Douglas Scheurich

Wolfgang Stuerzlinger
email: wolfgang@cse.yorku.ca

A One-Handed Multi-Touch Method for 3D Rotations

Keywords: 3D rotations, 3D user interfaces, multi-touch, tablets

Rotating 3D objects is a difficult task. We present a new rotation technique based on collision-free "mating" to expedite 3D rotations. It is specifically designed for one-handed interaction on tablets or touchscreens. A user study found that our new technique decreased the time to rotate objects in 3D by more than 60% in situations where objects align. We found similar results when users translated and rotated objects in a 3D scene. Also, angle errors were 35% less with mating. In essence, our new rotation technique improves both the speed and accuracy of common 3D rotation tasks.

Introduction

The most common interaction tasks in three dimensional, 3D, virtual environments are navigation, object selection, and manipulation, such as translation and rotation. Object translation positions objects within the scene, whereas rotations orient objects. Despite being a fundamental task, there is no established standard for rotating 3D objects. One issue is that there is no "best" input device for 3D manipulation. In practice users use two-dimensional, 2D, pointing devices, including the mouse and touchscreens. 2D pointing devices offer good control of 2 degrees of freedom (DOF). However and in a 3D environment, control over 3 DOF is required for translations or rotations (yaw, pitch, and roll), or 6 DOF for both simultaneously. In many user interfaces this is handled through combinations of different widgets or touch gestures, i.e. through a combination of 2 DOF and 1 DOF controls. A mouse button is often assigned to control 2 DOF rotations. The third DOF is typically controlled via a modifier or the scroll wheel. The computer-aided design program Solidworks recently introduced a simple form of object mating. There, clicking on a specific surface of an object followed by a click on another surface snaps these two together, so that the first surface "mates" onto the second. However, this simple mating technique may leave objects in positions where they interpenetrate.

Mating is a simple way to orient objects. Thus, we were surprised to discover that there was no documented work on mating methods that avoided or resolved colli-sions. This encouraged us to explore the idea of mating for rotating objects on a touchscreen interface while avoiding object interpenetration.

Previous Work

Relevant other work on 3D rotations uses either 2D or 3D input devices. For 2D devices we first discuss the mouse and then touchscreen methods. With a mouse, Bade et al. [START_REF] Bade | Usability comparison of mouse-based interaction techniques for predictable 3D rotation[END_REF] evaluated four different methods, Bell's [START_REF] Bell | Bell's Trackball[END_REF] and Shoemake's [START_REF] Shoemake | Arcball: A user interface for specifying three-dimensional orientation using a mouse[END_REF] virtual trackballs, and two variants of the Two-Axis Valuator [START_REF] Chen | A study in interactive 3-D rotation using 2-D control devices[END_REF], in a user study. They found the Two-Axis Valuator to be best. Jacob et al. [START_REF] Jacob | Evaluation of techniques for specifying 3D rotations with a 2D input device[END_REF] investigated inspection tasks requiring rotations and found a similar result. However, the tasks in both of these studies required only 2DOF rotation control! Again, investigating only a subset of all 3D rotations, Partala [START_REF] Partala | Controlling a single 3D object: Viewpoint metaphors, speed and subjective satisfaction[END_REF] found virtual trackballs to be superior. Zhao et al. [START_REF] Zhao | Comparison of multiple 3d rotation methods[END_REF] recently investigated tasks that require full 3D rotation control. They did not identify significant differences between Bell's and Shoemake's trackballs and the Two-Axis Valuator.

Reisman et al. [START_REF] Reisman | A screen-space formulation for 2D and 3D direct manipulation[END_REF] presented a multi-touch method to control the position and rotation of 3D objects. The solver-based method tries to keep the object stable under the fingers. Yet, the result is not always predictable and rotations are often limited to 90 degrees in two of three directions (e.g. when a cube is facing the viewer). Rotations then require clutching. Martinet et al. [START_REF] Martinet | The effect of DOF separation in 3D manipulation tasks with multitouch displays[END_REF] used this method in their 6 DOF manipulation system. Hancock et al.'s [START_REF] Hancock | Sticky tools: Full 6DOF force-based interaction for multi-touch tables[END_REF] technique permits 1 DOF rotation with a 2-finger "rotate" gesture and controls the other 2 DOF with a two-handed 2+1 finger gesture. Kin et al. [START_REF] Kin | Eden: A professional multitouch tool for constructing virtual organic environments[END_REF] controls 2 DOF rotations with a single finger and the third DOF with a two handed gesture.

Bier [START_REF] Bier | Snap-Dragging in Three Dimensions[END_REF] developed a system called Gargoyle3D based on the idea of "snap-dragging". This system uses a general-purpose gravity system combined with snapping in 3D to enable users to accurately position and orient objects in 3D. In the user interface Gargoyle3D offered more than 40 distinct commands to achieve these operations. This level of complexity makes it infeasible for tablet computing. Related work on SKETCH by Zeleznik et al. [START_REF] Zeleznik | SKETCH: an interface for sketching 3D scenes[END_REF] requires at a minimum a three-button mouse and a keyboard for a modifier. While less complex than Bier's system, the sheer number of mouse and keyboard combinations again does not lend this idea to a simple or efficient implementation on a tablet.

Zhai et al. [START_REF] Zhai | Quantifying coordination in multiple DOF movement and its application to valuating 6 DOF input systems[END_REF] and Boritz et al. [START_REF] Boritz | A study of interactive 6 DOF docking in a computerized virtual environment[END_REF] investigated 3D rotations as part of 6 DOF docking tasks. Hinckley et al. [START_REF] Hinckley | Usability analysis of 3D rotation techniques[END_REF] compared 3D rotation techniques using 2D and 3D input devices and found that those based on 3D input devices were approximately a third faster. Recently Kratz et al. [START_REF] Kratz | PalmSpace: Continuous around-device gestures vs. multitouch for 3D rotation tasks on mobile devices[END_REF] proposed a system where the orientation of a user's hand controls 3D rotations. Their comparison with a virtual trackball found also a ~30% improvement. Liu et al. [START_REF] Liu | Two-finger gestures for 6dof manipulation of 3d objects[END_REF] proposed a system for full 6 DOF manipulation using four distinct one or two-finger touch gestures. However, the authors note that their system is not well suited for fine control of model transformations.

A New Multi-Touch 3D Rotation Technique

Tablets and tablet use is now a permanent addition to computing, considering the sustained explosive growth of the tablet industry in the last few years. Especially since the advent of smaller tablet form factors, such as the 7.9" iPad mini, one cannot assume that a tablet is going to be used with two hands simultaneously. Such devices are used almost anywhere by holding it in one hand while interacting with the system with the other. A great example is a video on the Autodesk website showcasing their Inventor Publisher Mobile Viewer1 application for iOS and Android. Parts of these videos show an engineer working on a tablet. The engineer never once puts the tablet on a table or desk to work, and holds it with one hand while working with the other the entire time. Given this constraint, we noticed a lack of touch-based systems that require only a single hand for 3D manipulation. This also means that all previously presented, touch-based 3D rotation methods, which require two hands, are not ideally suited for tablet use.

We designed our new technique explicitly for one-handed use. We also wanted to avoid the unpredictable nature and the limitations of Reisman's [START_REF] Reisman | A screen-space formulation for 2D and 3D direct manipulation[END_REF] approach. Moreover, we were inspired by a recent set of observations on 3D user interface design by Stuerzlinger et al. [START_REF] Stuerzlinger | The value of constraints for 3D user interfaces[END_REF]. They point out that in the real world the vast majority of objects are aligned with planes or other objects. The reason is that (almost) all objects are in contact with others on our planet and "floating" objects are a rare exception. Tables usually stand on floors; pictures are attached to walls; light fixtures to the ceiling. Many such objects have only one free rotational DOF in their "normal" placement. In other words, truly random orientations are the exception in the real world. Consequently, we focus on user interfaces that are optimized for these pervasive cases and design our technique accordingly.

The idea of "mating" two surfaces fits this observation very well, except that naïve mating easily results in object interpenetration. Mating the seat of a chair "onto" the ground would put the backrest of the chair into the ground, which novices often find confusing [START_REF] Stuerzlinger | The value of constraints for 3D user interfaces[END_REF]. This is demonstrated in Figure 1 below. Therefore, we enhance basic mating by always putting the chair into a position that avoids collisions, while keeping the seat plane parallel to the ground. As an added bonus mating also translates the object, which may lead to additional timesaving. Given that our enhanced form of mating always put objects into contact, we globally prevent objects from "floating" in our system. This limits the system to 2 DOF positioning, but also matches the capabilities of touchscreens better as fewer DOFs need to be controlled and simplifies the user interface. Objects can still assume any 3D rotation in our system, which is the main focus of our work here. The plane of the chair seat is still parallel with the stone surface. Yet, the chair has been "raised" so that it is in a collision free position.

Two Multi-Touch Rotation Methods

As discussed above, previous research did not identify a clearly superior 3D rotation technique, especially one with a limited number of input controls suitable for deployment on a tablet. Hence, we base our multi-touch system on the Two-Axis Valuator to directly control 2 DOF rotations. To control the third DOF we use a different form of multi-touch gesture compared to previous work. We implemented two variations for this. One is designed for systems that permit only 3D rotations, the other for systems that support both positioning and rotation.

Rotation Only Method

Our first method targets 3D rotations only. It interprets a single finger drag as Two-Axis Valuator manipulation. This is usually done with the index finger. Dragging the finger left and right will rotate the object about the y axis while dragging the finger up and down will rotate about the x axis of the camera coordinate system. A two-finger touch rotates around the view direction (i.e. the z axis of the camera coordinate system, see Figure 3 below). Here we implement a new technique: if one finger stays in place and a second "scrolls" this is interpreted as a rotation. We found users preferred to accomplish this in one of two ways. When rotating objects in the middle of the screen, putting the index finger down and flicking the thumb left or right below it is a natural way to access this functionality. When operating on the right edge of the screen, placing the index finger down and scrolling with the middle finger seems most natural. Placing the middle finger down and scrolling with the index works well when working near the left edge of the screen. To summarize, a single finger drag rotates about the x and y axes, while a single finger anchored in place (i.e. index finger) plus a finger dragging (i.e. the thumb) rotates the about the z axis. Double tapping a point on the object will use the enhanced mate functionality to mate the specified surface of the object with the plane behind it, as illustrated in Figure 2 below.

Fig. 2.

Illustrating of mating for 3D rotations using method 1. In this image we can see the brick wall as a background object behind the chair. By double tapping on the seat of the chair, marked with the red dot, the object's surface that corresponds with the double tap location (i.e. the chair seat), will become aligned with the plane of the object behind it (i.e. the brick wall). Consequently and by double tapping the seat of the chair, the chair is automatically rotated so that the seat plane is parallel with the background surface. This figure also illustrates a trial in the first phase of the experiment. The user is able to manipulate the object on the left. The task is to match the pose of the left object with that of the right object.

Rotation and Translation Method

Our second method targets both rotations and translations. As a result this method is more targeted at "real world" usage compared to the first method, since in an interactive environment some (or many) objects may be moveable. In the second method single finger movements control the (constrained) translation of an object along the surfaces of the scene using a variant of the technique presented by Oh et al. [START_REF] Oh | Moving Objects with 2D Input Devices in CAD Systems and Desktop Virtual Environments[END_REF]. Basically, objects always snap to and/or slide on the surface beneath them. For example, imagine wanting to drag a block around a staircase. If you are dragging the block down the staircase, as you move your finger the block will slide across the surface of each step, and when it reaches the end of a step, it will snap from that step' surface onto the surface of the next step and continue to slide along that, etc. Fig. 3. For all frames the world space and camera coordinate systems are shown at the top of this illustration. The user is always looking down the z-axis. Frames 1 through 4 illustrate rotating a cube along the view direction (i.e. the z-axis). We can clearly see that only the camera coordinate system influences the rotation of the object.

Rotating objects in the second method is similar to that in method one described above, except there is one additional finger for each technique. Thus a two-finger drag gesture, typically used with two fingers side-by-side, controls the rotation through the Two-Axis Valuator. Moving two fingers left or right rotates the object about the y axis while moving them up or down rotates the object about the x axis of the camera coordinate system. With two-fingers in place, moving a third finger rotates the object around the view direction (i.e. the z axis of the camera coordinate system). Users commonly use the middle and index finger in place while moving the thumb below them, especially when rotating objects in the middle of the screen. When space is constrained at the edge of the screen, a different possibility is to use the middle, index, and to move the ring finger to rotate objects. A single finger tap on a surface of an object followed by a finger tap elsewhere in the scene mates the two surfaces. This is illustrated in Figures 4 and5 If mating results in a collision, the object is pushed away from the target surface until the object is only in contact. This was illustrated in Figure 1 above. The reason for this is that in the real world objects very rarely interpenetrate and we designed our system to conform to this. If in a 3D world the user wants to place a chair on the ground, it is unlikely their goal is to have parts of the chair above the ground and parts of the chair disappearing into the floor. The effect of pushing objects away from the surface is relative to the user and the object. For example and if an object is mated onto a wall and interpenetrates it, the object will be pushed towards the user so that the object remains visible and inside the scene. The alternative of pushing it away from the user and the object becoming potentially invisible, is much more confusing. This effect is illustrated in Figures 6 and7 The movement from the initial position to the final position is animated to help users understand the result and to prevent them from having to visually reacquire the object position and orientation. This is especially helpful if an object is being moved over large distances over the scene. Also, before the objected is moved, our system pre-determines the final position and checks for collisions. If a collision is found, our system pushes the object away from the surface until there are no collisions, and this becomes the new final position of the object. Since the rotation and translation of the object is animated, if the object ends up in an unintended position or location, say as the result of a tap at the wrong location, the user will be able to see this visually and make appropriate corrections.

Moreover, a recently mated object is temporarily constrained. The system then rotates the object in the local coordinate system of the target surface. This enables users to mate an object onto any surface and then to quickly adjust the remaining DOF using either a two-or three-finger rotation. This permits users to quickly snap an object, for example a coffee cup, onto a table and then to turn the cup on the table to correctly orient the cup. The initial mating operation will ensure that the bottom of the cup is in complete contact with the surface, ensuring that it is not floating, leaving the user with the task of controlling only a single DOF to correctly orient the cup. This is substantially easier than having to always control all 3 DOF.

Methodology

Participants

Twelve paid volunteer participants were recruited from the local university campus and city. The age of the 6 male and 6 female participants ranged from 19 to 35 years (mean = 26.17, SD = 4.47). All had never participated in a 3D study before. All were right handed and preferred to use the tablet with their right hand. 3D video game usage was between 0 to 4 hours per week (mean = 1.92, SD = 1.62). Potential participants were asked in advance of the study if they had previously participated in a 3D study from our lab (even with another examiner) and we excluded people who indicated they had performed a user study involving rotating or translating 3D objects.

Apparatus

We conducted the study on an 8" Gadmei T883-3D tablet with Android 4.0.3. A widescreen monitor on a desktop computer was used in the second half of the study (i.e. during method 2) to display target scenes. The reasoning for this is explained below in the methodology section. We built a variety of commonly recognizable 3D objects, as well as several inspired by the Shepard-Metzler test [START_REF] Shepard | Mental rotation of three dimensional objects[END_REF]. After a pilot study we decided on a car, chair, dog, and one Shepard-Metzler object as shown in Figure 8 below. Colorings were introduced to disambiguate poses as, for example, a view onto the bottom of a chair with legs with identical colors does not reveal the full 3D rotation of the whole object at a glance. The white parts of objects highlighted in different colors for feedback. This reasoning for this is explained in more detail below.

Fig. 8. Objects selected for use in both studies.

Procedure

The study was conducted in a quiet room with the investigator, the sitting participant, and at most one other student present. The software was first configured to the participant's handedness. This affected the first part of the study where the rotating object was on the side of the user's preference and the target displayed on the other one.

Then the study was explained along with a system demonstration. All participants acknowledged they understood how the system worked and had no questions.

Overall we used a 2x2 within subject design with 2 phases. The first phase targeted only 3D rotations, whereas the second investigated rotations with constrained translations. The conditions were mating enabled or not, and surface aligned target orientations or not. These conditions were counterbalanced over all trials. In each set of 48 trials, subjects were asked to rotate 4 models 6 times with either mating enabled or not. Targets were aligned three of these six times, while the others had random target orientations. The order of each of these 24 trial blocks was determined using a Fisher-Yates shuffle. To determine the starting pose of the rotatable object we used two randomly shuffled copies of a list of 12 difference angles: 15, 30, 45, … , 165, 180 degrees. Each copy of the list matches to targets being aligned or not. To compute the final starting 3D orientation we first defined a rotation axis by generating a random point on a unit sphere. The user rotatable object was then rotated "back" from the target orientation about this axis by the angle chosen above. The participants' task was to rotate the object to within a quaternion angle of 10 degrees from the target orientation. Users could not abort trials.

Figure 2 above illustrates a trial in the first phase. Participants were presented with 2 objects. The target object on the left (or right) could not be manipulated and was the shown in the desired orientation. The object on the other side was rotatable. When the user touched the rotatable object the white segments turned magenta to indicate selection. When the object was within the 10 degree limit the white segments turned green to signal the user that the object had been rotated within an acceptable accuracy tolerance (the quaternion angle of 10 degrees mentioned above). A button then appeared in the upper corner of the screen on the side of the un-moveable object. Users pressed this button to move to the next trial, where it disappeared until the next object was correctly aligned. In phase one the focus was only on rotating objects. Thus, it was feasible to display both the target orientation and the user controlled object on the tablet screen side-by-side.

The task in the second phase shown in Figures 4 and5 was to both translate and rotate the object into the target pose, a 5 DOF task. Said target pose was displayed on a second, desktop monitor in this phase. Since users performed tasks involving translations and rotations, which requires more space for interaction and scene display, we were unable to display both an interactive scene and the target scene on the same device. Hence the target scene was displayed on the monitor, giving the user a larger space to translate objects on the tablet. For example, the tablet would display the scene from Figure 4, while the desktop monitor would display the scene from Figure 5. The participants' task was then to orient the object from his scene to match the scene displayed on the desktop.

Here, white parts of the object highlighted in cyan when within 10 degrees of the correct orientation, in yellow when within 1/50 th of size of the scene, and green when close to the correct pose. When the user was close enough, a button appeared in the upper right corner of the tablet screen which when pressed went onto the next trial. When pressed, the scene on the computer monitor changed. Thus users were not able to see the next trial in advance of completing the current trial.

Results

We found that using our mating system decreased rotation times substantially. According to a repeated measures ANOVA and in the 3D rotation task investigated in phase 1, there were significant effects of mating on completion time (F 1,11 = 23.06, p < .001) and target alignment (F 1,11 = 100.92, p < .0001). Both mating and aligned targets were significantly faster. There was also a significant interaction between the conditions. A Tukey-Kramer posthoc test shows that aligned scenarios with mating were approximately 65% faster than all other combinations. Figure 9 below illustrates average completion times. The results for the error angles show a significant effect for mating (F 1,11 = 93.83, p < .001) and also confirm that aligned targets were positioned significantly more accurately (F 1,11 = 63.75, p < .001). In the 3D translation and rotation task in phase 2 there was again a significant effect of mating (F 1,11 = 37.68, p < .0001) and aligned targets (F 1,11 = 61.7, p < .0001) on task completion time. There was also a significant interaction between them and Tukey-Kramer identifies that aligned scenarios with mating were completed approximately 64% faster than all other combinations. Figure 10 below illustrates the average completion time per participant. In this phase, there was a significant effect on error angles for both mating (F 1,11 = 108.75, p < .0001) and aligned targets (F 1,11 = 24.71, p < .0005), as well as a significant interaction between them. Tukey-Kramer reveals that aligned objects were posed in the mating condition approximately 35% more accurately in terms of error angles compared to all other combinations. Fig. 10. Mean completion times for study 2 with standard error shown.

Discussion

Our enhanced mating-based 3D rotation technique substantially decreases the time required to match aligned target orientations by 64% or more, while significantly improving accuracy. Given that most objects are aligned to others in many real world scenarios, this is substantial and exceeds all improvements found in previous work. Participants generally found either the chair or the dog the easiest object to rotate. Unanimously, the Shepard-Metzler model was judged the most difficult. Participants found the mating interface simple to use and all perceived it as faster. Although our original design for the flick gesture was targeted at thumb flicking, about half the participants preferred to use the ring finger instead for this technique.

Although this is not currently implemented in our system, we can easily adapt our method to enable mating even when there are no other surfaces present. For this we would simply add a (potentially invisible) back plane surface that is orthogonal to the view direction and proceed with mating to said surface. Optionally, this surface may be partially transparent to offer visual guidance to the user. One limitation of our current implementation is that we do not support mating objects to two (or more) surfaces simultaneously. This is an area we plan to investigate in future work.

Conclusion

We presented a new multi-touch 3D rotation technique based on mating to accelerate common tasks. It is targeted at one-handed touchscreen use, especially on tablets. Our user study revealed that the new technique improves manipulation times by more than 60% for common 3D rotation tasks. Rotation accuracy is significantly improved as well. In the future, we plan to investigate the performance of this mating technique for full 6 DOF manipulation tasks.

Fig. 1 .

 1 Fig. 1. The original orientation is shown in panel A. The user seeks to mate the seat of the chair from the left to the stone ledge on the right. Panel B illustrates the result of mating without preventing collisions. Such an operation leaves the chair in a confusing position, where the plane of the seat of the chair is parallel with the plane of the stone. However, the chair interpenetrates the floor. Panel C demonstrates mating with our collision resolution.The plane of the chair seat is still parallel with the stone surface. Yet, the chair has been "raised" so that it is in a collision free position.

  below.

Fig. 4 .

 4 Fig. 4. The initial scene before performing a mating operation. By taping the Shepard-Metzler object at the location indicated by the red dot, and then taping elsewhere in the scene, say the green dot on the right hand side, the object is simultaneously rotated and translated (i.e. mated) onto the new surface. The final position is illustrated in Figure 5 below.

Fig. 5 .

 5 Fig. 5. Final position of the Shepard-Metzler object after the mating operation.

  below.

Fig. 6 .

 6 Fig. 6. In this example the Shepard-Metzler object is mated with the wooden floor to the left. If the user taps the object at the red dot and then taps the floor at the green dot, a naïve mating operation would result in the circled yellow part of the object disappearing into the wooden floor.

Fig. 7 .

 7 Fig. 7. The final position of the object in the scenario of Figure 6. The object has been pushedupwards, so that no parts interpenetrate the floor.

Fig. 9 .

 9 Fig. 9. Mean completion times for study 1 with standard error shown.

http://m.autodesk.com/mobile/servlet/product?siteID=17221380&id=17774143 This website is accurate and available as of January

th , 2013


Shota Yamanaka

Homei Miyashita

Switchback Cursor: mouse cursor operation for overlapped windowing

Keywords: Cursor, Graphical user interfaces (GUIs), Mouse, Pointer, WIMP

When we perform a task that involves opening a number of windows, we cannot access the objects behind them. Thus, we are forced to switch the foreground window frequently or to move it temporarily. In this paper, we propose a Switchback Cursor technique where the cursor can move underneath windows when the user presses both the left and right mouse buttons. We also discuss some of the advantages of our method and effective situations that may be suited to the Switchback Cursor.

Introduction

Numerous window manipulations are performed when we work on a PC running multiple windows, such as moving and resizing. Besides, we need to click background windows frequently to switch to foreground windows. These actions are performed simultaneously in our main task, such as application operation or file organizing, and we are sometimes required to perform many complicated window manipulations. These operations are required because there is a difference between the dimensions of the windows and the movement of the mouse cursor. In Fig. 1,(A) shows a 3D image of some overlapping windows, where (B) represents the picture that we normally view on the PC. The windows are distributed in 3D but the cursor can only move in 2D. Thus, the background windows can only come to the foreground if we click on them or use a keyboard command to control them.

In our novel approach, called Switchback Cursor, the mouse cursor can move underneath windows by hitting them (it does not move freely in 3D). When a user holds both the left and the right mouse buttons, the cursor moves from the edge of a window to the background, so that it can control the objects there. Fig. 2 shows how the cursor moves underneath windows using our proposed technique. A movie showing the behavior of the Switchback Cursor can be viewed at [START_REF]Switchback Cursor movie[END_REF]. Fig. 2. The cursor moves progressively deeper after hitting successive windows.

Related Work

Many techniques have been developed to address the problems of overlapping windows. Free-space Transparency (FST) [START_REF] Ishak | Interacting with Hidden Content Using Content-Aware Free-Space Transparency[END_REF] allows the free space in a window to become transparent so users can see through the objects behind the foreground window. This also allows us to perform basic interactions such as drag-and-drop and clicking icons using the white region in a window, which is similar to our proposed system. In the stack leafing technique [START_REF] Faure | Power tools for copying and moving: useful stuff for your desktop[END_REF], a mouse button is pressed and the foreground windows on the same layer switch to another layer by dragging. In QuickSpace [START_REF] Hutchings | QuickSpace: New operations for the desktop metaphor[END_REF], a user moves a window and it pushes friend-registered windows so they are not overlapped. Beaudouin-Lafon proposed a technique [START_REF] Beaudouin-Lafon | Novel interaction techniques for overlapping windows[END_REF] that allows some window manipulations such as tabbed windows and peeled-back windows. The tabbed windows technique has now been implemented in Google Chrome and this method is used widely to solve the overlapped windows problem. Metisse [START_REF] Chapuis | Metisse is not a 3D desktop![END_REF] is a windows management system that allows users to rotate windows in 2D and 3D, so the windows can be allocated without overlapping to use the desktop space efficiently. WindowScape [START_REF] Tashman | WindowScape: Lessons learned from a task-centric window manager[END_REF] addresses rearranging windows problem by photograph metaphor. Screenshots are stocked each time windows are miniaturized, and when the user selects one of the shots, WindowScape automatically allocates the windows state. Some systems have been developed that allow the cursor to adopt irregular behaviors and their goal is mainly to make the mouse operation more efficient. Bubble Cursor [START_REF] Grossman | The Bubble Cursor: Enhancing target acquisition by dynamic resizing of the cursor's activation area[END_REF] is a round-shaped cursor that extends the pointing range from one dot to a large circle, which reduces the movement distance. Dynaspot [START_REF] Chapuis | DynaSpot: Speed-Dependent Area Cursor[END_REF] enhances the size of the cursor area, depending on the cursor movement speed. When the cursor moves rapidly, the selection area becomes larger to increase the accuracy. However, area cursor methods such as Bubble Cursor and Dynaspot make it difficult to point when the targets lay side-by-side, but like our Switchback Cursor, these two techniques also allow movement into inaccessible areas using traditional techniques and clip manipulation. Delphian Desktop [START_REF] Asano | Predictive interaction using the Delphian Desktop[END_REF] moves the cursor to the target object immediately, while Drag-and-Pop [START_REF] Baudisch | Drag-and-Pop and Drag-and-Pick: techniques for accessing remote screen content on touch-and pen-operated systems[END_REF] is a technique that allows the target object to travel to the cursor. These methods reduce the mouse manipulation time in a direct manner by allowing the targets or the cursor to warp. Ninja Cursors [START_REF] Kobayashi | Ninja Cursors: Using Multiple Cursors to Assist Target Acquisition on Large Screens[END_REF] uses multiple pointers and the user operates them all, i.e., the user only moves the cursor nearest the target object. The double mouse system [START_REF] Nakamura | Design and Implementation of the Double Mouse System for a Window Environment[END_REF] operates two cursors using two mice with one in each hand, which has the same effect as Ninja Cursors in reducing the manipulation time by operating a convenient cursor. Semantic Pointing [START_REF] Blanch | Semantic pointing: improving target acquisition with control-display ratio adaptation[END_REF] allows the cursor to speed up when it is further from a target by estimating the object that the user wants to select. MAGIC [START_REF] Zhai | Manual And Gaze Input Cascaded (MAGIC) Pointing[END_REF] makes the cursor jump to near the gaze-point using an eye tracker. This technique exploits the tendency to look at a target first before moving the cursor there. Fold-and-drop [START_REF] Dragicevic | Combining Crossing-Based and Paper-Based Interaction Paradigms for Dragging and Dropping Between Overlapping Windows[END_REF] allows items to be drag-and-dropped into the back window by turning over the windows like papers. This limits the manipulations using drag-and-drop but the user can search folders in the windows and run an icon on the desktop with the Switchback Cursor.

3

The Problem

When we perform our main task on a PC, it is often necessary to operate a number of windows, which are associated with the main task. However, a problem arises from the difference between the dimensionality of the windows and that of the cursor.

Windows are set in depth layers from the front to back where the layers are structured in 3D. However, the cursor can only move in 2D. Thus, we cannot control objects hidden by windows and we have to click on a background window to perform our intended manipulation. This is a typical problem of the overlapping window system. A tiling window system does not have this problem, but it has bad visibility due to the small size of the windows so it is used less widely than the overlapping system.

There is also the problem with window focus, which refers to a window that receives inputs from the keyboard and mouse. A focused state is referred to as "the active window." In Windows7, a clicked window is focused (focus follows click; FFC). However, the active window comes forward and the foreground window becomes hidden. This does not cause a problem when we begin another task but if we only want to access a background object briefly it is necessary to switch the foreground window a number of times. Another approach to window focusing depends on the position of the mouse cursor (focus follows mouse; FFM). However, the active window can be changed accidentally if the mouse is moved carelessly, so this approach has not been adopted by the Windows OS or the Mac OS. Thus, the general window viewing method and mouse cursor manipulation cause problems. This is a major problem because unnecessary window operations are required when controlling background objects using the overlapping window approach. Therefore, we can make mouse operation more comfortable by solving these two problems, i.e., the cursor cannot reach objects behind windows so we are forced to switch the foreground window many times in an FFC environment.

Switchback Cursor

We developed our system for Windows7. The system obtains windows information such as the handler, position, size, window style, and z-order and monitors these parameters. When a user presses both mouse buttons, the cursor moves to the same layer as the window beneath it. For example, Fig. 2 shows that a user moves the cursor from its initial position to a position above window 1 and presses both buttons, so the cursor moves to the layer of window 1. If the user keeps pressing both buttons and moving the cursor to the left, it moves underneath window 0. In the same way, the cursor can move to progressively deeper layers by hitting successive windows.

When a user presses both buttons, the windows in front of the cursor are set as the topmost window, which become semi-transparent so the objects can be seen underneath them, and these windows are set through mouse actions. Subsequently, mouse actions such as click and drag are not received by the windows in front of the cursor and the actions are received by the window beneath the cursor. If the window receives a mouse signal, the order of the windows in front of the cursor is not changed because the front windows are set as the topmost windows. A transparency setting of 0% (where the windows are completely transparent) is discouraged because the user cannot perceive the position and shape of the windows, but this parameter can be changed by the user.

When both buttons are not pressed, the cursor aims to move to the front side but it hits the window above itself and remains in the layer behind the window. For example, in Fig. 2, a user releases the mouse button(s) when the cursor is underneath window 0, it remains behind window 0. If the cursor is returned from window 0 without pressing at least one button, it moves to the foreground and dissolves the topmost setting of window 0.

When a user presses both buttons, the cursor size becomes 15% smaller as it moves to a window. When the cursor is around a window while pressing both buttons, the angle of the cursor changes so the user can see the direction where it is going as it moves beneath a window. When the cursor moves to a rear layer, a metallic sound rings to indicate that it has hit a window.

When the maximum-sized windows are open, they become slightly smaller (40 pixels less from each edge) while pressing both buttons so the cursor can move underneath them, as shown in Fig. 3. Further, when a window hides one or more windows, the background windows slide slightly to produce a small gap (30 pixels), as shown in Fig. 4. The windows hidden by a front window (same size and same position, or completely covered) move to produce a gap when both buttons are pressed so that the cursor moves to their layers. The cursor cannot move under two window layers if not pressing both buttons. When pressing both buttons, the covered windows move so that the cursor can reach their layers.

Advantages and Effective Situations

In our proposed approach, the cursor moves from the foreground to the target window so the cursor moves in three dimensions within the display. A number of 3D mouse or 3D desktop systems have been developed in the past but in most cases the cursor moves in the Z direction freely and a special device or GUI is required for 3D input. Unlike these systems, the cursor moves backward in our approach but it hits a window and stays there. No special devices are needed and only a normal mouse with left and right buttons is used.

We do not suggest that users employ our technique alone instead of traditional window switching. If he/she uses another application for a while, it is better to switch the foreground window; if a keyboard shortcut is suitable, it is preferable that the user performs keyboard operations. However, in situations where these manipulations become cumbersome and our technique provides a better alternative, users might prefer to use our technique. Therefore, we developed this system for use in a traditional GUI environment so the user can invoke this technique anytime by pressing both buttons, depending on the situation. Our system has high compatibility with modern overlapping windows settings and it does not block existing manipulations. In the subsections below, we describe some scenarios that may be suited to our technique.

A Window Hides Other Windows when Switching the Foreground Window

Fig. 5 shows a situation where a person is browsing the web while listening to music. If we want to listen to a different piece of music, as shown in Fig. 5, we normally click on the background folder to switch to the foreground and drag-anddrop a file onto the music player (or double-click it). The browser then becomes hidden partly by the folder so we have to click the browser again to switch to the foreground to return to our browsing task. An alternative is to arrange the windows so they do not overlap one another, but the process is complicated in both cases. With the Switchback Cursor, we simply allow the cursor to reach the background of the browser and drag-and-drop the file so we do not need to click on the folder or the browser multiple times to switch to the foreground window.

5.2

Double-clicking an Icon on the Desktop

In Fig. 6, the top screenshot and the illustration show a situation where several windows are open. If we want to double-click on an icon on the desktop to run an application or open a file, we would typically minimize all of the windows using the command Show Desktop shortcut, or move them out of the way and then double-click on the target icon. We would also have to reconstruct the original window layout to return to our former task, which increases the number of operation steps. By contrast, our technique requires no window manipulations because the cursor moves directly to the desktop and double-clicks on the icon, as shown at the bottom of the screenshot and in the illustration in Fig. 6.

Conclusion

In this paper, we described the two problems of overlapping window systems: the difference in dimensions between the cursor and the windows, and the high number of manipulations required to switch foreground windows. To address these problems, we proposed the Switchback Cursor technique, which allows the cursor to move underneath the windows. We discussed the advantages of this methods and situations where using our method might prove effective. In our future work, we would like to test and verify the effectiveness of our technique by some tasks, such as moving icons within folders that exist in various layers. And we also plan to evaluate the limitation of Switchback Cursor; not only performance time and error rate but also the visibility of layers beneath the overlapped windows, and the window layout that makes the cursor hard to go underneath.

Fig. 1 .

 1 Fig. 1. (A): Observing overlapping windows from different perspectives. (B): The normal view of windows and the cursor on a PC. (C): The windows are piled up on the desktop and the cursor is always on the top.

Fig. 3 .

 3 Fig. 3. A maximized window(s) becomes slightly smaller when both mouse buttons are pressed. The red circles indicate cursor positions. The left screenshot shows a maximized window while the images on the right show the left images from a location rotated to 90°, as shown in Fig. 1 (C). The cursor can reach the desktop icon while both buttons are pressed.

Fig. 4 .

 4 Fig.4. The windows hidden by a front window (same size and same position, or completely covered) move to produce a gap when both buttons are pressed so that the cursor moves to their layers. The cursor cannot move under two window layers if not pressing both buttons. When pressing both buttons, the covered windows move so that the cursor can reach their layers.

Fig. 5 .

 5 Fig. 5. Web browsing while listening to music.

Fig. 6 .

 6 Fig. 6. The cursor moves underneath the windows and reaches the target icon on the desktop. The red circles indicate cursor positions. Some windows are pile up in the left screenshots while the images on the right show the left pictures from a location rotated by 90°. The user simply needs to press both buttons and move the cursor to the desktop before double-clicking the icon, without any window manipulations.


Nahid Wakil
email: nahidwakil06@hotmail.com

Peter Dalsgaard
email: dalsgaard@cavi.au.dk

A Scandinavian Approach to Designing with Children in a Developing Country -Exploring the Applicability of Participatory Methods

Keywords: Participatory Design, Developing Countries, Interaction Design, Future Workshop, Inspiration Card Workshop, Mock-ups

Participatory Design (PD) offers a democratic approach to design by creating a platform for active end-user participation in the design process. Since its emergence, the field of PD has been shaped by the Scandinavian context, in which many early PD projects took place. In this paper we discuss the challenges that arise from employing participatory methods in a different socio-cultural setting with participants who have had comparatively limited exposure to digital technologies. We offer a comparative study of two PD projects carried out with school classes in Scandinavia and India. While the setup for the two projects was identical, they unfolded in very different ways. We present and discuss this study, which leads us to conclude that PD can be a useful approach in both settings, but that there is a distinct difference as to which methods bring about fruitful results. The most prominent difference is the ways in which abstract and manifest participatory methods led to different outcomes in the two settings.

Introduction

In this paper, we address the Interact 2013 theme of 'Designing for Diversity' by examining how methods and techniques from Participatory Design (PD) translate from the setting in which they emerged, Scandinavia, to a rather different setting, namely an impoverished district in New Delhi, India. The aim of this work is to examine the role of PD and the challenges that arise from employing participatory methods in developing countries where access to and knowledge about technology and digital artifacts is yet relatively limited. As interaction designers increasingly work on projects outside of the settings in which participatory methods emerged and evolved, we find it pertinent to study if and how we can employ well known PD methods in new domains. Our work builds on the assumption that some methods may be employed more or less in their original format and setup, whereas other methods may need revision; some existing methods may prove of little or no use, while we may need to de-velop new methods to address issues at hand in new settings. Our work furthermore examines an assumption that we have encountered in various forums, namely that a relative lack of technological knowledge may limit the extent to which user can take part in shaping an interaction design process. In order to examine and challenge these assumptions, we have carried out a comparative study of two design projects with school children aged 12-19, one in India and one in Scandinavia. The setup and framing for the two projects was identical and consisted of employing three established PD methods: 1) a Future Workshop [START_REF] Kensing | Generating Visions: Future Workshops and Metaphorical Design[END_REF][START_REF] Vidal | The Future Workshop, Creative and Participative Problem Solving[END_REF]] 2) an Inspiration Card Workshop [START_REF] Halskov | Inspiration Card Workshops[END_REF]] and 3) a Mock-up session [START_REF] Ehn | Cardboard Computers: Mocking-It-Up or Hands-On the Future[END_REF]] to test, evaluate and develop the product. Since it is a single study, we focus on the specific findings; further studies are required to examine and develop more generalizable claims. The contributions of this paper are two-fold. Firstly, we offer a comparative case study using the same methods within the same topic and frames in two design projects in very different domains, which in itself is rare in the field of HCI. Secondly, our analysis of the cases lead us to propose that the concept of abstract and manifest methods for user involvement can help practitioners select, frame and employ methods well-suited for the domain they work in. [2011] have examined the potential contributions of PD through a case study of a participatory development project in Bangladesh, pointing out the need to further explore the potentials of PD in this region. [START_REF] Banaji | Beyond Wild Dreams and High-Tech Fetishes: Learning about Media from Children in the Global South. Keynote address[END_REF] offers a harsh critique of current IT projects in the global south by stating that many of them are "painfully ignorant of the everyday realities" in these domains. Our work can be seen as a response to these concerns, in that we study the commonalities and differences in employing PD in design projects in Scandinavia and South Asia.

Examining the origins and development of PD, [START_REF] Gregory | Scandinavian Approaches to Participatory Design[END_REF] identifies three characteristics particular to Scandinavian PD: a deep commitment to democratisation, discussions of values in design and imagined futures, and the use of conflict and contraditions as resources for design. PD seeks to create a platform for active end-user participation in the design process, although there is not a fully formed consensus as to the scope and consequences of involving users. While some argue that users can serve as sources of inspiration for designers [START_REF] Christiansen | Selecting and evoking innovators: combining democracy and creativity[END_REF], other contributions advocate a stronger role for users in design decisions. [START_REF] Kensing | The Trade Unions Influence on Technological Change[END_REF] argues that there are three fundamental conditions of user participation in PD: access to relevant information, the possibility for taking an independent position on the problems and participation in decision making [START_REF] Kensing | The Trade Unions Influence on Technological Change[END_REF]. These conditions emphasize an active engagement with end users, which have informed our studies in this paper. Muller [2002] argues that successful PD methods bring about a 'third space', a shared conceptual space in between designers' and users' respective domains, in which potential futures can be explored, developed and examined in collaboration. In the work presented here, we have built on these insights to establish what we label direct user involvement, based on the criteria that users should be involved in early stages of a project and take part in defining problems and visions as well as ongoing design decisions.

Case study: Participatory Workshops in India and Scandinavia

In order to examine the applicability of participatory methods, we carried out two design projects with identical setups and framing. The first project took place in New Delhi, India, while the second project took place in Aarhus, Denmark. Here we present the setup of the design projects and the findings from India and Scandinavia, respectively.

Setting up the design projects

We set up agreements with two schools to carry out a week-long design project with primary school pupils aged 12-19 1 . Each project was introduced and framed in the same way in order for us to examine the differentiation in use of participatory methods in a developing country and a Scandinavian country. The workshops were held in the children's classrooms in their respective schools and the theme for the workshops in both India and Scandinavia was how technology can be used to improve everyday life? We employed three established participatory methods to involve the users from the very beginning of the design project: Future Workshop [START_REF] Banaji | Beyond Wild Dreams and High-Tech Fetishes: Learning about Media from Children in the Global South. Keynote address[END_REF] to define problems in the current situation, Inspiration Card Workshop [START_REF] Christiansen | Selecting and evoking innovators: combining democracy and creativity[END_REF] which was employed to develop ideas on how problems can be solved using inspiration materials and mock-up sessions [START_REF] Dalsgaard | Designing for participation in public knowledge institutions[END_REF] to test, evaluate and develop the product. In order to maintain the children's attention in the workshops, they were introduced to one phase at a time. And to maintain equal frames in both domains the teachers were present during all events. The children worked in groups and every group was asked to choose a spokesperson for the presentations after each stage. All events were documented in recordings and extensive field notes which were subsequently codified, condensated and analyzed.

Findings from the workshops in India

Starting with the critique phase in the Future Workshop the children were asked to brainstorm over the problems they meet in their everyday lives. As the children only wrote down a few words within the given time, an ongoing adjustment of the estimated time became necessary. They were confused and uncomfortable with the situation. The children then were asked to write down at least five problems in the next five minutes. The time pressure made them work effectively but at the same time they needed to be confirmed that what they wrote down were "real" problems.

In the following fantasy phase each group were asked to choose 2-3 problems to discuss and solve using technology. In the presentations the children mentioned the opposites of the problems as solutions; e.g. the problem "mathematics" was solved by not having the subject at all. And the problem "being pushed in the bus" was solved by "not having many people in the buses". The setup did not lead them to use their imagination to solve the problems, resulting in breakdowns in the ideation process. However, due to limited time we decided to move on to the next phase. In the Inspiration Card Workshop the children were introduced to the inspirational material in the form of inspiration cards and digital products such as cell phones, disc-players, iPods, calculators, CDs etc. The inspiration cards ended up in a row and were not moved any further. None of the groups combined the cards or developed their own cards. The blank cards, however, were used to write the definitive "answer" on. No new concept or idea was presented and the workshop resulted in seven already existing concepts directly copied from the inspirational material; the "mathematics" problem was solved by using a calculator and the "feeling alone" problem was solved by "talking on the phone with friends" etc.

Since some of the groups had expressed a desire for a cleaner city, we chose to work with the concept "Cleaning machine". The final concept was a trash can with a coin system, inspired by deposit systems. We developed a basic mock-up, which was first tested through plays and then evaluated and developed in a second workshop. To simulate an outdoor environment garbage was thrown on the classroom floor. The scene was presented to the children but the coin function was not mentioned, as we wanted to avoid predetermining the test. The children could buy chips and rice cakes on paper plates with paper coins in the shop. The trash can was located close to the shop and the teacher had written "trash" on the trash can in Hindi. Two children acted as salesmen and one boy was responsible for the trash can coin system. The rest of the class lined up in front of the shop and none of them noticed the garbage on the floor. Once the coin system was discovered all of the children wanted to get rid of their paper plates.

After the mock-up test the groups discussed what they liked and disliked about the trash can and how they could improve it. Although the groups still had the same spokesperson it was not easy for them to present their ideas. They were careful about saying anything "wrong" or "negative" about the trash can. Instead we asked them to draw a trash can using their imagination. Surprisingly, this gave very good results indeed. The children were creative and imaginative and used technology as a part of the solution. They improved the functionality, suggested a better way to interact with the trash can, mentioned the social aspect of how to get people wanting to use the trash can, suggested a better visual appearance, mentioned health problems that garbage can cause and how it could be solved and not least they considered the eco system to create power for robotic trash cans. Their independent input showed an understanding of the concept the mock-up has presented through a variety of creative ideas.

Findings from the workshops in Scandinavia

In the critique phase the Danish children easily wrote down many things that they would like to change. This phase proceeded as expected and due to limited time the children presented only selected problems. In the fantasy phase the groups chose 2-3 problems to discuss and solve using their imagination and technology. The presented ideas were creative and imaginative and in the presentations the group discussed the presented concepts and ideas by asking each other question.

In the Inspiration Card Workshop the inspiration cards were used actively and the children also made their own cards. Few were inspired by the digital products and used sound as a part of the solution. In the presentations the groups defended their own ideas as the best. They had concrete scenarios in mind and were precise about the concept details. They were very specific in the choice of technology and it was obvious that they drew on their own experiences in the development of new concepts. The workshop resulted in five new creative concepts and the final product was a "memory box" based on the children's wish of an easier teenage life. The memory box had a scanning system to help the teenager remember things by placing her bag or wallet inside the box.

In the second workshop, the mock-up session, the memory box was tested, evaluated and to a certain limit improved. Three children were controlling the memory box by switching out the screens, changing the buttons to the right color and controlling the sound, which was played on an iPhone. One played the role of a busy teenager using the memory box while the rest of the class watched the play. After the mock-up test the groups were asked to answer a number of questions about how the memory box could be improved. Although the groups made a number of suggestions, the new memory boxes resembled the mock-up and had roughly the same functions and features. Many of the groups were locked into the idea of a square box with its already existing functions. One group made an egg shaped box and another came up with the idea of a camera function while the rest of the improvements referred to the box color.

Discussion

While both design projects led to interesting results and can be considered successful in bringing about new concepts through direct user participation, the ways in which the pupils arrived at them differed substantially. In the following, we compare the projects and introduce the notion of abstract and manifest design methods in order to account for these differences and discuss the applicability of participatory methods across different socio-cultural settings.

4.1

Comparing the design projects in India and Scandinavia

The first stages of the design process in India were problematic. The pupils were reluctant to engage in the design activities and were cautious in discussing events. They had trouble articulating problems and design opportunities, leading to breakdowns. This required ongoing adjustments and interventions from the facilitator in order to keep the process going. The two workshops were characterized by limited creative output and independent proposals. However, the mock-up session really turned things around, spurring creativity and out of the box thinking that also led them to revisit aspects that had been troubling in earlier stages. It was only in this stage that a true 'third space' was established. In the Scandinavian design project, things unfolded in almost the exact opposite way. The pupils were initially open towards the project and eager to discuss both the general project and the specific events. In both workshops, they also worked effectively and imaginatively and put forward new ideas and proposals. In many ways, these workshops unfolded, as we would expect on the basis of previous experience and accounts in literature. However, the relative level of creative output waned in the mock-up session. The ideas put forward resembled the existing one, and the proposals for changes were superficial. Table 1 summarizes the projects. Comparing the two projects, the loose and open structure of the first two workshops seemed to limit the engagement of the Indian pupils, whereas it was well received by the Scandinavian pupils. If we reconsider the aforementioned criteria for PD, it proved difficult to establish a productive session in spite of providing access to relevant information and allowing for the pupils to take an independent position on the problems and participation in decision making [Kensing 1993]. The Indian pupils conceived of the facilitator as an authoritative figure possessing the 'right answers' in the design project up until the mock-up session. The Scandinavian pupils, on the other hand, had no problems taking on the roles of position as co-creators in the initial phases, however they experienced design fixation when exposed to the mock-up.

Abstract and manifest methods for user participation

The contrast in how the two design projects in terms of active participation and creative output is quite striking. In light of our objective of understanding if and how tra-ditional PD methods can be employed in different domains, we have analyzed setup of the three PD methods in more detail. If we first consider the Future Workshop, it can be construed as being relatively abstract, in that it offers a loose framing in which the pupils' point of departure was their own situation and preconceptions. The Inspiration Card Workshop is also relatively abstract but with certain manifest properties, in that while it offers tangible representations of technologies and domain concerns but does not prescribe how they are to be combined; this relies on the pupils' preconceptions. Finally, the mock-up sessions can be defined as manifest, in that they offer a concrete artifact that brings the potential technology to life in a tangible form. In the two projects, we thus find a clear correlation between the abstract and manifest properties of the methods and the perceived creative output from the pupils (see Figure 1).

Fig. 1. Correlation between creative output and abstract/manifest properties of the PD methods

If we seek to understand why this correlation occurs, at least two prominent factors come into play: a) the Scandinavian pupils were accustomed to project-based group work, whereas the framing of school work for the Indian pupils was more traditional and rule-bound; b) the Scandinavian pupils were very familiar with interactive technologies and used them throughout their day, whereas the Indian pupils had relatively limited knowledge of them. Taken together, this indicates that if a design project is oriented towards technological solutions and the technological knowledge among participants is limited, the abstract representations offered in the traditional setup of the Future Workshops and Inspiration Card Workshops, which typically work well in Scandinavian settings, may not be sufficient to facilitate active participation. This is compounded if participants are not accustomed to the open and project-oriented format of the methods. On the other hand, the mock-up session as a manifest method was more productive by offering hands-on experiences and prompting participants to explore potential futures through construction.

Conclusions and future work: Applicability of participatory methods across different socio-cultural settings

Our findings from the comparative case studies lead us to argue that PD can indeed be a useful approach in a domain that differs substantially from the Scandinavian setting in which the field emerged. However, it is also clear from our findings that existing methods cannot be expected to yield the same outcomes across domains, to the extent that some methods may not be advisable for use in their current form. While a multitude of factors affect the outcome of a design projectmany of which are beyond the scope of a short paper to address or even introducewe suggest that the concept of abstract and manifest methods can enrich our understanding of the outcomes of user participation. Abstract methods rely on preconceptions and imagination and limited use of materials. Manifest methods involve the use of materials and artifacts as the basis for inspiration and creativity. We speculate that many of existing methods that rely on abstract components may need to be revised if they are to be useful in radically new domains. Encouraged by the success of the mock-up session in the New Delhi case, we suggest that manifest methods may be a good starting point for participatory projects or events, and that researchers and practitioners consider developing new methods for user participation with manifest properties.

Concerning the validity and generalizability of the findings, our work relies on one comparative case study, and we most definitely need more studies and reports from PD practitioners in order to challenge, corroborate and expand upon these findings. We hope to explore these issues in future studies and invite our colleagues in the Interact community to take part.

2 Background and related work: beyond the Scandinavian heritage of Participatory Design

Participatory Design (PD) as a field is concerned with user involvement and decision making in the development of new technologies, in which "[…] the people destined to use the system play a critical role in designing it." [Schuler & Namioka p. xi] Originating in Scandinavia in the 1980s, PD methods and approaches have since found widespread use, most notably in Europe and North America. The participatory agenda has also to some extent inspired systems and services thatrely upon participation in use

[START_REF] Dalsgaard | Designing for participation in public knowledge institutions[END_REF]

. While methods and approaches inspired by PD have found an uptake outside of Scandinavia, there are few studies of how these methods translate to other settings. Recently, Zander, Georgsen & Nyvang

Table 1 .

 1 Summary of the design projects in India and Scandinavia

		India	Scandinavia
	General attitude	Reluctant, cautious	Open, relaxed
		No discussions	Eager to discuss
	Future Workshop	Three breakdowns	No breakdowns
		More time required	Work effectively on the tasks
	Inspiration Card	Limited creativity	Good ideas
	Workshop	Limited independent proposals	Creative, imaginative
	Mock-up	Creative, imaginative	Design fixation
		Active out of the box thinking	Limited creative proposals

In the Scandinavian case, the school groups pupils in classes based on age, whereas the Indian school groups pupils on the basis of competencies, hence the spread in age.