Isabelle Kniestedt
email: ikniestedt@gmail.comma.gomezmaureira@gmail.com

Marcello A Gómez Maureira

Little Fitness Dragon: A Gamified Activity Tracker

Keywords: applied gaming, games for wearables, activity tracking, virtual pet

We propose the design of an activity game and virtual pet for smart-watches that combines casual game design principles, lessons from fitness trackers, and location-based features. Players take care of a newly hatched dragon that grows and changes depending on their activities, reflecting their general fitness in a playful and encouraging manner. Where most virtual companions are aimed at children, we designed this game with young adults in mind. An early PC prototype was tested by ten members of this target group to gauge interest and inform design iterations. The general design of the game and the virtual dragon were mentioned as strong points, while the emulation on the PC was considered not intuitive. Upcoming prototypes will be tested on smart-watches, with the ultimate goal of exploring the impact of connecting a virtual pet to the physical location of a player on engagement and activity levels.

Introduction

In recent years wearable fitness trackers and smart-watches have become more widely used and increasingly sophisticated. No longer are users limited to simple step counters; with devices like the Pebble and Apple Watch we now see smart-phone functionality integrated with fashionable technology that fits unobtrusively on our wrists.

Our goal is to explore the novel interaction possibilities that smart-watches provide and how they may be used to improve people's lives. In that light we have begun development on Little Fitness Dragon, and activity game for mobile phones and smart-watches. By building on existing research and incorporating lessons from the casual game industry, we aim to develop an engaging wellness tracker that encourages its players to be active on a regular basis by combining a virtual pet with location-based game mechanics. The novelty of this game lies in grounding a virtual character in a player's physical surroundings, as well as utilizing modern wearables which so far remain underused, both for gaming purposes and in research relating to activity trackers. This paper describes the preliminary design and conception of a PC prototype for the game. The prototype was tested with a small selection of participants, some of whom had game design experience. This was done purposefully to better inform the design of the game before moving forward with its development. We conclude this paper with our plans for future work and follow-up studies.

Related Work

Over the last decade researchers have studied both the successes and the limitations of wearable fitness devices. One documented project is Fish'n'Steps [START_REF] Lin | Fishnsteps: Encouraging physical activity with an interactive computer game[END_REF], which used a wearable pedometer and linked a user's daily step count to the growth and happiness of a virtual fish. The digital fish tank was displayed in a common area of the test participants' office space, and users were required to check in on a daily basis to log their activity. Out of 19 participants, several increased their daily step count over the testing period of six weeks. Another relevant example is UbiFit [START_REF] Consolvo | Flowers or a robot army?: encouraging awareness & activity with personal, mobile displays[END_REF]. It aimed to encourage users to monitor their own activity and to implement varied activities into their lives on a daily basis. It did this through a glanceable display background on the user's mobile phone showing a garden, which would change depending on the level of activity and the variety of activities the user participated in that week. Users of the glanceable display were able to maintain their activity levels over a period of several months (which included holiday weeks), while that of test participants not using the display dropped significantly. While these projects showed positive results, commercial activity trackers often end up being abandoned by their users. Barriers to continued use are that the devices do not record all physical activity, are inaccurate, do not provide a social functionality, or that the devices themselves are ugly or impractical [START_REF] Harrison | Activity tracking: barriers, workarounds and customisation[END_REF].

The Tamagotchi showed many years ago that users can grow attached to a digital creature or pet. Research has begun to explore this further, for instance with testing the use of virtual pets to influence changes in behavior. A study with 39 adolescents determined that those with a virtual pet providing positive and negative feedback on their breakfast habits were twice as likely to eat breakfast than those in the control group [START_REF] Byrne | Caring for mobile phone-based virtual pets can influence youth eating behaviors[END_REF]. With the continued development of mobile devices, location-based games and apps have also become more common. Gaea [START_REF] Centieiro | A location-based multiplayer mobile game to encourage pro-environmental behaviours[END_REF] uses mobile phones and a public display in a location-based multiplayer mobile game that encourages the public to recycle. Another interesting case of using location-based game features for encouraging behavior can be seen in the overnight commercial success of Pokemon Go, which has players walking long distances in their quest to 'catch them all' [START_REF] Novak | Sore legs become pandemic as Pokemon Go players accidentally get exercise[END_REF].

The Design

Little Fitness Dragon (LFD) is a game for both smartphones and smart-watches. While it works as a self-standing application on mobile phones, it can use more accurate sensors when used in combination with a smart-watch (i.e. the heart Its goal is to stimulate regular activity and it is aimed at young adults with a sedentary lifestyle who wish to increase their daily activity level. While much of the existing research, especially that related to virtual pets to stimulate lifestyle changes [START_REF] Byrne | Caring for mobile phone-based virtual pets can influence youth eating behaviors[END_REF][START_REF] Hswen | Virtual avatars, gaming, and social media: Designing a mobile health app to help children choose healthier food options[END_REF], has been focused on children, we argue that the use of virtual characters and 'cute' graphics can be just as effective in adults, as is illustrated by the wide appeal and success of casual games like Peggle and Farmville.

In LFD, players are tasked with taking care of a newborn dragon, which is always visible when the game is open (see Fig. 1a). The fully animated dragon keeps track of a player's activity (e.g. calories burned and step count), and will grow and change depending on the player's activity level. A player who moves the minimum recommended daily amount will have a calmer, more relaxed dragon, while a player who exercises a lot will have a more energetic dragon. A similar approach was used in Fish'n'Steps and showed that users were pleased to see their progress reflected in the growth of their virtual fish. The study discovered that negative feedback for underperformance could lead to feelings of guilt and reluctance to return to the application. By having the dragon's behavior change with the user's activity level we provide an abstract way for users to reflect on their performance without negative connotations. The dragon will always be excited to see its owner and encourage them to engage, lowering the barrier to return to the game when it has not been used in a while.

During walks the player may come across 'resource locations', where he or she can find ingredients to use in the game. These locations are generated by the game, following certain constraints (e.g. keeping a minimum distance between locations). They can vary in type (and therefore resources that may be found there), and are discovered by coming in close physical proximity of their GPS coordinates. One aspect of the game is a compass screen on which players can see both visited and unvisited resource locations in their surroundings. Whenever the player comes across a resource location, they will be prompted by their dragon for an interaction or mini-game. Mini-games are optional and not necessary to complete for those who simply wish to collect the resource. For these players they will have a simple interaction with the dragon, after which it will return to them with a resource its managed to hunt, depleting the location for that day. Locations can be revisited on a daily basis to collect more resources and enable players to replay the corresponding mini-game.

Resources can be used to cook and craft items for the dragon, e.g. toys and different nests. Each dragon has different preferences for food and items. Additionally, feeding the dragon different types of food allows players to gradually change its appearance, e.g. color, scales, horns, wings. The default view of the game shows the dragon's den, where the player can feed their dragon and place toys and other items for it to play with. Tapping the dragon shows a zoomed in view of what it is currently doing, e.g. eating, sleeping, or playing, as well as the progress towards the daily activity goals. Here the player can also interact with their dragon to which it will respond with different animations.

By developing for current day smart-watches we can overcome some of the barriers encountered in previous studies [START_REF] Harrison | Activity tracking: barriers, workarounds and customisation[END_REF], such as inaccurate tracking or the need for additional tracking devices. Furthermore, the availability of a highresolution display allows us to provide players with appealing graphics and positive reinforcement. During the development of this project we follow theorybased design principles for apps that track daily activity levels [START_REF] Consolvo | Theory-driven design strategies for technologies that support behavior change in everyday life[END_REF], for instance by making use of 'abstract' and 'reflective' data in showing the player's performance through changes in the dragon rather than numbers and statistics. We expect that basing the design of LFD on these principles will make it an encouraging activity companion, while the addition of location-based play creates a real-world connection to an otherwise virtual creature.

Player Experience

To test the viability of the design we created an initial prototype for PC systems using GameMaker Studio (see Fig. 1b). While this prototype could not be used to test the effectiveness of the game as an activity tracker (as it lacks the mobility necessary to collect meaningful data on the subject), we consider this as the first step in the development process. With this basic prototype we created a functional discussion point with other designers and were able to gauge initial user response to the game concept.

Care was taken to simulate the controls and mechanics of the intended design as intuitively as possible in a PC application, while giving a clear idea of the intended game play and aesthetics. A tutorial explained the game, while daily exercise was emulated by adding an avatar on a map screen that was controlled with the keyboard. A total of ten people played the game with ages ranging between 21 and 32, all with relatively high gaming literacy or a background in game development. Feedback was collected in open discussions with the testers, first allowing them to freely voice their initial impressions of the game and then asking more specific follow-up questions. With two of the testers, both working in game development, a more in-depth interview took place to ask about suggestions for the next stage of development.

All ten testers responded positively to the prototype, with the only negative comments referring to the PC controls not being intuitive. The combination of activity tracking with casual game play was mentioned as an interesting idea that testers could see themselves using in their lives. Testers specifically enjoyed the style and quality of the aesthetics, as well as the design of the dragon. Several concerns also came to light during the discussions. The user interface, in the prototype presented in 800 by 600 pixels resolution on a computer display, showed to potentially become too cluttered on a smaller display, especially that of a smartwatch. It also became clear that the initial plan of using resources for both cooking and crafting, and the large amount of available resources planned resulted in an overly complicated system. The compass also needed to be redesigned, as players were observed to not understand the representation of themselves and the resource locations.

It is possible that the high levels of gaming literacy of our participants influenced the receptiveness to the proposed game concept. This was a conscious decision, however, as at this stage it was deemed important to discuss potential issues in the game's design. We argue that game literate participants are better equipped to provide in-depth comments. They furthermore tend to be more critical, as they tend to spend a lot of time interacting with games and technology. Overall, we feel the prototype served its function as a discussion point for desired features and showed a positive interest in further development of the game.

Future Work

The next step is the creation of a second prototype for the target platform that has the basic functionality needed to test the game as an activity tracking tool. Based on the comments received during the initial test we will be making several changes to the design as well. One such change is that while we at first intended the game to be completely self-standing on smart-watches, it has become clear that the extra screen space offered by mobile phones will be needed to include all the features we envision. Core features will work independently from the phone on the smart-watch side, while some non-essential features will be available on the phone side and data is synced between the two. Additionally we will be streamlining the design of the resources and crafting mechanics, and focus on increasing interaction with and feedback from the dragon. We will also implement a reward mechanic that can take stationary activities (e.g. gym activities) into consideration for users who do not have a watch with a heart rate monitor.

The main limitation of the prototype is that it could not be used to test the validity of the design as a wearable activity tracker. We argue, however, that there is merit in testing games and applications before considering them for further study. Although we could not yet test the validity of the game as an activity tracker, we were able to gauge the interest in the design from our target audience. More importantly, it allowed us to identify issues and make design changes that would have been more costly at a later stage of the projects, or could have hampered our research further down the line. We argue that the use of early prototypes like these can improve the quality of both future research and the applications produced for it.

Our next study will focus on testing the efficacy of this second prototype. We will continue to involve users over the course of the development, although as we move forward we will also be including those less used to playing games. Later on we also see potential of using the game to explore the potential impact of connecting the physical environment to the virtual domain in regards to player engagement and activity levels, specifically compared to virtual companions that do not react to the player's physical environment.

  (a) Photograph of mock-up implementation. (b) Screenshot of the prototype application.

Fig. 1 :

 1 Fig. 1: Target platform mock-up (left) and prototype screenshot (right)


Amir Zaib Abbasi
email: amir_zaib_abbasi@yahoo.co.uk

Ding Hooi

Helmut Hlavacs

Proposing a New Conceptual Model Predicting Consumer Videogame Engagement Triggered Through Playful-Consumption Experiences

Keywords: Experience, hedonic consumption experience, playful consumption experience, imaginal experience, emotional experience, sensory experience, engagement, consumer engagement, consumer videogame engagment, cognitive, affective and behaviroal engagement. 1

The aim of the study is to propose a conceptual model which predicts consumer videogame engagement triggered by the playful-consumption experience of videogame-play. The proposed conceptual model is based on a review of past literature on experience and engagement in videogame studies. Moreover, this study employs the hedonic theory of consumption experience and the concept of consumer engagement in order to conceptualize and operationalize the construct of playful-consumption experience and consumer videogame engagement and accordingly, develops the conceptual model. Based on the conceptual model, this study has drawn related hypothesis. This study is unique in its investigation as it examines the idea of experience from the perspective of hedonic theory of consumption experience and whereas, engagement is studied from the previous work on consumer engagement. Besides, this conceptual model is new in the field of videogame literature that examines consumer videogame engagement and playful consumption experience concurrently and this model also predicts consumer videogame engagement that is provoked by the playful-consumption experience of videogame play.

Introduction

The prevalence of playing videogames such as computer, mobile, portable and console videogames, has been raised significantly in the past decade [START_REF] Takatalo | User Experience in Digital Games Differences Between Laboratory and Home[END_REF]. Due to the popularity of videogame playing, the total consumers' spending on games industry has increased to $22.41 billion [START_REF] Association | Essential Facts about the Computer and Video Game Industry[END_REF]. This prominent growth in the videogame industry has encouraged academicians to research on videogame related issues. One of the key issues in videogame literature that has much debated is exploring and measuring the consumer's experiences, which arise from the interaction of a player, playing a videogame [START_REF] Seo | Advancing research on computer game consumption: A future research agenda[END_REF].

In similar vein, numerous academicians have investigated the concept of experience in videogame studies; some of the studies have qualitatively explored the term experience [START_REF] Brown | A grounded investigation of game immersion[END_REF][START_REF] Ermi | Fundamental components of the gameplay experience: Analysing immersion[END_REF] while, some studies have quantitatively measured the notion of experience [START_REF] Cheng | Game immersion experience: its hierarchical structure and impact on game-based science learning[END_REF][START_REF] Jennett | Measuring and defining the experience of immersion in games[END_REF]. The term experience has been studied through several theoretical constructs "absorption and flow, presence, immersion and engagement, gameflow, immersion and flow, presence, immersion, flow and absorption" by these studies [START_REF] Brown | A grounded investigation of game immersion[END_REF][START_REF] Ermi | Fundamental components of the gameplay experience: Analysing immersion[END_REF][START_REF] Jennett | Measuring and defining the experience of immersion in games[END_REF][START_REF] Costello | A tool for characterizing the experience of play[END_REF][START_REF] Funk | How children experience playing video games[END_REF][START_REF] Ijsselsteijn | Characterising and measuring user experiences in digital games[END_REF][START_REF] Sweetser | GameFlow: a model for evaluating player enjoyment in games[END_REF] to measure the subjective-experience of videogame-play. Moreover, the study has related the notion of experience with immersion, which has been further explored in the application of new technologies. For instance, immersive virtual environments in digital humanities that further create a new human experiences by consuming the new media technology like interactive immersive environments with videogames [START_REF] Lugmayr | Immersive Interactive Technologies in Digital Humanities: A Review and Basic Concepts[END_REF].

In literature, there are other studies [START_REF] Brockmyer | The development of the Game Engagement Questionnaire: A measure of engagement in video game-playing[END_REF][START_REF] Procci | The Subjective Gameplay Experience: An Examination of the Revised Game Engagement Model (PhD Diss)[END_REF] that have investigated the subjective experience of videogame-play but they termed as "game-engagement". Authors of these studies [START_REF] Brockmyer | The development of the Game Engagement Questionnaire: A measure of engagement in video game-playing[END_REF][START_REF] Procci | The Subjective Gameplay Experience: An Examination of the Revised Game Engagement Model (PhD Diss)[END_REF] have used the following dimensions "presence, flow, immersion, absorption and involvement" to measure the subjective game-play experience.

Doing a critical analysis of the past studies, the present study has found that the main issue in the previous studies is, they have studied two different concepts (experience and engagement) with similar theoretical constructs for instance; authors of the study [START_REF] Jennett | Measuring and defining the experience of immersion in games[END_REF] have measured the subjective experience of videogame-play through these theoretical lenses (presence, flow, immersion and psychological absorption) and named as immersion. Whereas, authors of these studies [START_REF] Brockmyer | The development of the Game Engagement Questionnaire: A measure of engagement in video game-playing[END_REF][START_REF] Procci | The Subjective Gameplay Experience: An Examination of the Revised Game Engagement Model (PhD Diss)[END_REF] have measured the term "engagement" in videogames as game-engagement and used the following theoretical dimensions flow, presence, absorption, involvement and immersion in order to quantify the subjective game-play experience. The same viewpoint has also been raised in the recent study [START_REF] Hookham | Comparing usability and engagement between a serious game and a traditional online program[END_REF] in which authors of the study have stated that prior studies have applied the concept of experience/immersion and engagement interchangeably to examine the subjective game-play experience as well as player's engagement in videogame playing. Another issue in the previous studies [START_REF] Jennett | Measuring and defining the experience of immersion in games[END_REF][START_REF] Brockmyer | The development of the Game Engagement Questionnaire: A measure of engagement in video game-playing[END_REF][START_REF] Procci | The Subjective Gameplay Experience: An Examination of the Revised Game Engagement Model (PhD Diss)[END_REF][START_REF] Nordin | Too Many Questionnaires: Measuring Player Experience Whilst Playing Digital Games[END_REF] is, they have restricted the construct of experience and engagement to the use of only psychological dimensions presence, flow, immersion and psychological absorption. Besides, these studies have ignored the importance of studying behavioral elements in both of the constructs.

The main purpose of the study is twofold; first, this study considers engagement and experience as a separate concept whereby, experience recognizes as consumer's consumption experience that occurs from the consumption of the product which influences a consumer to further engage in the product [START_REF] Bowden | The process of customer engagement: A conceptual framework[END_REF][START_REF] Hollebeek | Demystifying customer brand engagement: Exploring the loyalty nexus[END_REF]. These studies have also cleared the understanding between experience and engagement that consumption experience comes before the engagement in the product. This viewpoint is consistent with the following study [START_REF] Lugmayr | Categorization of ambient media projects on their business models, innovativeness, and characteristics-evaluation of Nokia Ubimedia MindTrek Award Projects of 2010[END_REF] who has discussed in his study that consuming experience of ambient media leads consumers to further engage in the ambient media.

Moreover, this study follows the viewpoint of [START_REF] Malthouse | Comment: Engagement and Experiences: Comment on Brodie, Hollenbeek, Juric, and Ilic[END_REF] who added that engagement arises from the experiences that come from the interactions of the main stimuli (product or service) and therefore, this study attempts to propose a new conceptual model that predicts consumer videogame engagement triggered by the playful-consumption experience of videogame play. Another objective of the study is to expand the conceptual model through conceptualizing and operationalizing the construct of playful-consumption experience and consumer video-game engagement.

Literature review

Experience in videogame studies is a multifaceted construct, which has been explored and studied by several studies [START_REF] Brown | A grounded investigation of game immersion[END_REF][START_REF] Ermi | Fundamental components of the gameplay experience: Analysing immersion[END_REF][START_REF] Cheng | Game immersion experience: its hierarchical structure and impact on game-based science learning[END_REF][START_REF] Jennett | Measuring and defining the experience of immersion in games[END_REF]. Among these studies, research done by [START_REF] Brown | A grounded investigation of game immersion[END_REF] was first study in the videogame literature, who explored the experiences of videogame-players and defined such experiences as game immersion. In Addition, authors have further categorized the definitional construct of game immersion into three sub levels of experiences such as "engagement, engrossment, and total immersion". Another study by [START_REF] Ermi | Fundamental components of the gameplay experience: Analysing immersion[END_REF] who investigated the concept of immersion to understand the basic essentials of videogame-play experience. The study resulted in three factors "sensory-immersion, challenge-based immersion and imaginative-immersion" affecting the construct of immersion.

Literature review reports that these studies [START_REF] Cheng | Game immersion experience: its hierarchical structure and impact on game-based science learning[END_REF][START_REF] Jennett | Measuring and defining the experience of immersion in games[END_REF][START_REF] Ijsselsteijn | Characterising and measuring user experiences in digital games[END_REF][START_REF] Ijsselsteijn | Measuring the experience of digital game enjoyment[END_REF][START_REF] Poels | FUGA-The fun of gaming: Measuring the human experience of media enjoyment[END_REF] have examined the experiences of videogame-play for instance; the following studies [START_REF] Ijsselsteijn | Characterising and measuring user experiences in digital games[END_REF][START_REF] Ijsselsteijn | Measuring the experience of digital game enjoyment[END_REF][START_REF] Poels | FUGA-The fun of gaming: Measuring the human experience of media enjoyment[END_REF] have considered the idea of experience as a multidimensional construct that comprises these dimensions "imaginative and sensory-immersion, competence, challenge, annoyance/tension, flow, positive and negative affect". Based on these dimensions, authors have developed and labeled a scale as game experience questionnaire (GEQ) for measuring the experiences of videogame play. But, the questionnaire lacks empirical validation [START_REF] Norman | Geq (game engagement/experience questionnaire): a review of two papers[END_REF]. In contrast to game experience questionnaire, these studies [START_REF] Brown | A grounded investigation of game immersion[END_REF][START_REF] Ermi | Fundamental components of the gameplay experience: Analysing immersion[END_REF][START_REF] Cheng | Game immersion experience: its hierarchical structure and impact on game-based science learning[END_REF][START_REF] Jennett | Measuring and defining the experience of immersion in games[END_REF] have employed the theory of immersion to develop the instruments such as "immersion questionnaire [START_REF] Jennett | Measuring and defining the experience of immersion in games[END_REF] and game immersion questionnaire [START_REF] Cheng | Game immersion experience: its hierarchical structure and impact on game-based science learning[END_REF]" for describing the experiences of videogame-play. Moreover, immersion questionnaire has been developed through the efforts of [START_REF] Jennett | Measuring and defining the experience of immersion in games[END_REF] in which authors have applied such theoretical constructs "flow, presence, cognitive absorption and immersion" to develop a scale for measuring the experience of immersion in videogame-playing. While, another study [START_REF] Cheng | Game immersion experience: its hierarchical structure and impact on game-based science learning[END_REF] has employed the definition of immersion [START_REF] Brown | A grounded investigation of game immersion[END_REF] to develop a scale for "game immersion experience" which is intended to measure the experiences of videogame-play. According to the study [START_REF] Brown | A grounded investigation of game immersion[END_REF], immersion is defined as "three sub-levels of experiences" such as "engagement, engrossment and total immersion".

Recently, the research done by [START_REF] Hookham | Comparing usability and engagement between a serious game and a traditional online program[END_REF] has debated that few studies have employed the notion of experience/immersion and engagement in a similar manner to examine the experiences of videogame-play. This can be supported by these studies [START_REF] Brockmyer | The development of the Game Engagement Questionnaire: A measure of engagement in video game-playing[END_REF][START_REF] Procci | The Subjective Gameplay Experience: An Examination of the Revised Game Engagement Model (PhD Diss)[END_REF] who have applied the term engagement to quantify the subjective experience of videogame-play. Another interesting point that has been raised is, authors of these studies [START_REF] Brockmyer | The development of the Game Engagement Questionnaire: A measure of engagement in video game-playing[END_REF][START_REF] Procci | The Subjective Gameplay Experience: An Examination of the Revised Game Engagement Model (PhD Diss)[END_REF] have applied similar dimensions "flow, presence, absorption and immersion" to measure the construct game engagement, which have already been employed in the following study [START_REF] Jennett | Measuring and defining the experience of immersion in games[END_REF] to measure the experiences of videogame-play.

A critical evaluation of past researches that have utilized the notion of experience/immersion and engagement in videogame studies, the current study has found the following issues for instance; first, the concept of experience/immersion and engagement have been used interchangeably to measure the subjective experience of videogame play [START_REF] Jennett | Measuring and defining the experience of immersion in games[END_REF][START_REF] Brockmyer | The development of the Game Engagement Questionnaire: A measure of engagement in video game-playing[END_REF][START_REF] Procci | The Subjective Gameplay Experience: An Examination of the Revised Game Engagement Model (PhD Diss)[END_REF]. Second, authors have applied similar theoretical dimensions "flow, presence, absorption and immersion" to measure the experiences as well as player's engagement in videogame-play. Besides, authors have applied only psychological dimensions in the construct of game engagement and experience/immersion.

To address the above stated issues, the next section aims to propose a unique conceptual model that studies the concept of experience and engagement as two separate theoretical constructs. In this conceptual model, the present study employs the concept of experience from the context of hedonic theory given by [START_REF] Hirschman | Hedonic consumption: emerging concepts, methods and propositions[END_REF] and whereas, engagement from the work of following studies [START_REF] Brodie | Customer engagement: conceptual domain, fundamental propositions, and implications for research[END_REF][START_REF] Brodie | Consumer engagement in a virtual brand community: An exploratory analysis[END_REF][START_REF] Hollebeek | Exploring customer brand engagement: definition and themes[END_REF].

The Development of Conceptual Model and Study Propositions

The notion of experience was initially presented by [START_REF] Hirschman | Hedonic consumption: emerging concepts, methods and propositions[END_REF] in the field of consumption and marketing. Now onwards, the studying of experience has turned into a significant component to realize consumer's behavior [START_REF] Addis | On the conceptual link between mass customisation and experiential consumption: an explosion of subjectivity[END_REF]. Formerly, the researchers of marketing and consumer field, have applied the idea of consumption in only purchasing decisions. But, this viewpoint of the consumption, has been extended by the study [START_REF] Hirschman | Hedonic consumption: emerging concepts, methods and propositions[END_REF] who has introduced the experiential features of the consumption. Moreover, a study [START_REF] Holbrook | Consumer research: Introspective essays on the study of consumption[END_REF] has contributed that a researcher can investigate the idea of consumption in terms of buying, usage and disposal. In similar vein, the following studies [START_REF] Holbrook | The millennial consumer in the texts of our times: Experience and entertainment[END_REF][START_REF] Brakus | Experiental Attributes and Consumer Judgments[END_REF][START_REF] Arnould | Consumers-International edition[END_REF] have also added that consumption experience occurs in numerous ways for instance; when consumers are looking for a product, when consumers purchase the product or acquire any service and lastly, when consumers make use of the product or service. Among these consumption experiences, the present study is mainly interested in investigating the consumption experience that comes from the use of the product. Applying the concept of consumption experience in context of videogame-play, the consumption experience is assumed to achieve through the playful-consumption of a videogame product because a study has added that "playing a videogame is truly as experiencing a videogame" [START_REF] Salem | Rules of play[END_REF]. Moreover, researchers [START_REF] Buchanan-Oliver | Play as co-created narrative in computer game consumption: The hero's journey in Warcraft III[END_REF][START_REF] Holbrook | Play as a consumption experience: The roles of emotions, performance, and personality in the enjoyment of games[END_REF] have considered the act of playing a videogame or consuming videogames as "playful-consumption experience". This is due to the reason that playful-consumption experience affiliates to intrinsically motivated consumer behavior that is usually done for its own benefit. Such consumption experience of videogame-play, further facilitates the videogame-consumers to experience a variety of hedonic elements relating to videogame-play such as imagination, emotional responses and multisensory attributes [START_REF] Holbrook | Play as a consumption experience: The roles of emotions, performance, and personality in the enjoyment of games[END_REF][START_REF] Abbasi | An integrated conceptual model for predicting behavioral learning triggered by video-game engagement: A mediating role of observational learning[END_REF]. Furthermore, these hedonic elements "imagination, emotional responses and multisensory attributes" come under the umbrella of hedonic consumption. Authors of these studies [START_REF] Hirschman | Hedonic consumption: emerging concepts, methods and propositions[END_REF][START_REF] Alba | Pleasure principles: A review of research on hedonic consumption[END_REF], have defined hedonic consumption as "those facets of consumer behavior that relate to consumers' emotive-responses, imaginary and multi-sensory aspects in using products". Besides, according to [START_REF] Hirschman | Hedonic consumption: emerging concepts, methods and propositions[END_REF], videogame is one of the hedonic product because, the consumption of a videogame product as "playful-consumption" involves consumers' emotive-responses, imaginary and multi-sensory aspects.

In the following studies, researchers have further operationalized and categorized the hedonic consumption experience into three main experiences, explicitly, imaginal, emotional and sensory experiences [START_REF] Hirschman | Hedonic consumption: emerging concepts, methods and propositions[END_REF][START_REF] Wang | The influence of hedonic values on consumer behaviors: an empirical investigation in China[END_REF]. Imaginal experience states about mental events of visualizing things that are not considered as real and such visualizing is internal, personal and unspoken [START_REF] Macinnis | The role of imagery in information processing: Review and extensions[END_REF]. Hedonic consumption is connected with imaginal experience as a product has the potential to help consumers imagine actions that they want [START_REF] Hirschman | Hedonic consumption: emerging concepts, methods and propositions[END_REF]. While, emotional experience denotes to emotive states that consumers experience with respect to particular activities. The following research [START_REF] Hirschman | Hedonic consumption: emerging concepts, methods and propositions[END_REF] has added a product has the ability to arouse consumers' emotional state and therefore, emotional experience is linked with hedonic consumption. The last experience that is tied to hedonic consumption is sensory experience. Whereas, the study [START_REF] Hirschman | Hedonic consumption: emerging concepts, methods and propositions[END_REF] has defined sensory experience as "the receipt of experience in multiple sensory modalities comprising sense of touch, sight, and sound".

In earlier debate, the study has defined and operationalized the term experience as "playful-consumption" from the perspective of hedonic consumption theory given by [START_REF] Hirschman | Hedonic consumption: emerging concepts, methods and propositions[END_REF]. However, the term engagement is less defined in the above studies and therefore, the next debate will shed light on the concept of engagement in videogame.

The current article studies the concept of engagement in videogame literature as "consumer videogame engagement". This study takes a theoretical support from the following studies [START_REF] Hollebeek | Demystifying customer brand engagement: Exploring the loyalty nexus[END_REF][START_REF] Brodie | Customer engagement: conceptual domain, fundamental propositions, and implications for research[END_REF][START_REF] Brodie | Consumer engagement in a virtual brand community: An exploratory analysis[END_REF] in order to define and conceptualize the concept of consumer videogame engagement. According to the authors, "engagement is a multi-dimensional construct which is subject to a context-specific expression of relevant cognitive, emotional and behavioral dimensions". Moreover, the study by [START_REF] Hollebeek | Demystifying customer brand engagement: Exploring the loyalty nexus[END_REF] has further promoted that the process of engagement exhibits due to having two-way communications among the engagement-subject like "consumer/customer" and a specific engagement-object like a product, service or a brand, which finally helps in generating consumer engagement levels in terms of consumers' cognitive, affective and behavioral engagement. As a result of these definitions given by [START_REF] Hollebeek | Demystifying customer brand engagement: Exploring the loyalty nexus[END_REF][START_REF] Brodie | Customer engagement: conceptual domain, fundamental propositions, and implications for research[END_REF][START_REF] Brodie | Consumer engagement in a virtual brand community: An exploratory analysis[END_REF], this study defines consumer videogame engagement as "A psychological state that triggers due to two-way interactions between the consumer and videogame product, which generates different level of consumer engagement states (cognitive, affective and behavioral)". According to the definition of consumer videogame engagement, the construct of consumer videogame engagement is further conceptualized as three main states of engagement comprising cognitive, affective and behavioral engagement.

In spite of the fact, consumers gain playful-consumption experience through the consumption of a videogame product as "playing a videogame". Such playful-consumption experience refers to the notion of hedonic consumption experience, which relates to consumers' imaginal, emotional and sensory experience in the videogame-play. A study [START_REF] Caru | A critical approach to experiential consumption: fighting against the disappearance of the contemplative time[END_REF] has further added that this kind of experiences (playful-consumption experiences) are so interactive and co-creative that consumers get engaged cognitively, affectively and behaviorally in playing more videogames. On this basis, the present study proposes a unique conceptual model as shown in Figure : 1 that predicts consumer videogame engagement in terms of consumers' or video-gamers' cognitive, affective and behavioral engagement triggered by consumers' or video-gamers' playful-consumption experience in terms of their imaginal, emotional and sensory experience.

Conceptual Model

The following proposed conceptual model explains that when consumers play a videogame, they actually get an experience of playing which is termed as playful-consumption experience. Playful-consumption experience is further categorized as imaginal experience, emotional experience and sensory experience. This is consumers' playful-consumption experience that further motivates consumers to engage into videogame playing. This engagement is coined as consumer videogame engagement in the proposed conceptual model. The consumer videogame engagement is further classified into cognitive engagement, affective engagement and behavioral engagement.

Study hypothesis

According to the proposed conceptual as shown in the Figure : 1, this study develops the following hypothesis.

Imaginal experience has a positive significant impact on cognitive engagement.

Imaginal experience has a positive significant impact on affective engagement. Imaginal experience has a positive significant impact on behavioral engagement. Emotional experience has a positive significant impact on cognitive engagement. Emotional experience has a positive significant impact on affective engagement. Emotional experience has a positive significant impact on behavioral engagement. Sensory experience has a positive significant impact on cognitive engagement. Sensory experience has a positive significant impact on affective engagement. Sensory experience has a positive significant impact on behavioral engagement.

Conclusions

This study took an initiative to consider the concept of engagement and experience in videogame studies as a distinct construct and these constructs cannot be employed interchangeably to understand and examine the experiences of videogame-play as well as players' engagement in videogame playing. This perspective can be well understood from the work of [START_REF] Holbrook | The millennial consumer in the texts of our times: Experience and entertainment[END_REF][START_REF] Brakus | Experiental Attributes and Consumer Judgments[END_REF][START_REF] Arnould | Consumers-International edition[END_REF] who defined that experience exits when customers consume the product or service and whereas, the state of engagement comes from such experiences that consumers have had with the consumption of a product [START_REF] Malthouse | Comment: Engagement and Experiences: Comment on Brodie, Hollenbeek, Juric, and Ilic[END_REF]. Applying these concepts in the videogame context, experience is recognized as consumers' playful-consumption experience that gains when consumers consume the videogame product as "playing" a videogame on any platform. When consumers find such playful-consumption experiences as co-creative and interactive, then such experiences further provide consumers a kind of interface, whereby consumers become engaged in the videogame-play [START_REF] Caru | A critical approach to experiential consumption: fighting against the disappearance of the contemplative time[END_REF]. Therefore, this study has proposed a unique conceptual model that predicts consumer videogame engagement triggered by the playful-consumption experience of videogame-play.

Contribution and Future Research

This study contributes to videogame literature in several ways for instance; this study is first to employ the hedonic theory of consumption experience in the field of videogame studies, to examine the playful-consumption experience, namely, imaginal, emotional and sensory experience in videogame-play. Secondly, this study differentiates between the concept of experience and engagement in videogame studies because, previous researches [START_REF] Jennett | Measuring and defining the experience of immersion in games[END_REF][START_REF] Brockmyer | The development of the Game Engagement Questionnaire: A measure of engagement in video game-playing[END_REF][START_REF] Procci | The Subjective Gameplay Experience: An Examination of the Revised Game Engagement Model (PhD Diss)[END_REF] have applied the concept of experience and engagement interchangeably to examine the player's experiences and engagement in videogame play. This study further contributes to the past studies that experience comes first then such experiences further influence consumers to get engaged in the videogame-play. Moreover, this study employs the definition of consumer engagement that has been mentioned in the following studies [START_REF] Hollebeek | Demystifying customer brand engagement: Exploring the loyalty nexus[END_REF][START_REF] Brodie | Customer engagement: conceptual domain, fundamental propositions, and implications for research[END_REF][START_REF] Brodie | Consumer engagement in a virtual brand community: An exploratory analysis[END_REF] to conceptualize consumer videogame engagement in videogame literature. The new perspective of engagement as "consumer videogame engagement", brings new insights in the previous studies [START_REF] Brockmyer | The development of the Game Engagement Questionnaire: A measure of engagement in video game-playing[END_REF][START_REF] Procci | The Subjective Gameplay Experience: An Examination of the Revised Game Engagement Model (PhD Diss)[END_REF] that have studied the notion of engagement in their studies. Thirdly, all previous work in the field of videogame literature, especially on measuring experiences [START_REF] Cheng | Game immersion experience: its hierarchical structure and impact on game-based science learning[END_REF][START_REF] Jennett | Measuring and defining the experience of immersion in games[END_REF][START_REF] Ijsselsteijn | Characterising and measuring user experiences in digital games[END_REF][START_REF] Ijsselsteijn | Measuring the experience of digital game enjoyment[END_REF] as well as engagement [START_REF] Brockmyer | The development of the Game Engagement Questionnaire: A measure of engagement in video game-playing[END_REF][START_REF] Procci | The Subjective Gameplay Experience: An Examination of the Revised Game Engagement Model (PhD Diss)[END_REF], are scarce to simultaneously examine the notion of experience and engagement within a model, which the current study addresses in the proposed model that predicts consumer videogame engagement triggered by playful-consumption experience of videogame play. This study is conceptual in nature and therefore, future study is warrant to validate the proposed model and the study propositions. Moreover, future work is in progress to develop a scale on playful-consumption experience and consumer videogame engagement.

6.

Figure: 1

 1 Figure: 1 Predicting Consumer Videogame Engagement Triggered by Playful-Consumption Experience


Pedro Ribeiro

Ido Iurgel

Wolfgang Müller
email: mueller@md-phw.de

Christian Ressel

Enrichment of Story Reading with Digital Media

Keywords: Reading, Stories, E-books, Augmented reading, Digital media. 1

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

Introduction

Reading is a vital skill to function in today's society. But why do we read? What are the reasons? In a research, Clark and Rumbold [START_REF] Clark | Reading for pleasure: a research overview[END_REF] explain the link between reading enjoyment and reading motivation and stated that readers who are intrinsically motivated are more likely to benefit from enjoyment and achieve a deep learning.

Nowadays, we witness to a shift in the way we read and in the materiality of the book brought about by digital technology. E-books are a digital replication of a paper book that in some cases is augmented with functionalities such as dictionary or games. Typically, these augmentations happen in the same medium where the text is. But how can we foster enjoyment and meet the reader's motivations better without compromising the reading performance? In this paper, we describe a concept that aims to allow the interaction with the reading space just by reading. In this space, digital media infrastructures react to the reading performance and the narrative, promoting enjoyment and immersion.

A significant number of studies have investigated how to digitally augment the book. The MagicBook project [START_REF] Billinghurst | The MagicBook: a transitional AR interface[END_REF] explored the potential of augmented reality to enrich the reading-experience. Since then, several academic and commercial books employed augmented reality. Recently, researchers developed the SequenceBook [START_REF] Yamada | SequenceBook: interactive paper book capable of changing the storylines by shuffling pages[END_REF], an interactive book with blank pages that serves as medium for a dynamic projection. Another interesting concept explored the experience of a textbook with a fold-out screen-margin extension [START_REF] Figueiredo | Bridging book: a not-so-electronic children's picturebook[END_REF], [START_REF]Marginalia[END_REF]. The margin space allows complementary content.

A small number of studies have been done in the area of automated environments that reacts to the reading activity. [START_REF] Back | The SIT Book: Audio As Affective Imagery for Interactive Storybooks[END_REF] presented The SIT book [START_REF] Back | The SIT Book: Audio As Affective Imagery for Interactive Storybooks[END_REF], a prototype, able to use the reader hands' speed as control parameter for a narrative soundscape. Later in 2005, Bahna and Jacob presented a system [START_REF] Bahna | Augmented reading: Presenting additional information without penalty[END_REF] in which extra information is peripherally conveyed through a video projection. In 2013, Alam et al. proposed the augmentation of an e-book reading-experience by controlling haptic and audio-visual interfaces existing in a living room [START_REF] Alam | Mobile haptic e-book system to support 3D immersive reading in ubiquitous environments[END_REF]. Finally, Schafer et al. developed a system that uses a multimedia room to transform an interactive read-aloud experience, providing feedback that supports children's enjoyment and meaning-making [START_REF] Schafer | An interactive, cyberphysical read-aloud environment[END_REF].

Prototype

Story reading enrichment (SRE) means to synchronize the reading with one or more digital media experiences. A SRE system must allow 1) the definition of how digital media infrastructures will respond to the reading performance and narrative; 2) the control and perception of a SRE. In order to explore the SRE, we developed a prototype composed by a Tablet and a Smart bulb. The Tablet displays the story, identify the reading position and control the bulb. In order to obtain, the reading position, the system employs speech recognition. Then, depending on the specification of how the light must behave, in a specific reading position, the Tablet controls light's properties.

Scenario

Emma uses a Tablet to read "The Hobbit" [START_REF] Tolkien | The hobbit[END_REF] to her son Matt. Matt can see on his Tablet a map of "Middle-earth". He easily realizes where they stopped and by touching the spot, the text appears on both Tablets. The room turns dark, and a cavern soundscape can be heard. When Emma mentions a character, she also associates it to a light (by pointing the lamp). The Light reflects the character's emotions. While reading, the riddles' "battle", the lights of Bilbo and Gollum start to oscillate between white (fear), yellow (joy) and red (angry). At the same time, a melody intensifies the drama. Later, Matt uses the map to jump to a beloved section, where dwarves sing in choir. Matt can then see a lyric and starts to read it. Matt follows a word highlighting feature, which provides the correct pace. When Matt starts to read, a melody starts playing. The longer Matt respects the pace, the more instruments and voices densify the music. By reading correctly he unlocks different music channels, coming from different positions. This game progressively immerses him in a joyful environment.

Story reading enrichment: features

Based on the scenario, we identified the four main features of a SRE: Required attention: Reading is a high attentional activity, demanding constant foreground visual attention. The SRE must be able to display information both to the peripheral attention and to the foreground attention. Peripheral interaction aims to subtly augment the reality with the narrative's context, e.g. white light to reflect the fear felt by Bilbo. On the other hand, the interaction can obviously encompass a more concrete stimulation e.g. an image of a frightened Bilbo, providing an interactive context that supports the storytelling or meaning-making.

Virtuality: The SRE is characterized by its virtuality and can vary in a continuum that ranges between a) real environment b) virtual environment, wherein the intermedium is characterized by a mixed reality experience.

Locus of agency: A SRE can be proactive and/or reactive. In the simplest usage, a SRE shall be proactive, because whenever the reader is focused on reading, an implicit enrichment must happen e.g. melody intensifying the drama. On the other hand, enrichment can be reactive when a reader explicitly requires enrichment e.g. storyteller that uses SRE to complement his performance -make a gestures to set all lights off.

Interactivity: SREs can be controlled and perceived by readers through a multimodal interaction. Regarding the control of a SRE, the reading position and performance can be detected through different input modalities (touch, speech recognition, eye gaze direction, gesture recognition or even emotion recognition). The perception of a SRE can be promoted by different modalities such as visual, auditory, haptic, etc.

Story reading enrichment: roles

Based on the SRE's features, we envision roles with a focus on multiple aspects of the intrinsic motivation [START_REF] Clark | Reading for pleasure: a research overview[END_REF] such as curiosity, involvement or social interaction. Meaning-making: What if the reader does not know a specific object or idea? In order to foster the curiosity and to avoid losing involvement, the SRE can function as a facilitator of meaning-making e.g. when several characters are introduced in a short amount of text, reader may benefit from additional digital media. This kind of SRE can be explicitly initiated by the reader or implicitly through concentration sensing.

Intensification/clarification: Another way to promote involvement, is by intensifying the reading. A scene can be intensified through music targeting an emotional state or a fictional genre. The SRE can also serve as a clarification to interpret text. A good example is, when a figure of speech like irony or metaphor is used.

Support: In another perspective the SRE can support the reading performance. This functionality is characterized by a playful manner of using a SRE, targeted to extend the reader's expressivity e.g. a storyteller controlling the SRE through gestures or speech. This supportive role shall promote social activities such as storytelling.

Training: The SRE as a playable environment can be used in a gamified experience e.g. rewarding by mastering reading and interpretation skills. Another example is to encourage a focused reading, by providing a SRE based on neurofeedback technic.

Topography: The SRE can also be used to simplify the text navigation. We believe that, if the reader can use a simple metaphor to map and mark the written content, we can promote a feeling of being in control of the reading. An example is the creation of a virtual map where the reading-experiences or digital marginalia are mapped.

Inspiration: The SRE can also spark the imagination. When an author deliberately describes a scene, in an ambiguous way, he is challenging reader's imagination. SRE can have the mission of supporting the imagination challenge. For example, by allowing readers to decide in which kind of virtual environment they want to read (forest, city, etc.) or by synchronizing the SRE with the narrative and reading performance.

Cumulative reading: The SRE must be able to learn from each reading session and enhance the reader's capacity to recall/relate thoughts and emotions from previous readings and adapt SRE's behaviours based on reader's preferences.

Conclusion

In this paper, we explore a concept that employs digital media infrastructures, that react to the reading performance and the narrative, promoting a more joyful and immersive reading-experience. Based on the user experience envisioned through a key scenario, we analyse the principal features of a SRE and discuss how SRE can assume a variety of roles, promoting experiences that aim to match readers' intrinsic motivations. This paper highlights the potential and open questions of this concept. It also serves as a conceptual framework for developing SREs. Further work will involve building a functional SRE system that allows the proof-of-concepts development. Furthermore, evaluations will be performed to understand how to effectively enrich the story reading and to identify story genres' constraints and side effects.




Abstract-The objective of this paper is to share Kernix's approach to build flexible recommender systems based on graph oriented databases. The integration of entities, and relationships between them, into a unique graph structure allows to design recommendations as graph traversals. This approach offers a flexible framework allowing to handle the variety of entities of interest and enabling to design rich strategies in order to compute recommendations for various use cases.

Index Terms-Graph database, Recommender systems, Data Management

I. INTRODUCTION ernix is a company of forty-five people whose activity rely on a digital factory, crafting custom websites, and a data lab, providing data oriented solutions for business use cases. These solutions span from predictive maintenance to credit risk scoring but also fraud detection and recommender systems. In the latter context, Kernix has designed and built several custom recommender engines aiming at fulfilling its customers' needs. In order to cope with the variety of these needs and with the data available, Kernix has decided to adopt a flexible approach essentially based on the use of a graph oriented database.

Basic approaches to recommendation [START_REF] Ricci | Introduction to Recommender Systems Handbook[END_REF] consist in building separate models for content-based (CB) and collaborative filtering (CF) strategies, respectively relying on the exploitation of items-items similarities and users-items interactions. In general, these approaches lack some kind of flexibility in the integration of complex interactions between entities. As an illustration, in the case of movie recommendation, it is not easy to merge in one approach the explicit taste of a user about its favorite actors and genres with its ratings for specific movies.

A flexible approach would ease the exploitation of the multiple kinds of possible interactions between different entities (users, actors, genres and movies in our example). Graphs are natural mathematical structures allowing to encode these interactions, and, as we will show in what follows, recommendations can be computed thanks to graph traversals. In the following, we present how Kernix is leveraging on a graph oriented database technology in order to build different so-called flexible recommendation engines. Part II briefly describes the use of a graph oriented database, allowing us to introduce the vocabulary further used. Part III deals with a toy example of a CF recommendation based on the MovieLens dataset. Part 2 refers to a hybrid recommender engine that Kernix has built for one of its client. Part IV summarizes the stack of technologies on which our solutions are based, and the workflow associated to it. In the conclusion, we share some advantages and caveats of our approach and draw some perspectives.

II. BRIEF DESCRIPTION OF THE USE OF A GRAPH DATABASE

A graph database models and stores data as nodes and edges of a graph structure [START_REF] Angles | Survey of graph database models[END_REF]. These elements can bear types allowing their categorization and can embed additional information specifying their properties. For instance, in the case of movie recommendation, node types could be User, Actor, Genre and Movie and edge types could be Has_rated, Has_actor, Has_genre for edges respectively linking users to movies, movies to actors and movies to genres; while properties of a User node could be the name, age and sex of the user and a property of the Has_rated edge could be the rating itself.

Graph databases allow efficient and fast retrieval of complex hierarchical structures that are difficult to model in relational systems. Information retrieval is performed thanks to specific query languages [3] based on the semantic of graph traversals, generally proposing optimized routines for computing shortest paths for instance.

Within this graph framework, for a given dataset, several kinds of recommendations can be elaborated by combining and scoring paths between entities. In our example, similarity between users can be evaluated through the paths that connect one user to movies, actors and genres, that are themselves connected to other users, each type of path being potentially weighted by different coefficients. The two following parts will concretely illustrate the way these concepts can be implemented.

III. EXAMPLE OF A CF RECOMMENDER SYSTEM

To illustrate the case of a graph-based CF recommender system, we have built a movie recommender engine based on the ML-100k dataset [12]. This dataset has been gathered by GroupLens Research on the MovieLens website and consists in 100,000 ratings (1-5) from 943 users on 1682 movies. The Flexible recommender systems based on graphs J. Pellegrino, Kernix Software K dataset has been cleaned up such that each user has rated at least 20 movies. The model chosen for the graph consists in:

• two kinds of nodes: User and Movie.

• one kind of edge: Has_rated, relating users to movies. The rating r(mj,ui) given by user ui to movie mj is recorded as a property of the edge.

For a given user u1, we have chosen to recommend movies that are mostly appreciated by users giving similar ratings as u1. For reasoning, this strategy implies the following conceptual steps.

Step 1: Selection of the users who are the most "similar" to u1.

The similarity between u1 and ui is here defined as:

𝑠𝑖𝑚(𝑢 1 , 𝑢 𝑖 ) = 𝑐𝑎𝑟𝑑(𝑆 𝑢 1 ,𝑢 𝑖 )/𝑐𝑎𝑟𝑑(𝑅 𝑢 1 )
where

𝑆 𝑢 1 ,𝑢 2 = ⋃ 𝑚 𝑗 |𝑟(𝑚 𝑗 ,𝑚 2 )-𝑟(𝑚 𝑗 ,𝑚 1 )|≤1
, is the set of movies commonly rated by u 1 and u 2 with a difference of rating less are equal to 1; and Ru1 is the set of all movie rated by u1.

Thanks to this similarity measure, we form the subset Usim of users ui with similarity with u1 above a certain threshold t (here arbitrarily set to 0.5).

Step 2: Ranking of movies seen by these users.

The recommendation score of each movie mj rated by the users belonging to Usim is then computed as the mean rating. In this case, movies will be ranked from « most appreciated by similar users » to « least appreciated by similar users ». If Vm is the subset of users who have rated movie m, and Wm its intersection with Usim, then the score of movie m can be expressed as:

𝑠(𝑚) = ∑ 𝑟(𝑚, 𝑢 𝑖 ) 𝑢 𝑖 ∈𝑊 𝑚 𝑐𝑎𝑟𝑑(𝑊 𝑚 )
Despite the fact that the above description of the method is mainly set-theoretical, the approach is in fact really natural in terms of graph traversal as illustrated by Fig. 1 and can be easily implemented as a request to the graph database.

Although this toy recommender system shows reasonable performances for this case, an assessment on a more significant set of users must performed to draw any solid performance metrics. One has to mention that this model doesn't involve any training phase as machine-learning based approaches requires so it is really well suited for cases of fast addition/deletion of entities and evolution of their connections. The following part extends the approach to a richer use case.

IV. EXAMPLE OF A HYBRID RECOMMENDER SYSTEM

In this part, we will share the design of the approach we took for building a recommender system for one of our client. This company proposes to ease interactions between individuals and professionals through "do it yourself" workshops. Our goal was to integrate to the website of this company an engine recommending workshops to users. The recommendation has been built on connections between different "entities", namely User, Craftsman, Workshop, Session and Category. The types of these entities and the relationships we decided to implement in the graph database are summarized in the Fig. 2.

In order to compute the recommendation of workshops, we decided to combine the three following strategies based on the same graph structure.

Strategy 1: Scoring through categories

For a given user, the ranking of workshops to recommend is based on the number of times they are linked to categories for which the user has shown an interest. This mark of interest, as illustrated in Fig. 3, take into account several paths between the user and the categories:

• direct edges of type "follow" from the user to the categories • paths through workshops followed by the user • paths through workshops to which the user attend a session This strategy is analogous to the CF recommendation example of the previous part, except that paths taken into account between users can be deeper than just one node. Indeed, to select the subset Usim of users similar to the target user, we exploit the paths through workshops for which the user has shown a mark of interest by:

• following the workshop • participating to a session of the workshop • following the craftsman that proposes the workshop

The users defined as similar to the target user are those counting a sufficient number of workshops in common with him. Finally, workshops are ranked based on the number of times they are linked to the subset Usim, through the same kinds of paths as described above.

Startegy3: Scoring through workshops similarity

This last strategy leverages on the computation of semantic similarity between the descriptions of the workshops. In order to compute these similarities, we have implemented a NLP pipeline performing the vectorization of the descriptions (through tokenization, stemming and tf-idf weighting) and the fit of these data points by LSI model (in order to merge frequently co-occurring terms into main concepts). The similarity between descriptions is obtained by the cosine of the angle formed by their corresponding vectors. The similarity scores are then materialized in the graph database as the property of "similarity" edges drawn between corresponding workshops as illustrated in Fig. 5: Recommended workshops are defined as the most similar to the workshops for which the target user has shown an interest, as described in the previous strategy. Analogously to the above toy example, these three strategies are implemented as requests to the graph database.

Their results are subsequently combined to give a list of workshops that is further filtered by the geographical region of interest of the user and sorted by remaining days before available session.

One advantage of this approach is that it is very flexible schemes of computation and combination of recommendation based on the same graph structure. Another subtle advantage is that a small amount of data is sufficient to start serving reasonably adapted recommendations. This rely on the fact that recommendations are based on local request to the graph structure such that they can start making sense as soon as portions of the graph are sufficiently well connected.

V. TECHNOLOGICAL STACK AND WORKFLOW

This part draws the main lines of the architecture we use in order to build an engine serving the kind of flexible recommendation described above. Basically, the engine lies on the synchronized exploitation of a Neo4j database [4] and a MongoDB database [7]. The Neo4j technology is made for storing data structured as graph and requesting it with the Cypher language. MongoDB, a document oriented database, is used in order to store potentially large content associated with each entity (the descriptions of the workshops in the previous use case for instance), whereas the graph database is not really suited for this functionality.

The overall application is built with the Node.js [9] framework. Packages of this framework (mainly async.js) allow to design asynchronous workflows that are useful for handling real-time addition/deletion of entities and relationships, and managing complex execution schemes. Other packages (mainly express.js) allow to expose web services useful if the engine has to communicate with websites (as needed by a majority of our use cases). Finally, connectors to Neo4j and MongoDB are also available. All these features allow the application to orchestrate data collection and processing, writing to the databases and requesting them to serve recommendations.

NLP and machine-learning tools we are using for computing similarity between texts for instance, mainly belong to the python library Gensim [6]. Python processes are integrated to the overall Javascript platform thanks to communication via a RabbitMQ queuing system [8].

Finally, to ease the deployment of the whole application, each of its micro-services is containerize thanks to the Docker technology [10] .

VI. CONCLUSION AND PERSPECTIVE

We have presented in this paper the way Kernix is building recommender engine based on a graph database. To conclude, we share some advantages and caveats of this kind of flexible recommender system.

We have mainly adopted the approach described above because of the ease of addition/deletion of entities and their connections and the adaptability of the recommendation computation to the various client's use cases we have encountered over time. This flexibility of the system also relies on the possible enrichment of the graph of entities thanks to data processing as mentioned above concerning semantic similarity. Beside these motivating points, two other points remain challenging. Firstly, we are still investigating ways to assess recommendations quality either by in production A/B testing and by offline evaluation. Secondly, we are studying the potential scalability of these techniques to high data volume and denser stream of information.

Fig. 1 .Fig. 2 .

 12 Fig. 1. Schematic representation of the method

Fig. 4 .Fig. 5 .

 45 Fig. 4. Example of paths taken into account for the scoring through users similarity (deeper paths passing by sessions and craftsmen are not shown for compactness)


Laurent Romary

The open access agenda of the Max Planck Society, initiator of the Berlin Declaration, envisions the support of both the green way and the golden way to open access. For the implementation of the green way the Max Planck Society through its newly established unit (Max Planck Digital Library) follows the idea of providing a centralized technical platform for publications and a local support for editorial issues. With regard to the golden way, the Max Planck Society fosters the development of open access publication models and experiments new publishing concepts like the Living Reviews journals.

In 2003, the Max Planck Society has been the initiator of the Berlin Declaration, which expresses a global vision on open access (OA) to scientific knowledge, and is now quoted as a reference statement in any open access endeavours. Among these, the recent years have seen many initiatives intended to foster the archival of scientific publications in open repositories (green way to OA) as well as the definition of new business models (gold way) that would lead to the large-scale implementation of the Berlin Declaration principles. Still, there remains work to be done before scientists and the general public all over the world have at their disposal the wide compendium of research results in all forms of presentation. In this respect, the Max Planck Society wants to keep the agenda moving ahead by exploring how it may integrate open access activities related to traditional publications, new publishing models and dissemination of research data in one single vision. The so-called open access agenda of the Max Planck Society addresses those issues along various dimensions, namely: • Scientific: going towards the definition of scientific collaborative environments that would implement the role of open access in a wider notion of eScience; • Technical: identifying the need for integrated and sustainable platforms for the management of research assets; • Editorial: defining the measures to be taken to help researchers adhere to the open access principles and make their results usable to a wide scientific community; • Political: contributing to increase open access awareness and the stronger coordination of institutions worldwide. Our perception is that many roads to open access are still to be developed and we would like that the scientific community will join forces to creatively implement the Berlin Declaration. In this context, this paper, while not try to be exhaustive as to the issue of open access, would like to exemplify the debate in the light of the specificities of the Max Planck Society.

• The MPS is a multidisciplinary research organisation, covering most scientific fields in natural and human sciences. • It is organized as a network of highly autonomous institutes, which, once founded, have full liability to plan and deploy their activities according to their own research agendas. This implies that generic and centralized solutions for scientific information management can only be devised in close articulation with the local activities carried out in institutes. In particular, one has to keep in mind the central role of the libraries attached to most of them, which by essence are closely related to the local research needs. As a consequence, it has always been difficult to align the strong global visibility of the Max Planck Society in the domain of open access, as backed-up by strong scientific personalities and highly relevant local initiatives, and the difficulty to deploy a general access policy within the institutes. This is one of the reasons that has lead to the foundation of a unitary service unit dedicated to scientific information management and dissemination, the Max Planck Digital Library (MPDL).

The MPDL provides services to help the researchers in the Max Planck Society manage their scientific information workflow. Such services comprise the provision of actual content and technical solutions, but also by acting as a centre of competence and community facilitator in scientific information management. Importantly as well, the MPDL is in charge of the strategic issues related to the wide dissemination of research results towards the scientific community, and in particular in contributing to the design and implementation of the MPS open access policy.

The activities of the MPDL can be outlined along the following lines:

Content provision: The MPDL is in charge of negotiating and providing access to digital content to the institutes. The selection of such content is to be made in strong collaborations with the institutes (mainly through their libraries); Technological development: The MPDL focuses on providing technological platforms and tools as a complement to what is being locally implemented in the institutes. The MPDL is thus in charge, in collaboration to the FIZ Karlsruhe, of the eSciDoc project, a platform for the management of digital publications and research data; Expertise provision: Beyond the two preceding core activities, it is important to act as an interlocutor towards institutes, in order to advise about the best standards, practices and technological state of the art and make sure that each new project related to digital information is at least aware of what has been done elsewhere in the MPS; Strategic planning: The MPDL is part of the various decision processes within the MPS, whenever they comprise aspects related to scientific information management. This will ensure both a coherence of the decisions and a memory of the underlying rationales of the decision taking process; Networking: The MPDL contributes in grouping together scientists, institutes or other stakeholders that have similar (or complementary) needs and activities in the Max Planck Society.

Still, as we will see in this paper, the MPDL should not be in charge of the curational activities related to the creation (digitization) or management (metadata) of data. This should be kept at institute level, even if the MPDL may provide support to the planning and setting up of such activities.

OA@MPG

Archiving publications

The mainstream view on open access, as defended by its core supporters, is to foster the depositing of scientific articles in a publication archive, so that, according to community of practices, legal possibilities and/or institutional backing, the full text of the paper can be made widely accessible on-line. The corresponding version of the paper can either be the author's initial draft (pre-print), the manuscript after peer review (post-print) or the publisher's version, associated of course with various levels of dissemination freedom.

As a matter of fact, there are quite a few reasons why we may want a have our scientific outputs be archived systematically within a repository, and, when having a closer look at them at them these are only partially related to the issue of open access. Still, they all aim at being beneficial to scientists and scientific institutions, since having a full coverage of one's production within a reliable repository provides a digital memory of research results, which is an essential tool for scientific activities at large. Beyond bringing immediate access to the full text, it also gives the possibility to produce multiple views on publications, which in turn can be used to generate publication lists, web pages, selections of most relevant publications (thematic selections or to provide compendia for assessment committees). It thus brings the capacity for an institution to have a whole photography of its outputs that may be used for strategic planning or bibliometrical analyses (in complement to commercial tools), and allows it to keep an archive of past activities when departments or institutes are closed. Of course, by providing also open access to part of the content, such a repository can become a strong instrument of dissemination.

Still, such a view on publication repositories can only make sense if strong technical and editorial support is provided to provide simple yet effective services, and also guaranty the quality and relevance of its content, in particular from the point of view of metadata. This in turn implies finding a good organisational scheme that optimizes the means puts on such an archive both from the viewpoints of reliability, cost-effectiveness and scientific proximity. We thus defend an organisation based, on the one hand, upon a highly centralized technological framework, and on the other hand, on a local editorial support to scientist. The central deployment of the archive prevents a technological fragmentation whereby several IT groups are uselessly duplicating maintenance, updating, and sometimes development works. It also allows to provide good central services for issues like dissemination and long-term preservation, but above all to provide quick and responsive answers to users's needs in domains like, workspace management, usage statistics or full text search. On the contrary, the editorial support, i.e. the validation and possible enrichment of the data deposited by the scientists has to remain as local as possible, and is probably the natural extension of the usual missions of the libraries. This digital curatorship has to be made effective in the context of a good knowledge of the research communities and understanding of the corresponding expectations. One of the main duties here is in particular to check and improve the quality of the affiliations associated to the published articles. Libraries are also the level at which information concerning the publication archive can be provided, and conversely where user feedback can be gathered up and brought to the technical side All this can only make sense if the perspective is to achieve as wide a coverage as possible within one's publication archive. This is why the Max Planck Society finds it necessary to go beyond incentive measures towards publication archiving and issues a deposit mandate for all publications corresponding to work carried out in its institutes. This decision, which will be finalized in the fall of 20071 will put no specific constraint on the further visibility of archived documents, but will allow us to have a stable basis for further open access related activities.

Turning up publication models

The commitment of the Max Planck Society in gold open access results from the analysis that it makes no sense to push the green way without accompanying the unavoidable changes in publication practices and the related business models. To our view, the core factors that will lead to a fruitful collaboration between research institutions and publishers can be outlined as follows:

• Copyright transfer should be left out of any such agreement, so that independently of the certification and/or dissemination service provided by the publisher, full liability is left to the author to issue new dissemination formats or variants that he/she feels necessary to propagate his/her results; • The institution should have the capacity to mirror the final paper in its own archive.

This is an essential aspect for providing reliable data in situation like assessment campaigns; • A strong collaboration has to be carried out to normalize affiliations so that researchers corresponding to a given institution are presented in a coherent way. Independently of addresses appearing on printable papers, it is essential to work towards agreements that would lead, in the long run, to a full compatibility between metadata in publishers' databases, institutional archives, and consequently commercial bibliographical databases; • Last but not least, transparent cost models should allow research institutions or universities to choose the level of service they may require from publishers, with the expectation that cost saving can become a natural, and shared trend. These various constraints together with priorities set by researchers themselves within the Max Planck Society have thus led us to articulate our policy along three main action lines:

• Taking part in multi-organisation consortia working towards global switches from traditional subscription based models to full open access. The MPS has thus strongly supported and contributed to the establishment of the SCOAP3 proposal; • Design collaborative framework with full open access journals and publishers, in particular when there is a strong back by scholarly groups. This is typically the case with Copernicus, which, with the support of the European Geoscience Union, offers probably at present the most transparent and scientifically motivated open access scheme; • Avoid the fragmentation of our financial and decisional surrounding by rejecting

paper-based open access scheme in favour of global negotiation with traditional publishers. The underlying objective for us is here to make the gold open access process as transparent and administratively innocuous as possible.

As a whole, the policy of us going Gold is not to contribute to the preservation of the existing publishing ecology, but above all to contribute to make this ecology evolve in the direction we think would provide better services and at a better price for our scientists.

Are research data concerned at all?

There are quite a few reasons to consider that open access to research data will become in the future an essential, or even the main, component of an open access policy for a research institution like the Max Planck Society. Indeed, this is already an issue that has been put high on the agenda by several research communities such as astronomers, geneticians or researchers in the history of science, who have started to develop communities and infrastructures to provide a wide dissemination of their digital assets. Depending on the scientific domain, the underlying urge to archive and disseminate research data comes from the need to pool together primary sources, to compare results but also, in relation to traditional publications to provide means to supply the evidence behind asserted claims.

Still, whereas sharing research data is obviously a need, a lot of factors precludes us from adopting a blunt and global open access policy in this respect. First, there can be quite a few legal issues preventing wide dissemination, related either to copyright restrictions on the sources (e.g. contemporary documents, museographic data) or the relation to personal information (personal data, photographies, medical descriptions). There is also the difficulty, when one deals with complex data structures, not only to provide the data itself, but also the corresponding tools to have actual means to exploit them. As a whole, the only relevant strategy in this respect is to accompany scientific communities when expressing needs related to strong research needs.

From the point of view of the Max Planck Society, we both contribute to disseminate the technical experience of communities which have already developed complex environments for the management and dissemination of data, while offering technical support, through the MPDL, for newcomers, focusing on generic solutions that may bring more and more researchers to a better management of their digital production. As the data to be preserved are very heterogeneous among the various MPIs virtual groups of institutes should be formed to bring together those of similar demands and interests.

As an example the seven MPIs working in the field of astronomy can all take advantage of the activities currently undertaken under the auspices of the International Virtual Observatory Alliance (IVOA). The German Astrophysical Virtual Observatory project GAVO, initiated by the MPIs for Extraterrestrial Physics (MPE) and for Astrophysics (MPA), is representing the German astronomy community. Aim of the 16 national VObs collaborating within the IVOA is the development of standards to ensure interoperability of their highly distributed datacentres containing very heterogeneous data-sets (in particular with respect to registries, metadata, protocols for accessing images, spectra, catalogues, numerical simulations, and related literature). The concept is designed in such a generic way that it can be adapted by other communities or for other purposes.

In the long run of course, the MPS will have to consider also mandating the archival and, when possible, the wide dissemination of all data produced associated to the publication of a research result. Still, it appears that this cannot be achieve before we have a comprehensive view of the means to be deployed to achieve this objective. An essential component of such strategy is related to having strongly trained personnel in digital curation techniques that will accompany researchers in their management of research data.

New Publication Platforms, New Publication Models

Whether Green or Gold the traditional views on open access are based on the assumption that publication vectors remain unchanged, i.e. in the form of fixed published articles in journals as resulting from a closed peer-review process. Still, it is probably our duty to see what the development of new technical means can bring to us and explore new forms of scientific communication that could be adopted by all or some research communities.

In a way, this is exactly what has led to the creation of Arxiv2 , with a community of scientists extending their natural trend to exchange drafts among themselves and using the internet infrastructure to do so in a simplified manner. They actually opened the way for generalizing such environments, whether through thematic or institutional archives. One can observe though that each scientific community has projected its own perception on how such archives could be used, with very few scientists actually disseminating pre-prints through this channel.

There is also quite some room for evolution in the domain of "traditional" publishing and we can take two examples related to the Max Planck Society to illustrate this. First, the impact on new technologies upon journal publishing can facilitate the management of paper versioning. This is the case with the Living Reviews series3 , which, in scientific fields ranging from physics to the humanities, publish several journals dedicated to high level state of the art papers. These are completely open access publishing vectors, with a high focus on scientific quality. Regular revisions contribute to make the corresponding papers unavoidable reference materials in the corresponding fields.

As a second example, we can have a quick glance at the publishing model deployed in most of Copernicus4 journals (many of which are undertaken under the auspices of the European Geoscience Union). In this case, the capacity of providing immediate online access to information is used to provide a open access peer review process. From the stage of submission to that of final publication, all papers, and above all the corresponding reviews, are freely accessible thus ensuring a kind of global controlling capacity for the scientific community. The model has resulted in a clear change in publication practices within these journals. Less paper submissions, better reviews, and higher acceptance rates while preserving, even increasing, the scientific impact show that we should not be reluctant in providing new types of scientific communication.

Finally, there is a strong demand from some communities to have access to publishing channels allowing them to get scientific recognition for the activity they conduct in the domain of research data. Already explored in communities like genomics, where short papers can be associated to the deposit of a genomic sequence in a database, it appears to be a necessary environment for disciplines whose core activity is to analyse primary sources or objects, such as linguistics, archaeology or history. This leads to the idea (aka "living sources") that real peer reviewed publishing environment must be implemented whereby researchers can deposit data sets, together with annotations and/or commentaries, that in turn they can quote as part of their actual research production. This is to our view an important dimension for the future development of infrastructures such as eSciDoc, if we want them to be accepted by scientists.

Improving awareness

As one can see from this overview of the various issues at hand, open access is a highly complex issue, even more, if it is taken for granted independently from the scientific diversity as observed in the various institutes of the Max Planck Society. Since there is no global OA solution, we want also to defend the idea that an OA dissemination policy should not be based on education (or evangelization), but on the capacity to listen to the scientists' needs or worries with regards to communication of their scientific results. By doing so, we have already identified that their main expectations rely not so much on OA as a principle, but on the capacity of the corresponding infrastructures to provide reliable and effective research environments for preserving and handling their own information. This rather self-interested view on scientific information has then to be matched against more systemic views on community or institution interests, so that the idea of open access per se becomes a natural component of the scientists' ecology.

Joining efforts

Most of the elements presented in this paper are not specific to the Max Planck Society and could be taken up by any other research institution or university in the definition of its scientific information strategy. In particular, most of the technological developments, as well as editorial support policies, are likely to be implemented or defined by others simultaneously. As a consequence, it is essential to contemplate the various possibilities that one has to join efforts nationally and internationally to avoid duplicate works, but also contradictory actions towards similar interlocutors, whether scientists, publishers or decision makers.

In this respect, endeavours aiming at coordinating activities on publication archives (Driver5 ), research data management (Dariah6 ) or open access communication (OA information platform7 ) play an essential role in ensuring a better synergy between institutions, but also foster the development of new ideas in the field of open access. These are also places where we could probably implement the dual central-decentral strategy that we presented for the Max Planck Society. As a final word of conclusion, we can say that in the long run, open access is a non-avoidable target. It is technologically feasible in principle, but above all, it is the only way to improve the quality and dissemination of research worldwide. Still, if we want this movement to be really useful for science, we have to consider how research organisations as well as individual scientists can go towards a coherent and efficient scheme for the wide dissemination of scientific results.

And will be published on the OA information platform by that time

http://arxiv.org

http://www.livingreviews.org/

http://www.copernicus.org/

http://www.driver-repository.eu/

http://www.dariah.eu/

http://open-access.net/

For further contact about the Max Planck Society activities, contact the OA group: Christoph Bruch and Anja Lengenfelder. See http://open-access.net/de/oa_informationen_der/maxplanckgesellschaft/

http://openaccess.inist.fr/

http://www.inria.org/publications/archiveouverte/

Acknowledgments

This paper has been written on the basis of numerous discussions that have been held within the Max Planck Society. I am in particular most grateful to my colleagues in the sInfo steering committee and Max Planck Digital Library 8 for having brought so many complementary ideas in the debate. It has also benefited from the experience gained in the French research environment both at CNRS 9 and INRIA 10 .