Graphvizgl L Garnier

OPENSCIENTIST

It is an integration of open source products working together to do scientific visualization and data analysis, in particular for High Energy Physics (HEP).

The environment of OpenScientist use OpenGL[3] as a rendering layer which is now a de facto standard that comes on all interactive platforms.

Thanks to its modularity, OpenScientist can be connected to several packages. For graphviizgl library, we will add two new packages to render OpenGL :

-Graphviz : to render graphs and route algorithms -FTGL [4]: to render freetype[5] fonts

GRAPHVIZ LIBRARY

Graph visualization is a way of representing structural informations as diagrams of abstract graph and networks. Automatic graph drawing has many important applications in software engineering, database and web design, networking, and in visual interfaces for many other domains.

Graphviz is an Open Source graph visualization software use for example in doxygen graph generation. Thanks to multiples routing algorithms, it is very goodat visualizing scene containing boxes connected by lines. For ower use, we will have to connect another library with graphviz, in order to render fonts : FTGL FTGL It is a free, open source library to enable developers to use arbitrary fonts in their OpenGL applications.

Unlike other OpenGL font libraries, FTGL uses standart font flie formats so it does not need a preprocessing step to convert the hight quality font data into a lesser quality, proprietary format.

FTGL uses Freetype font library to open and "decode" the fonts. It then takes that output and stores it in a format most efficient for OpenGL rendering.

IMPLEMENTATION DETAILS

Graphviz library can generated graph from two ways : -You could give a dot file witch will look like : digraph g { tree [color = red]; "item 1"; "item 2"; "item 3"; "item 4"; "item 5"; "item 6"; tree -> "item 1"; tree -> "item 2"; tree -> "item 3"; tree -> "item 4"; "item 1" -> "item 5"; "item 1" -> "item 6"; "item 6" -> "item 2"; "item 6" -> "item 4"; "item 4" -> "item 5"; "item 5" -> "item 4"; } -Or directly code your graph description in the .cxx file. The code bellow render the same graph.See It can also export graphs in a lot of formats like "jpeg", "ps", "vrml", "svg",thanks to a plugins mechanism.

As we wanted to use graphviz as a library, dot file is not the good solution. We have implemented a new plugin witch made the link between OnX and graphviz library.

Figure 1 :

 1 Figure 1 : A picture product with the LHCb Panoramix event display built with OnX

Figure 2 :

 2 Figure 2 : Example of graphviz output on OnX GUI component.

  figure 3. n = agnode(fGraph, "tree"); n1 = agnode(fGraph, "item 1"); n2 = agnode(fGraph, "item 2"); n3 = agnode(fGraph, "item 3"); n4 = agnode(fGraph, "item 4"); n5 = agnode(fGraph, "item 5"); n6 = agnode(fGraph, "item 6"); e = agedge(fGraph, n, n1); e1 = agedge(fGraph, n, n2); e2 = agedge(fGraph, n, n3); e3 = agedge(fGraph, n, n4); e4 = agedge(fGraph, n1,n5); e5 = agedge(fGraph, n1, n6); e6 = agedge(fGraph, n6, n2); e7 = agedge(fGraph, n6, n4); e8 = agedge(fGraph, n4, n5); e9 = agedge(fGraph, n5, n4); agsafeset(n, "color", "red", "");

Figure 3 :

 3 Figure 3 : graph render by code describe previously RESULTS

Now, in just a few line of code to call the graphviz library, and a few lines to initialize the graph, we are able to draw in grapgs in OpenGL into openScientist.


Noëlle Carbonell
email: noelle.carbonell@loria.fr

Ambient Multimodality: an Asset for Developing Universal Access to the Information Society

Our aim is to point out the benefits that can be derived from research advances in the implementation of concepts such as ambient intelligence and ubiquitous/pervasive computing for promoting Universal Access to the Information Society, that is, for contributing to enable everybody, especially people with physical disabilities, to have easy access to all computing resources and information services that the coming worldwide Information Society will make available to the general public as well as to expert users in the near future.

Following definitions of basic concepts relating to multimodal interaction, the significant contribution of multimodality to developing Universal Access is briefly discussed. Then, a short state of the art in ambient intelligence research is presented, including references to some of the major recent and current research projects in this area. The last section is devoted to bringing out the potential contribution of advances in ambient intelligence research and technology to the improvement of computer access for physically disabled people, hence, to the implementation of Universal Access. This claim is mainly supported by the following observations:

(i) most projects aiming at implementing ambient intelligence focus their research efforts on the design of new interaction modalities and flexible/adaptive multimodal user interfaces; outcomes of these projects may contribute to improving computer access for users with physical disabilities; (ii) these projects target applications meant to support users in a wide range of daily activities which will have to be performed simultaneously with the related supporting computing tasks; therefore, users will be placed in situational contexts where they will be confronted with similar difficulties to those encountered by physically disabled users, since they will have to share out their perceptual and motor capabilities between two tasks at least, a current daily activity and a computing task; (iii) ambient intelligence applications being intended for the general public, a wide range of interaction devices together with flexible software for processing related modalities will be available, making it possible to provide physically disabled users with appropriate human-computer interaction tailored to their individual needs at reasonable expense.

Introduction

Ambient intelligence and ubiquitous or pervasive computing are concepts that refer to emerging technologies and potential software applications meant to populate our daily environment with smart artefacts and cooperative personal assistants. Numerous strategic objectives in the 6 th European Research Framework on Information Sciences and Technologies focus on issues relating to these concepts which motivate a growing interest from both researchers in human-computer interaction and user interfaces designers.

To implement these related concepts appropriately, a great variety of input and output modalities or combinations of modalities is necessary. In particular, adaptive multimodality is required for enabling efficient interaction with the "intelligent" artefacts and agents of all kinds which will soon assist us in our everyday life activities, hence in varied contexts of use: at home or in cars, on the street, on buses and trains, in public places such as shops, museums, etc.

Switching from one daily routine activity to another often implies switching interaction modalities. In addition, implementing ubiquity necessitates to accommodate user mobility, therefore to invent new interaction devices that can be embedded in ordinary objects belonging to the user's everyday environment, or in wearable objects. For instance, surfaces of everyday objects may be used as substitutes for pointing devices [START_REF] Schmidt | Ubiquitous Interaction -Using Surfaces in Everyday Environments as Pointing Devices[END_REF]. Intelligent clothing or "interactive wear" may host a high diversity of computer applications (see, for instance, the Infineon web site). In addition, users' gestures, gaze, head and body movements can now be tracked and interpreted reliably, which makes it possible to further diversify the media and modalities offered to users for interacting with smart, local or remote, artefacts and agents.

While the diversification of context of use has favoured the development of new input modalities and combination of modalities, it has had but little influence on output media and modalities which are still much less diversified. Thanks to recent advances in speech synthesis, text to speech translation [START_REF] Dutoit | An Introduction to Text-To-Speech Synthesis[END_REF], interactive 3D visualisations [START_REF] Ware | Information visualization. Perception for design[END_REF], talking heads and embodied animated agents [START_REF] Bosseler | Development and Evaluation of a Computer-Animated Tutor for Vocabulary and Language Learning for Children with Autism[END_REF], speech and graphics can be used effectively by designers for conveying a wide range of information, sensations and emotions to the user. However, further research is needed in order that haptics, sounds and odours may be considered as reliable easy to implement output modalities capable of enriching human-computer interaction.

Besides, thanks to the availability of reliable GPS information and wearable bio-sensors, useful information on the user's current environment and the interaction context can be inferred from the knowledge of their location, while being aware of their current physiological and emotional state may prove useful for assisting them. For instance, the context-aware MatchMaker prototype application, which was experimented on the CMU campus, can help a user to rapidly identify an expert user with appropriate knowledge for solving an unexpected problem or answering an urgent question. Awareness to spatial and temporal contexts enables MatchMaker to include proximity to the user and availability of the expert among the criteria used for selecting an expert [START_REF] Smailagic | Towards Context Aware Computing: Experiences and Lessons[END_REF].

Efforts to promote Universal Access in the coming Information Society could benefit from research advances in the implementation of ambient intelligence and pervasive computing. Such advances will enable the development of applications for the general public that will provide users with flexible multimodal interaction involving novel modalities with richer expressive power and greater transparency. Universal Access refers here to a long-term objective, difficult to attain: providing everybody with easy computer access. At present, technological solutions exist that can satisfactorily compensate for many motor and perceptual handicaps. Numerous laboratory prototypes have been developed that implement them appropriately. However, only a few of them have been turned into commercial products, due mainly to the cost of developing and putting on the market appliances dedicated to small user communities. In addition, the diversity of motor and perceptual handicaps is such that most devices and software have to be tailored to individual capabilities and needs, which is impossible to achieve at reasonable expense, at least for the time being. Besides, applications meant to implement the emerging concepts of ubiquitous computing and ambient intelligence, using novel interaction modalities and new user interface technologies, are fast developing. Such applications are likely to spread into the general public in the near future. Some possible side-effects of this evolution may prove beneficial and useful for promoting Universal Access. In particular, as the implementation of ambient intelligence implies the development of adaptive multimodal interaction based on a wide spectrum of media and modalities, this likely evolution will make it possible to propose a wide range of human-computer interaction devices and modalities to users with a great diversity of motor and/or perceptual disabilities. Designers and manufacturers will then have the means to offer them satisfactory computer access, namely, interaction facilities that can be appropriately tailored to their actual individual capabilities, and that can follow the possible evolution of their needs and requirements in the course of time. They will also have the opportunity to develop cheap flexible products from laboratory prototypes for compensating motor and perceptual handicaps appropriately. In addition, they will be able to propose novel assistance services aimed at helping users with physical disabilities to carry out everyday tasks, thanks to context awareness development tools [START_REF] Dey | A conceptual Framework and a Toolkit for Supporting the Rapid Prototyping of Context-Aware Applications[END_REF].

Current definitions of medium, modality, multimedia and multimodality will be presented in the next section together with a brief discussion of the potential contribution of multimodality to the implementation of Universal Access. Then, the state of the art in research on ambient intelligence, ubiquitous computing and "disappearing computer" will be briefly reviewed in section 3. Special emphasis will be laid on novel input and output devices, on new interaction modalities and combinations of modalities. Section 4 will focus on proposing new research directions in assistive technologies that may benefit from recent scientific advances in the implementation of concepts such as ambient intelligence and ubiquitous computing, in the design of applications and user interfaces intended for the general public. We suggest research directions that may lead to fruitful applications, namely, applications contributing effectively to reduce computer access difficulties resulting from motor or perceptual handicaps, with a view to further extending the implementation of Universal Access design principles. In particular, a major aim of this reflection is to improve computer accessibility for users with physical disabilities that may evolve in the course of time, for instance as a corollary of age (cf. the growing perceptual and motor handicaps of senior users).

Definitions: medium vs modality, and multimedia vs multimodality

Multimodality, that is the simultaneous or alternate use of several modalities, appears as an emerging, useful interaction paradigm for advancing the implementation of universal accessibility.

Modality refers to the use of a medium, or channel of communication, as a means to express and convey information [START_REF] Coutaz | A taxonomy for multimedia and multimodal user interfaces[END_REF]Maybury, 1993). Within the framework of a communication exchange, the sender translates concepts (symbolic information) into physical events which are conveyed to the recipient through an appropriate medium, and the recipient interprets the incoming signal in terms of abstract symbols. These processes involve the user's senses and motor skills and, symmetrically, the system input/output devices. According to the taxonomy presented in [START_REF] Bernsen | Foundations of multimodal representations, a taxonomy of representational modalities[END_REF], several modalities or modes may be supported by the same medium (e.g., text and graphics used as output modalities). In other words: "… by media we mean the carrier of information such as text, graphics, audio, or video. Broadly, we include any necessary physical interactive device (e.g., keyboard, mouse, microphone, speaker, screen). In contrast, by mode or modality we refer to the human senses (more generally agent senses) employed to process incoming information, e.g., vision, audition, and haptics." (Maybury, 2001, p. 382) Similarly, the terms Multimedia and Multimodality refer to two different realities. Multimedia systems have the capability of storing data conveyed through several input media, and to present them to the user through a set of appropriate output media. In addition, multimodal user interfaces are capable of resorting to several modalities for communicating information to the user (e.g., for generating system messages and responses); they have also the capacity to "understand" multimodal commands from the user, that is commands the information content of which is expressed using several modalities.

To characterize the various possible combinations of modalities or forms of multimodality, a taxonomy composed of four classes has been proposed [START_REF] Coutaz | A taxonomy for multimedia and multimodal user interfaces[END_REF]. As we focus here on issues relating to usage rather than implementation, we only need to consider two classes in this taxonomy:

• alternate multimodality1 , which characterizes a multimodal sequence of unimodal messages,

• synergic multimodality, which refers to multimodal utterances or, in other words, to the simultaneous use of several modalities in a single message.

The benefits that interface designers can draw from the implementation of multimodality are threefold. Firstly, alternate multimodality can advance computer accessibility, as it provides users with the means to choose among available modalities/media according to the specific usability constraints induced by the current context of use [START_REF] Oviatt | Multimodal system processing in mobile environments[END_REF]. Secondly, alternative media, modalities, and styles of multimodality are necessary for providing physically disabled users with computer access [START_REF] Carbonell | Multimodality: a primary requisite for achieving an information society for all[END_REF]. Finally, synergic multimodality represents an indisputable improvement on unimodal interaction, in terms of expressive power, usability, and efficiency. For instance, the case study reported in [START_REF] Cohen | The efficiency of multimodal interaction: a case study[END_REF] suggests that multimodal interaction involving pen and speech may prove more efficient, in terms of speed mainly, than direct manipulation, at least for map-based tasks. According to the authors, "this advantage holds in spite of a 68% multimodal success rate, including the required error correction".

In particular, a significant advance in the implementation of universal computer access may be achieved, thanks to the integration of speech into standard user interfaces either as an alternative or a supplementary input modality.

Integrating speech into user interfaces as a supplementary modality beneficially increases the limited expressive power of hand gestures and body movements. In addition, speech has major assets as a means of expression: it is flexible and currently viewed as the most natural human means of expression and communication. In addition, reliable speech processing technology is now available: the accuracy and robustness of present speech recognisers are sufficient to meet standard usability requirements. Products offering generic software tools for developing oral dialogue interfaces are available on the market (e.g., Speech SDK2 ). Appropriate software architectures and efficient " fusion" algorithms have also been proposed for integrating speech into multimodal user interfaces as an input modality (see, for instance, [START_REF] Nigay | A Design Space for Multimodal Systems: Concurrent Processing and Data Fusion[END_REF][START_REF] Johnston | Unification-based multimodal parsing[END_REF]).

In the next section a tentative definition of the emerging concept of ambient intelligence is proposed. Then, some major scientific projects in this area are briefly described with a view to illustrating this definition.

3 Ambient intelligence and ubiquitous computing: an emerging research area

Definitions

Ambient intelligence refers to a broad scientific thematic including research activities on ubiquitous, pervasive and mobile computing mainly.

According to (Want, Farkas & Narayanaswani, 2005, p. 14): "pervasive computing aims to integrate computation into our daily work practice to enhance our activities without being noticed. In other words, computing becomes truly invisible." Mark Weiser uses similar terms to characterise ubiquitous computing (see his web page):

"it is invisible, everywhere computing that does not live on a personal device of any sort, but is in the woodwork everywhere."

Trends in computing and electronics are opening up new possibilities for interacting with computers. Faster networks and wireless technologies make it possible to interact with interconnected smart artefacts which behave in a coordinated way, using other devices than the standard peripherals of desktop PCs (i.e., mouse, keyboard, screen and speakers). These trends introduce new off-the-desktop application scenarios involving mobile users, mobile devices, and richer forms of interaction with cooperative artificial agents accessible from everywhere. The long-term objective of ubiquitous computing and ambient intelligence is to enable users to interact with a dynamic suite of devices embedded in their everyday environment so that they may be unaware of many of them. Phrases like "disappearing computer" or "context-aware systems/environments" refer to implications of these concepts.

In particular, contextual awareness is a key feature of ubiquitous computing systems. Context here means situational information relevant to the interaction between a user and an application: "A context-aware intelligent environment is a space in which a ubiquitous computing system has contextual awareness of its users and the ability to maintain consistent, coherent interaction across a number of heterogeneous smart devices." (Shafer, Brumitt & Cadiz, 2001, p. 363). According to (Starner, 1999, p. 25-26), a context-aware interactive system must be capable of:

• perceiving the user and their interaction environment through various sensors some of which may be wearable; • interpreting and modelling sensor data on the user (e.g., their current location, activity, physiological and emotional state), their physical environment, the interaction and task progress; • interacting with the user through a contextually-driven user interface or distributed interaction devices embedded in everyday objects.

Ubiquitous computing and ambient intelligence imply mobile computing. Therefore, user mobility appears as a major design requirement for applications that aim at implementing these concepts appropriately. Obviously, monolithic standard GUIs meant for standalone PCs cannot meet this requirement. It is then necessary to break traditional styles of human-computer interaction. In particular, user interface functionalities have to be replicated in peripheral devices distributed in objects accessible to the user everywhere and at any time during their daily activities. These devices can be embedded either in objects in the user' s everyday physical environment or in wearable objects, according to the activity the user is engaged in and the service or assistance they are meant to receive from the smart distributed system. Interaction with such distributed user interfaces has to be flexible as it takes place in various physical settings and, most often, while users are engaged in some daily routine activity (e.g., driving, cooking). This specific context of use places constraints upon the selection of input and output modalities. These constraints which restrict the availability of the user's perceptual resources and limits the range of their physical actions need to be taken into account. As a side-effect, the volume and content of information exchanges between user and system have to be tailored to fit the specific expressive power and throughput of the chosen media and devices (e.g., PDAs, laptops, etc.). The implementation of these constraints raises new research issues which constitute a fast developing research area focused on achieving user interface plasticity [START_REF] Calvary | A Unifying Reference Framework for the Development of Plastic User Interfaces[END_REF], especially through what may be called "adaptive multimodality". Additionally, the feasibility of user interfaces enabling interaction with smart artefacts embedded in everyday physical environments or in wearable objects offers the opportunity to design new styles of multimodal interaction.

As for context awareness, the implementation of this concept, thanks to sensors capable of providing useful information on the user, the system and the interaction environment, makes it possible to extend the range of present computer applications, especially to design and implement novel, sophisticated forms of assistance to everyday life activities.

The next subsection presents a few research projects that contribute to the implementation of ubiquitous computing and ambient intelligence, especially by proposing realistic application scenarios or appropriate distributed computer environments and architectures, or new technologies for implementing context awareness and flexible multimodal interaction.

Examples

EasyLiving is one of the first major projects3 that attempted to implement intelligent everyday environments (see the Microsoft web site). It includes a test laboratory equipped with distributed sensors and input-output devices embedded in the daily physical environment of the user. Main software tools include:

• for achieving context awareness by capturing situational information relevant to the interaction: computer vision (person tracking) and sensors (tracking of events, changes in the physical environment, etc.), geometric model of the physical environment; • for providing flexible multimodal interaction: multiple sensor/actuator modalities, modality fusion, user interface adaptation; • for facilitating the development of applications: automatic or semi-automatic calibration of sensors, and building of a geometric model of the user physical environment; • for ensuring system extensibility: device-independent communication and data protocols.

In [START_REF] Shafer | Interaction Issues in Context-Aware Intelligent Environments[END_REF], a realistic scenario of interaction with EasyLiving is described to illustrate the new interaction facilities that a context-aware intelligent environment can offer to users in their daily activities at home. Lights in a room can be remotely turned on using a speech command. Sitting in the living room on a sofa that faces the TV automatically activates the display of a menu with various options (e.g., "Watch a movie", "Play music" …), etc. Modalities used for information exchanges between the user and the distributed system can change according to the situational context (alternate multimodality). For instance, a switch -instead of a speech command -may be used to turn on the lights in a room, so as to avoid disturbing a light sleeper in an adjoining room. Similarly, the system may resort to speech synthesis to convey an urgent warning to the user when asleep, instead of displaying it.

In [START_REF] Smailagic | Towards Context Aware Computing: Experiences and Lessons[END_REF], a design framework for context-aware applications is proposed. It is based on the assumption that "context aware applications are built upon at least two fundamental services, spatial awareness and temporal awareness" (p. 38), where temporal awareness amounts to the scheduled time of public and private events. As mobile computing is often performed simultaneously with another attention consuming primary task (e.g., walking, driving, etc.), the user may be distracted from their primary activity or neglect the other less important activity (i.e., computing). The aim of the Activity/Attention framework is to reduce user distraction and optimise the simultaneous execution of a primary task and a mobile computing task, using a Distraction matrix that characterizes activities by the amount of attention they require. Individual computer activities4 are categorized by the amount of distraction they introduce in the primary activity.

Authors present some interactive applications that were developed to validate this design framework, demonstrate how to use it, and illustrate the benefits that can be gained from using it. For example, the Portable Help Desk (PHD) enables a mobile user to get maps of their immediate vicinity, including static and dynamic information. Thus, while walking on a campus, the user can obtain information on the location, contact information and availability of members of the academic staff, using their PHD.

More recent or current research projects are focused on further developing and implementing core concepts in pervasive computing and ambient intelligence.

The Oxygen project at MIT aims at supporting highly dynamic and varied human activities at home, at work and on the go. This ambitious project lays emphasis on enabling users to work together with other people through space and time (see the Oxygen web site). Ozone, an EU funded project (5 th FWP, 2001FWP, -2004)), pursued roughly similar objectives, since it aimed to "investigate, define and implement/integrate a generic framework to enable consumer oriented ambient intelligence applications." The only difference lies in the user tasks and activities to be supported. While Oxygen was focused on supporting collective work, the main utility and usability objectives of Ozone were to "enhance the quality of life by offering relevant information and services to the individual, anywhere and at any time". A major outcome of this European project is the implementation of research results in two demonstrators, one for home activities, the "home demonstrator", and the other one for nomadic use, the "away demonstrator" (Ozone Final Report, section 5.5, 2005). See also [START_REF] Diederiks | Sociability and Mobility Concepts for the Connected Home[END_REF] for applications involving home activities. The CHIL and AMI European projects (6 th FWP) focus on enhancing and augmenting communication between users; see the web sites of these projects in progress. CHIL (Computers in the Human Interaction Loop, 2004Loop, -2006) ) aims at creating "environments in which computers serve humans who focus on interacting with other humans". This goal will be achieved thanks to the design and implementation of computer services that will be capable, from the observation of people interacting face-to-face with each other, to infer the state of their activities and their intentions. These services will be endowed with perceptual context awareness to provide, whenever possible, implicit assistance which requires a minimum of human attention compared to explicit interaction. The main research issues addressed include:

• multimodal recognition and interpretation of all available perceptual cues in the environment with a view to explaining human collaborative activities and anticipating participants' intentions, • quantifiable cognitive and social models of interactions between humans. Smart rooms, namely office and lecture rooms, are the privileged applications that CHIL partners will use for demonstration and evaluation purposes. AMI (Augmented Multi-party Interaction, 2004Interaction, -2006) ) focuses on the design and implementation of new multimodal technologies capable of supporting human interaction in the context of smart meeting rooms and remote meeting assistance agents. It aims to make human interaction more effective in real time by developing new tools for supporting cooperative work and assisting navigation in multimodal meeting recordings. The project addresses several difficult research issues in two main areas:

• multimodal input processing, namely multilingual speech recognition and speaker tracking, gesture interpretation, handwriting recognition and shape tracking, integration of modalities and multimodal dialogue modelling; • content abstraction, including multimodal information indexing, summarizing and retrieval. Envisaged outcomes of the project include several demonstrators (e.g., an offline meeting browser and an online remote meeting assistant), and dissemination of large collections of annotated multimodal meeting recordings.

Ambient multimodal intelligence contribution to advancing Universal Access

As shown in the preceding section, past and present research on the implementation of concepts such as ubiquitous or mobile computing, pervasive or ambient intelligence has led to significant scientific and technological advances which have great potential to promote and stimulate the progress of research dedicated to the implementation of Universal Access (i.e., computer access for everybody) in the coming Information Society. In addition, they open up new possibilities for providing physically disabled people with enhanced assistance in their daily activities, thus improving their social integration.

All research attempts at implementing ambient intelligence (see section 3) aim at assisting users in their daily activities. In this context, computing tasks are viewed as secondary tasks that simply contribute to the completion of primary daily activities. They have then to be carried out in parallel with primary activities. This explains why most research projects on ambient intelligence lay emphasis on the design of new human-computer interaction modalities and flexible multimodal interaction so as to enable users to carry out computing tasks simultaneously with everyday activities without disrupting these activities. It also implies that users of these future ambient intelligence environments will be placed in situational contexts where they will be confronted with similar difficulties to those encountered by physically disabled users, since they will have to share out their perceptual and motor capabilities between two tasks at least, a current daily activity and a computing task. Therefore, many solutions initially designed for enabling users of ambient intelligence applications to carry out computing tasks while performing some daily activity will prove appropriate for providing physically disabled users with easy computer access. Commercialised products meant for ambient intelligence users, such as new interaction devices with sophisticated modality and multimodality processing software, will also satisfy the needs and requirements of disabled users at reasonable expense, since ambient intelligence applications are meant for a very large user community including the general public. The great diversity of available new modalities will make it possible to provide physically disabled users with personalized and adaptable or adaptive user interfaces in order to take account of their specific disabilities which may evolve in the course of time5 . Flexible synergic multimodality will be particularly useful for ensuring satisfactory computer access for users with complex disabilities (e.g., some kinds of palsies or visual deficiencies). Thus, significant advances in the implementation of Universal Access will be made rapidly and at reasonable cost.

For instance, successful implementation of alternate multimodality to ensure user interface plasticity may prove very useful for providing perceptual or motor disabled users with easy access to electronic information services.

Solutions have already been proposed, and products will soon appear on the market for adapting information presentation and input formats to interaction devices endowed with varying information exchange capabilities and supporting varied media and modalities. The requirements and needs of mobile/nomadic users being roughly similar to those of a wide range of physically impaired users, applying these solutions to the latter category of users will significantly improve their access to computers.

In particular, the "translation" of information expressed in one medium into another medium, which is required for achieving user interface plasticity or for automating search through a multimodal database, is also necessary for providing users suffering from some specific perceptual disability with access to data stored in the medium corresponding to their deficiency. Some such translations/conversions are difficult to automate and prove costly to perform manually. For example, visual information has to be indexed to be accessible to blind users; such indexing is also required in the framework of the AMI project (see section 3) in order to optimise search in the large collections of multimodal meeting recordings that will be collected and analysed during the project. Efficient assistance to search through multimodal databases, a future application for the general public, implies the capacity to index visual data. In the same way, converting audio information into another modality (e.g., text) may prove useful for improving both multimodal data processing and computer access for deaf users. Thus, convergence between the needs and expectations of both the general public and users with some physical disability is an invaluable asset for speeding up both the design of solutions that will meet the requirements of the latter users and their implementation into appropriate commercial products.

Context awareness also may contribute to improving computer access for users with motor or perceptual impairments in-as-much as it offers the possibility to embed interaction devices in ordinary objects in the user everyday environment.

In addition, context awareness has a great potential for promoting social integration of users with physical disabilities, beyond improving their access to computing and electronic information resources. Its main contribution to helping these users overcome their motor or perceptual handicaps lies in the new possibilities it opens up for increasing their autonomy and their effective participation in collaborative and social activities.

For instance, awareness to the user location makes it possible to guide visually impaired people through places unknown to them. Context aware agents can be used for monitoring senior users in the course of their daily activities at home. Such agents can also provide useful assistance in nursing people who suffer from severe diseases, especially chronic diseases, and help motor disabled people to complete daily tasks, thus contributing to their autonomy. Some research projects on ambient intelligence, such as Oxygen and AMI, lay emphasis on supporting mobile computing and remote meetings or, for the CHIL project, on augmenting face-to-face communication. Outcomes of these projects will prove useful for enabling users with motor or perceptual disabilities to participate in face-to-face and remote meetings.

Context awareness together with user interface distribution all over the user environment may significantly contribute to improving the daily life and social integration of people with physical disabilities. These contributions, however, will not be further detailed, since they are beyond the scope of the present paper which is focused on the potential contributions of ambient intelligence to advancing Universal Access in the Information Society.

Conclusion

This paper is an attempt at demonstrating and illustrating the potential benefits that can be derived from research advances in the implementation of ambient intelligence -a concept that subsumes ubiquitous (or pervasive) and mobile computing -for promoting Universal Access in the coming Information Society. Promoting Universal Access here means enabling everybody, especially people with physical disabilities, to have easy access to all computing resources and information services that will soon be made available to both the general public and expert users all over the world.

Basic concepts relating to multimodality and ambient intelligence are explained in section 2 and subsection 3.1, respectively. Then, a short review of recent and current research projects on the design of ambient intelligence environments and the development of appropriate tools for implementing them (see subsection 3.2) shows that main efforts focus on the following issues:

• creating new interaction modalities that take advantage of recent technological advances, especially wireless connections which make it possible to distribute sensor and actuators in the user environment, hence to distribute and embed user interface components in ordinary objects; • developing flexible adaptable multimodal interaction in order to implement user interface plasticity, a major requirement for the implementation of mobile computing; • designing and developing applications meant to support users in a wide range of daily activities at home, at work and on the go, which implies taking advantage of system context awareness, that is, the system capability to "perceive" the user and their physical environment.

Our claim is that advances in research on ambient intelligence and the development of applications implementing this concept both for the general public and expert users can contribute significantly to the implementation and spreading of Universal Access. This claim is discussed in section 4 where it is supported by the main following argument.

As targeted ambient intelligence applications aim at assisting users in a wide range of daily activities, these activities will have to be performed simultaneously with appropriate supporting computing tasks. Therefore, users of such applications will be placed in situational contexts where they will be confronted with similar difficulties to those encountered by physically disabled users in-as-much as they will have to share out their perceptual and motor capabilities between two tasks at least, a current daily activity and a computing task. The convergence between the needs and requirements of small user communities made up of people suffering from similar disabilities, and those of a very large community including both the general public and expert users is a great opportunity for these small user communities. They will indirectly benefit from the outcomes of the research and development efforts that will focus on satisfying the needs and expectations of the larger user community. Thus, the likely spreading, in the near future, of ambient intelligence applications into the general public will significantly contribute to advancing the implementation of Universal Access and its spreading into society.

This class results from the grouping of the "alternate" and "exclusive" multimodality classes in[START_REF] Coutaz | A taxonomy for multimedia and multimodal user interfaces[END_REF].

Speech SDK is a software toolkit developed by Philips for implementing speech command recognition and natural dialogue functionalities.

It started in 1997 and seems to have been active until 2001.

Authors consider three classes of computer activities: information, communication and creation tasks.

Taking account of the possible evolution of disabilities is crucial for an increasing number of physically disabled users including seniors.


LAL J Hrivnac

Optimized access to distributed relational database system

Efficient and friendly access to the large amount of data distributed over the wide area network is a challenge for the near future LCG experiments. The problem can be solved using current standard open technologies and tools. A JDBC standard solution has been chosen as a base for a comprehensive system for the relational data access and management. Widely available open tools have been reused and extended to satisfy HEP needs.

• An SQL backend has been implemented for the Abstract Interface for Data Analysis (AIDA), making relational data available via standard analysis API. Interfaces to several languages, plugins to Java Analysis Studio as well as Web Service access are available and interfaced with Atlas Event Metadata (Tag) database.

• Clustered JDBC (Sequoia) from ObjectWeb Consortium has been reused to enable transparent and optimized access to distributed relational database. Several extensions are under development.

• Octopus replication tool from ObjectWeb Consortium has been extended with specific requirements of the Atlas experiment and used to replicate Atlas data over heterogeneous database network.

JDBC

Java Database Connectivity (JDBC) [1] is the foundation of almost all Java database application. It can access most relevant SQL databases. Enormous amount of high-quality applications (free or commercial) is based on JDBC. JDBC allows to construct a complete databased-based framework with a minimum additional code. Both SQLTuple and ColMan are available as JAS[8] plugins (see Fig. 2). All functionality is available via standard JAS GUI. Specific functionality (like SQL queries) is added to the JAS GUI. Interoperability with other JAS plugins is assured.

SQLTUPLE AND COLMAN

JAS Plugins

Multilanguage Interfaces

Selected SQLTuple/ColMan functionality is available to legacy C++ applications via proxies created by JACE [9]. All SQLTuple/ColMan functionality is available to Python applications using Jython [10] or JPype [11] (when access to C++ is needed too). Access from other languages (Ruby[12], Groovy[13],...) is possible directly.

Web Service

ColMan Event Selector is available via XML-RPC[14] service (see Fig. 3). The service is generally deployed as /ColMan/EventSelector Web Service application and can be accessed via ColMan Web Service Client. JSP (Java Server Pages)[15] GUI for ColMan tools has been deployed as /ColMan-GUI Web Service application and can be accessed directly from the standard Web Browsers.

SEQUOIA

SQL tables can be spread over several database Servers, some tables may be replicated. User wants a single frontend. Sequoia[16] (described on Fig. 4) acts as a (Proxy) Virtual SQL Server forwarding all requests to appropriate databases (real or another virtual). Replicated and/or complementary tables are supported (even on heterogeneous Servers), similar to RAID disks. Sequoia is used via its JDBC driver, so any application using JDBC API can directly use Sequoia. No application modification is required to use Sequoia. Sequoia directly handles any SQL query. No pre-knowledge is needed, no specialized interface is required. Sequoia handles both query (read access) and update (write access). JDBC interface can be transparently accessed from other languages (Python, Ruby, Groovy, C++,...). Sequoia has been developed by Continuent[17].

OCTOPUS

SQLTuple[ 2

 2 ] extends FreeHEP[3] implementation of ITupleAIDA[4] interface so that ITuples can be stored in an SQL database. It supports any relational DB backend via JDBC standard interface. All AIDA operations (projections, filters, evaluators,... ) are supported in a standard way. Some new functions have been included on top of standard AIDA Interface. SQLTuple can be used in any AIDA-compliant tool. SQLTuple understands LCG[5] Pool[6] AttributeList data. ColMan[7] provides higher level utilities for managing (Event) Collections. See Fig.1for SQLTuple and ColMan Design Overview.

Figure 2 :

 2 Figure 2: JAS Plugins.

Figure 1 :

 1 Figure 1: SQLTuple and ColMan.

  Octopus[18] (described on Fig.5) is a Java-based Extraction, Transformation, and Loading tool. It may connect to any JDBC data sources and perform transforma-tions defined in an XML file. Octopus has been customized to support non-standard SQL features used in LCG and to overcome LCG-specific bugs. Octopus is routinely used to replicate Atlas Detector Description database. It has been successfully tested with other Atlas databases. Octopus has been developed by Enhydra[19].

Figure 3 :

 3 Figure 3: Web Service.

Figure

  Figure 4: Sequoia.

Figure 5 :

 5 Figure 5: Octopus.


Using Java Analysis Studio as an interface to the Atlas Offline Framework J.Hrivnac, LAL, Orsay, France Abstract Huge requirements on computing resources have made it difficult to run Frameworks of some new HEP experiments on the users' personal workstations. Fortunately, new software technology allows us to give users back at least a bit of the user-friendliness they were used to in the past. A Java Analysis Studio (JAS) plugin has been developed, which accesses the Python API of the Atlas Offline Framework (Athena) over the XML-RPC layer. This plugin gives a user the full power of JAS over the resources otherwise only available within Athena. A user can access any Athena functionality and handle all results directly in JAS. Graphical adapters to some Athena services have been delivered to ease the access even further.

ATHENAEUM

Remote Script

Any Python script can be send from Athenaeum to the running Athena. Its results (either a plane text or an XML fragment) are automatically send back and can be processed using the standard JAS mechanisms.

User can mix Python running within JAS and Python running in a (remote) Athena. Athena Python scripts could be moved to JAS.

Record Source

JAS with Athenaeum plugin can steer Athena Event Loop, interpreting Athena as a Record Source. Processing functions or classes can be then written which are called for each event delivered by Athena.

REMOTE PROXY

For some specific Athena data structures, Proxies have been created to provide their customized automatic presentation. Those Proxies are in general implemented by:

• Athena Python script to extract data from Athena.

• JAS wrapper to present/handle data inside JAS.

• XML schema to describe data. See Fig. 2 for the overview of the Proxies Design. Because implementing pre-defined interfaces from Athenaeum, those Proxies will make themselves automatically available inside JAS system in an organic way. They will, for example, appear on the appropriate menus.

XML SCHEMA REPRESENTATION

Because the same data are shared between different Frameworks/Applications implemented in different languages (Java, Python, C/C++), its common definition is needed. An XML Schema has been written describing some common Athena data structures. All data representations are then automatically derived (generated) from that XML Schema. The whole mechanism is described on the Fig. 3. Cool databases using Athena Python component. Specific Athenaeum proxies have been written to make that connection automatic.

INTERACTION WITH COOL

See Fig. 4 for an example of the running Cool Browser.

Cool data are received in an XML form. They can be then represented in several ways:

• Directly as XML fragments.

• As derived Objects of several kinds.

• As a graphical Tree of elements.

• As a set of (AIDA)[8] NTuples.

• As an HTML page created using XSLT stylesheet.

All those data can be accessed via JAS Graphical Interface, using scripting interface in several languages (Java, Python, Pnuts) or directly from Java or Python.

DISTRIBUTED INTERACTIVE ENVIRONMENT ARCHITECTURE PROJECT

Athenaeum is a component in a planned Distributed Interactive Environment (see Fig. 5). In this environment, user will interact with the Framework using lightweight client (JAS) and all data will accessed using a network of Virtual Servers connecting to actual databases. All data will be described by the application and language neutral XML Schema.

Other components of the Architecture are SQLTuple[9]/ColMan[10] and Sequoia [11].

ARCHITECTURE ADVANTAGES

Presented Architecture has many advantages: • Server on a powerful machine: It can be close to data, replicated and hierarchised when useful.

PROBLEMS

Interacting with framework based on proprietary interfaces poses several problems. In the case of connection on LCG-based Athena, following limitations are most serious:

• Python API to Athena is incomplete. Only a subset of C++ Athena API is available via Python. The API is undocumented. The C++ documentation created by Doxygen[14] is not enough for documentation of its Python API. It is not easy to guess the meaning of weakly-typed methods. Available code fragments on Web/Wiky are often out-of-date. The API is also very unstable, there are too many change too often.

• No abstract data definition is available. The actual data model is hidden very deep in the C++ header files forest. Athenaeum XML Schema has been written for data passed around. XML, Java, Python and C++ incarnations can be created from them.

  Athenaeum[1] is a Java Analysis Studio (JAS)[2] plugin which allows to access (remote) XML-RPC[3] Server. It is currently used to access Python Server running as a part of the Atlas offline Framework -Athena[4]. Any Python script can be send directly from JAS to Athena. Results (usually in XML) are send back and can be processed within JAS. Special Python scripts are provided to automatically present some standard Athena data within JAS. See Fig. 1 for the overview of the Athenaeum Architecture.

Figure 1 :

 1 Figure 1: Athenaeum Architecture.

  Cool[6] is a Conditions Database developed by CERN LCG[7] project. It is available only via its proprietary API which makes access to it from independent applications (like JAS) difficult. Athenaeum offers a way to access

Figure 2 :

 2 Figure 2: Construction of Proxy.

Figure 3 :

 3 Figure 3: XML Schema Representations.

Figure

  Figure 4: CoolBrowser.

Figure 5 :•

 5 Figure 5: Distributed Interactive Environment Architecture Project.

PLANS

The work on the Athenaeum will continue. Several subjects will be attacked in the near future:

• Athenaeum will be generalized to be usable with other Monolithic Frameworks within HEP.

• Lazy and Compressed data transport will be supported to speed operations up.

• User will be able to supply customized XSLT stylesheet.

• More standard Proxies will be delivered.

• A possibility of the Athena startable remotely from Athenaeum will be investigated.

• A deployment of Athena Servers network will be studied.


Fabien Malbet
email: fabien.malbet@obs.ujf-grenoble.fr

Inner disk regions revealed by infrared interferometry

Keywords: accretion disks, stars: pre-main-sequence, stars: emission-line, stars: mass loss, stars: winds, outflows, planetary systems: protoplanetary disks, infrared: stars, techniques: interferometric, techniques: spectroscopic

I review the results obtained by long-baseline interferometry at infrared wavelengths on the innermost regions around young stars. These observations directly probe the location of the dust and gas in the disks. The characteristic sizes of these regions found are larger than previously thought. These results have motivated in part a new class of models of the inner disk structure. However the precise understanding of the origin of these low visibilities is still in debate. Mid-infrared observations have probed disk emission over a larger range of scales revealing mineralogy gradients in the disk. Recent spectrally resolved observations allow the dust and gas to be studied separately. The few results shows that the Brackett gamma emission can find its origin either in a wind or in a magnetosphere but there are no definitive answers yet. In a certain number of cases, the very high spatial resolution seems to reveal very close companions. In any case, these results provide crucial information on the structure and physical properties of disks surrounding young stars especially as initial conditions for planet formation.

Introduction

Many physical phenomena occur in the inner regions of the disk which surrounds young stars. The matter which falls onto the stellar surface spirals in a more or less accreting circumstellar disk subject to turbulence, convection, external and internal irradiation. The disks which are rotating in a quasi Keplerian motion are probably the birth location of future planetary systems. Strong outflows, winds and even jets find often their origin in the innermost regions of many young stellar systems. The mechanisms of these ejection processes are not well understood but they are probably connected to accretion. Most of young stellar systems are born in multiple systems which can be very tight and therefore have a strong impact on the physics of the disk inner regions.

The details of all these physical processes are not yet well understood because of lack of data to constrain them. The range of physical parameters which define best the inner regions of disk in young stellar objects are:

• radius ranging from 0.1 AU to 10 AU • temperature ranging from 150 K to 4000 K • velocities ranging from 10 km/s to few 100 km/s The instrumental requirements to investigate the physical conditions in such regions are therefore driven by the spectral coverage which must encompass the near and mid infrared from 1 to 20 µm. Depending on the distance of the object (typically between 75 pc and 450 pc) the spatial resolution required to probe the inner parts of disks ranges between fractions and a few tens of milli-arcseconds. Since the angular resolution of astronomical instruments depends linearly on the wavelength and inversely on the telescope diameter, 2 Fabien Malbet observing in the near and mid infrared wavelength domain points toward telescopes of sizes ranging from ten to several hundreds of meters. The only technique that allows such spatial resolution is therefore infrared interferometry. [START_REF] Millan-Gabet | Protostars and Planets V[END_REF], published in Protostars and Planets, review the main results obtained in infrared interferometry in the domain of young stars between 1998 and 2005. The purpose of the present review is to concentrate on the inner disk regions and to give the latest results in this field. Section 2 briefly explains the principles of infrared interferometry and lists the literature on the observations carried out with this technique. Section 3 focuses on the main results obtained on disk physics (sizes, structures, dust and gas components,...) and Sect. 4 presents results on other phenomena constrained by interferometry (winds, magnetosphere, multiple systems,...). In Sect. 5 I finish the review with the type of results that can be expected in the future.

Infrared interferometry

Principle and observations

Long baseline optical interferometry consists in mixing the light received from an astronomical source and collected by several independent telescopes separated from each other by tens or even hundreds of meters. The light beams are then overlapped and form an interference pattern if the optical path difference between the different arms of the interferometer -taking into account paths from the source up to the detector-is smaller than the coherence length of the incident wave (typically of the order of several microns). This interference figure is composed of fringes, i.e. a succession of stripes of faint (destructive interferences) and bright (constructive interferences) intensity. By measuring the contrast of these fringes, i.e. the normalized flux difference between the darkest and brightest regions, information about the morphology of the observed astronomical source can be recovered. Figure 1 illustrates this principle.

Instruments available for inner regions studies

Interferometric observations of young stellar objects were and are still performed at six different facilities on seven different instruments (see Table 1). We can classify these observations into three different categories:

• Small-aperture interferometers: PTI, IOTA and ISI were the first facilities to be operational for YSO observations in the late 1990's (see Figs. 2 and3). They have provided mainly the capability of measuring visibility amplitudes and lately closure phases. The latest one, CHARA, has aperture diameter of 1 m. The instruments are mainly accessible through team collaboration.

• Large-aperture interferometers: KI, VLTI and soon LBT are facilities with apertures larger than 8 m. The instruments are widely open to the astronomical community through general calls for proposals. Lately, these facilities have significantly increased the number of young objects observed.

• Instruments with spectral resolution: CHARA, MIDI and AMBER provides spectral resolution from a few hundred up to 10,000 whereas other instruments mainly provided broadband observations. The spectral resolution allows the various phenomena occurring in the environment of young stars to be separated.

Elements of bibliography

Figure 2 displays the number of published results, and show that it is increasing with time and improved facilities. At the date of the conference there were 31 refereed articles published in the field of young stars corresponding to 66 young stellar objects observed Figure 1. Principle of interferometry. Upper panels: the Young's slit experiment (left) compared to optical interferometry (right): in both cases the light travels from a source to a plane where the incoming wavefront is split. The telescope apertures play the same role as the Young's slits. The difference lies in the propagation of light after the plane. In the case of optical interferometry, the instrument controls the propagation of light down to the detectors. At the detector plane, the light beams coming from the two apertures are overlapped. Lower panels: interference fringes whose contrast changes with the morphology of the source. Left panel shows fringes whose contrast varies from 0 to 1. Right panel displays actual stellar fringes but scanned along the optical path. The measure of the complex visibilities corresponds to the amplitude of the fringes for the visibility amplitude and the position of the fringes in wavelength units for the visibility phase.

(see by chronological order: Malbet et al. 1998;Millan-Gabet et al. 1999;Akeson et al. 2000;Millan-Gabet et al. 2001;Tuthill et al. 2002;Eisner et al. 2003;Colavita et al. 2003;Wilkin & Akeson 2003;Leinert et al. 2004;Eisner et al. 2004;van Boekel et al. 2004;Malbet et al. 2005;Akeson et al. 2005b;Eisner et al. 2005;Monnier et al. 2005;Boden et al. 2005;Akeson et al. 2005a;Eisner et al. 2006;Millan-Gabet et al. 2006a;Preibisch et al. 2006;Ábrahám et al. 2006;Millan-Gabet et al. 2006b;Monnier et al. 2006;Quanz et al. 2006;Eisner et al. 2007;Malbet et al. 2007;Tatulli et al. 2007;Kraus et al. 2007;Lachaume et al. 2007;Eisner 2007;Ratzka et al. 2007).

Graphs in Fig. 3 show that the distribution of observed object is rather well distributed among the various facilities. Several categories of young stellar systems have been observed at milli-arcsecond scales mainly in the near-infrared wavelength domain, but also in the mid-infrared one. They include the brightest Herbig Ae/Be stars, the fainter T Tauri stars and the few FU Orionis. Finally most observations were carried out in broad band but the advent of large aperture interferometers like the VLTI and KI allow higher spectral resolution to be obtained.

Inner disk physics

Most of the studies carried out on YSOs are focused on the physics of inner regions of disks. They started with the determination of rough sizes of emission then led to more Fabien Malbet constraints on the disk structure. Mid infrared spectrally resolved observations were able to identify different types of dust grains. Near infrared spectrally resolved observations are coming out and permits to spatially discriminate between gas and dust.

Sizes of circumstellar structures

About 10 years ago, the paradigm was that disks were present around a majority of young stars. These disks were believed to behave "normally" with a radial temperature distribution following a power-law T ∝ r -q with q ranging between 0.5 and 0.75. The value of q depends on the relative effect of irradiation from the central star in comparison with heat dissipation due to accretion. This model was successful to reproduce ultraviolet and infrared excesses in spectral energy distributions (SEDs). Malbet & Bertout (1995) investigated the potential of optical long baseline interferometry to study the disks of T Tauri stars and FU Orionis stars. They found that the structure would be marginally resolved but observations would be possible with baselines of the order of 100 m with a visibility amplitude remaining high.

First observations of brighter Herbig Ae/Be stars showed that the observed visibilities were much smaller than the expected ones especially in these objects were the accretion plays a little role. Monnier & Millan-Gabet (2002) pointed out that the interferometric sizes of these objects were much larger than expected in the standard disk model. They plotted the sizes obtained in function of the stellar luminosity and found out that there was a strong correlation following a law in L 0.5 over two decades. This behavior is con- sistent with the variation of radius of dust sublimation with respect to the central star luminosity: the more luminous the object the further the dust can survive in solid form because of temperature lower than the sublimation limit (∼ 1000 -1500 K). Only the most massive Herbig Be stars seem to be compliant with the standard accretion disk model.

In the meantime, in order to account for the near-infrared characteristics of SEDs and in particular a flux excess around λ = 3µm, Natta et al. (2001) proposed that disks around Herbig Ae/Be stars have optically thin inner cavity and create a puffed-up inner wall of optically thick dust at the dust sublimation radius. More realistic models were developed afterward which takes more physical properties into account (Dullemond et al. 2001;Muzerolle et al. 2004;Isella & Natta 2005). However as pointed out by Vinković et al. (2003) the models are not the unique ones that can reproduce the measurements and they proposed another model with a disk halo.

Observations at KI (Colavita et al. 2003;Eisner et al. 2005;Akeson et al. 2005b) found also large NIR sizes for lower-luminosity T Tauri stars, in many cases even larger than would be expected from extrapolation of the HAe relation. It is interpreted by the fact that the accretion disk contributes significantly to the luminosity emitted by the central region and therefore this additional luminosity must be taken into account in the relationship . However in these systems the error bars are still large and very few measurements have been obtained per object. In order to interpret all the T Tauri measurements, Akeson et al. (2005b) need to introduce new physical phenomena like optical thick gas emission in the inner hole and extended structure around the objects.

Characteristic dimensions of the emitting regions at 10 µm were found by Leinert et al. (2004) to be ranging from 1 AU to 10 AU. The sizes of their sample stars correlated with the slope of the 10 -25 µm infrared spectrum: the reddest objects are the largest ones. Such a correlation is consistent with a different geometry in terms of flaring or flat (selfshadowed) disks for sources with strong or moderate mid-infrared excess, respectively, demonstrating the power of interferometry not only to probe characteristics sizes of disk but also to derive information on the vertical disk structure.

Constraints on disk structure

Theoreticians start discussing slightly different scenarios of the inner regions around young stars. For example, the shape of the inner puffed-up wall is modeled with a curved shape by Isella & Natta (2005) due to the very large vertical density gradient and the dependence of grain evaporation temperature on gas density as expected when a constant evaporation temperature is assumed. Recently, Tannirkulam et al. (2007) proposed that the geometry of the rim depends on the composition and spatial distribution of dust due to grain growth and settling.

Vinković & Jurkić (2007) presented a model-independent method of comparison of NIR visibility data of YSOs. The method based on scaling the measured baseline with the YSO distance and luminosity removes the dependence of visibility on these two variables. They found that low luminosity Herbig Ae stars are best explained by the uniform brightness ring and the halo model, T Tauri stars with the halo model, and high luminosity Herbig Be stars with the accretion disk model, but they admit that the validity of each model is not well established.

At the current moment, only one object has been thoroughly studied: FU Orionis (Malbet et al. 1998(Malbet et al. , 2005;;Quanz et al. 2006). This young stellar object has been observed on 42 nights over a period of 6 years from 1998 to 2003 with 287 independent measurements of the fringe visibility at 6 different baselines ranging from 20 to 110 m in length, in the H and K bands. The data not only resolves FU Ori at the AU scale, but also allows the accretion disk scenario to be tested. The most probable interpretation is that FU Ori hosts an active accretion disk whose temperature law is consistent with the standard model. In the mid infrared, Quanz et al. (2006) resolved structures that are also best explained with an optically thick accretion disk. A simple accretion disk model fits the observed SED and visibilities reasonably well and does not require the presence of any On the pure theoretical side, very few physical models achieved to fit interfermoetric data simultaneously with SEDs. Using a two-layer accretion disk model, Lachaume et al. (2003) found satisfactory fits for SU Aur, in solutions that are characterized by the midplane temperature being dominated by accretion, while the emerging flux is dominated by reprocessed stellar photons (see Fig. 4). Since the midplane temperature drives the vertical structure of the disk, there is a direct impact on the measured visibilities that are not necessarily taken into account by other models.

Very interesting results have been presented in this conference by Kraus et al. (this volume) showing that they are able to derive the temperature radial distribution of the disk around MWC 147 from the interferometric measurements using the spectral variation of the visibilities in low resolution. A similar work has been attempted at PTI with larger error bars (Eisner et al. 2007).

Dust mineralogy

The mid-infrared wavelength region contains strong resonances of abundant dust species, both oxygen-rich (amorphous or crystalline silicates) and carbon-rich (polycyclic aromatic hydrocarbons, or PAHs). Therefore, spectroscopy of optically thick protoplanetary disks offers a diagnostic of the chemical composition and grain size of dust in disk atmosphere.

van Boekel et al. ( 2004) spatially resolved three protoplanetary disks surrounding Herbig Ae/Be stars across the N band. The correlated spectra measured by MIDI at the VLTI correspond to disk regions ranging from 1 to 2 AUs. By combining these measurements with unresolved spectra, the spectrum corresponding to outer disk regions at 220 AU can also be derived. These observations have revealed that the dust in these regions was highly crystallized (40 to 100%), more than any other dust observed in young stars until now. The spectral shape of the inner-disk spectra shows surprising similarity with Solar System comets. Their observations imply that silicates crystallize before terrestrial planets are formed, consistent with the composition of meteorites in the Solar System. Similar measurements were also carried out by Ratzka et al. (2007) on the T Tauri system, TW Hya. According to the correlated flux measured with MIDI, most of the crystalline material is located in the inner, unresolved part of the disk, about 1 AU in radius.

3.4. Gas/dust connection [START_REF] Gil | The Power of Optical / IR Interferometry: Recent Scientific Results and 2nd Generation VLTI Instrumentation[END_REF] observed the young stellar system 51 Oph confirming the interpretation of Thi et al. (2005) and more recently Berthoud et al. (2007) of a disk seen edge-on: the radial distribution of excitation temperatures for the vibrational levels of CO overtone (∆v = 2) emission from hot gas is consistent with the gas being in radiative thermal equilibrium except at the inner edge, where low vibrational bands have higher excitation temperatures.

In not yet published results, Tatulli et al. (priv. comm.) confirm the high inclination of the disk but also detect the CO bandheads allowing the dust responsible for the continuum to be separated from the gas emitting this CO bands. As a matter of fact, the visibilities in the CO bands is lower than the ones measured in the continuum implying that the region responsible for this gas emission is smaller than the region responsible for the dust emission. Figure 5 illustrates this result.

This result shows that the combination of very high spatial information with spectral resolution opens brand new perspectives in the studies of the inner disk properties by discriminating between species.

Other AU-scale phenomena

Several other physical phenomena have been investigated in the innermost region of disks: wind, magnetosphere and close companions.

Outflows and winds

The power of spectrally resolved interferometric measurements provides detailed wavelength dependence of inner disk continuum emission (see end of Sect. 3.2). These new capabilities enable also detailed studies of hot winds and outflows, and therefore the physical conditions and kinematics of the gaseous components in which emission and absorption lines arise like Brγ and H 2 lines. With VLTI/AMBER, Malbet et al. (2007) spatially resolved the luminous Herbig Be object MWC 297, measuring visibility amplitudes as a function of wavelength at intermediate spectral resolution R = 1500 across a 2.0 -2.2 µm band, and in particular the Brγ emission line. The interferometer visibilities in the Brγ line are about 30% lower than those of the nearby continuum, showing that the Brγ emitting region is significantly larger than the NIR continuum region. Known to be an outflow source, a preliminary model has been constructed in which a gas envelope, responsible for the Brγ emission, surrounds an optically thick circumstellar disk. The characteristic size of the line-emitting region being 40% larger than that of the NIR disk. This model is successful at reproducing the VLTI/AMBER measurements as well as previous continuum interferometric measurements at shorter and longer baselines (Millan-Gabet et al. 2001;Eisner et al. 2004), the SED, and the shapes of the Hα, Hβ, and Brγ emission lines. The precise nature of the MWC 297 wind, however, remains unclear; the limited amount of data obtained in these first observations cannot, for example, discriminate between a stellar or disk origin for the wind, or between competing models of disk winds (e.g. Ferreira et al. 2007 andShu et al. 2007 both in this volume).

Magnetosphere

The origin of the hydrogen line emission in Herbig Ae/Be stars is still unclear. The lines may originate either in the gas which accretes onto the star from the disk, as in magnetospheric accretion models [START_REF] Hartmann | [END_REF], or in winds and jets, driven by the interaction of the accreting disk with a stellar (Shu et al. 1994) or disk (Casse & Ferreira 2000) magnetic field. For all models, emission in the hydrogen lines is predicted to occur over very small spatial scales, a few AUs at most. To understand the physical processes that happen at these scales, one needs to combine very high spatial resolution with enough spectral resolution to resolve the line profile.

One one hand, Tatulli et al. (2007) performed interferometric observations of the Herbig Ae star HD 104237, obtained with the VLTI/AMBER instrument with R = 1500 high spectral resolution. The observed visibility was identical in the Brγ line and in the continuum, even though the line represents 35% of the continuum flux. This immediately implies that the line and continuum emission regions have the same apparent size. Using simple toy models to describe the Brγ emission, they showed that the line emission is unlikely to originate in either magnetospheric accreting columns of gas or in the gaseous disk but more likely in a compact outflowing disk wind launched in the vicinity of the rim, about 0.5 AU from the star. The main part of the Brγ emission in HD 104237 is unlikely to originate in magnetospheric accreting matter.

On the other hand, Eisner (2007) measured an increase of the Brγ visibility in MWC 480 implying that the region of emission of the hydrogen line is very compact, less than 0.1 mas in radius which could be interpreted as an emission originated in the magnetosphere of the system.

At the present time, given the limited number of samples, it is difficult to derive a general tendency but it seems that all possible scenari can be found. Boden et al. (2005) performed the first direct measurement of pre-main sequence stellar Fabien Malbet masses using interferometry, for the double-lined system HD 98800-B. These authors established a preliminary orbit that allowed determination of the (subsolar) masses of the individual components with 8% accuracy. Comparison with stellar models indicates the need for subsolar abundances for both components, although stringent tests of competing models will only become possible when more observations improve the orbital phase coverage and thus the accuracy of the stellar masses derived.

Binaries and multiple systems

Another example, based on a low-level oscillation in the visibility amplitude signature in the PTI data of FU Ori, Malbet et al. (2005) claim the detection of an off-centered spot embedded in the disk that could be physically interpreted as a young stellar or protoplanetary companion located at ∼ 10 AUs, and could possibly be at the origin of the FU Ori outburst itself. Using another technique, Millan-Gabet et al. (2006b) reported on the detection of localized off-center emission at 1-4 AU in the circumstellar environment of AB Aurigae. They used closure-phase measurements in the near-infrared. When probing sub-AU scales, all closure phases are close to zero degrees, as expected given the previously determined size of the AB Aurigae inner-dust disk. However, a clear closure-phase signal of -3.5 • ± 0.5 • is detected on one triangle containing relatively short baselines, requiring a high degree of asymmetry from emission at larger AU scales in the disk. They interpret such detected asymmetric near-infrared emission as a result of localized viscous heating due to a gravitational instability in the AB Aurigae disk, or to the presence of a close stellar companion or accreting substellar object.

Future prospects and conclusion

As emphasized in this review, more interferometric data is required with better accuracy and also wider coverage of the baselines in order to constrain better the models that have been proposed. Like for radio astronomy, these supplementary data will allow image reconstruction without any prior knowledge of the observed structure. Several projects are already ready to obtain interferometric images although with few pixels across the field: MIRC at CHARA and AMBER at the VLTI in the near-infrared. However at the moment MIRC is limited in sensitivity and AMBER in number of telescopes (3) which makes it difficult to routinely achieve imaging. In the mid-infrared the MATISSE instrument is being proposed to ESO to provide imaging with 4 telecopes at the VLTI. VSI is also a proposed VLTI instrument of second generation which can combine from 4 to 8 beams at the same time so that imaging becomes easier. LBT will also provides imaging capability.

All these instruments provide spectral resolution that make them indeed spectroimager. Therefore in the future, one should be able to obtain a wealth of information from the innermost regions of disks around young stars. However in the meantime, observations are already mature enough to allow detailed modeling of the phenomena occuring in these inner regions.

Figure 2 .

 2 Figure 2. Young stellar objects observed by interferometry and number of refereed papers published in the period 1998-2007. The statistics of the year 2007 is not complete.

Figure 3 .

 3 Figure 3. Young stellar objects observed by interferometry in the period 1998-2007. Upper left: distribution by interferometer. Upper right: distribution by YSO type. Lower left: distribution by wavelength of observation. Lower right: distribution by spectral resolution. The statistics is the same as the one of Fig. 2.

Figure 4 .

 4 Figure 4. Radial distribution of temperature at different location in the disk computed with a two-layer model by Lachaume et al. (2003). Left: temperature in the equatorial plane. Center: effective temperature. Right: surface temperature. The different lines represent the various contribution to the heating: viscosity, reprocessing of the stellar light, thermalization with the ambient temperature.additional structure such as a dusty envelope. This is why one should remain careful with results coming from surveys having only few measurements per object.Millan-Gabet et al. (2006a) obtained K-band observations of three other FU Orionis objects, V1057 Cyg, V151 Cyg, and Z CMa-SE and found that all three objects appear significantly more resolved than expected from simple models of accretion disks tuned to fit the SEDs. They believe that emission at the scale of tens of AU in the interferometer field of view is responsible for the low visibilities, originating in scattering by large envelopes surrounding these objects. In a not yet published study, Li Causi et al. have measured again interferometric visibilities of Z CMa with VLTI/AMBER and propose to interpret the data by the presence of a very close companion.On the pure theoretical side, very few physical models achieved to fit interfermoetric data simultaneously with SEDs. Using a two-layer accretion disk model,Lachaume et al. (2003) found satisfactory fits for SU Aur, in solutions that are characterized by the midplane temperature being dominated by accretion, while the emerging flux is dominated by reprocessed stellar photons (see Fig.4). Since the midplane temperature drives the vertical structure of the disk, there is a direct impact on the measured visibilities that are not necessarily taken into account by other models.Very interesting results have been presented in this conference byKraus et al. (this volume) showing that they are able to derive the temperature radial distribution of the disk around MWC 147 from the interferometric measurements using the spectral variation of the visibilities in low resolution. A similar work has been attempted at PTI with larger error bars(Eisner et al. 2007).

Figure 5 .

 5 Figure5. Spectrally dispersed visibility amplitudes of 51 OPh in the CO bandhead spectral region. Overimposed is the spectrum as measured by VLTI/AMBER (black line). The blue curve corresponds to the addition of simple uniform disk model for the excess emission in the line with a typical dimaeter of 0.2 AU. FromTatulli et al. (priv. comm.)

Table 1 .

 1 Interferometers involved in YSO science

	Facility	Instrument Wavelength Numbers of Aperture	Baseline
			(microns)	apertures	diameter (m) (m)
	PTI	V 2	H, K	3	0.4	80 -110
	IOTA	V 2 , CP	H, K	3	0.4	5 -38
	ISI	heterodyne 11	2 (3)	1.65	4 -70
	KI	V 2 , nulling K	2	10	80
	VLTI/AMBER V 2 , CP	1 -2.5	3 (8)	8.2/1.8	40 -130
		(imaging) /spectral			/8 -200
	VLTI/MIDI	V 2 (/CP) 8 -13	2 (4)	8.2/1.8	40 -130
			/spectral			/8 -200
	CHARA	V 2 , CP	1 -2.5	2/4 (6)	1	50 -350
		(imaging) /spectral
	LBT	imaging,	1 -10	2	8.4	6 -23
		nulling
	V

2 : visibility measurement; CP: closure phase. Acronyms. PTI: Palomar Testbed Interferometer ; IOTA: Infrared and Optical Telescope Array (closed since 2006); ISI: Infrared Spatial Interferometer ; KI: Keck Interferometer ; VLTI: Very Large Telescope Interferometer ; CHARA: Center for High Angular Resolution Array; LBT: Large Binocular Telescope (not yet operational).