the information, reactivity and returns can be improved. The gradual certifications constitute a more precise evaluation than a Boolean one. Furthermore, it is more easy to automate the administration of the system, by letting the user share their privileges up to their own ones. We implemented our model as an element of a modular architecture of biodiversity information system, declined in two Web applications. The deported mode provides the essential information for each card whereas the main mode gathers all the certifications in order to pinpoint statistics and evaluation's requests. In future work, we will analyze the usage made by contributors by focusing on their experience, exchanges between them, activity on the module and a comparison between authoritative and community information for the same cards.

Fig. 2 .

 2 Fig. 2. The three declinations of modules

Fig. 4 .Fig

 4 Fig. 4. Levels used for evaluation

Fig. 8 .

 8 Fig. 8. Main mode of the SIE implementation Fig. 7. Elements for the evaluation injected in the cards

ACKNOWLEDGEMENT

The ETIC program promotes the enhancement of insular tropical environment contents from biological researchers using Information and Communication Technologies. The European Union, the French National Government, and the Regional Council of Reunion funded it in the frame of the DOCUP-FEDER 2002-2006, A9-04 ICT measure. NEXTIC is the next ETIC project for distributing Biodiversity edited contents on the Web with Webservices, then with Data and Immersive services. It is supported by the PO-FEDER 2007-2013 measure. We are also grateful to Mr. Laurent Cochet and Mr. Lucien Stojcevski, engineers on NEXTIC project, for the implementation information provided to our research team.


domain: math info

text:
Didier Sébastien
email: didier.sebastien@univ-reunion.fr

Olivier Sébastien
email: olivier.sebastien@univ-reunion.fr

Noël Conruyt
email: noel.conruyt@univ-reunion.fr

Conruyt

Noël

Providing services through online immersive real-time Mirror-Worlds The Immex Program for delivering services in another way at university

Keywords: virtual worlds, metaverse, mirror-worlds, information system, data accessibility

    Providing services through online immersive real-time mirror-worlds. The Immex Program for delivering services in another way at university

INTRODUCTION

Universities are equivalent to big companies that generate a lot of heterogenous data targeted to various profiles of persons. They are organized around large campuses, with many buildings, and are difficult to apprehend for newcomers but also for other people, for instance when they are in need for a specific service for the first time. Even data centralized on well structured and urbanized information system (IS) [START_REF] Angot | Information System for companies[END_REF] is not fully exploited because only a few experts are able to access and process it to generate information and integrate such content into a communication scheme. E x a m p l e s o f t h e s e c o u l d b e we b s i t e s information, maps, files, databases of all subparts of the university. To ease the apprehension of this information, a dedicated tool to discover and give access to all this content through a centralized, consistent and ludic environment may be an original solution.

The Immex "Immersion Experience" program aims at experimenting and providing innovative services based on immersive representation technologies. This initiative of the University of La Réunion tries to offer an alternative way (compared to traditional interfaces) to access content from information systems, in this frame, the IS of the university. The idea is to shape immersive environments to provide a first-person vision, as if the user was immersed in a simulation. The virtual world, or "metaverse" [START_REF] Smart | Metaverse Roadmap, Pathways to the 3D Web. A Cross-Industry Public Foresight Project[END_REF] , reproduces the real-world environment, that is why it is called a mirrorworld. It naturally associates documents and digital services with their geo-positioning to create a serious game [START_REF] Susi | Serious Games -An overview[END_REF] .

In this paper we first present our past related works and the new approach we engaged in for Immex. Then we describe the created environments, their services and the results of a first survey conducted with users. We conclude by a discussion and the perspectives opened by our work.

Previous experimentations and methodology 2.1 e-Campus

e-Campus was a virtual world reproducing the campus of La Reunion island university [START_REF] Sebastien | 0 8 . e -C a m p u s : a M M O R P G providing e-Services to campus users[END_REF] . This platform was created between 2004 and 2007 in the context of a collaboration between the university and a private company specialized in video games. During 3 years, this project funded by the European Union, the French Government, and the Regional Council of Réunion, allowed a team of computer science engineers, computer graphics experts, animators and designers to create a desktop software reproducing accurately the central part of the campus.

This connected application was based on a game engine initially dedicated to Massive Multiplayer Online Role Playing Game (MMORPG). It provided the same video game features that can be found in a real campus: persistent world and massive multiplayer support. The aim was thus to provide users (students, teachers and administrative members) with the e-services a campus gives, from the online courses [START_REF] Smart | Metaverse Roadmap, Pathways to the 3D Web. A Cross-Industry Public Foresight Project[END_REF] to the restaurant's menu, through immersive representations. Eventually, the project did not meet with the numerous expectations in terms of services, mainly because of the game-engine limitation.

Immex Approach

Since 2011, we decided with Immex to try a new approach, in several ways at the opposite of the way e-Campus was conducted. Indeed, e-Campus was a big project, based on european fundings, employing a team of engineers, qualified computer graphics experts working on blueprints, collaborating with companies mastering proprietary tools and technologies, like their own 3D engine, landscape generator and data integration softwares.

Thanks to the evolution of the 3D engines market, 4 years after e-Campus, an accessible offer had raised and we have been able to evaluate and compare their features. The requirements to create immersive environments h a d c h a n g e d t o a l l o w m o r e fl e x i b l e developments. We then decided to make Immex as a program made up of several projects, each project being a virtual environment, offering its own services. At the opposite way of the e-Campus project was conducted, we worked mainly with students, during courses, pedagogical projects and through internship. Fo cusing on services more than visual appearance, we accepted the fact that the Immex environments will not have the same accuracy and modeling optimizations offered by experts work. However, working with students provided us with a larger team, able to reproduce and cover a larger area, eager to learn and reproduce their campus in order to play in it. This approach also have the advantage to require a dramatically lower funding.

Immex Environments

As we explained, the Immex program is composed of several pro jects, each one corresponding to a metaverse. 6 mirror-worlds were created to experiment a wide variety of services that make sense depending on their nature. They can be sorted in the 3 categories presented below.

Campuses outdoors

Campuses outdoors refer to the possibility to explore the outsides of the building composing the campus. The aim of this modality is to allow the user to navigate and discover the campus through its whole reproduction. The spatial range of the area is wide and the accuracy of the mo dels approximative. Three of the main campuses were reproduced:

• Moufia Virtual Campus. This metaverse is one of the first realized, as it reproduces the largest campus of the university. Almost all faculties, services, departments or laboratories have a dedicated area in it. The basic outdoors services were experienced in the Moufia Virtual Campus.

• V i r t u a l U T P. U T P s t a n d s f o r University Technological Park and refers to the campus located on the science park of the city.

• Tampon Virtual Campus. This campus is located in the south of the island and has specific infrastructure for sports learning.

Inside building focus

As its name refer, this type of metaverse focuses on one building and its related features and services. A special effort is made on the presence of the tools and objects available in the place. 2 particular indoor environments were created:

• Virtual Library. This project was developed with the documentation service of the university, in order to provide some of the services offered in the real world, through its virtual reproduction. Each year, new students visit the building in small groups, an event which causes disturbance to regular users. The idea of this virtual environment is thus to allow them to discover the place and its services through the playful approach of the project.

• Virtual Data Center. The University of La Reunion owns a state-of-the-art Data Center that hosts several servers. The building matches high-end security standards, with restricted access, an attractive configuration could lead to commercial offers for partners. That is why, the information system service partnered with Immex program in order to ease the visit and the promoting of the place though a metaverse.

Complete environment

Complete environment refers to a place where the outsides and the insides of the buildings can be visited. A compromise had to be found between level of details and the range of the reproduced area.

The Virtual Maïdo project is dedicated to the Atmospheric Sciences Observatory at La Reunion. This scientific station is difficult to access (away from all cities, located 2200m above the sea level high in the mountain), with an instrumental set composed by more than 40 instruments. The LACy laboratory, that runs the Observatory, teamed with us to create a virtual immersive replica. Their goal is to ease the discovery of the site, the buildings and the main instruments for general public, but also for researchers who will have to carry out missions there.

IMMEX SERVICES AND TECHNOLOGIES

As we worked for data accessibility, we built Immex with technologies providing the easiest appropriation level for end-users. Each metaverse is available through simple a Web page, using a Web-browser and the Unity plugin from Unity Technologies [START_REF] Jackson | Unity 3D UI Essentials[END_REF] . We also had the constraint to not force content providers, who feed the information system, to modify their practices. Our services must adapt to the IS the way i t i s but not t ry t o change i t . Each metaverse was the opportunity to develop and test new services that can be sorted in 3 categories.

Movement-based services

The very first natural service offered by a real-time metaverse is the possibility to freely stroll in the environment to discover its structure from several perspectives. This requires users to be able to move in the direction of their choice inside the 3D space. As a first person point of view was selected for this program, we chose to rely on the most common interaction scheme based on keyboard (to move) and mouse (to set the angle of viewing). This tend to be rapidly natural as most 3D immersive video games rely on this convention. But to help those who are not used to navigate in an immersive environment, we implemented 3 features:

• assisted moves, when toggled, this feature limits the angle of inclination of the vision to 20° above and below the horizon, and reduces the speed of movements. Indeed, we noticed during early testing that certain users were uncomfortable with first person view resulting in them looking to the sky or the floor because of bad mouse control.

• point and click to move, so that it is n o t n e c e s s a r y t o m a s t e r t h e combination of mouse and keyboard to reach a visible location. The application calculates the shortest path, getting around the obstacles, and automatically moves the user to the targeted place.

• reset position, that restores the initial position of the camera when the defined key is pressed. This feature is useful if the user feels lost or in case of bugs (for instance an invisible hole in the floor).

Orientation-based services

These services aim at helping users to realize where they are, find their way to the place they want to go, and match their experience in the virtual world and its counterpart in real world. To achieve this goal, we developed 6 features:

• mini-map is a classic of Head-Up Display (HUD) for Graphical User I n t e r f a c e ( G U I ) y e t u s e f u l t o comprehend the direct surroundings.

• global map, when the dedicated keyboard key is pressed, displays the full map of the metaverse and locates the user on it. • photo-sphere, positioned as an icon at interest points of the environment, triggers the immersion in a sphere whose interior is textured with a 360°p hoto of the real place. This feature completes the immersive view, which is flexible but limited in term of Level Of D e t a i l s ( L O D ) , by p r ov i d i n g a panoramic photo which is a detailed point of view from a fixed position.

• navigation to remarkable place offers an automatic guiding, adapted to the current position of the user in the metaverse. At anytime, the user can display the list of remarkable places of the metaverse and select one of them. This action triggers an analysis of the shortest path and an automatic driving to the chosen position.

• introduction sequence, as its name refers, is the integration of a video that introduces the environment and the original position where the user is placed at the b eginning of the simulation. For outdoors metaverses, a relevant approach is to match the end of a sequence shot with a drone that lands in a particular position with the same position in the virtual world, hence allowing the user to start his exploration at a well defined place. It provides a smooth transition between the realistic view of video and the simulation.

Information-based services

These services aim at offering information to users experiencing the simulation. The idea is to gather information from the IS and dynamically connect it with the virtual environment. Several modalities were developed i n or d e r t o d i s s e m i n at e t h e p r ov i d e d information:

• contextual information automatically displays a message depending on the location of the user in the metaverse. It i s a s t a t i c i n f o r m a t i o n w h o s e appearance is triggered by the user entering into a geographically defined area, often near a building or in a room.

• dynamic data injection refers to the importation and display of files in the metaverse. Their appearance is adapted to the needs and actions of the user in the simulation. We implemented the connection between a 3D object and several file formats : plain text to provide textual descriptions of buildings o r i n s t r u m e n t s , R e a l l y S i m p l e Syndication (RSS) to automate the display of up-to date news, and pictures that dynamically wrap a 3D model when the metaverse is loaded. Indeed, in our case, university campuses support offices have their own websites that regularly post news referenced as RSS feeds. We added a board on their F i g u re 4: remarkable places list with automatic guiding respective buildings to indicate the availability of news. When no RSS feed is available, and the information is only shared on static websites, we used an automatic and periodic web-page cutting system that generated a picture used as a texture. This allowed us, for instance, to display the menu of the u n i v e r s i t y r e s t a u r a n t . As this feature can be triggered by clicking on an object or a specific keyboard key, we used this latter with textual input to display all the s i m u l a t i o n c o m m a n d s a n d t h e application credits.

• 3D information layer allowed us to represent specific information, dedicated to a particular metaverse, through simplified visualisations. These layers can be activated on demand, like in Geographic Information Systems (GIS).

In the frame of Immex, we experienced a static representation of the position of WiFi and its coverage

• educational module is a short scripted exp erience where the user must accomplish a succession of tasks to fulfill a mission. It is a mini-serious g a m e d e d i c a t e d t o a s p e c i fi c environment. For Virtual Maïdo, we developed an educational module simulating the main steps to activate the atmospheric laser of the station, acquire and visualize data.

• web-link allows to connect a model in the metaverse with an URL. On click, the link is triggered and either downloads a file or opens a popup browser with the targeted web-page. We used this feature to connect the main buildings of the university faculties, services, departments or laboratories to its dedicated website. It is another way to navigate between the websites of the university, through the positioning of their infrastructures.

FIRST FEEDBACKS

As Immex aims at offering new ways of accessing content for university users, we found useful to set a survey especially dedicated to students (but not only) at an early stage of the project. The goal was to determine their profile regarding immersive technologies as well as to gather their feelings toward the Immex environments. 50 replies were obtained, 3 from university staff and 47 from students ranging from first postgraduate year to Master of Science in the fields of Laws, Economics and Computer Science. The number of participants involved is not so high, but it is sufficient to gather early feedbacks that are to be used firstly to set development directions for the future and secondly to prepare a larger evaluation stage. In the frame of this article, they are useful to present a trend on how the community welcomes such a service.

All testers were thus presented the application and the first choice they were given was to try it on their own or not. One quarter of them made the effort to install the Unity plugin to access Immex outside the campus. This is a first interesting feedback because this particular action requires the user to have the knowledge to download and install such a plugin. 91% of the persons who tried it reported that it was a very simple action. This is quite

Figure 5: educational module in Virtual Maïdo

encouraging as this plugin is a requisite until a real time 3D-content playback standard for the Web emerges. Indeed, WebGL [START_REF] Parisi | WebGL: up and running[END_REF] and X3D [START_REF] Brutzman | X3D: extensible 3D graphics for Web authors[END_REF] are interesting technologies but despite their support from major organisms and companies (including main browsers editors), they are not so popular.

The second point that was evaluated was the maneuverability. This is a major concern as moving in a 3D immersive environment with a first person point of view is of course easy for gamers (the typical controls are always the same whatever the application is) but may be difficult for newcomers. Regarding this point, 83% of testers responded that it was easy, an answer that goes beyond the number of students in Computer Science who might be sometimes considered as a specific public, who tend to be more used to videogames. Ease of use was also rated as rather good as only 20% of testers found Immex quite hard to use. The same feeling was perceived concerning the attractiveness of the solution, with the same amount of users seeing it as low.

Finally, the last aspect evoked was related to the desirability of features. Each person was asked to rate the following proposed features that are sp ecific to immersive worlds: Figure 6 shows the feedbacks for each one with a visualization ranging from 1 (= no interest) to 5 (=strong interest). All the features receive a rather p ositive opinion, therefore it is interesting to focus on the subset of them which are shown the strongest interest. The most awaited ones, features (b) and (c) and at a lower point (a), relate to spatial localization indicating that users are very concerned by the relationship between the real world and the virtual world for their moves. The social aspect of the virtual environment then follows : a strong interest is shown from more than one user out of three for feature (g) which aims at enabling virtual interaction. This can be explained by the current trend that promotes various social media along with mobility. Quite surprisingly, using the application to study and learn in the 3D space is less popular than the previous features.

Figure 6: interest in several services (a) Virtually visit of technical or scientific locations that are not opened to general public (b) Locate a place before having to go to it (c) Benefit from a visual guidance system to a building or a room (d) Match buildings or rooms to their corresponding website (e) Retrieve contextual information by clicking on 3D objects (f) Learn new knowledge in 3D worlds dedicated to a given topic (g) Enable discussions and interactions between campus users

Through the different projects of the Immex program, we increased the number of services. The idea is to match the needs of the two main types of users: those using the simulation to freely stroll in the virtual environment and discover the experience, and those who came with a precise idea and want to fulfil a goal, like identify the path to reach a precise place.

For each new environment, we tried to deploy the previously conceived services and imagine new ones. In terms of re-usability, the services could be sorted in 3 categories:

• replicable services rely on scripts and assets that can be directly deployed from a scene to another. For instance, it is the case for all the presented movement-based services.

• transposable services is about features that are relevant from a metaverse to another one, but need transformation in order to be adapted to the new e nv i r o n m e nt . Fo r e x a m p l e , t h e navigation to remarkable place had to be adapted from the Moufia Virtual C a m p u s ( l e a d t o a s p e c i fi c amphitheater) to the Virtual Library metaverse (lead to a thematic section, adapted to multi-floor building).

• specific services are dedicated to a specific environment. It is the case for educational modules : the mission to activate the atmospheric laser obviously only makes sense for the Virtual Maïdo environment. In this way, even if these services are often the more relevant in the context of a virtual world, they also are the less re-usable.

If the information based services represent our main goal, we realized that we spent a lot of time creating services dedicated to movement and orientation. Indeed, as evoked previously, we made the university community test our metaverses during the whole developing process [START_REF]2 0 0 1 . U s e r -C e n t e red D e v e l o p m e n t[END_REF] . Depending on the public, we received feedback about the three categories of services in different proportions. Elderly and middleaged colleagues mainly focused on their m ove m e nt a n d o r i e nt a t i o n d i ffi c u l t i e s . Implementing these assistance services was a necessity. To work on data accessibility, we first had to ensure a good level of appropriation of our simulations.

Once the helpers are in a mature state, it is possible to focus on information based services, namely, develop more connectors between the university IS and the metaverses. A challenge is to find a way to enrich the data so that they can b e represent ed i nsi de t he v i rt ual environment. Although a transitional approach is to use a simple icon that links outside the metaverse though a popup, the best integration scheme should avoid to force the user to change the environment and allow him/her to consult all informations directly in the 3D space. Thus, apart from developing a connector, integrating a piece of information in a metaverse means identifying:

• a proper representation, that is to say a 3D model with the suitable texture to display information,

• a precise p osition (geographical positioning and orientation/inclination), obviously, in mirror-worlds, the georeferencing of each object is strongly linked to its use,

• a behavior, when the user will interact with its representation. For instance, a 3D chart should orientate itself toward the user in order to ease its reading whatever his approach is.

That is why our recent researches led us to c o n c e i v e a m o d u l e d e d i c a t e d t o t h e c e nt r a l i z a t i o n a n d t h e e n r i ch m e nt o f information, in order to prepare their injection into multiple metaverses through metaphor of representation. The idea is that this metaphor instantiation system (MIS) would gather the connectors and the data flows to the IS so that human content provider can choose what piece of information should be inserted in a given metaverse, at a given place and through a given representation to support a specific interaction. Thereby, a component added on each metaverse would, on each load, check MIS and fetch each flow dedicated to him. This system is currently in early development stage in our team and focuses on connectors with the pedagogical and schooling parts of our IS, in order to involve students.

This system could also be used for 3D objects that have a direct representation in met averses, but need t o change t hei r arrangement regularly. For instance, Virtual Library was modeled as a reproduction of all the shelving and indexing configuration. However, this configuration changed and the static positioning realized is now obsolete. By using a module like MIS, it would be possible to insert all shelves dynamically and let the library staff change only their positions when needed. Apart from this major structuration work that targets to facilitate the filing of the virtual worlds the automation and reuse of processes, we are also considering two ways to enhance the experience of the simulation. The first one is the possibility to personalize the virtual worlds. Indeed, in the frame of the university, users have different roles and access to different flows of information. For instance, researchers working on Virtual Maïdo instruments can access in real time to all the measures provided by the station sensors. By authenticating them before their immersive navigation, a click on each three-dimensional repro duction of instrument should allow them to access their data at the level of accuracy they are granted for. In the same way, an authenticated student should easily access his personal course schedule on campuses.

T h e s e c o n d e n h a n c e m e n t w e a r e considering is to offer a multi-users experience. It is one of the major feature we lost from eCampus, who was built on an MMORPG engine, to Immex. Indeed, the current simulation let the user visit virtual worlds full of objects but empty from people. First feedbacks also encourage us to develop this feature. Even if the experience does not support a massive amount of users, group simulations could improve the experience [START_REF] Mcardle | Exploring the Use of 3D Collaborative Interfaces for E-Learning[END_REF] and allow new kind of collaborative educational module scenarios [START_REF] Beuschel | Virtual Campus: Scenarios, Obstacles and Experiences[END_REF] .

CONCLUSION AND PERSPECTIVES

In this paper we presented the Immex program, that aims at providing services through virtual, real-time, online environments. As we have seen, Immex is more than just a collection of virtual worlds or a list of features : it is a real attempt to experiment and offer users an alternative to discover and share information in an alternative, ludic way. First feedbacks are encouraging, especially those from young students, although we also produced services to ease the use of older publics.

Future developments of the program aim at centralizing the data flow in a module that will enrich it and dynamically inject them in the targeted metaverses, through the chosen appearance. An improvement of the user experience will also mean offering simulations supporting personalized multi-user to open a

Figure 1 :

 1 Figure 1: virtual UTP metaverse

•

  p a n o r a m i c j u m p , f o r o u t d o o r s metaverses, produces the highest vertical jump possible, while tilting down the view. It offers an automatic, smooth, transition sequence between

Figure 3 :

 3 Figure 3: virtual Maïdo metaverse

Figure 7 :

 7 Figure 7: MIS positionning in IS

ACKNOWLEDGMENTS

The Immex program was funded by the UNR RUN-CO and the French Ministry of Higher Education and Research. The authors are grateful to the university services that contributed to the program. We also would like to thanks M.-H. Rakotobe, C. Porlier, P. Letellier and all students that worked on the Immex program.


Hayder F N Al-Shuka
email: hayder.al-shuka@rwth-aachen.de

Rui Song
email: rsong@sucro.org

Decentralized Adaptive Partitioned Approximation Control of Robotic Manipulators

Keywords: Adaptive Approximation Control, Decentralized Control, Orthogonal Basis Functions

Partitioned approximation control is avoided in most decentralized control algorithms; however, it is essential to design feedforward control with improved tracking accuracy. As a result, this work is focused on decentralized adaptive partitioned approximation control for complex robotic systems using the orthogonal basis functions as strong approximators. In essence, the partitioned approximation technique is intrinsically decentralized with some modifications. The proposed decentralized control law consists of three terms: the partitioned approximation-based feedforward term that is necessary for precise tracking, the high gain-based feedback term, and the adaptive sliding gainbased term for compensation of modeling error. The passivity property is essential to prove the stability of local stability of the individual subsystem with guaranteed global stability. A two-link robot is simulated to verify the effectiveness of the proposed technique.

Introduction

For complex robotic systems, such as humanoid robots or any robot having a number of degrees of freedom (DOFs) larger than 6-DOFs, difficulties are encountered in the implementation of the control algorithms. Therefore, over 30 years, the robotics researchers have focused on the problem of computational efficiency; see [START_REF] Saha | Recursive dynamics algorithms for serial, parallel and closed-chain multibody systems[END_REF] for more details. However, the adaptive control algorithm that deals with controlling the robotic systems despite their uncertain parameters may decrease the computational efficiency of the dynamics O (n) algorithms [START_REF] Fu | Robotics: control, sensing, vision, and intelligence[END_REF]. Therefore, most researchers have used a local controller (decentralized controller) such as PID family for controlling complex dynamic systems [START_REF] Spong | Robot dynamics and control[END_REF]. However, Liu [START_REF] Liu | Decentralized control of robot manipulators: nonlinear and adaptive approaches[END_REF] has proved that decentralized PD control for robotic manipulator can ensure local stability without guaranteed global stability. Therefore, the author proposed decentralized a PD + nonlinear cubic controller with guaranteed global stability. Yang et al. [START_REF] Yang | Decentralized adaptive robust control of robot manipulators using disturbance observers[END_REF] have used disturbance observer and adaptive sliding mode control for compensation of low-pass and high-pass coupled uncertainties respectively. In general, most available control strategies are based on designing PD control plus robust and or/adaptive term(s) for compensation of modeling errors and the interconnections. For more details on decentralized robust/adaptive control, see [START_REF] Yang | Decentralized adaptive robust control of robot manipulators using disturbance observers[END_REF] and the references therein. Apart from conventional robust control, adaptive approximation control is a powerful tool to control robotic manipulators with unknown dynamics. There are two possibilities of adaptive approximation techniques: lumped (global) approximation-based adaptive control and partitioned (local) approximation-based adaptive control [START_REF] Lewis | Neural net robot controller: structure and stability proofs[END_REF]- [START_REF] Al-Shuka | On local approximation-based adaptive control with applications to robotic manipulators and biped robots[END_REF]. The former deals with collecting the uncertainty in one term and using the linear-in-the-parameters property to represent the uncertainty in terms of weighting and basis-function vectors. Then the controller is selected based on updating the weighting vector using Lyapunov stability. This strategy requires nominal (ideal) model for the unknown parameters. On the other hand, partitioned approximation adaptive control approximates each dynamic coefficient matrix of the equation of motion of the target robot separately using the linear-in-theparameters property. The control law is then designed based on updating the weighting-coefficient matrices of the corresponding basis-function matrices using Lyapunov stability. The interesting point is that the partitioned approximation does not require a nominal model for the dynamic coefficients easing the control task. However, most decentralized approximation control algorithms used lumped approximation term combined with either PD term or nominal values [START_REF] Panagi | Decentralized Adaptive approximation based control of a class of large-scale systems[END_REF]- [START_REF] Fateh | Decentralized direct adaptive fuzzy control of robots using voltage control strategy[END_REF]. In view of above, partitioned approximation control is avoided in most decentralized control algorithms despite its importance in the design of feedforward control with improved tracking accuracy. As a result, this work is concerned with decentralized adaptive partitioned approximation control for complex robotic systems using the orthogonal basis functions as strong approximators. In essence, the partitioned approximation technique is intrinsically decentralized with some modifications. The proposed decentralized control law consists of three terms: the partitioned approximation-based feedforward term that is necessary for precise tracking, the high gain-based feedback term, and the adaptive sliding gain-based term for compensation of modeling error. The passivity property is essential to prove the stability of local stability of the individual subsystem with guaranteed global stability.

The remainder of the paper can be organized as follows. Methodology is presented in Section 2. Section 3 described simulation results and discussions. Section 4 concludes.

Remark 1. Preliminaries for adaptive approximation control and the related theorems such as Weierstrass theorem are described with some details in [START_REF] Al-Shuka | On local approximation-based adaptive control with applications to robotic manipulators and biped robots[END_REF][START_REF] Farrell | Adaptive approximation based control: unifying neural, fuzzy and traditional adaptive approximation approaches[END_REF].

Methods

Dynamics of Contact-Free Motion Robots

The equation of motion for n-DOF robotic manipulators in free space can be expressed as

      ) , ( ) ( ) , ( ) ( q q q g q q C q q D     f (1) where n R  D is the inertia matrix of the links, n R  C
is the Coriolis and centripetal matrix of the links,

n R  g is the gravity vector, n R  q represents the angular joint displacement, n f R  
is the friction joint torque vector, and n R   denotes to the output joint torques. Based on Eq. ( 1), the k th subsystem of the target robot, where n k  can be ex- pressed as

k k k fk k j n 1 j kj j n 1 j kj τ ) q , (q τ q g q ) q (q, c q (q) d              ) ( (2)
The inertia, Coriolis and centripetal, and the gravity terms of Eq. ( 2) include coupled nonlinear functions, therefore, they are written in terms of general state variables. The objective of decentralized control is to control every DOF individually; therefore, Eq. ( 2) can be further expressed as

k k k kk k kk q q q q q c q q d      ) , ( ) , ( ) (      (3a) with ) q , (q τ (q) g q ) q (q, c q (q) d k k fk k j n k j 1 j n k j 1 j kj j kj k                 (3b)
The following properties assumptions are necessary for adaptive approximation control assuming robotic manipulators with revolute joints [START_REF] Spong | Robot dynamics and control[END_REF][START_REF] Mulero-Martí Nez | Uniform bounds of the coriolis/centripetal matrix of serial robot manipulators[END_REF].  satisfies condi- tions of Weierstrass approximation theorem [START_REF] Farrell | Adaptive approximation based control: unifying neural, fuzzy and traditional adaptive approximation approaches[END_REF], i.e., they can be represented as a linear combination of basis functions.

Property

Decomposition Technique

Let us recall the partitioned approximation technique described in details in [START_REF] Al-Shuka | On local approximation-based adaptive control with applications to robotic manipulators and biped robots[END_REF]. Accordingly, Eq. ( 1) can be expressed as 4), the partitioned approximation technique has inherently decentralization features that can be exploited for decentralized control. In view of properties 1, 2, assumptions 1, 2, and Eq. ( 4), Eq. ( 3) can be reformulated as

                                                  n T n
k k k T k k Ck T Ck k Dk T Dk τ ε q q          w w w    (5)
where

Dk Dk T Dk kk ε (q) d    w , Ck Ck T Ck kk ε (q) c    w , k k T k k ε (q)        w (6) with (.)
ε is the corresponding modeling error. Accordingly, the dynamics of the cou- pled robotic system is transformed to decoupled subsystems based on linear combinations of basis function with constant weighting coefficients that should be updated using the Lyapunov theory.

Remark 2.

A significant property that is inherently featured by Eq. ( 5) is that the whole system can freely be transformed to arbitrary subsystems. For example, a 6-DOF robot can be decoupled to two 3-DOF robotic subsystems, and so on.

Controller Design

The intuitive control law can be selected as

) ˆk k k k k k kk k kk k (s (t)sgn Γ s K v ) q ( c v (q) d τ         (7) with , e Λ - q v c d k k dk k k T k k Ck T Ck kk Dk T Dk kk         , , , ˆ   w w w dk k k k k k k k k q q e , e Λ e v - q s       
where the symbol ( . ˆ) refers to the estimation, denotes to the adaptive sliding gain that should be updated in order to avoid the demand of modeling error bounds, please for more details on adaptive sliding mode control see [START_REF] Utkin | Adaptive sliding mode control[END_REF], and

s s sgn(s) (8)
The mathematical relationship of Eq. ( 8) is very useful in the stability proof discussed later. Substituting Eq. ( 7) into Eq. (3a) leads to the output position closed loop dynamics

k k T k k Ck T Ck k Dk T Dk k k k k k kk kk ε v v ) (s sgn (t) Γ s K s c s d           ) ( ˆ   w w w   (9)
From Eq. ( 9), the closed loop control system is stable if

0, ε k   , 0 ~(.) w and k k k ε δ (t) Γ   ˆ.
This requires finding suitable update laws for the weighting coefficients and the adaptive sliding gain. Let us select the following updating adaptive laws for the weighting vectors and adaptive sliding gain as follows.

k k k k k k k k k Ck Ck Ck k k Dk Dk Dk ρ s (t) Γ s s v s v                , , , ˆ   Q w Q w Q w ( 10
)
where

β β (.) R  

Q

is a positive-definite adaptation matrix, and k  is an adaptation gain.

Theorem 1. The k-th subsystem of the robotic manipulator, n k  , described by Eq. ( 5) combined with the input control law of Eq. ( 7), and with the adaptation laws of the weighting vectors, and the adaptive sliding gain of Eq. ( 10) is stable in the sense of Lyapunov stability [START_REF] Al-Shuka | Dynamic modeling, walking pattern generators and adaptive control of biped robot[END_REF]- [START_REF] Huang | Adaptive control of robot manipulators: a unified regressor free approach[END_REF].

Proof.

Consider the following Lyapunov-like function ( k V ) along the trajectory of Eq. ( 9)

2 k k T Δk 1 Δk T Δk T Ck 1 Ck T Ck T Dk 1 Dk T Dk 2 s kk k Γ ρ 2 1 s d V 2 1 2 1 2 1 2 1         w Q w w Q w w Q w (11)
Taking the derivative of the last equation leads to

(t) Γ (t) Γ ρ s d s s d V k k k k 1 k T k Ck 1 Ck T Ck Dk 1 Dk T Dk 2 k kk k k kk k        2 1             w Q w w Q w w Q w ( 12
)
By substituting Eq. ( 9) into Eq. ( 12), using the adaptation laws of Eq. ( 10), and applying passivity property 2 lead to

k k k k k k k k 2 k k k s (t)) Γ (δ ) (t)sgn(s Γ s ε s s K V        (13)
Using Eq. ( 8) yields

k k k k 2 k k k s δ ε s s K V      ˂ 0 (14)
Both

Remark 3.

Although k δ should be larger than or equal to the upper bound of the modeling error, it is not included in the design of the proposed control law. Accordingly, the proposed control law of Eq. ( 7) does not require the bounds of the modeling error.

Simulation Results and Discussions

A simple 2-link manipulator is simulated to prove the validity of the proposed controller (Fig. 1). The parameters of the simulated manipulators are borrowed from [START_REF] Huang | Adaptive control of robot manipulators: a unified regressor free approach[END_REF].

It is assumed that the two joints are actuated with direct drive (gear ratio=1). The target manipulator moves freely (without constrained motion) with the following desired trajectories [START_REF] Slotine | Applied nonlinear control[END_REF]: t)) cos( 2(1 30 q 0 d1    and t)) cos( 2(1 45 q 0 d2    .

Fig. 1. The 2-link manipulator

Accordingly, the control law of Eq. ( 7) with the corresponding updating adaptive laws of the weighting vectors, Eq. ( 10), is used for precise tracking the desired references.

A decentralized control is applied to each link subsystem using the proposed algorithms. The number of terms of basis orthogonal basis functions is 15 neglecting the modeling error (assuming a sufficient number of basis functions are used

I Q I Q Q k       k Ck Dk k K
. The adaptive partitioned approximation control (APAC) is compared with the decoupled proportional-derivative controller (PD) that is used extensively for control of robotic manipulators. The PD control law can be described as (Liu, 1999 [4]):

) (

k k k k k k e e K s K        , with 100  k K
. Figures 2 and3 show the position errors and the input control torques respectively considering both the APAC and PD controllers. Both controllers work well with small position error; however, the APAC shows more accuracy than the PD considering the same high gain. One important point should be mentioned is that although the APAC control law does not track precisely the dynamic coefficients of the equation of motion for each subsystem, the controller tracks well the desired references. The system signals should be persistently excited in order to ensure good estimation for unknown parameters [START_REF] Farrell | Adaptive approximation based control: unifying neural, fuzzy and traditional adaptive approximation approaches[END_REF].

Conclusions

This paper proposes decentralized adaptive control based on partitioned approximation technique. The control law consists of three terms: adaptive partitioned approxi-mation-based feedforward term, high-gain feedback term, and an adaptive sliding term for compensation for modeling error. Further work is required to consider the joint flexibility and actuator dynamics.

  -coefficient and basis-function vectors respectively, and n R   denotes to the accumulated modeling error vector. According to Eq. (

Fig. 2 .Fig. 3 .

 23 Fig. 2. The position error for the 2-link robot

  The state variables of the target robots are measureable and bounded.

	This property can be extended such that the dynamic coefficients and the disturbance
	term	(d	,	d	,	c	,	c	,	g	,	τ	)	, with	j k  ,	n	are uniformly bounded.
				kk	kj		kk			kj		k		fk
	Property 2. The matrix		M	D  		C 2	is a skew-symmetric matrix, i.e.,
	T s	Ms		, 0	 s		R	n	, if	) C  is defined using the Christoffel symbols. , ( q q
	Accordingly, the diagonal elements of	M are equal to zero, i.e.,	m		, 0	i  	n	.
																		ii
	The last property is important in deriving the stability of the proposed controller.
	Assumption 1. Assumption 2. Each entry of dynamic matrices of	, D	C	,	g	,	and
																		f

1. The inertia matrix, Coriolis and centrifugal matrix, and the gravity vectors are uniformly bounded.