Sowmya Somanath
email: ssomanat@ucalgary.ca

Allan Rocha
email: acarocha@ucalgary.ca

Hamidreza Hamdi
email: hhamdi@ucalgary.ca

Ehud Sharlin

Mario Costa Sousa

ReservoirBench: An Interactive Educational Reservoir Engineering Workbench

Keywords: Physical user interface, education, design, reservoir engineering. Fig. 1: ReservoirBench and workflow example

ReservoirBench is an interactive workbench for educational geological science and engineering tasks. It is designed to facilitate education of novice audiences to teach them basic concepts of reservoir modeling and simulation workflow.

Traditional training using lectures and software practice can lead to information overload, and retainability is questionable. As an alternative, we propose a physical workbench that is coupled with digital augmentation for the purpose of learning. We take advantage of the crucial role that spatiality and 3D representations play in petroleum reservoir modeling and allow basic domain concepts to be introduced and explored in a tangible and experiential manner. We describe the design of our prototype and reflect on the findings from our preliminary design critique.

Introduction

The domain of petroleum engineering aims at studying the processes involved in the exploration, production and extraction of oil and gas [START_REF] Dake | Fundamentals of Reservoir Engineering[END_REF]. Introduction of domain concepts via presentations and software tutorials can be difficult to grasp for novice audiences such as first year geology undergraduates or non-domain experts who join the industry (e.g. computer scientists). Generic slideshows can cause information overload, and content retainability is questionable [START_REF] Pugsley | Traditional Lecture or Experiential Learning: Changing Student Attitudes[END_REF][START_REF] Specht | The different effects of experiential learning activities and traditional lecture classes in accounting[END_REF]. On the other hand, simulation software packages such as Petrel TM [START_REF]Petrel E&P Software[END_REF] are designed for the expert user. Since the goal is to become familiar with fundamental concepts and general modeling workflows (engineering data integration, layer interpretation from seismic data, well modeling, reservoir simulation and identifying challenging cost-benefit scenarios for well drilling), more suitable and interactive training methods are called for. The question then becomes, "How can interactive interfaces be used to scaffold comprehension for novice users?"

Modeling the petroleum reservoirs in 3D requires having the knowledge of spatial configurations, structures and properties that are central to efficient data integration and reservoir characterization. This was motivated before via cardboard box models used to demonstrate the functionality of Petrel TM , a commercial oil-and-gas software package [START_REF]Boxcut -Phil and Tyson Skit[END_REF]. Interactive physical interfaces can help in automating this 3D spatial approach and can be designed to map interactions to varying visualizations to enhance the learning process [START_REF] Ishii | Tangible Bits: Towards Seamless Interfaces between People, Bits and Atoms[END_REF]. We propose the use of a physical interactive workbench coupled with digital augmentation for teaching the basics of reservoir modeling workflows (Figures 1,2). ReservoirBench is the first experiential learning reservoir engineering tangible user interface (TUI) for novice users and the uniqueness emerges from the application specific tasks.

Related Work

Physical and tangible user interfaces have been previously introduced for the purpose of teaching [START_REF] Ishii | Tangible Bits: Towards Seamless Interfaces between People, Bits and Atoms[END_REF][START_REF] O'malley | Literature Review in Learning with Tangible Technologies[END_REF][START_REF] Fjeld | Augmented Chemistry: an Interactive Educational Workbench[END_REF] and have contributed to develop ways to enhance learning [START_REF] Marshall | Do Tangible Interfaces Enhance Learning?[END_REF]. It has been noted that in situations where perception and cognition can be coupled [START_REF] Barsalou | Grounded Cognition[END_REF], using physical materials in a learning task can change the nature of awareness gained relative to that gained through interacting with virtual materials [START_REF] Klemmer | How Bodies Matter: Fives Themes for Interaction Design[END_REF].

Our workbench design supports experiential learning which encourages one to generate their own ideas about a phenomena while learning and prepares the individual for future learning [START_REF] Bransford | Rethinking Transfer: a Simple Proposal with Multiple Implications[END_REF]. More detailed knowledge could be developed as part of actual reservoir modeling tasks where the limitations of current software impede easiness and efficiency of implementing the various modeling and design scenarios. Our workbench can also be looked through the theoretical lens of boundary object's [START_REF] Star | Institutional ecology, translations' and boundary objects: Amateurs and professionals in Berkeley's museum of vertebrate zoology[END_REF]. The structure of the interface is common enough to be recognized by the domain of oil and gas in general, but each sub-domain (i.e. geologist, reservoir engineer) can use it as a medium for different task explorations.

Within the realm of geology and reservoir engineering, TUI's [START_REF] Couture | GeoTUI: a Tangible User Interface for Geoscience[END_REF][START_REF] Harris | Designing Snakey: a Tangible User Interface Supporting Well Path Planning[END_REF][START_REF] Piper | Illuminating Clay: a 3-D Tangible Interface for Landscape Analysis[END_REF], tabletop interfaces [START_REF] Sultanum | Touching the Depths: Introducing Tabletop Interaction to Reservoir Engineering[END_REF][START_REF] Tateosian | TanGeoMS: Tangible Geospatial Modeling System[END_REF] and a web-based interface [START_REF] Allen | A Workflow Approach to Designed Reservoir Study[END_REF] have been previously introduced. However, the focus in these instances of research has mainly been on data exploration. For instance, Snakey [START_REF] Harris | Designing Snakey: a Tangible User Interface Supporting Well Path Planning[END_REF] is a TUI designed exclusively for expert users engaged in the particular task of well design in reservoir engineering. It is not an educational toolkit and does not attempt to address the breadth of essential reservoir modeling concepts that ReservoirBench is addressing.

ReservoirBench: Design and Implementation

Physical Interface

The physical interface is a simplified representation of an underground reservoir (Figure 1). It consists of a wood frame structure (roughly 18 inch (l) X 18 inch (w)) with three slots on each of the vertical poles (Figure 1a). The two vertical poles serve the dual purpose of being support structures as well as being representations of two already drilled oil wells used for seismic well-tie [START_REF] Dake | Fundamentals of Reservoir Engineering[END_REF]. The top of the frame is sealed with a plane that represents the ground level. Three orthogonal planes, symbolic of seismic planes can be inserted into the empty slots using different configurations as seen in the Figure 1a. The seismic planes define the boundaries between the different earth layers. Physical oil well trajectories can be inserted between the planes using either the 3Doodler (handheld fabrication tool [1]) or pipe cleaners (Figure 1b).

The design rationale behind different configurations for the seismic planes comes from the fact that (in reality) the low resolution seismic volumes can impose a large uncertainty in defining the hydrocarbon producing layers. However, for the purpose of learning some options in terms of placements of seismic planes are sufficient to explore the concept of stratigraphic uncertainty in layers' thicknesses and their effects on calculation of volumetrics (e.g. initial hydrocarbon in place), reservoir performance and drilling plan of new infill wells for production optimization.

On the other hand, since the well trajectories are relatively more flexible in terms of design (i.e. can have configurations such as horizontal, vertical and multi-lateral [START_REF] Dake | Fundamentals of Reservoir Engineering[END_REF]), we choose to test two different material options -the 3Doodler TM and pipe cleaners. One of the fundamental constraints to input well trajectories is that the material should have the ability to retain shape and yet be malleable. Pipe cleaners are advantageous as they are flexible and afford for molding, but are limited as they do not afford the property to be easily molded back to their original state. In contrast, 3Doodle TM is a step forward towards supporting free form sketching of 3D objects and thus, can better support quick iterative design explorations. However, it is important to note that accurate design of horizontal wells is rather difficult using the 3Doodler TM due to gravity effect. In contrast to Snakey's [START_REF] Harris | Designing Snakey: a Tangible User Interface Supporting Well Path Planning[END_REF] rigid and difficult to manipulate interface that is built from camera tripods, both the 3Doodler and the pipe cleaner afford further flexibility for free-form and iterative well design.

Digital Interface

The digital interface represents the visual feedback for the physical interactions (Figure 2). The use of a monitor to display the visualizations was done keeping in mind the availabilities in a regular office setting. Placing the monitor above the physical interface was considered to be a better alternative to a side-by-side setup and can also work for demonstration purposes. In our current prototype the physical source object (Figure 2a) can be digitally augmented in the four ways explained below. The visualizations are simplified reservoir modeling visualizations that professionals use during the regular workflow of examining seismic planes, gridding and well trajectories.

Figure 2b:

shows the visualization of the geological layers of the earth mapped to the tracked physical seismic planes configuration that can be (re)arranged by the user. We use a Kinect to track the positions of the colored markers placed on the edge of the physical planes (Figure 2a). The positions of the markers extracted from the Kinect image are converted into 3D coordinates to render the virtual seismic planes. A bounding box encompassing the virtual planes is computed and drawn to represent an approximate reservoir model. The purpose of this visualization is to provide contextual information regarding how a reservoir looks beneath the surface of the earth and helps identify in which layer oil is currently present and what is in the surrounding layers (e.g. aquifer, cap rock etc.).

Figure 2c:

shows the visualization of the well trajectories input physically by the user. To reconstruct the virtual well we first compute the difference between the initial source image (before the well was inserted) and the current frame image (after the well was inserted) from the Kinect 2.0. Zhang-Suen thinning algorithm [START_REF] Zhang | A fast parallel algorithm for thinning digital patterns[END_REF] is applied to the segmented image to extract the well trajectory skeleton. The skeleton and the depth image are then used in the calculations for 3D well reconstruction. The Kinect is placed at an angle as seen in Figure 1 to capture maximum information. Our current prototype is limited by the use of a single Kinect camera and thus, occlusions cannot be resolved. However, since accuracy was not our primary concern when introducing basic concepts, we think this is a reasonable limitation. The well visualization is also coupled with a graph that shows the cost for drilling the infill well. From the vector direction of the well skeleton, the program automatically classifies the wells as either vertical (low cost) or horizontal wells (high cost), and the graph is updated to show the corresponding cost for drilling.

Figure 2d: shows the visualization of the gridded simulation model. The rendered grid is adapted to align according to the top and bottom of the seismic plane orientation allowing the viewer to learn about the variability in vertical thickness in each cell layer. The resolution of the grid can be changed using a physical slider. The purpose for changing grid sizes is to allow the user to get a sense of how discretization is performed in real modeling cases and understand its effect on the time needed for completing a flow simulation run (which can be a very time consuming task based on the resolution of the grid). Thus, when the user interacts with the slider a graph showing the amount of time required for simulation is displayed.

Figure 2e: shows the intersection between the grid cells and the created well trajectories. In terms of learning, observing such intersections helps: (a) identify the cells with interesting heterogeneities, which might require further treatments in terms of nested local grid refinement and (b) identify the most and least contributing cells to the oil production rate.

Workflow Example and Presented Concepts

Figures 1 and2 show the workflow of a user interacting with the ReservoirBench. The workflow is also a pointer to the various concepts that one can learn and explore. The typical workflow starts with positioning the interpreted (Concept #1) seismic planes configuration (obtained in actual workflow from 3D seismic data) [START_REF] Dake | Fundamentals of Reservoir Engineering[END_REF] (Figure 1a). Once the seismic configuration is in place (Figure 1a), the user can explore the automatically generated (Concept #2) geological layers (i.e. between the seismic planes, Figure 2b) and plan to (Concept #3) create a suitable new well trajectory to extract more oil from the reservoir. Figure 1b shows a user creating a new well trajectory using the 3Doodler TM . Once the well is in position, the well is virtually reconstructed (Figure 2c). The well trajectory can be positioned at any depth position of the plane. In practice, the well should be drilled starting from the ground surface, in the current prototype the user only needs to position the well in the target layer in which oil is found. This is also common practice in reservoir modeling software programs. The connection from the reservoir top to the ground surface is automatically computed by our program. Depending on the well created by the user, the program presents a graph of the (Concept #4) drilling cost of such a well (Figure 2c). Finally, the user can (Concept #5) grid the reservoir model for simulation and understand the impact of the grid resolution on the (Concept #6) time for the reservoir simulation runs (Figure 2d).

Preliminary Design Critique

To evaluate the limitations and advantages of the different components of our interface we conducted a preliminary design critique session with a domain and a non-domain (computer science graduate student) participant. The domain expert, a post-doctoral fellow in reservoir modeling with several years of experience in geoscience research and reservoir engineering, was involved in the iterative design and development of our interface. With the obvious limitations of our preliminary design critique (small number of participants, possible biases), it did provide interesting design reflection on ReservoirBench, including those of an expert reservoir engineer with considerable experience in this design space. Following we believe the insight we share below, while limited in scope, is still valid. We took a hands-on approach to design critique, asking both the participants to complete the following tasks: (a) arranging the seismic planes to the experimenter provided configurations, (b) creating a vertical and/or horizontal well to extract oil and (c) choosing the appropriate simulation model grid size and observe the costs and simulation time. At the end of the tasks we gathered qualitative feedback.

Domain Participant:

In the opinion of the domain expert ReservoirBench can be useful for educating novices' about conceptual ideas, for example, what is a seismic plane? And, where is oil? He envisions that with increasing the complexity of the system and by combining the interface with an actual simulation program, the current interface can be used by the domain experts for testing out complex tasks i.e. reservoir characterization, economics calculations and well test design. ReservoirBench could also be used to design and/or to fine tune a 3D digital model and to explore various production scenarios for well placement. The domain expert found automatic reconstruction of physical well trajectories to be a useful feature for quick design iterations. Although the 3Doodler TM is a flexible fabrication tool, it was difficult to use and found to be distracting due to its current limitations (speed of use, fat pen, gravity etc.) Therefore, the domain expert preferred the pipe cleaners, especially for designing horizontal wells. One of the noted limitations for the pipe cleaners was their length. Since the performance of a horizontal well depends on factors i.e. length and location within the layer, this was considered to be an important feature to keep in mind while choosing the right material.

Non-Domain Participant:

In addition to the hands-on tasks, the non-domain participant also answered the following eight questions: (1) what is a reservoir? (2) What is between the seismic planes? (3) What is a reservoir model? (4) What is the purpose of a reservoir model? (5) Which processes are involved in extracting oil? (6) When gridding the reservoir model, when do you think a low resolution grid (less number of cells) could be beneficial? (7) Similarly, when do you think a high resolution grid (more number of cells) could be beneficial? And finally, (8) rationalize the well trajectories you created in the well design task. The collected responses were all valid in terms of expected keywords (determined by domain-expert), pointing towards a positive outcome in terms of learning. From the discussions we learnt that lack of both, feedback during the tasks and prior knowledge, the participant felt less confident in answering the questions. The participant also mentioned that compared to the definition type questions (e.g. questions 1 and 2), she found the interface to be quite useful for answering task related questions (question 8). Beyond learnability, the participant found the interface to be fun, enjoyable and engaging. She mentioned, "It was encouraging of curiosity, and made me want to learn more things. It was satisfying as I felt like it was doing something".

Discussion

Role of Spatiality and 3D representations: Spatiality and 3D representations play a crucial role in reservoir engineering. The benefit of having an associative and spatial system can help externalize traditional digital representations and present a physical view that people are familiar with [START_REF] Ishii | Tangible Bits: Towards Seamless Interfaces between People, Bits and Atoms[END_REF] and is fundamental to geological entities [START_REF] Harris | Designing Snakey: a Tangible User Interface Supporting Well Path Planning[END_REF]. Having working knowledge of oil and gas software tools the domain expert mentioned that practical learning with commercial software alone is rather difficult, specifically for non-domain audiences, since the software is designed for experts and not novices. Within this context, in the opinion of the domain expert our hybrid approach (physical-digital coupling) can be useful for training Novice users and arguably also be useful for domain experts to evaluate design choices for well placement tasks.

Control and Representation:

Due to the meticulous nature of tasks conducted by reservoir engineers, interfaces such as ours will be limited in terms of the level of control that can be achieved. As mentioned by both the domain and non-domain participants', although the 3Doodler was a flexible fabrication tool for design iterations, it was difficult to use and found to be distracting due to the limitations of the current 3Doodler (speed of use, fat pen, gravity etc.). It was found to be lacking in precision and accuracy. Scaling is also a challenge. While part of the scaling issue can be mitigated by the use of digital representations, we need to be careful in our design considerations to ensure that the level of physical-digital coupling is not reduced to the point of creating disconnects in interaction behavior (a noted limitation of Snakey [START_REF] Harris | Designing Snakey: a Tangible User Interface Supporting Well Path Planning[END_REF]). Alternatively, an advantage of interfaces such as ours is that the low-cost prototype production will allow users to quickly modify the design of the system. Readily available physical mediums can be added as interaction components to create representations that are meaningful to the users and programmatically coded as manipulatives.

Interactivity: Within ReservoirBench's context, externalizing geological concepts into easy to grasp physical representations presents a smart interaction alternative to the orthodox approach in which novice users are introduced to the domain (e.g. presentations and textbooks). The potential of systems such as ours lies in their ability to allow people to create and manipulate objects to support hands on learning. It can also function as a boundary object during interdisciplinary interactions. From a design perspective, ReservoirBench can be used not just for the purpose of learning the fundamental concepts but also in other design process such as designing rough 3D reservoir models. Active hands-on learning can also make the experience enjoyable and engaging as mentioned by the non-domain participant.

Conclusion and Future Work

We presented ReservoirBench, an interactive and educational TUI that facilitates learning about reservoir modeling workflow. Our preliminary critique highlights the usefulness of such systems for both learning and exploring reservoir modeling workflows. Efforts are underway to further improve our prototype to better facilitate instructional and smarter interactions. The design critiques point at promising benefits for such interfaces, but in future we will need to compare and contrast the ReservoirBench approach to training versus the existing traditional approaches. For long term future work we would like to explore the use of other physical manipulatives such as, grid meshes and fault constraints, to allow novice user's to gain added understanding on their effect on well planning and simulations. For example, the actual seismic planes combined with the complex 3D structures such as faults and folds can be efficiently used to represent the actual reservoir structures. The strategies to place wells can then be tested more realistically and better gridding strategies could be proposed. It will also be interesting to explore the possibilities of projection mapping and more advanced interaction techniques using 3D printed models.

Fig. 2 :

 2 Fig. 2: Physical interface (a) and the corresponding mapped visualizations (b-e).


Marios Belk
email: belk@cs.ucy.ac.cy

Panagiotis Germanakos
email: panagiotis.germanakos@sap.com

Argyris Constantinides
email: argyris.constantinides.14@ucl.ac.uk

George Samaras
email: cssamara@cs.ucy.ac.cy

A Human Cognitive Processing Perspective in Designing E-Commerce Checkout Processes

Keywords: Human Cognitive Factors, E-Commerce, Usability, User Study

Designing a usable checkout process is of paramount importance for both E-Commerce and M -Commerce success. Aiming to understand humancomputer interactions during checkout and improve the usability and user exp erience of checkout tasks, this research work investigates the relation among users' cognitive styles, and alternative checkout designs in terms of user preference and task performance. A controlled user study with 38 participants was conducted which entailed a psychometric-based survey for highlighting the users' cognitive styles, combined with a real usage scenario with two variations of checkout designs that were deployed on standard desktop computers and mobile touch-based devices. Results suggest that human cognitive differences could play an important role in designing E-Commerce and M -Commerce checkout processes, and particularly users' cognitive styles may affect the way users perceive and perform during such tasks.

Introduction

The checkout process has become widely known over the years in online co mme rcial environments, and making purchases on the World Wide Web has become a fairly standard process, with clear s teps and expected outcomes [START_REF] Nielsen | Ecommerce Usability[END_REF]. Nevertheless, recent research has shown that a high number of E-Commerce and M-Commerce environments entail usability issues, from the user's conceptual understanding of commercial Web-sites, to how users interact with form fields [START_REF] Kukar-Kinney | The Determinants of Consumers' Online Shopping Cart Abandonment[END_REF][START_REF] Close | Beyond Buying: M otivations Behind Consumers' Online Shopping Cart Use[END_REF][START_REF] Appleseed | E-Commerce Checkout Usability: Exploring the Customer's Checkout Experience[END_REF][START_REF] Appleseed | M-Commerce Usability: Exploring the Mobile Shopping Experience[END_REF]. In addition, studies revealed that usability issues of M-Commerce Web-sites as well as the small screen displays discourage users from accessing M-Commerce Web-sites [START_REF] Shim | Empirical Findings on Perceived Value of M obile Commerce as a Distributed Channel[END_REF].

In this realm, research has shown that both E-Commerce and M-Commerce Websites should satisfy the needs and preferences of users via the visual and interaction design of the system aiming to improve the shopping experience of users [START_REF] Bellman | Predictors of Online Buying Behavior[END_REF]. Thus, it is necessary to understand human-computer interactions in such realms and follow user-centered design approaches when designing checkout processes , by incorporating the unique needs, characteristics and preferences of u sers. Taken into consideration that users do not necessarily share common cognitive backgrounds in which online purchase decisions are required to be taken, we suggest that individual diffe rences in cognitive processing should be investigated and integrate d in the user interface design process of checkout environments.

Accordingly, the work presented in this paper aims to understand and investigate whether individual differences in cognitive processing styles (Wholist/Analyst) affect user preference and task performance in different checkout designs that are deployed on alternative interaction device types (standard desktop vs. touch-based devices). The work is primarily motivated by existing research and theory that relates the Wholist/Analyst cognitive style to the way individuals navigate within hypermedia environments and the way hypermedia content is structured [START_REF] Riding | Cognitive Styles -An Overview and Integration[END_REF][START_REF] Chen | An Integrated Approach for M odeling Learning Patterns of Students in Web-Based Instruction: A Cognitive Style Perspective[END_REF][START_REF] Belk | M odeling Users on the World Wide Web based on Cognitive Factors, Navigation Behavior and Clustering T echniques[END_REF].

The rest of the paper is structured as follows: we present the underlying theory of this work in the next two sections. Thereafter we describe the context of a controlled user study and methods. Finally, we analyze and discuss the findings of the study and outline the implications of the reported research.

Individual Differences in Cognitive Styles

Research on individual differences in cognitive styles aims to understand how individuals differ in mental representation and processing of information. Among various theories on cognitive styles [START_REF] Riding | Cognitive Styles -An Overview and Integration[END_REF][START_REF] Kozhevnikov | Cognitive Styles in the Context of M odern Psychology: Toward an Integrated Framework of Cognitive Style[END_REF][START_REF] Peterson | Researching the Psychology of Cognitive Style and Learning Style: Is there Really a Future?[END_REF], we have utilized the Wholist/Analyst cognitive style [START_REF] Riding | Cognitive Styles -An Overview and Integration[END_REF] since it is considered a widely accepted and accredited cognitive style dimension. The Wholist/Analyst cognitive style distinguishes individuals as Wholists that prefer and tend to structure incoming information as a whole to get the big picture, and experience surroundings of the environment in a relative passive and global manner, or as Analysts that prefer and tend to structure the incoming info rmation in detail, and experience surroundings in an active manner and with an internal perspe ctive. A high number of studies which investigated the effect of cognitive styles on users' task usability and interaction patterns within Web environments, revealed implications of cognitive styles on users' performance and preferred ways of using different navigation tools and display options [START_REF] Chan | Cognitive Styles and the use of Electronic Journals in a M obile Context[END_REF][START_REF] Lo Storto | Subjective Judgment, Cognitive Style and Ecommerce Website Evaluation: A Non-parametric Approach[END_REF][START_REF] Belk | An Individual Differences Approach in Adaptive Waving of User Checkout Process in Retail Ecommerce[END_REF]. On the contrary, various studies concluded that cognitive styles do not have a main effect on users' task performance and preference within hypermedia environments [START_REF] Brown | Reappraising Cognitive Styles in Adaptive Web Applications[END_REF].

Checkout Designs

We investigated the checkout designs of the most popular commercial Web-sites [START_REF] Appleseed | E-Commerce Checkout Usability: Exploring the Customer's Checkout Experience[END_REF][START_REF] Appleseed | M-Commerce Usability: Exploring the Mobile Shopping Experience[END_REF], and concluded that the majority of them utilized two broad checkout d esigns that could be categorized as follows: i) a single one-page checkout process that contains all the necessary information for performing the purchase in a single page; and ii) a guided step-by-step checkout process in which users have to fill out their information in multiple steps, usually across multiple pages.

Based on theory of cognitive styles, the single one-page checkout design could be related to the analytical approach that Analysts follow since it enables users to freely access all sections of the checkout process in a single page. On the other hand, the guided step by step design could be related to the Wholist dimension of cognitive styles since it presents content through a constrained and guided environment. In this respect, this work investigates the following research questions:

-Do users with different cognitive processing styles prefer a particular visual and interaction design of checkout processes? -Do users with different cognitive processing styles perform differently in terms of task completion efficiency in different visual and interaction designs of chec kout processes? -Is there an observable interaction effect between cognitive processing styles of users and device type towards user preference and task performance of different checkout designs? For the purpose of this study, we utilized different checkout designs of two existing commercial Web-sites: nordstrom.com (Nords trom) and amazon.com (Amazon). Nordstrom checkout design follows a simple top-down navigation style in which users can freely enter the required information for performing the checkout process (Figure 1). All required information (shipping information, payment information, etc.) is visible in one single Web-page. Amazon illustrates content in a guided horizontal step -by-step navigation style in which users can only enter information of a particular section, and then proceed to t he next section (Figure 2). In the desktop version, a horizontal menu is utilized illustrating the active section of the checkout process. The instructions provided to the participants for both navigation scenarios were as follows: i) select a product of their choice and add it to the shopping basket of the system; and ii) start the checkout process until buying the product with a virtual credit card that was provided to them at the beginning of the study. A client -side logging tool measured the total time spent for completing the checkout process, aiming to compare the usability of each checkout process in terms of task efficiency. At the end of the study, focus group sessions were conducted and questionnaires were provided in order to elicit the users' subjective preference and perception of each d esign.

Cognitive Style Elicitation

Users' cognitive styles where elicited by exploiting Riding's Wholist/Analyst Cogn itive Style Analysis test (CSA) [START_REF] Riding | Cognitive Styles Analysis -Research Administration[END_REF]. As reported in Peterson et al. [START_REF] Peterson | The Reliability of Riding's Cognitive Style Analysis Test[END_REF], the reliability of the test is r=0.81, p<0.01. The psychometric test highlights individual differences in Wholist/Analyst cognitive style by requiring from users to respond to 40 questions as true or false. In particular, 20 of the questions ask whether a pair of geometric shapes is identical or not ("Is shape X the same as shape Y?"), and the remaining 20 questions ask whether a single geometric shape is part of another complex geometric figure ("Is shape X contained in shape Y?"). It is assumed that Wholists respond faster in the task that involves the comparison of two figures than Analysts , whereas Analysts respond faster in the task that requires dis -embedding the simple geometric shape from the complex one than Wholists. Depending on the resp onse time and provided answer to each of the stimuli type, users are classified as Wholists or Analysts.

Analysis of Results

Users were grouped as follows based on their responses to the psychometric test: Wholists (N=21, f=55%), Analysts (N=17, f=45%).

Task Efficiency

A Repeated Measures Analysis of Variance (ANOVA) test was conducted using co gnitive styles (Wholist or Analyst), device type (standard desktop or touch-based), and environment (Nordstrom or Amazon) as independent variables and the time spent to complete the checkout process as the dependent variable. Table 1 illustrates the mean of time to complete the process per checkout design and cognitive style group. The analysis revealed that, the effect of checkout design on time needed to co mplete the checkout proces s is not significant (F(1,34)=0.032, p=0.860). In contrast, there was a statistically significant interaction between cognitive styles and checkout design on the time to complete the checkout process (F(1,34)=7.525, p=0.01, partial eta 2 =0.181). Furthermore, there was no interaction effect between cognitive styles and device type on the time to complete the checkout process (F(1,34)=0.232, p=0.633, partial eta 2 =0.007). Pairwise comparisons between checkout designs for each cogn itive styles group and device type revealed that Analysts were significantly more efficient in completing the single page checkout design (Nordstrom) when this was deployed on desktop computers (MD=-26.583, SE=12.583; F(1,34)=4.463, p=0.042).

Furthermore, when the interaction was performed on touch-based devices, again, Analysts were faster in completing the single page checkout process but with no st atistical significant differences (MD=-13.600, SE=19.494; F(1,34)=0.487, p=0.490). On the other hand, Wholists were significantly more efficient in completing the guided step-by-step checkout process (Amazon) when this was deployed on touch -based devices (MD=23.933, SE=11.255; F(1,34)=4.522, p=0.042), whereas no significant differences where observed when the interaction took place on desktop computers (MD=21.833, SE=17.795; F(1,34)=1.505, p=0.288). Furthermore, a comparison between the two cognitive style groups revealed that An alysts were significantly faster than Wholists when interacting in Nordstrom (F(1,38)=7.056, p=0.012). On the other hand, no significant differences were observed between Wholists and Analysts in Amazon (F(1,38)=0.422, p=.520).

User Preference

Focus-group sessions were concentrated around the participants' subjective prefe rence and perception of the different checkout designs. The focus groups followed a semi-structured process based on predetermined questions that lasted approximately 15 minutes. The participants were asked to rank the checkout designs based on their preference. In particular, participants ranked the checkout designs with 1 and 2 to represent their first and second choice. Table 2 lists the number of participants who chose a specific design as their first choice. A Chi square test revealed that there is statistical significant association between cognitive styles and checkout design preference in desktop computers (Chi square value=6.343, df=1, p=0.012). For interactions that took place on desktop computers, Analyst users significantly preferred the single one page design, whereas Wholists preferred the guided step-by-step approach. On the contrary, in cases where users interacted with touch-based devices, no significant association between cogn itive styles and checkout design has been revealed (Chi square value=1.534, df=1, p=0.216) since the majority of participants preferred the single page checkout design (Nordstrom). Based on comments, this might be based on the fact that users preferred to have all information in a single page due to size and interaction limitations . In the case of Wholists, although the task efficiency analysis revealed that they were significantly faster when interacting in a guided step-by-step checkout design (Amazon), they preferred the other type of checkout given the limitations of the touch -based device.

Conclusions

Designing a usable checkout process is of paramount importance for both E-Commerce and M-Commerce success. Thus, supporting users that are engaged in such tasks with more efficient decision-making and information processing is of critical importance. Aiming to understand how individual differences in cognitive processing styles affect users' interactions in different checkout designs, a co ntrolled user study was conducted that explored the impact of the Wholist -Analyst cognitive style on user preference and task performance of different checkout designs within E-Commerce and M-Commerce settings. We primarily intended to focus on the Wholist/Analyst dimension since it highlights differences in the way individuals view the structure presented by their visual field as well as react and behave in various situations triggered by their contextual surroundings (e.g., desktop vs. touch -based interactions). Analysis of results suggests that cognitive styles affect users' task co mpletion across device types (desktop computers and mobile touch-based devices). In particular, Wholist users have performed more efficiently in checkout processes that followed a guided approach, whereas Analyst users were more efficient and preferred a single page checkout design which did not follow a guided approach and provided more flexibility while entering information.

Results of the study suggest that personalizing the checkout process based on intrinsic cognitive characteristics could support the users in terms of usability and improve the users' buying experience, and eventually benefit the providers since perso nalized tasks improve user acceptance of their services, and thus gain a competitive advantage. Nonetheless, the practical feasibility of such an approach entails a number of issues and challenges that need closer attention. An important challenge relates to the prior knowledge required by the system, about the u sers' cognitive characteristics in order to provide personalized checkout designs without engaging users in a ps ychometric test. Given the complexity of cognitive styles' research, implicit elicitation methods of cognitive styles without engaging users in a psychometric test is still at its infancy. In this context, existing noteworthy works could be used for implicitly eliciting the users' cognitive styles based on the users' navigation behavior [START_REF] Chen | An Integrated Approach for M odeling Learning Patterns of Students in Web-Based Instruction: A Cognitive Style Perspective[END_REF][START_REF] Belk | M odeling Users on the World Wide Web based on Cognitive Factors, Navigation Behavior and Clustering T echniques[END_REF]. Another point relates to practitioners adopting the cognitive style elicitation process since the current paradigm of interactive systems might limit the proposed approach of applying cognitive style as a user profile and personalization factor. In view of our long-term goal of personalizing checkout tasks based on cognitive differences, this work aims to point out the importance of personalizing such tasks. In this respect, findings of this research build on the promise that human cognitive factors could offer an alternative perspective to the current one-size-fits-all paradigm of checkout processes.

Limitations of the study relate to the rather small sample size and non -varying user profiles (e.g., age, experience). Furthermore, the study did not control possible influencing factors such as content, images, etc., since different commercial Web-sites were used. On the other hand, we aimed to initially investigate the accumulated experience of users in real life settings aiming to increase the ecological validity of the study. Future work entails investigating different combinations of content presenta-tion and navigation within such tasks, and recruiting participants with varying profiles in order to increase our understanding about the effects of cognitive styles on users' checkout process behavior and thus increase the external validity of this research.

Fig. 1 .

 1 Fig. 1. Nordstrom checkout process design.

Fig. 2 .

 2 Fig. 2. Amazon checkout process design.

Table 1 .

 1 M eans of task performances (in seconds).

		Wholists	Analysts
		Desktop	Touch	Desktop	Touch
	Nordstrom	140.00 (36.15)	159.66 (57.39)	100.75 (24.28)	151.00 (18.74)
	Amazon	118.16 (50.81)	135.73 (32.99)	127.33 (31.30)	164.60 (14.53)

Table 2 .

 2 User preference of checkout design.

		Wholists		Analysts
		Desktop	Touch	Desktop	Touch
	Nordstrom	2	7	8	6
	Amazon	7	5	2	1

Acknowledgements. The work is co-funded by the Cyprus Research Promotion Foundation project PersonaWeb (ΤΠΕ/ΠΛΗΡΟ/0311(ΒΙΕ)/10) and EU project M iraculous-Life (#611421).


Leonhard Lichtschlag
email: lichtschlag@cs.rwth-aachen.de

Philipp Wacker
email: wacker@cs.rwth-aachen.de

Martina Ziefle
email: ziefle@cs.rwth-aachen.de

Jan Borchers
email: borchers@cs.rwth-aachen.de

The Presenter Experience of Canvas Presentations

Keywords: Canvas presentations, slideware, zoomable user interfaces, lab study 1

M ost presentations are given with supporting visuals and driven by specialized presentation software. Today, this software either follows the classic slideware metaphor, presenting a series of discrete screens-or it implements the more recent canvas presentation metaphor, using a zoomable free-form canvas to arrange information. Both paradigms were previously evaluated with presentation authors and audiences. In this paper, we extend our understanding to how they impact the presenter herself during delivery of a talk. In a lab study participants gave presentations with slideware and canvas tools, and we measured their emotional state through self-reporting. We find that a recommendation for a tool depends on the experience of the presenter or their spatial ability.

Introduction

Visual presentation support is prevalent in talks in research, industry, education, and many other areas. Most software, e.g., Microsoft's PowerPoint or Apple's Keynote, employs the slide metaphor, which originates from the technical restrictions of phys ical slides used on overhead projectors. Yet today, presentation visuals are usually displayed using a computer connected to a video projector. This removes the necess ity to show a series of slides, one at a time, and this format has been criticized repeatedly for the limitations it imposes on authors and presenters [16,[START_REF] Tufte | The Cognitive Style of PowerPoint[END_REF]. A recent alternative to the slide format are canvas presentations, which dismiss the slide metaphor in part or entirely. Instead, they place either the slides [START_REF] Good | Zoomable user interfaces as a medium for slide show present ations[END_REF] or individual elements [START_REF] Lichtschlag | Fly: a Tool to Author Planar Presentations[END_REF]17] on an infinite canvas. Authors then define viewports and transition paths across the canvas to define the presentation sequence, or present ad-hoc without a planned path.

It was previously studied how authors deal with the two paradigms when preparing for a talk [START_REF] Lichtschlag | Fly: a Tool to Author Planar Presentations[END_REF][START_REF] Lichtschlag | Canvas Presentations in the Wild[END_REF], and how audiences perceive talks given in the two formats [START_REF] Lichtschlag | Fly: Studying Recall, M acrostructure Understanding, and User Experience of Canvas Presentations[END_REF], but the effect on the presenter herself has not been investigated, yet. The canvas format should be especially helpful for navigations that deviate from the planned presentation delivery, e.g., in response to a question [START_REF] Bederson | The promise of zoomable user interfaces[END_REF][START_REF] Good | Zoomable user interfaces as a medium for slide show present ations[END_REF]. The presenter can quickly pan-andzoom, thereby creating impromptu overviews and showing the macrostructure of the talk to the audience. However, we also hypothesize that the free format may be too demanding for a presenter who is preoccupied on talking. In this paper, we present a lab study with presenters who gave short talks in each format to investigate these issues. We measure the emotional state of the presenters during a presentation delivery in which several kinds of interruptions occur.

Related Work

Several tools have adapted the zoomable user interfaces paradigm [START_REF] Bederson | Pad++: a zooming graphical interface for exploring alternate interface physics[END_REF][START_REF] Bederson | The promise of zoomable user interfaces[END_REF] specifically for presentation support [START_REF] Good | Zoomable user interfaces as a medium for slide show present ations[END_REF][START_REF] Lichtschlag | Fly: a Tool to Author Planar Presentations[END_REF]17]. CounterPoint [START_REF] Good | Zoomable user interfaces as a medium for slide show present ations[END_REF] broke new ground by positioning PowerPoint slides inside a zoomable user interface. It lets authors place slides at varying distances from a virtual camera and create a spatial layout of slides. Fly [START_REF] Lichtschlag | Fly: a Tool to Author Planar Presentations[END_REF] and Prezi [17] have no notion of s lides at all and present content elements (text, figures, etc.) directly on a canvas. Without the limitations of the slide frame, au thors adapt their approach to presenting content less linearly and incorporate good present ation behaviors such as overviews [START_REF] Lichtschlag | Fly: a Tool to Author Planar Presentations[END_REF][START_REF] Lichtschlag | Canvas Presentations in the Wild[END_REF]. Canvas presentations perform on par with slideware with regards to audiences' content recall and macrostructure understanding [START_REF] Lichtschlag | Fly: Studying Recall, M acrostructure Understanding, and User Experience of Canvas Presentations[END_REF]. No studies investigated how presenters interact with canvas presentations.

Defining emotion is very difficult, and there are numerous attempts in the literature. A popular approach is to characterize emotion using a component model where expressions, bodily reactions, and the subjective experience have "long-standing status as modalities of emotion" [START_REF] Scherer | What are emotions? and how can they be measured?[END_REF]. There are different ways to combine these components; here we use a dimensional approach (e.g., [START_REF] Russell | Evidence for a three-factor theory of emotions[END_REF]) with valence and arousal as the main components [START_REF] Scherer | What are emotions? and how can they be measured?[END_REF]. Valence dimension contrasts pleasure and displeasure, while the arousal describes intensity. The term feelings is defined in the component model as the subjective experience of an emotion and can occur separate from bodily reactions (e.g., [START_REF] Frijda | The psychologists' point of view. Handbook of emotions[END_REF]). As many people are anxious about public speaking , it is the presenter's feelings that we are interested in. Scherer [START_REF] Scherer | What are emotions? and how can they be measured?[END_REF] writes that these feelings can only be accessed through a person's self-reporting.

The self-assessment manikin (SAM) [START_REF] Bradley | M easuring emotion: The self-assessment manikin and the semantic differential[END_REF] (figure 1, right) is one way to elicit ratings from subjects. Each row represents change along one dimension of emotion as pict orial depictions of a person. In our study we used SAM without the dominance domain. While this method requires fewer ratings from a person, the two dimensional rating does provide little insight into the aspects that produced the emotion [START_REF] Scherer | What are emotions? and how can they be measured?[END_REF]. A more detailed technique is the semantic differential (SD) which measures the meaning of words [START_REF] Osgood | ) 16. Parker, I.: Absolute PowerPoint: Can a software package edit our thoughts?[END_REF] (figure 1). A semantic differential consists of point rating scales with bip olar word pairs on either end of the scale (e.g., good-bad). It has been used to measure attitude and feelings, for example in a classroom scenario [START_REF] Evans | Use of the semantic differential technique to study attitudes during classroom lessons[END_REF]. A person rates a co ncept by indicating for each word pair where she places the concept between the limits.

Study Design

We conducted a lab study with every tester giving two presentations for about 7 min each (figure 1, left). One presentation was given with Apple's Keynote [START_REF]Apple Keynote[END_REF], representing slideware, and one with Prezi [17], representing the canvas condition (During presentation delivery, the differences between the different canvas tools are negligible and we do not expect our choice of software to impact the study. Similarly for slideware). In this format, we were able to have comparable talks for all users and to include interesting tasks in the presentations as well as simulated technological pro blems. In each presentation, we first asked the tester to give their presentation normally by stepping forward through the presentation. Then we interrupted them and asked to move to a well defined position in the presentation (e.g., going back to a specific previous slide in response to a question) and then to skip forward towards the end (e.g., due to time constraints ). Finally, we asked to search for a loosely defined position (e.g., the presenter has to find the slide to a question). One of the two talks also included simulated errors: a misinterpreted input (simulated by a step backwards on a forward command), and an unresponsive program (simulated by no action on the first command). We counterbalanced the order of conditions. Our setup excludes many confounding variables (e.g., varying documents, audiences, stakes, presentation occasions, length, etc.) to build a baseline understanding in the lab with high control. As such, the results of this setup are limited until a field study can investigate their generalizability (cf. the approach taken by [START_REF] Lichtschlag | Fly: a Tool to Author Planar Presentations[END_REF][START_REF] Lichtschlag | Canvas Presentations in the Wild[END_REF]).

In both talks, testers presented the 2014 Soccer W orld Championship, a topic presented heavily in the media at the time, so that we could expect our testers to have at least some prior knowledge. The topic was also a good fit for a spatial layout by placing players on their actual position on the pitch. Therefore, the topic could be presented spatially in the canvas condition in a manner that was approachable to our testers (cf. [START_REF] Lichtschlag | Fly: Studying Recall, M acrostructure Understanding, and User Experience of Canvas Presentations[END_REF] discussing of the problem of comparable documents between presentation software). Additionally, we introduced the participants to the documents and the tools, then they used the software to familiarize themselves with the matter. The documents were created by the authors; while is common to present foreign slides, this remains a limitation of the lab setup. Left: each participant presents two talks, after each she rates her feelings with the Self-Assessment M anikin (SAM ) and the Semantic Differential (SD) described on the right. Top Right: One row changes from an unhappy person to a happy person (the valence dimension), one row from a person who has the eyes closed to a person experiencing int ense feelings (arousal dimension). Bottom Right: SD dimensions used to quantify more precise feelings. by the presenter. Using the same input device for all presentations lowered the possible differences in interacting with the different software. Both software animated transitions, canvas with the inherent flyover, slideware with a slide-in from right to left between each slide. During the presentation delivery, the input modalities are step forward, step backward, as well as zoom and pan. All materials and presentation documents to replicate the study are available at http://hci.rwth-aachen.de/fly.

During the presentation, the moderator acted as an interested audience member that smiles and acknowledges the information given. Two cameras recorded each talk, this increased the stakes for our testers as playacting the presentation in this manner gives similar results to the "real" situation [START_REF] Higgins | The Validity of Role-Play Assessments of Assertiveness[END_REF][START_REF] Kern | Enhancing the Validity of Role-Play Tests: A Comparison of Three Role-Play M ethodologies[END_REF]. Secondly, the cameras allowed us to watch the recording afterwards together with the presenter. Although memory of feelings lessens over time [START_REF] Robinson | Belief and feeling: Evidence for an accessibility model of emotional self-report[END_REF], the participant could relive the situation and assess her fee lings, and we avoided interrupting the presentation. We used the self-assessment manikin with a nine-point rating scale [START_REF] Bradley | M easuring emotion: The self-assessment manikin and the semantic differential[END_REF] (figure 1) to measure the valence and arousal of the participant in the task situations. We also used the semantic differential [START_REF] Osgood | ) 16. Parker, I.: Absolute PowerPoint: Can a software package edit our thoughts?[END_REF] to ask her to rate twelve feelings on a nine-point rating scale to measure feedback on specific feelings. To find out which dimensions to use, seven weeks before our study, we had asked in an online survey which feelings presenters had experienced themselves or observed in others. We combined the reported emotions with directions from literature [START_REF] Good | Zoomable user interfaces as a medium for slide show present ations[END_REF] and produced the dimensions in figure 1. Accounting for the possibility that underlying moods affect the feelings of the participants, we used the PANAS test, a reliable and valid method to measure mood over various periods of time [START_REF] Watson | Development and validation of brief measures of positive and negative affect: the PANAS scales[END_REF]. Finally, in the exit questionnaire, we asked for informal feedback on the experience with the software, differences to their regular presentations, and how their feelings in the study related to feelings in real presentations. To see whether spatial ability influence the experience of presenting, we measured the participants spatial ability using a paper folding test [START_REF] Ekstrom | M anual for Kit of Factor-referenced Cognitive Tests[END_REF]. We formulated these hypotheses: H1 : Feelings in canvas presentations are rated differently than feelings in slide presentations. H2 : Presentations with technical difficulties are rated differently than presentations without technical problems. H3 : Order of presentation and presence of errors does not influence ratings. H4 : Participants experience the same feelings during the study compared to a real world presentations.

Evaluation

We recruited 21 participants for the study with varying proficiency in presentation skills in general and technological skills in particular. The participants were 8 teac hers, 7 students, 6 other professions, none familiar with the lab, aged 17-66 (mean=37.09, SD=16.02). To quantify the presentation experience we calculated a presentation age by subtracting the age at which a participant had given their first presentation from their current age. This presentation age (PAge) had a mean of 18.33 years and standard deviation of 11.73. The technological expertise (TE) was assessed by calculating the mean between how often the participant uses canvas tools and slideware respectively (rated on a five-point scale where higher values mean more often). TE had a mean of 1.33 and a standard deviation of 0.56. We also asked participants how much they liked to present (L) on a five-point rating scale (1-5, 1=most enjoyment, mean=2.19, SD=0.93). Other gathered characteristics were spatial ability (SA, 0-20, number of correct solutions in the paper folding test; mean=12.76, SD=4.77) and mood (PANAS test, separated for positive affect (PA) (mean=31.14, SD=4.95) and negative affect (NA) (mean=12.57, SD=2.34)). A correlation of PAge, SA, TE and L showed that presentation age and spatial ability had a significant negative correlation. Hence we could not analyze them separately, and when we report on PAge below, SA can also be an explaining factor. For the evaluation we categorized the PAge, TE and L each into two groups.

As for the hypothesis of program influence (H1 ) we conducted two repeatedmeasures MANCOVAS with the valence/arousal ratings (SAM) and the semantic differential (SD) ratings as dependent variables respectively. PAge, TE and L were taken as between-subjects factors and positive affect (PA) and negative affect (NA) as covariates. For the valence/arousal ratings we found no main effect of the delivery method (F(2,10)=3.00, ns) but a significant between-subjects effect of TE (F(2,10)=6.78, p<.05) and a significant interaction effect of Program*PAge (F(2,10)=7.82, p<.01).

Between-subjects, TE had a significant effect on the valence ratings (F(1,11)=11.24, p<.01) with more TE leading to higher ratings (figure 2a). The interaction effect of Program*PAge was significant for the valence ratings (F(1,11)=14.66, p<.01). An analysis of the means showed that less experienced presenters gave higher valence ratings for the canvas presentation (5.97 to 7.01) while more experienced presenters gave higher ratings for the slideware presentation (5.25 to 7.46) (figure 2b). The results from the analysis of SD ratings indicated a main effect of the delivery method (F(11,1)=825.93, p<.05), an interaction effect of Program*NA (F(11,1)= 1481.85, p<.05), an interaction effect of Program*PAge (F(11,1)=2249.68, p<.05) and an interaction effect of Program*TE (F(11,1)=349.55, p<.05). While the individual SD dimensions did not differ significantly between the programs, the overall trend was that the slideware presentation received more positive emotional response. The interaction effect of Program*PAge was significant for pleasantness (F(1,11)=8. [START_REF] Bradley | M easuring emotion: The self-assessment manikin and the semantic differential[END_REF] More experienced presenters gave positive ratings for slideware on all these dime nsions, while less experienced presenters showed only minor differences. Th e interaction effect of Program*TE was significant for surprise (F(1,11)=9.99, p<.01), unsatisfied (F(1,11)=9.21, p<.05), and lost ratings (F(1,11)=5.47, p<.05). Presenters who had less TE gave higher ratings for slideware on all these dimensions while presenters with more TE showed only minor differences. In conclusion, we accept H1.

Exploring the data, we noted that the ratings for the search for a loosely defined position task showed a flipped behavior. An interaction effect Program* PAge occurred once again and valence values were significantly different for this task (F(1,11)=9.31, p<.05). Further analysis showed a great difference between slideware and canvas presentations for experienced presenters, with canvas presentations having a better rating, while no difference was found for less experienced presenters (figure 2c).

To explore the error hypothesis (H2 ) we conducted two repeated-measures MAN-COVAS with the valence/arousal ratings and the semantic differential (SD) ratings as dependent variables respectively. PAge, TE and L were taken as between-subjects factors and positive affect (PA) and negative affect (NA) as covariates. The analysis of valence/arousal ratings indicated a main effect of the error condition (F(2,10)=5.55, p<.05), an interaction effect of Error*PA (F(2,10)=6.62, p<.05) and an interaction effect of Error*TE (F(2,10)=5.88, p<.05). Arousal ratings were significantly different between the error conditions (F(1,11)=7.90, p<.05). Examination of means showed that arousal was rated higher in the no-error condition (figure 2d). The interaction effect of Error*PA was significant for the arousal ratings (F(1,11)=8.19, p<.05), and the plot indicated that while the positive affect rating had no effect on the arousal rating in the no-error condition, it had a positive effect on the arousal ratings in the error condition. The interaction effect of Error*TE was significant neither for valence nor for arousal ratings. The results from the analysis of SD ratings indicated betweensubjects effects of NA on stress ratings and of TE on nervousness, pleasantness and positive-negative ratings. Further analysis showed that higher NA ratings correlated with more experienced stress, and that lower TE participants felt more nervous, more unpleasant, and more negative across both conditions. In conclusion, we accept H2.

Checking the quality of counterbalancing (H3 ), we compared presentations by order and found no differences between ratings for the programs (Canvas: F(2,18)<1, ns; Slide: F(2,18)<1, ns) or the errors (error: F(2,18)=1.73, ns; no-error: F(2,18)<1, ns). Thus, we accept H3.

As for H4 , almost all (20) participants expressed that they felt similar to a real presentation. 14 mentioned that they felt less pressure since they had less stakes in the presentation, 10 mentioned an additional burden (e.g., the unfamiliarity of the topic), while 2 felt that the study was outright harder than their own presentations because of that. With this, we cautiously accept H4: the limitations of the lab study were ma nageable, and our setup was comparable to a real presentation.

Discussion and Summary

Our evaluation shows that presenters experience canvas and slide tools differently. More specifically, participants of our study that scored high on spatial ability or were less experienced preferred the canvas condition, while experienced or lower spatial ability presenters preferred classic slideware. Due to the strong overlap in our tester population between experience and lower spatial ability, we cannot attribute this e ffect to a single or a combination of these factors. We expected lower spatial ability to interact with the canvas condition due to its ZUI nature, but we could also explain that more experienced presenters are well versed in slideware and hence feel right a t home. Interestingly, this difference is lessened in the search for a loosely defined position, a task that benefits particularly from the canvas format as the presenter can quickly zoom out to get an overview and pinpoint her target.

In summary, we have improved our understanding of canvas presentations and gained insight into who benefits from the format. Combined with the existing body of research [START_REF] Frijda | The psychologists' point of view. Handbook of emotions[END_REF][START_REF] Higgins | The Validity of Role-Play Assessments of Assertiveness[END_REF][START_REF] Kern | Enhancing the Validity of Role-Play Tests: A Comparison of Three Role-Play M ethodologies[END_REF][START_REF]Apple Keynote[END_REF] we now have an understanding of all the actors involved in presentations. One may think of author and presenter as the same person, but the results of [START_REF] Lichtschlag | Fly: a Tool to Author Planar Presentations[END_REF][START_REF] Lichtschlag | Canvas Presentations in the Wild[END_REF] and this paper indicate opposing forces in the tools: The authoring work b efore the talk benefits from the freedom of expression of the canvas format. The same freedom of navigation while pres enting comes with a drawback. Here, time and attention are limited and, as we have seen, a simpler linear format can be easier to handle for some presenters (cf. [START_REF] Good | Zoomable user interfaces as a medium for slide show present ations[END_REF]). One could conclude to always limit the format during presentation delivery, but we have also shown that for some presenters this would be unfavorable. We suggest that during delivery, canvas tools should (1) a llow the user to limit the navigation to the linear format until she needs the free format, and (2) offer her a simple way to get back to a safe place on the presentation path.

Limitations and Future Work

By design, our study was a lab study, and therefore is controlled situation that might not be representative of real-life use. A field study with presenters presenting their own presentations, with their own agendas on their own topic of expertise, and own audiences could corroborate the results of this paper. We were unable to attribute the interaction effect of program use to spatial ability or presentation age, as both ind ependent variables correlated. A study with separated variables could investigate this issue further. Other limitations are the short nature of presentations and the novelty of the canvas condition. We invite replication of this study and the materials used in this experiment can be downloaded at http://hci.rwth-aachen.de/fly.

  Fig.1. Left: each participant presents two talks, after each she rates her feelings with the Self-Assessment M anikin (SAM ) and the Semantic Differential (SD) described on the right. Top Right: One row changes from an unhappy person to a happy person (the valence dimension), one row from a person who has the eyes closed to a person experiencing int ense feelings (arousal dimension). Bottom Right: SD dimensions used to quantify more precise feelings.

Fig. 2 .

 2 Fig. 2. a) SAM ratings for technical expertise show significant difference. b) Presentation exp erience influences emotional response. c) SD ratings show experienced presenters rated the search task differently from the trend. d) Arousal rating is influenced by presence of errors.

  , p<.05), positivity (F(1,11)=10.11, p<.01), afraid (F(1,11)=14.67, p<.01), satisfaction (F(1,11)=20.38, p<.01), stress (F(1,11)=13.91, p<.01), desperation (F(1,11)=5.81, p<.05), controlled (F(1,11)=6.01, p<.05), and lost ratings (F(1,11)=16.83, p<.01).


Jens Bornschein
email: jens.bornschein@tu-dresden.de

Denise Prescher
email: denise.prescher@tu-dresden.de

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

Inclusive Production of Tactile Graphics

Keywords: Tactile graphics, blind users, collaboration, pin-matrix device

In this article a collaborative workstation for creating audio-tactile graphics is presented. The system is based on a common open source office suite and supports a transcriber for tactile graphics with several tools. In addition the system allows a blind reviewer to get involved at every stage of the creation process. This is achieved through a refreshable two-dimensional tactile display. The blind participant can independently manipulate graphical objects and make annotations in parallel. As a result, a tandem team of a sighted graphic creator and a blind partner may create a tactile graphic with better quality.

Introduction

While the visual world gets more connected and data gets more complex, visual presentation is an effective means to convey information. Problems arise if participants cannot access the presented information, in particular blind people. Non-visual access to graphics is often provided by a verbal description, which is not always a satisfying solution. To create an alternative textual description can be challenging for some graphics, for example maps, complex diagrams or images containing some kind of graphical notation. In addition, verbal descriptions can be incomplete or can contain wrong interpretations. This can change the meaning of an image or can lead to misunderstanding its intention. For this reason, a combination of a description and a transcribed tactile representation should be provided for important graphical data as it improves comprehension by blind people [START_REF] Edman | Tactile Graphics[END_REF]. For some photographs or art it is hard to create even a suitable tactile counterpart, access to them remains to be limited. Creating tactile graphics is also not an easy task, especially if the creator has only little experience. In a survey in German speaking countries, we found that only 5% of the 78 blind and visually impaired participants generally prefer image descriptions over tactile graphics [START_REF] Prescher | Production of Accessible Tactile Graphics[END_REF]. Conversely, most blind people wish to get more tactile graphics as they not only allow for an independent exploration, but also for a better spatial comprehension of the content. However, a basic requirement for an effective reading is a sufficient quality of tactile graphics. In most institutions it is common to check some of their produced materials by visually impaired colleagues to ensure a good quality [START_REF] Prescher | Production of Accessible Tactile Graphics[END_REF]. In the conventional production process it is necessary to produce a digitally mastered tactile graphic for every change again to show it to a blind reader.

In contrast, we use a refreshable tactile pin-matrix device to include a blind user in early stages of the production process within a collaborative workstation.

Tactile Graphics

Tactile graphics allow readers to feel presented structures, graphic elements or Braille text, through their tactile perception. Several different production methods exist. They all differentiate in their ability of presenting tactile structures. Differing features are, for example, possible resolution, the ability of allowing different raise levels, stability, speed and costs for reproducibility. While microcapsule paper and matrix embossers can produce tactile graphics from digital data without big additional effort, reliefs and other production methods need some manual post-processing or long production times. In this paper we focus on digital production methods, such as normal printing and embossing. Tactile embossers allow resolutions form 10 dpi for Braille embossers up to 20 dpi with different height levels for matrix embossers. Microcapsule paper is able to present detailed tactile structures printed with a normal printer on a special paper that rises on dark areas while heated under a special lamp.

Instead of conventional static production media refreshable two-dimensional tactile displays can be used to interactively present tactile graphical and textual information. For instance, the BrailleDis 7200 [START_REF] Prescher | Redesigning Input Controls of a Touch-Sensitive Pin-Matrix Device[END_REF] allows to show content on a 120 x 60 pins large display area as binary tactile image with a resolution of about 10 dpi. Because of its zooming and panning possibilities, theoretically, each type of graphic can be shown on the pin device. However, there are some limitations. For instance, it is hard to handle graphics that use colors or different height levels. Very fine-grained structures, rounded objects and non-orthogonal lines can also lead to problems in their recognizability on such low-resolution devices. Reducing the complexity is a main requirement for tactile graphics; therefore these kinds of structures should be avoided in any case.

Tools for Preparing Tactile Graphics

The creation of a tactile graphic is not the challenging part of a transcription process. Almost every source image can be directly transformed into a grayscale or binary image which can then be produced as tactile version, for example, on microcapsule paper or with a matrix-embosser. The main problem is the readability and recognition of objects. Structures and shapes often get lost due to the low resolution. Therefore, a transcriber needs to prepare the image with respect to simplification and readability. Several drawing tools exist to support transcribers. They contain functions for filling objects with different tactile patterns or allow redrawing image parts in a way that they fit into the embossing matrix of the related embosser. Some of them also apply graphic filters for grayscale or binary transformation as well as for finding and highlighting the outlines of objects (e.g. PictureBraille 1 task for transcribers. The TGA system [START_REF] Jayant | Automated tactile graphics translation: in the field[END_REF], for example, supports the translation of text in images by semi automatic OCR-mechanisms. However, it seems that mostly standard office or image processing software is used [START_REF] Prescher | Production of Accessible Tactile Graphics[END_REF].

In contrast, suppliers for tactile graphic production hardware often deliver their own production software. For example, the audio-tactile graphic exploration system IVEO2 comes with a touch-sensitive image frame and its own tactile graphic production software for creating scalable vector graphic (SVG) images with the feature to add a two-level description to graphic elements. Technically, SVG is utilized for annotating a title and description of tactile objects.

Tactile Graphics by Blind People

Drawing graphics without vision is difficult. Blind pupils learn to create drawings by different techniques. Most of them are based on handicraft techniques or combine tactile primitives to more complex structures [START_REF] Prescher | Production of Accessible Tactile Graphics[END_REF]. Creating freehand drawings can be done by scratching tactile perceptible structures into special foils or wood plates. These are all analog methods and, therefore, hard to reproduce. The digital creation of a drawing by a blind user is more complex and with limited tactile feedback. Often Braille characters form drawings or command languages define graphical structures. All analog techniques have the disadvantage that an error correction is almost impossible for the creator. For the digital methods this is also very exhausting because it needs a lot of mental imagination.

Quality of Tactile Graphics

The dissemination of tactile graphics among blind people lacks behind their importance. Due to lack of training many blind users have difficulties in recognizing complex tactile graphics [START_REF] Bentzen | Tangible graphic displays in the education of the blind persons[END_REF]. Reasons may be, for instance, the overloading of a graphic with too much information, the reduced distinctiveness among different objects as well as the limited preservation of orientation [START_REF] Prescher | Production of Accessible Tactile Graphics[END_REF]. To minimize such problems some kind of quality management for tactile graphics is important. There are several guidelines (see [START_REF]and Canadian Braille Authority: Guidelines and Standards for Tactile Graphics[END_REF]), which should improve the quality of tactile materials. However, such guidelines are often complex and general, which complicates their practical application -especially for non-expert sighted persons who commonly produce tactile graphics [START_REF] Prescher | Production of Accessible Tactile Graphics[END_REF]. We propose the inclusion of blind users into the creation process. Therefore, we have developed a collaborative workstation as described in the following section.

The main purpose of our system is to allow a simplified inclusion of blind users in the production process as well as to support inexperienced sighted users. Besides, the system can also be used for sketching difficult concepts with and for a blind user, for instance in learning or working scenarios. First user observations in a collaborative graphic production scenario have shown that it is not effective to let the blind user follow the creation of a graphic from the beginning. It is more effective to include the blind user after a first draft of the graphic is produced. The blind reviewer can than check the graphic and make some annotations and changes if necessary. The sighted user can also ask for specific problems which can lead to further discussions and improvements of the resulting tactile graphic.

Collaborative Workstation for Tactile Graphics

Compared to cooperation, where each individual works separately on his own part, collaboration requires direct interaction and discussions among the participants [START_REF] Kozar | Towards better group work: Seeing the difference between cooperation and collaboration[END_REF].

For an efficient collaboration between a sighted and a blind user, the visual and the non-visual workspace have to remain consistent and have to be synchronized in a multimodal sense. The Tangram collaborative workstation not only has to allow for the creation and modification of tactile and visualized graphics by both users. It also has to support the communication between the partners by focusing on objects of interest jointly. Beyond basic graphics operations, the workstation also has to include functions for annotation and quality management. In the following, the general architecture of the Tangram workstation as well as the mechanisms for supporting the collaborative production of tactile graphics by sighted and blind users are presented.

Architecture of the Tangram Workstation

The Tangram workstation consists of two parallel I/O workspaces connected to one computer (see Fig. 1). The sighted user uses mouse and standard keyboard as input and a monitor screen for the visual output. The blind user on the other hand uses the dynamic pin device BrailleDis 7200 for tactile output and its 28 buttons as well as its touch-sensitive display area as input device for keying in commands, Braille text and gestural input [START_REF] Prescher | Redesigning Input Controls of a Touch-Sensitive Pin-Matrix Device[END_REF]. In addition, auditory feedback is given, consisting of sound and text-to-speech output. With the exception of non-visual drawing, all basic tasks for transcription can be mapped to interactive operations at which the two partners do not hinder each other while working on the same document independently and in parallel.

Fig. 1. Schematic representation of the Tangram workstation

As basic drawing system the open source office suites OpenOffice 3 and LibreOffice4 can be used. These programs are free to use, even in a commercial context, and produce vector graphics which can be exported to several different document formats. Multiple tools have been added to implement the working process for creating audio-tactile graphics.

For the blind user a special screen reader has been implemented that allows access to the accessible interface of the office suite as well as to the document object structure [START_REF] Bornschein | Collaborative Tactile Graphic Workstation for Touch-Sensitive Pin-Matrix Devices[END_REF]. This enables the blind user to manipulate the graphical and textual document elements. The presentation of the graphical content is realized by rendering a tactile screenshot of the working area window on the pin device. Thereto, a configurable filter is applied to the screenshot, converting lighter points to lowered pins and darker points to raised ones. The user can freely explore the tactile screenshot by zooming and panning operations. Additional information is added to the screenshot image, such as a dotted frame resembling the size and position of the sheet to draw on within the working area. The blind user can retrieve further information on document objects by pointing at them while pressing a button.

The blind users' input and output system is realized with our open-source framework BrailleIO [START_REF] Bornschein | BrailleIO -a Tactile Display Abstraction Framework[END_REF]. This framework allows for a fast and easy implementation of a basic windowing system for two-dimensional tactile pin devices. Furthermore, the framework also allows the Tangram workstation software to be applied to other pin device types besides the BrailleDis 7200.

Supporting the Sighted User

Especially for sighted producers with little experiences, the provision of a specialized toolbar by the graphic editing software itself can reduce some of the deficits when designing tactile graphics on a visual screen. This can include the specification of predefined sets of filling patterns, line styles or elementary graphical primitives, such as arrows or tactile symbols. Moreover, an easier access to important properties of graphical objects, such as position, size and textual information (title and description), can also be helpful for enhancing the productivity of a sighted user. The implemented toolbar supports the following tasks (compare Fig. 2): Fig. 2. Toolbar for supporting the sighted user in producing tactile graphics ─ position properties: edit x and y position of the selected object. ─ size properties: specify width and height of the selected object. ─ keep ratio toggle: enable and disable preservation ratio of width and height. ─ unit selection: select measuring unit for presentation of position and size. ─ line styles: select a tactile perceivable line style (solid, dotted and dashed) for the selected object. ─ pattern styles: select a texture for filling the selected graphical object. We have tested the suitability and discriminability of the provided patterns for utilization with different tactile graphics technologies (microcapsule paper, matrix embossed printing and pin-matrix device) in an unpublished study with 12 blind users. ─ pattern-border spacing: add or remove white space between the filling pattern and the border of the selected object to increase distinctiveness and outline perception.

Supporting the Blind User

The blind user manipulates graphic objects independently on the pin-matrix device by a rotating menu with five different editing modes. Input is realized by the buttons of the right cursor key pad of BrailleDis 7200 (see Fig. 3). If an element of the graphic is selected, the user can start it's editing by pressing the center key. Initially, the move mode is activated. By pressing one of the four direction buttons the element is moved into the chosen direction. The current editing mode can be changed by pressing the center key iteratively. In this way an element can be moved, scaled, rotated, and its texture and line style can be changed. The assignment of functions to the cursor key pad buttons is dependent on the current mode (see Fig. 3). Therefore, the user doesn't have to remember many button combinations. Furthermore, one hand may remain on the cursor key pad while the other hand can monitor the changes on the element in real time. Bi-manual operation has been found to be effective for most interaction tasks [START_REF] Morash | Effects of using multiple hands and fingers on haptic performance in individuals who are blind[END_REF]. One drawback is the reduced efficiency due to the modal menu. Nevertheless, an informal discussion with four blind users showed that this is acceptable if there are not too many modes.

Besides the editing of the appearance of graphic objects, the blind user also can annotate the tactile graphic, for instance, by adding a title and description for each element. Thereto, he can open a dialog in the detail region of the pin-matrix device, where reading and editing of Braille content is performed. Either a text field for the title or for the description is shown. The user can switch between these two by using the up or down button of the right cursor key pad. For writing, the Braille input keys on the BrailleDis are used. Finally, the data have to be saved by calling the save menu, which is realized by pushing the center button of the right cursor key pad. Using the left or right button the user can choose between the following menu options: save, not save or cancel. All options are presented in Braille, where the current selected option is underlined and also is spoken out.

Collaboration

The blind user can edit the graphic elements independently from the sighted user, as mentioned above. Therefore, it is necessary to have two separate foci: the standard GUI focus, which will be called mouse focus in the following, and the pin device focus which refers to the DOM objects of the drawing document. The latter will be called Braille focus. To enable an effective collaboration, the users have to be aware of these focus concepts.

Allowing the blind user to follow his sighted partner's activities, the selected GUI element can be highlighted on the pin device, and a follow mouse focus mode can be activated. In this mode, the element which is currently selected by the sighted user, is not only spoken by audio output, but also is signaled by a blinking pin frame and is shown in the center of the pin device. If the sighted user selects another element, the tactile output is refreshed automatically. In this way the blind user can easily track the mouse focus. If he wants to edit the element which has the mouse focus, he can set the Braille focus to that element and quit the follow mouse focus mode with a single button command. By this means, the sighted is able to show the blind user an element and ask him to do some improvements, for example.

On the other side, the blind user can also highlight the Braille focus for his sighted partner on the GUI to indicate the element he is currently editing. Therefore, a blinking overlay window is shown for some seconds above the corresponding element.

Conclusion and Outlook

A collaborative workstation for producing tactile graphics was implemented. This allows blind users to actively take part in the transcription process for tactile graphics from early stages. As they are the target user group of the materials created, this should increase the quality of the resulting images. First prototyping tests with four blind users showed that the editing functionalities on the pin device were rated as useful and intuitive. Nevertheless, a high learning curve was mentioned. The focus concepts were rated as understandable, but the effective usage in collaboration with a sighted partner needs a lot of training, practice and coordination.

As the next step a real scenario user study with pairs of blind and sighted subjects reworking a previously transcribed tactile graphic will be conducted. Thereby, we will be able to assess usability and accessibility of the Tangram workstation's approach to collaboration. It already became clear that blind reviewers would like to do some changes in existing tactile graphics. In our studies, we want to find out if materials produced by professionals will be improved by a blind user, too.

  ─ title & description dialog: open or hide a docking window for annotating title and description of graphical objects. ─ open Tangram workstation: start the Tangram workstation for the blind reviewer. Besides, document properties are adapted, such as standard colors and font style. ─ open check tool: open a dialog for reviewing tactile graphics based on our authoring guidelines.

Fig. 3 .

 3 Fig. 3. Usage of the cursor keys within the five editing modes in the non-visual user interface

http://www.pentronics.com.au/index_files/PictureBraille.htm ). Creating Braille labels is another

http://www.viewplus.com/products/software/hands-on-learning/

www.openoffice.org

www.libreoffice.org

Acknowledgements. We thank our blind participants for the rich discussion about the concepts of our tactile user interface. The Tangram project is sponsored by the Federal Ministry of Labour and Social Affairs (BMAS) under the grant number R/FO125423.