Antonia L Krummheuer
email: antonia@hum.aau.dk

Users, Bystanders and Agents: Participation Roles in Human-Agent Interaction

Keywords: Embodied conversational agent, human-agent interaction, participation role

Human-agent interaction (HAI), especially in the field of embodied conversational agents (ECA), is mainly construed as dyadic communication between a human user and a virtual agent. This is despite the fact that many application scenarios for future ECAs involve the presence of others. This paper critiques the view of an 'isolated user' and proposes a micro-sociological perspective on the participation roles in HAI. Two examples of an HAI in a public setting point out (1) the ways a variety of participants take part in the interaction, (2) how the construction of the participation roles influences the construction of the agent's identity, and (3) how HAI, as a mediated interaction, is framed by an asymmetric participation framework. The paper concludes by suggesting various participation roles, which may inform development of ECAs.

1

Introduction 1An embodied conversational agent is a computer interface in the form of a "virtual human" ( [START_REF] Cassell | Human Conversation as a System Framework: Designing Embodied Conversational Agents[END_REF]:39). ECAs are said to have social, embodied and linguistic abilities so that they can engage in 'human-like' face-to-face interaction with the aim of developing "computers that untrained users can interact with naturally" ([4]: 60). Core studies have conceptualized the ECA interaction as a dyadic conversation between one agent and one user (e.g. [START_REF]Embodied Conversational Agents[END_REF], [START_REF]Intelligent Virtual Agents[END_REF]) and do not address how to include several human participants simultaneously. This is a striking omission, as standard application scenarios tend to be settings in which other people are likely to be present and thus influence the interaction, as in a museum or clinical settings ( [START_REF] Kopp | A Conversational Agent as Museum Guide -Design and Evaluation of a Real-World Application[END_REF], [START_REF] Moosaei | Naturalistic Pain Synthesis for Virtual Patients[END_REF]). One exception is the anti-bullying system in [START_REF] Vannini | Fearnot!": A Computer-Based Anti-Bullying-Programme Designed to Foster Peer Intervention[END_REF], in which several agents with different participation roles were created. The system, however, is designed for individual use, even though it is tested in a school setting. The scenario in [START_REF] Rehm | She is just stupid' -Analyzing User-Agent Interactions in Emotional Game Situations[END_REF] is the only study in which an agent addresses two users at the same time. This paper sheds light on situations in which many participants are present during the HAI and shows how the identities of the participants (users, bystanders and the agent) shape and are shaped by the ways the parties take part in the ongoing production and interpretation of the HAI. This paper adds to the discussion of the term 'user' in HCI, which is often criticized for its simplistic perspective on the human relationship with the computational machine. While the term 'user' evokes the idea of a 'typical user' often conceptualised as interacting in isolation, [START_REF] Grudin | Interface: An Evolving Concept[END_REF] and [START_REF] Hyysalo | The User as Relational Entity. Options that Deeper Insight into User Representations Opens for Human-Centered Design[END_REF] point out that systems are used by several users with different background knowledgesuch as experts and novices, developers and test-persons, or ' marginal' people, such as those maintaining the machine. Furthermore, the different practices of the individual's usage, the routines and practices of a task and the social-material context of e.g. the company shape the understanding of the user [START_REF] Agre | Conceptions of the User in Computer System Design[END_REF].

This paper understands 'user' and 'agent' as categories that describe participation roles within the participation framework of an HAI. These concepts stem from an ethnomethodological point of view, taking the perspective of participants who mutually negotiate their own and each other's action and identity in the ongoing production and interpretation of interaction, as in Suchman's classical study on the user's situated interpretation of an interactive copying machine [START_REF] Suchman | Human-Machine Reconfigurations. Plans and Situated Actions[END_REF]. A micro-sociological concept of participation ( [START_REF] Goffman | Footing[END_REF], [START_REF] Goodwin | Participation[END_REF]) is applied to two video recordings of a HAI in a public setting. While in both examples a communication problem is solved successfully, the encounter is framed by an asymmetric and mediated participation framework, in which different kinds of participants align in different ways to the production and interpretation of the event. In one, the user solves a communication problem together with the agent. In this case the agent is treated as an equal communication partner. In the other, the user solves the problem involving bystanders as helpers, while the agent is excluded from the interaction and treated as an unequal partner. On the basis of these examples, this paper emphasises that the construction of categories such as 'user' and 'agent' is situated, dynamic and reflexive, and suggests a variety of participation roles in HAI that may inform the development of ECA in social settings.

Participation Framework and Participation Status

Goffman stresses that interactions are socially situated [START_REF] Goffman | The Interaction Order[END_REF], as many interactions take place in the presence of others, who are taken into account. In his paper on footing, Goffman deconstructs traditional linguistic concepts of hearer and speaker. He differentiates between the participation status, or participation role ([17]: 162), that concerns the relation between the participants, what is said, and their understanding of their self, and the participation framework defined as the relations of all those present at a given moment of the encounter. Goffman's model not only suggests the perspective of interaction as a social encounter, but also defines a nonexclusive list of participation roles as dynamic concepts that affect each other and can change during the interaction. Participants can, for ex-ample, be involved in an interaction as ratified or unratified participants, addressed or unaddressed hearers, and eavesdroppers or bystanders. This also has consequences for the status of communication. Goffman identifies different kinds of subordinate communication in relation to a dominating communication, such as byplay, a conversation of a subset of ratified participants (e.g. two people whispering to each other during multiparty conversation), or a crossplay, a communication between a ratified participant and a bystander across the boundaries of the dominant communication (e.g. calling the waitress during a conversation with a friend at a restaurant) ( [START_REF] Goffman | Footing[END_REF]: 134). Furthermore, Goffman offers a complex understanding of a speaker, as he distinguishes for example between the animator producing the talk, the author who is responsible for the production of the words, and the principal who is socially responsible for what is said ([7]: 144).

Goffman's work is often criticized for not being empirical [START_REF] Levinson | Putting Linguistics on a Proper Footing: Explorations in Goffman's Concepts of Participation[END_REF] and offering only a "static set of categories" ( [START_REF] Goodwin | Participation[END_REF]: 225) that cannot account for the situated dynamics of interaction. Goodwin and Goodwin adjust Goffman's ideas for interactional analysis and define participation as "actions demonstrating forms of involvement performed by parties within evolving structures of talk" ([9]: 222). In a detailed analysis of talkin-interaction, they show the situated and interactive "practices through which different kinds of parties build actions together by participating in structured ways in the events" ([9]: 225). Participation status and the ongoing interaction are thereby reflexively intertwined as they shape and reshape each other. From this theoretical basis, this paper will demonstrate how participants in a HAI in a public setting take part in different ways and how this influences their participation status, the participation framework and the actions themselves.

Data Collection

The data derives from an ethnographic study of recorded video, naturally occurring (not experimental) interactions between users and the ECA, Max, during a public presentation of the agent in a shopping centre where people could volunteer to communicate with Max ( [START_REF] Krummheuer | Conversation Analysis, Video Recordings, and Human-Computer Interchanges[END_REF] and [START_REF] Krummheuer | Interaktion mit virtuellen Agenten? Zur Aneignung eines ungewohnten Artefakts[END_REF]). The data were transcribed and analyzed according to the principles of conversation analysis, including embodied and material aspects [START_REF] Heath | Video in Qualitative Research: Analysing Social Interaction in Everyday Life[END_REF]. Max is a human-sized agent who can be seen on a large screen. To communicate with Max, users send messages to the agent by typing text on a keyboard in front of the screen. The actual production of the text can be seen and corrected in the white space at the bottom of the screen. After the users press Enter, the text is sent to the system and can be seen in the grey space above the white one. The dialogue system searches the user's text for key symbols and grammatical phrases, assigns a single functional purpose to the message and selects a pre-programmed utterance combined with a bodily reaction performed by the agent (movement of lips, facial expression, gestures, etc.)( [START_REF] Kopp | A Conversational Agent as Museum Guide -Design and Evaluation of a Real-World Application[END_REF] and [START_REF] Kopp | Max -A Multimodal Assistant in Virtual Reality Construction[END_REF]). During the presentation at the shopping centre, Max was constructed as a presenter. He could inform the user about certain topics (e.g. AI or the event), take part in small-talk or play a game, for example.

The Participation Framework of a Human-Agent Interaction

The recorded HAIs can be described as mediated interactions between two different entities located in two different situations and with different abilities to access each other's situation. Max's presence was mediated by screen and loudspeakers to the user, and the user's presence was mediated to Max by written text. Furthermore, the programmed structures that form the agent's understanding of actions differ fundamentally from the user's situated interpretations of the technology during the course of interaction (see [START_REF] Krummheuer | Conversation Analysis, Video Recordings, and Human-Computer Interchanges[END_REF], [START_REF] Krummheuer | Interaktion mit virtuellen Agenten? Zur Aneignung eines ungewohnten Artefakts[END_REF] and [START_REF] Suchman | Human-Machine Reconfigurations. Plans and Situated Actions[END_REF]).

As the user accesses the virtual world from the keyboard and text-production, he is present in two situations: his physical situation in front of the screen and his engagement (as text-message) in the virtual world. Thus, the HAI is situated in a participation framework that is asymmetrically assessed by user and agent. While Max is programmed to engage in communication with a single user, the user is a participant of a larger social encounter in which various parties are involved in constructing meaning from the HAI. The following analysis demonstrates how this asymmetric participation framework affects the construction of participation roles and activities. Figure 1 shows a sequence in which Max and the user, Dave, are playing a game. The agent tries to guess an animal the user has in mind. The agent asks questions and the user answers with yes or no. 2 In line 1, Max asks the user if the animal he has in mind has a mane. Dave does not answer the question but pauses briefly before he types and sends the text "pardon?" (line 3), which marks a problem of understanding. Dave leans forward (lines 4-5) as if he wants to listen closely to Max's next utterance. Max announces that he will repeat his former utterance and does so word by word (line 6). Dave slowly straightens up, puts his hands on the keyboard and eventually says "no" to Max's former question (line 12). Max treats the problem as solved, so he asks his next question and continues the game (line 13). In this sequence, Max and Dave mark and repair [START_REF] Schegloff | The Preference for Self-Correction in the Organization of Repair in Conversation[END_REF] a communicative problem in understanding so the game can continue. 3 Dave and Max treat each other as ratified and directly-addressed communication partners and are engaged in a focused interaction.

Solving a Communication Problem with the Agent

Solving a Communication Problem without the Agent

In contrast to Dave, who solved the problem with Max, figure 2 shows how the user, Sonja, excludes Max from the problem-solving activity. came to the stand with her friend, Carl. He is standing in the background and observes the interaction with the computer scientist who programmed Max (indicated by the initials "CS" in the transcript), as well as other people observing the interaction. In common with Dave, Sonja experiences the same problem of understanding during the guessing game.

Fig. 2. Troubleshooting: solving a problem without Max

After Max asks if the animal has a mane (line 1), Sonja pauses and looks down at the keyboard, before she turns to the audience and asks, "has it what?" (line 2-4). Emphasising the word "what", she identifies the communication problem as specificshe could not understand the word "mane". Sonja's question is taken up by several people in the audience who repeat the problematic term "mane" for her (lines 5-7). Turning back to Max, Sonja announces "no it does not" (line 9), demonstrating to the audience that the problem is solved, and turns back to the communication with Max, writing the missing answer "no" (line 10). Max formulates his next question and the game continues.

By turning to the audience Sonja engages in a crossplay, a side-sequence with the bystanders to inform the dominant communication (playing a game with Max). The participation status of former observing-only bystanders changes to that of directly addressed participants. In this side sequence, Sonja and the bystanders engage in troubleshooting [START_REF] Haase | Computer aus Nutzerperspektive. Von der Nutzeranalyse zum Interface-Design[END_REF] and achieve a mutual understanding of the communication prob-lem and its remedy. While the observers become addressed helpers, the agent is no longer treated as an addressed participant. Max is excluded from parts of the communication and part of the HAI becomes an object of a subordinate communication. Sonja seems to assume that Max is not able to repair her problem (at least not in the way she might hope) and thus treats Max as an unequal or inexperienced communication partner. At this point, the consequences of the asymmetric participation are evident -from Max's perspective, the crossplay did not happen. He is engaged in conversation with one person only.

Conclusion and Discussion

This paper described a HAI as an asymmetric, mediated and social encounter in which different kinds of participants take up different participation roles in producing and interpreting a HAI. User and agent have different abilities in accessing the situation of the other and are, as such, involved in different participation frameworks. The agent's actions are designed on the basis of a dialog with one single user, while the user is situated in a larger social encounter with other participants. While example 1 showed how Max could be constructed as a quasi-equal conversation partner in an interaction, example 2 highlighted the impact of the asymmetric participation frameworkwhile the user was engaged in a crossplay with the bystanders, Max was not aware of it. The agent's participation status changed to that of an unequal or inexperienced communication partner. Considering the whole event at the public presentation of the agent, it is possible to differentiate various kinds of participation roles that could inform other studies of HAIs in public or multiparty settings. The user was a person who left the audience and went to the table to write a message to the agent. Becoming a user included a change of footing as they 'took the stage' and performed the interaction with Max in front of an observing audience. Sometimes another person (e.g. a friend or the computer scientist helping out) joined the user at the keyboard, construing himself or herself as co-user. Other participation roles included those of by-passers who glimpsed or more or less ignored the HAI on their way through the shopping centre. Observers or bystanders formed the audience that surrounded the table and the screen. Most of the bystanders were observing silently, sometimes laughing, commenting on the performance or engaging in subordinated conversation. Some parts of the audience became helpers during the course of the interaction, as in example 2, suggesting how to solve a problem or what to write to the agent. People helping out the user often became authors or co-authors of the text that was written to Max, which also affected the role of the user who became the animator of another person's text. Some helpers demonstrated themselves as experts in this case, showing a familiar knowledge of the agent-system and how it worked. These were often, but not always, the computer scientist who developed the agent. They often became principals of the agent, as they spoke in favour of the agent or explained why it was doing what it did. This is not a closed list of participation roles in HAI, but it does indicate that the view of an isolated and standardised user is a reductionist way of conceptualizing HAI. Users engage in HAI in various ways and often together with others. Different participation roles have also been found by other authors. Blomberg already has mentioned the special role of advanced users [START_REF] Blomberg | Social Interaction and Office Communication: Effects on User's Evaluation of New Technologies[END_REF] and Woolgar observes commentators and observers during usability trials. He and argues that people take different roles towards the technology as "they can speak as insiders who know the machine and who can dispense advice to outsiders" ( [START_REF] Woolgar | Configuring the User: the Case of Usability trials[END_REF]: 88).

Studies of ECA aiming for applications in social encounters where several parties are present therefore need a theoretical framework that accounts for the different participation roles. This is already done in other areas of interactive technologies. In [START_REF] Mutlu | Footing in Hu-man-Robot Conversation: How Robots Might Shape Participant Role Using Gaze Cues[END_REF], for example, Goffman's concepts are taken for developing a robot that shapes participation roles by gazing differently at addressees, bystanders and eavesdroppers of the human-robot interaction. However, more work needs to be done to understand the complex and situated ways in which people engage with technologies, so that interaction can be made more effective.

Fig. 1 .

 1 Fig. 1. Repair: solving a problem with Max

I am grateful to the Artificial Intelligence Group (Bielefeld University) and the participants of the recorded data for their cooperation. I also want to thank the reviewers for their constructive comments. This research has been supported by the German Research Foundation.

The transcripts are simplified and translated form German [16]. Pauses are shown in brackets. Double brackets indicate nonverbal communication. Square brackets mark overlapping actions. Capital letters indicate stress and text within ** is the message sent to the agent.

The pause in line 9-10 indicates that Dave still might not have understood Max. However, Dave produces the relevant answer to Max's question (line 12), which gives the communicative basis for continuing the game. On an interactional level, the problem is solved.


Limin Zeng
email: limin.zeng@tu-dresden.de

Gerhard Weber
email: gerhard.weber@tu-dresden.de

Alexander Fickel
email: alexander.fickel@tu-dresden.de

ETA Wizard App: Make Design and Evaluation of Accessible Electronic Travel Aids Easy

Keywords: Electronic travel aids, user-centered design, auditory and haptic user interface, Wizard of Oz

To support designers and researchers a touch-screen based Wizardof-Oz application is demonstrated. It can be used to develop electronic travel aids for blind and visually impaired people and allows evaluating audio and haptic user interfaces in an early development stage. A scenario for presentation of obstacles combines sonification and feedback from vibration of a tactile belt.

Introduction

More and more innovative electronic travel aids (ETAs) are proposed in order to overcome the disadvantages of traditional assistive mobility tools, like white canes and guide dogs. Both the larger and the narrower context are important to improve mobility. For example, users cannot use the white cane to detect obstacles above knee level, specifically for dangerous obstacles at head level (Manduchi and Kurniawan, 2011). Besides numerous technologies studied for capturing contextual information, the design of multimodal output is crucial in order not to overload users in everyday scenarios.

Aiming at presenting spatial information about obstacles and hazards in an accessible way, ETAs employ auditory output, haptic/tactile output or a combination of them (Meijer, 1992; Dakopoulos and Bourbakis, 2009; Zeng et al., 2012). However, for the developers it is challenging to acquire users' feedback on their user interface design in an early stage of an ETA development (i.e., before the obstacle detector module is available), specifically when a user-centered design method is employed for designing an accessible user interface.

In this paper, we demonstrate a touch-screen based Wizard of Oz (WoZ) app (namely ETA Wizard App) for helping researchers and designers to evaluate their ETA's user interface design in an early development stage. In addition to setting up test environments (e.g., room size and distribution of obstacles) and importing virtual and real obstacles, the ETA Wizard App offers an auditory and haptic interface which allows researchers and designers to implement their own design easily.

ETA Wizard App

When the user-centered design approach is adopted for designing and developing an ETA, in addition to collect user requirements at the beginning, it is important to acquire user feedback about the prototypes at an early stage. As illustrated in Figure 1, the proposed ETA Wizard App supports developers and researchers to design two parts of an interactive demonstration:



Figure 1. EAT Wizard App in the life circle of a user-centered design

In the two modules, several features have been implemented:

WoZ Test Preparation Module (a). Test Room Setting:

Set the test room size, including the size of visual grid which is helpful to update subjects' position quickly and easily. (b). Real & Virtual Obstacle Setting: In addition to specify different types of obstacles (e.g., doors and grounded obstacles), the feature allows to add virtual obstacles which might be dangerous in a real world, like drop-offs and descending stairs, and add special obstacles at fixed sites, such as a real hanging paper board.

WoZ Field Test Module

(c). Update Subject's Position & Heading Orientation: Touch-based interaction allows to update subject's position and heading orientation, see Figure 2. (d). Support Auditory User Interfaces: Regarding to the auditory output, in addition to playback basic sounds (e.g., WAV files) the ETA Wizard App also support playing spatial sounds, via the Open Audio Library (OpenAL) [START_REF] Dakopoulos | Towards a 2D tactile vocabulary for navigation of blind and visually impaired[END_REF] . It is possible to extend by adding other auditory library, like Libpd2 . (e). Support Haptic User Interface: Obstacles' spatial information is presented also by haptic (vibrotactile) output. In this App, a tactile belt with 8 vibrators [START_REF] Meijer | An experimental system for auditory image representations[END_REF] is supported, which is connected to the host tablet via a Bluetooth interface (see Figure 3). It can be extended to support other haptic/tactile devices.

Figure 2 .

 2 Figure 2. The touch interaction to simulate subject's position and heading orientation

Figure 3 .

 3 Figure 3. The tactile belt with 8 vibrators (the interval angel of each vibrator is 45°)

Figure 4 .Figure 5 .

 45 Figure 4. The screenshot of the ETA Wizard App on a tablet

  WoZ Test Preparation: the module helps researchers quickly setting up a test environment, consisting of obstacles and their spatial distribution. It supports augmenting the scene by adding real or virtual obstacles.  WoZ Field Test: the module can simulate localizing the user by tapping and trigger actions from gestural input to perform researchers' user interface designs and deploy them in a WoZ field test easily.

	User Requirement & Features of Obstacle	UI Design (Audio & Haptic)	Suitable UI Design
	Detector
	User Feedback	User-centered Design	WoZ Test Preparation
			ETA Wizard
		WoZ Field Test	APP

OpenAL Soft: http://kcat.strangesoft.net/openal.html

Libpd: http://puredata.info/downloads/libpd

Elitac Science Suit: http://elitac.nl/products/sciencesuit.html

Range-IT project, http://www.range-it.eu/

Acknowledgement

This study was supported by the Range-IT 4 project within the framework of EU FP7 SME Program (Grant no. 605998).


Cindy Mayas
email: cindy.mayas@tu-ilmenau.de

Stephan Hörold
email: stephan.hoerold@tu-ilmenau.de

Anselmo Stelzer
email: stelzer@bahn.tu-darmstadt.de

Frank Englert
email: frank.englert@kom.tu-darmstadt.de

Heidi Krömker
email: heidi.kroemker@tu-ilmenau.de

Evaluation of Dispatcher Requirements on Automated Customer Feedback in Public Transport

Keywords: Dispatching systems, public transport, user requirements 1

ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Introduction

Public transport is a widespread mobility service for the society, which is based on a network of defined stations and routes, that operate at defined times. In order to guarantee an optimal execution of the mobility services, dispatchers monitor and manage the actual situation within the mobility system and take measures to react on shortterm interruptions. New possibilities of automated customer feedback, for instance via the "Travellers' Realtime Information and Advisory Standard" (TRIAS) [1], provide more precise real-time data about actual traveler flows and needs. By having timely access to feedback from travelers, the dispatchers are able to assess the actual situation more precisely and reach better decisions. Exemplarily, the information about actual and future traveler flows can support dispatchers in minimizing the total traveler delay in case of service interruptions or demand peaks [START_REF] Stelzer | Using Customer Feedback in Public Transportation Systems[END_REF].

By contrast, the increasing data volume might lead to a growing complexity of the dispatching systems and an information overload of the dispatchers. For this reason, the introduction of automated customer feedback has to be adapted to the dispatchers' workflow [START_REF] Db Fernverkehr | Transportleitung Personenverkehr[END_REF] and the dialogue principles [START_REF]Ergonomics of humansystem interaction -Part 110: Dialogue principles[END_REF]. However, there is a lack of research, regarding the dispatchers' requirements on real-time customer data for dispatching systems. Thus, the aim of this study is to analyze these requirements, considering the dispatchers' expectations and the relevance of different data for dispatching decisions.

Method

A survey among dispatchers was conducted anonymously in November 2014 based on an online questionnaire. 34 dispatchers, who took the survey voluntarily, were acquired from nationwide and regional transport companies. These surveyed dispatchers represent the typical range of duties and roles in German transport companies. The majority of the dispatchers perform tasks for operational dispatching decisions or dispatching management. Additionally, some dispatchers also maintain the customer information service or conduct further activities, such as operational command. The standardized questionnaire included questions in regard to the individual assessment of influencing factors on operational decisions, the supply with actual data about customers, attitudes towards using automated customer feedback, and the relevance of customer feedback contents. While the influencing factors, attitudes, and relevance of contents were surveyed in single items on a five-point Likert scale, the participants had to quantify their demand of actual data by multiple selection.

Results

Supply with Actual Data about Customers

According to the statements of the dispatchers, dispatching decisions in transport companies are mainly influenced by the operational procedures. 97 percent of the dispatchers assess the operational procedures as very relevant or relevant for their decisions. Nevertheless, other influencing factors, such as customer needs, personal experiences, and external situational factors, are also rated as very relevant or relevant by 77 to 85 percent of the dispatchers. Furthermore, the dispatching decisions of regional companies are more oriented on the management of external situational influences than on customer needs. This might be caused by the higher frequency of vehicles per route and the resulting higher variety of route alternatives for customers in cities, in comparison to long-distance traffic. In contrast to these results, which indicate that customer needs are at least relevant factors for dispatching decisions, the answers about the actual data supply reveal that 83 percent of dispatchers in regional transport companies do not have any actual data about customers available. Most customer data is available in nationwide transport companies, for instance regarding the number of travelers (73 percent), who are affected by an interchange, and their destinations (36 percent). This information is mainly provided by messages from the staff in the vehicles [START_REF] Db Fernverkehr | Transportleitung Personenverkehr[END_REF].

Attitudes towards Using Automated Customer Feedback

The analysis of the attitudes towards the integration of automated customer feedback considers the need and the possible realization of such dispatching systems. While the assessment of the needs includes the improvement, support, and appraisal of decisions, the realization considers the workload, integration, and automation of the data [START_REF] Stelzer | Using Customer Feedback in Public Transportation Systems[END_REF]. The results reveal that half of the dispatchers confirm the need and realization of automated customer feedback for operational dispatching decisions with quite positive attitudes (cf. fig. 1). However, nearly 24 percent of the surveyed dispatchers associate quite negative opinions with the usage of automated customer feedback for dispatching decisions. The answers of the single items of the negative attitudes show that these opinions refer to an expected higher workload, in contrast to a suspected low added value.

Relevance of Different Contents of Automated Customer Feedback

The assessments of the relevance of customer information for dispatching decisions show considerable differences according to the type and content of information. For instance, the survey reveals that the real-time information about travelers is most relevant as an aggregation of the number of interchangers per connection (cf. fig. 2). Furthermore, additional information, such as destinations and itineraries of travelers, can provide valuable information about travel alternatives and allow conclusions about the prioritization and the characteristics of the required decisions. Direct customer feedback can not only comprise the success of interchanges, but also the reasons and consequences of failures from the travelers' point of view. Due to the fact, that this customer feedback could provide valuable data for the evaluation of the dispatching quality in retrospect, the relevance of this information is mainly rated moderately. In contrast to the previous customer information and feedback, the relevance of damage reports by customers is rated high and very high, especially by the dispatchers of regional transport companies. Due to the fact, that the regional dispatchers also often supervise the according infrastructure, such as tram wires and station facilities, these results indicate the highest acceptance and need of automated customer information.

Discussion

The evaluation reveals fundamental user requirements of dispatchers on the content, the processing, and the design of automated customer feedback. Due to the chosen methods, these results enable a representative overview of the situation within transport companies in Germany. In the following step, the results have to be linked to the individual tasks and working environments of different kinds of dispatchers. Therefore, additional methods are required, such as contextual inquiries, which include the individual context and extend the results to the context of use [START_REF]Ergonomics of humansystem interaction -Part 110: Dialogue principles[END_REF] of the dispatching interactions. Some dispatchers are concerned about a suspected higher workload due to the higher system complexity with integrated automated customer feedback. In order to allay these concerns, the introduction of user-friendly and workflow-oriented dispatching systems is required to support the dispatching decisions and compensate for the higher amount of information.

In addition, the development of information systems for automated customer feedback is related to the functions of mobile applications for travelers and also requires the integration of the customers' point of view, for instance in usability tests.

Conclusion

The fundamental user requirements of dispatchers are an essential input for the further development of dispatching systems, and consequently for the further development of mobile information systems for travelers.

In general, dispatchers are open-minded about automated customer feedback, if the content actually has a direct reference to their tasks and is expected to improve the dispatchers' decisions. The results of this survey reveal differences in the requirements of dispatchers for different contents of automated customer feedback, regarding real-time customer information, interchange customer feedback, and damage reports. In summary, the results indicate that the user-oriented integration of automated customer feedback is an essential condition for the further development of dispatching systems.

Fig. 1 .

 1 Fig. 1. Attitudes towards the need and realization of automated customer feedback

Fig. 2 .

 2 Fig. 2. Appraisals of the relevance of the content of automated customer feedback


Vicki Hanson

Gemma Webster
email: gwebster@abdn.ac.uk

Matt Dennis
email: m.dennis@abdn.ac.uk

Workshop on Interactivity in Healthcare Systems (IHS)

Keywords: healthcare, interactivity, ehealth, healthy living

ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Workshop Theme

We are all living longer with average life expectancy increasing across the globe [START_REF]A Wealth of Information on Global Public Health[END_REF]. However, chronic conditions such as heart disease, strokes and cancer, coupled with an increasing global obesity problem still cause a growing number of premature deaths [START_REF]A Wealth of Information on Global Public Health[END_REF]. These conditions combined with an aging population cause a huge strain on healthcare provision. There are two approaches to reduce the burden on healthcare services -encouraging healthy lifestyles through increased knowledge, and improving people's ability to affect the quality of care for those living with long-term conditions and age related illnesses. Although these issues appear to be separate, they have an effect on each other. For example, if someone has a healthier lifestyle they are less likely to develop certain chronic conditions. Furthermore, if someone is used to maintaining a healthy lifestyle then they are more likely to actively engage with their healthcare providers. We have now reached a critical point in healthcare -both healthcare professionals and patients alike recognize the potential for technology to provide them with personalized healthcare and support [START_REF] Mc Schraefel | Interacting with eHealth[END_REF]. The WHO has recognized the importance of using such technology by encouraging investment and forming an internal eHealth division which focuses on promoting and strengthening the use of technology in health [START_REF]World Health Organization: EHealth at WHO[END_REF].

eHealth can be used in a diverse range of areas to promote access, improve efficiency and enhance quality within healthcare [START_REF] Churchill | mHealth + Proactive Well-being = Wealth Creation[END_REF]. Key goals in this field are to facilitate personalized health information to promote self-management, to identify and act upon support needs, to improve communication between patients and healthcare workers, to assist with the use of medicine and assistive technology and inform decision-making between healthcare workers [START_REF]Scottish Government: eHealth Strategy 2011-2017[END_REF]. Additionally, any health technology has to be designed to be usable, efficient, effective and accepted by the healthcare community. This workshop aims to promote discussion between multidisciplinary researchers on novel, innovative and connective approaches within eHealth, improving engagement and patient outcomes. This workshop is aimed at multidisciplinary researchers and healthcare professionals from all areas interested in novel approaches to interactivity in technology for healthy living, healthcare and eHealth. The areas of interest are, but not limited to:  Usability of eHealth technologies  Technologies to support health education, promotion and advice, and healthy independent living  Personal health technologies or personalized assistance  Social Care  Novel approaches to health technologies  Tailored decision support (for patients and practitioners)  Mobile and wearable healthcare systems for eHealth  Personalization in online support for health and wellbeing

Outcomes

This workshop aims to promote discussions within the community around the future of healthy living and healthcare. We are aiming to produce a special issue of a journal, with accepted authors potentially being invited to write extended versions of their papers.


Dorothé Smit
email: g.d.smit@student.tue.nl

Saskia Bakker
email: s.bakker@tue.nl

BlurtLine: A design exploration to support children with ADHD in classrooms

Keywords: research-through-design, ADHD, blurting, classroom, interaction 1

This paper presents BlurtLine, an interactive belt designed to support children with ADHD in regaining control over their impulsive speaking in class. Two exploratory evaluations of BlurtLine indicate that the design can indeed identify indicators of blurting and was experienced positively by a boy with ADHD and his mother and teachers.

Introduction

The number of students with extra needs in regular primary schools is increasing. The largest subgroup of these students is diagnosed with Attention Deficit Hyperactivity Disorder (ADHD) [START_REF] Smeets | Op de drempel van passend onderwijs[END_REF]. A symptom of ADHD is verbal impulsivity, or 'blurting' [START_REF] Barkley | ADHD and the nature of self-control[END_REF]: speaking in direct reaction to stimuli, without first considering the appropriateness to the situation. Supporting children with ADHD in regaining control over their blurting behaviour could potentially improve their learning situation in the classroom.

This paper presents the iterative design and evaluation of 'BlurtLine'; a belt that informs children when they are about to blurt through a softly vibrating signal (Fig. 1). BlurtLine monitors the wearer's breathing patterns. Since respiratory rate is changed extensively by emotional changes [START_REF] Homma | Breathing rhythms and emotions[END_REF], rapid inhaling can be seen as a precursor for blurting. BlurtLine measures the chest circumference and constantly compares this to a baseline measurement. If BlurtLine is stretched beyond a certain set value, it This paper presents two exploratory studies using a prototype version of BlurtLine: a lab study in which the practical functionality of BlurtLine is explored and a field study to gain first insights in how BlurtLine is experienced in the classroom.

BlurtLine in the Lab

The lab study with BlurtLine served to assess both its most suitable placement on the body, and its suitability to recognize breathing patterns in adults. The test took place in a controlled setting with seven adults of 19 to 23 years old. The participants performed a reading exercise and a breathing exercise twice: once with the BlurtLine prototype worn around the chest, at the height of the sternum, and once with Blurt-Line worn around the abdominal area, at the height of the navel, as excited breathing often engages the chest while relaxed breathing engages the abdominal area [START_REF] Stevenson | Alterations in cardiac function and circulatory efficiency during periods of life stress as shown by changes in the rate, rhythm, electrocardiographic pattern and output of the heart in those with cardiovascular disease[END_REF]. Participants were asked to read three paragraphs of text in three different volumes: normal speaking volume, very low volume and very loudly. After reading, the participants were asked to breathe in deeply, first slowly, and then quickly. If they felt a vibration from BlurtLine during the exercise, they were to ring a bell. Afterwards, the BlurtLine was moved to the second location and the test was performed again. The goal of this test was to determine whether BlurtLine can distinguish between different volumes of speech and to confirm that rapid breathing is more prevalent in the chest area than in the abdominal area. During reading at high volume, three out seven of participants set off the vibration motor with their chest breathing patterns when speaking loudly, while only one participant set off the vibration motor when speaking at high volume wearing the band around the abdominal area. The prototype did not vibrate for any participant during reading at normal and low volume. These findings indicate it is unlikely that a wearer will receive a false signal during normal speaking. When asked to take a quick, deep breath, all participants triggered the vibration motor when wearing BlurtLine around the chest, while four out of seven participants failed to trigger the vibration motor when wearing BlurtLine around the abdomen. This indicates that fast, impulsive breathing is mainly situated in the chest.

BlurtLine in the Field

Following the promising findings after exploring BlurtLine in the lab, a second study was set up at a primary school with an 8-year-old boy diagnosed with ADHD. The goal was to gain first insights into the child's experience of wearing BlurtLine to regain control of his blurting behaviour. Secondarily, we aimed to determine whether the child or teachers derived any benefit from it, and to gain insight in whether child, teachers or parents experienced moral concerns regarding the use of BlurtLine.

User Study Setup

The field study with BlurtLine spanned three consecutive mornings. The participating child wore the prototype during the last two mornings. The first morning was included for the child to get used to the presence of the researcher, and for the researcher to gain insight in the child's normal blurting behaviour. The second morning was used as a habituation period. During the third day, the participant was closely monitored to review the possible effects of BlurtLine on his behaviour in class. During the whole study, a webcam was set up in the classroom, directed towards the table of the participant. The first author monitored the participant's behaviour from a different room via a live stream. This video stream was also recorded for later analysis. To grasp the experience of using BlurtLine, interviews were conducted with the child, his mother and his teachers on the final day of the user study. Both teachers of the child were asked whether they had noticed any differences in the behaviour of the child. The participant and his mother were asked about their experiences during this user study.

Results

Throughout the study, the participant mentioned several times that the signals he received made him mindful of his behaviour, and encouraged him to think about the ways in which he could contribute to the class conversations. However, he also indicated that he did not always feel like he was about to blurt when he received a signal. As a result, the participant would sometimes ignore the signals and still speak out in class. The signals that the participant received from BlurtLine were described as clear, non-invasive, but sometimes too present due to their frequency. During the interview, the participant disclosed that he did not mind wearing Blurt-Line. It was clear that he was very excited about participating in the test. After initial enthusiastic interest from his peers, the children in the classroom went about their day without taking much notice of BlurtLine. One of the child's teachers said that she did not notice much difference in the participant's behaviour; the other teacher mentioned that he behaved very differently, though she remarked that this might have resulted from the presence of the camera. Overall, both of the teachers were positive towards the idea of using this tool, when its function has been proven.

The mother of the participant recounted that she did not notice any extraordinary behaviour in her child. None of the interviewees had any moral objections against the use of BlurtLine to support the child in gaining control of his blurting behaviour. The mother and teachers agreed that if it helps the child, there is no apparent problem.

Discussion

This paper presents a lab and a field study with BlurtLine, a belt designed to support children with ADHD to control speech impulsivity, in order to improve their learning environment. Both studies were exploratory, yielded a number of points for discussion and brought along a few limitations. Firstly, a limitation of the presented field study is the clear presence of the Hawthorne effect [START_REF] Smeets | Op de drempel van passend onderwijs[END_REF], indicating that a longer accli-matisation period may have been helpful. Secondly, since the user study was conducted with a first prototype version of BlurtLine, false positives have likely been present, affecting the participant's experience. Future work should therefore involve a more sophisticated, accurate prototype that can be used for an extended period of time. Despite these limitations, the performed explorations led to valuable insights into the possibilities to help children gain awareness of their blurting behaviour. During the field study, it became clear that the prototype performed well in a real life setting. However, the participant also mentioned that he wasn't always aware of his imminent blurting when he received a signal, which could either indicate false positives or unawareness of his blurting behaviour. This might pose a limitation of the study; we cannot be sure if signals were false or not. However, it may also indicate the potential value of BlurtLine: children indeed seem unaware of their blurting behaviour right before they are about to blurt. BlurtLine may thus assist them recognizing the signals that indicate impending blurting. A potential risk of using devices such as BlurtLine is that it may have a stigmatizing effect for the user. During the field study this did not seem the case, nor did the participant's mother or teachers observe negative effects. Despite the small scale and exploratory nature of the study, we believe this is a promising finding, which deserves more exploration in future work.

Conclusion

This paper presents BlurtLine, a belt designed to support children with ADHD, who show impulsive speaking behaviour (blurting), thereby unintentionally interrupting their own learning process in the classroom. BlurtLine provides tactile feedback at moments the wearer is about to blurt, potentially enabling them to regain control of their behaviour. Two exploratory studies with a prototype version of BlurtLine indicated that (1) BlurtLine can accurately measure rapid inhaling, a precursor for blurting, when worn around the chest, (2) the 8-year-old participant in our field-study positively experienced wearing the prototype and was encouraged to consciously think about his speaking intentions and (3) no stigmatizing effects were found. While exploratory, we believe these findings are encouraging future research in which Blurt-Line would be used for a longer period, by a larger number of children in a classroom. Considering increasing diversity among students in classrooms, this paper contributes by laying out an opportunity to support children with ADHD to improve their learning experience and increase their ability to reach their full potential in regular education.

Fig 1 .

 1 Fig 1. BlurtLine prototype


Manuel Prätorius
email: manuelpraetorius@uni-muenster.de

Aaron Scherzinger
email: scherzinger@uni-muenster.de

Klaus Hinrichs

SkInteract: An On-Body Interaction System Based on Skin-Texture Recognition

Keywords: mobile, input, sensors, fingerprint, skin, on-body, smartring, smartwatch, biometrics

In this paper we propose SkInteract, a system for on-body interaction utilizing the diverse texture of the human skin. We use an area fingerprint sensor to capture images and locate the corresponding area within a previously created map of the skin surface. In addition to the location of the sensor it is possible to calculate its orientation with respect to the reference map. This allows to assign arbitrary semantics to areas of the user's skin and to use the rotation as an additional input modality. In order to evaluate the feasibility of SkInteract a user study with a preliminary prototype was conducted. We propose two different interaction concepts which are based on either attaching a fixed sensor to a wearable device or using a moveable sensor, for instance attached to a pen, to perform on-body input.

Introduction

Miniaturization has fostered the research and development of small mobile and wearable interaction devices. The diminishing interaction space of these devices, which comes at the cost of their mobility, has become a major challenge in the field of human computer interaction.

Recently an increasing number of mobile devices have integrated small fingerprint sensors as a means of user authentication. In this paper we propose the SkInteract system which utilizes those sensors to expand the limited interaction space of wearables to the skin surface. With our approach especially area type sensors provide the opportunity to design novel interaction techniques based on biometric features of the skin texture by creating a map of the skin surface and recognizing the position and orientation of sensor images within the mapped regions. Specific user interfaces can then be realized by assigning semantics to distinct areas of the map and utilizing the rotation as an additional modality. Because of a user's proprioception the interaction on the skin can be performed eyes-free which is advantageous especially in a mobile context.

Related Work

Several input systems have been proposed which are based on recognizing the body part that is used for interaction. This allows to perform user authentication, map different semantics to the body parts, select sets of input metaphors, or increase the precision of the interaction [START_REF] Holz | Fiberio: A touchscreen that senses fingerprints[END_REF][START_REF] Harrison | On-body interaction: armed and dangerous[END_REF][START_REF] Holz | The generalized perceived input point model and how to double touch accuracy by extracting fingerprints[END_REF].

Harrison et al. [START_REF] Harrison | TapSense: enhancing finger interaction on touch surfaces[END_REF] have presented a system which is able to recognize different objects and parts of the finger such as the pad, tip, knuckle, and nail by analyzing the acoustic signal produced while tapping on a touch surface. Another system by Harrison et al. [START_REF] Harrison | Skinput: appropriating the body as an input surface[END_REF] appropriates the forearm and the hand as an input surface by analyzing the vibrations caused by finger taps on those areas. The enhancement of expressiveness in multi-touch interaction by utilizing fiduciary-tagged gloves is presented in [START_REF] Marquardt | What caused that touch?: expressive interaction with a surface through fiduciary-tagged gloves[END_REF]. A finger-worn device which is equipped with a camera to recognize the texture the user is touching is presented in [START_REF] Yang | Magic finger: always-available input through finger instrumentation[END_REF]. The device is able to distinguish 22 different materials, e.g., wood, jeans, and skin.

The first user interface based on fingerprint recognition has been proposed by Sugiura and Koseki [START_REF] Sugiura | A user interface using fingerprint recognition: holding commands and data objects on fingers[END_REF]. Their approach is to assign commands to the user's fingertips and perform the corresponding action once a fingerprint is recognized.

The user performance in a scenario where a push button is able to identify the user's fingers was evaluated in the work of Wang and Canny [START_REF] Wang | FingerSense: augmenting expressiveness to physical pushing button by fingertip identification[END_REF]. In order to recognize the fingers they used colored markers attached to the fingertips. They compared several input situations considering input speed between multi-finger and single finger tapping.

In contrast to previous work on user interaction on the human skin we propose the novel approach to create a map of the skin texture which enables us to recognize the location and orientation of a sensor. This technique appropriates the skin for both discrete and continuous input.

Prototype System Outline

To evaluate the capabilities of the SkInteract approach we have created a simple hardware prototype and software implementation which is capable of both generating maps of specific skin texture areas and detecting the position and rotation of input images within those areas.

Hardware Setup

Since capacitive area sensors have already been integrated into mobile devices such as Apple's iPhone we have chosen to use this type of sensor for our first prototype.

We use an FPC1011F3 model which has a resolution of 363 dpi. The resulting size of the recorded images is 152 x 200 pixels for an area of 10.64 x 14.00 mm. We read data from the sensor using the SPI interface of a RaspberryPi and transfer each complete image via Ethernet to a standard laptop with an Intel Core i7-2670QM CPU which performs the expensive image processing and recognition tasks. Using this setup, which is shown in Figure 1a, we are able to retrieve four images per second from the sensor.

Scanning and Mapping the Hand

To create a map of a region of the skin surface a simplified version of the image stitching method proposed in [START_REF] Brown | Automatic panoramic image stitching using invariant features[END_REF] is applied to the images captured by the sensor. For both the image stitching as well as the later recognition and classification of the input images our method utilizes scale-invariant feature transform (SIFT) without the need for any preprocessing [START_REF] Lowe | Distinctive image features from scale-invariant keypoints[END_REF]. Although more sophisticated feature extraction and image enhancement methods have been proposed for the use of fingerprint images in user authentication applications, SIFT features work well in our context as they provide a more generalized method which is also applicable to regions of the palm and the wrist.

In the stitching process new images are added sequentially to an intermediate stitching result by computing matches between the SIFT features of the two images and calculating a homography matrix using random sample consensus (RANSAC) [START_REF] Fischler | Random sample consensus: a paradigm for model fitting with applications to image analysis and automated cartography[END_REF]. For robustness we perform several checks regarding the determinant of the matrix as well as the transformed bounding box of the input image.

For the prototype system evaluation presented in section 4 we have focused on creating separate sub-maps of the skin surface as shown in Figure 2 instead of a single global map, since the stitching of larger numbers of images can lead to accumulated distortion effects caused by the projection of non-planar soft tissue into twodimensional space, depending on the particular region of the skin. Although this problem could be alleviated to a certain degree by applying an additional global optimization to minimize the accumulated errors, continuous interaction could be realized more efficiently by specifying transitions between the separate sub-maps, thus narrowing down the recognition to such areas. Fig. 2. Several examples of stitched skin textures. The green squares mark the areas that were used for the user study.

Region Detection

For a new input image we first compute the SIFT features. We then iterate over the list of previously recorded areas of the fingers, palm, and the wrist (which are each represented by a stitched reference image) and match the features of the input image and the reference image. Feature matching is performed using an exhaustive bruteforce approach in order to obtain the best matching results. For each feature we compute the two best matches and only keep matches where the ratio of the distance between the best and the second-best match is better than a threshold t. Our experiments have shown that t = 0.8 generally seems to be a good value for our prototype implementation.

For the region with the largest number of good matches we perform RANSAC to calculate a homography matrix H that transforms our input image with respect to the reference image. If we cannot find enough good matches or the determinant of H is near zero we reject the input image. Otherwise we apply H to transform the bounding box of the input image, and use the vertices and edges of the transformed image to compute the rotation and translation with respect to the reference image (see Figure 3). This allows us to not only recognize the region of the finger or palm but also to determine the orientation of the sensor which can be used as an additional interaction modality.

System Evaluation

To evaluate the feasibility of SkInteract we have conducted a user study and performed some additional tests to characterize the system parameters. We have focused on three main aspects of the system which are the recognition rate, runtime duration of the recognition, and the required size of the sensor for use in a potential user interface.

Fig. 3. Transformation of the sensor image

Recognition Rate

In order to quantify the recognition rate of our prototype system we have conducted a user study with a total of 8 participants from our department, 7 male and one female.

For each participant we have captured reference images for 11 different skin regions (green squares in Figure 2) with the stitching method outlined in section 3.2. Examples for the stitched reference images are given in Figure 2. For each of the reference regions we have captured 8 test images with different orientations of the sensor (gray arrows in Figure 1c). Image capturing has been triggered manually once the sensor was placed appropriately and the preview of the image did not show significant artifacts caused by the oiliness and the moisture of the skin (see section 4.4). The acquisition of test images was randomized regarding both region and orientation. Each test image was then matched using the algorithms described in section 3.3. From the total of 704 test images 698 were classified correctly, resulting in a recognition rate of 99.15%. From the total of 6 recognition failures 5 were rejected as non-matchable. One test image was captured at the wrong position but has correctly been recognized and thus resulted in a false positive. Other than that no false positive matches occurred in the user study.

Computational Cost of the Area Recognition

We have tested the duration of the area recognition and homography matrix calculation using OpenCV's standard implementations of SIFT, brute force feature matching, and RANSAC. For a small number of reference regions (corresponding to a small area of the skin surface) the computation of the SIFT features for the input image limits the processing speed, while for larger areas the matching of the features becomes the limiting factor. For our tests we have gradually increased the area A of the scanned reference region in each testing cycle by adding an additional image of the sensor, each corresponding to an area of 1.49 cm 2 and not overlapping with any of the other reference images. For A > 12 cm 2 the influence of the feature computation step becomes negligible and the required processing time t for the matching step and homography can be estimated by t = A•f with f = 0.03 s/cm 2 . Although a reduction of matching time could presumably be achieved by implementing a more sophisticated matching strategy such as the Locally Sensitive Hashing algorithm proposed in [START_REF] Auclair | How to use SIFT vectors to analyze an image with database templates[END_REF], the impact on the recognition rate of the system would have to be evaluated to consider its applicability for SkInteract. Since no optimization has been applied, the processing time has to be considered an upper limit. More adapted features and feature selection may reduce the feature set, and thus give a significant speed-up.

Required Size of the Input Region

To evaluate the required sensor size we have gradually decreased the input area size by cropping the images captured by our sensor from their center. In each of several testing cycles conducted with a single test person we have reduced the image size by 12 pixels in both x-and y-dimension, starting with an image size of 152 x 152 pixels which corresponds to a surface area of 10.64 x 10.64 mm 2 . In each testing cycle we have tested 10 input images against the same set of 5 reference regions. The recognition rate in our tests remained constant at 100% up to an input image size of 56 x 56 (which corresponds to a surface area of 3.92 x 3.92 mm 2 ) and decreased drastically afterwards. For an input image size below 32 x 32 pixels or 2.24 x 2.24 mm 2 the system could not perform the recognition at all. The minimum area size required for a robust recognition could potentially be decreased even further by using a fingerprint sensor with a higher resolution compared to our 363 dpi model.

Drawbacks of the Capacitive Fingerprint Sensor

During the user study we have observed that the moisture and oiliness of the skin have a considerable impact on the quality of the images captured by the sensor, making it necessary for some users to occasionally clean the sensor. While this was not necessary in most cases it may restrict a continuous interaction for some users. Other types of sensors like ultrasonic or optical sensors, however, may not be affected by this problem. Additionally, capacitive fingerprint sensors have a short sensing range and therefore need a good contact to the skin to capture images of appropriate quality, which makes it difficult to sense areas around knuckles and joints.

Design Space and Applications

SkInteract can be used as a basic platform for several different user interface applications. These applications can be divided into two main categories, the first being a system with a fixed sensor and the second a system with a moveable sensor.

An example of a system with a fixed sensor is a smartwatch or a smartring which allows to interact with an integrated sensor using the fingers and palm of the other hand (see Figure 4a). In addition to mapping different functions onto the selected interaction areas of the skin surface, rotating could be used as a gesture for additional functions, for instance controlling the volume in a music player. An alternative would be to map distinct functions to discrete states defined by the relative orientation between the user's hand and the sensor. However, it would be necessary to perform an in-depth user study to evaluate the usability and comfort of potential interaction areas on the hand under the constraints of a smartwatch or a smartring scenario.

As the required size of the input area of the sensor in the current setup is only 3.92 x 3.92 mm 2 we hypothesize that an appropriate sensor can be integrated into a small moveable device. Such a device could be a pen as shown in Figure 4b or a thimble with the sensor attached to its tip. Besides the discrete selection of functions by tapping on the respective areas, the continuous motion of a moveable sensor on the skin surface could be used to provide gestural interaction. To alleviate the cognitive load of remembering all of the input areas and the function mapping they could be visualized by an augmented reality head-mounted display. Furthermore, privacy issues regarding both the potentially required data transfer as well as the storage of the captured images would have to be taken into account to avoid any exploitation of the biometric information included in the data.

Conclusion and Future Work

In this paper we have presented SkInteract, a novel system that appropriates the skin as an interaction surface. A device which can sense the texture of the skin can be utilized to generate maps of the skin which allows to recognize the position and the orientation of such a sensor. We have conducted a user study to evaluate the feasibility of the approach with a prototype which is based on a capacitive area fingerprint sensor.

In future work we plan to test several setups with different sensors and to design actual interfaces to explore the interaction space.

Fig. 1 .

 1 Fig. 1. (a) Preliminary SkInteract prototype setup. (b) A user capturing images of the skin with the area fingerprint sensor. (c) An example of a position and orientation as indicated during the user study. The arrows depict the eight orientations of the sensor which were tested for each position.

Fig. 4 .

 4 Fig. 4. (a) Fixed sensor setup integrated into a smartwatch. (b) Moveable sensor attached to the tip of a pen.