Proceedings of the 2009 13th International Conference on Computer Supported Cooperative Work in Design
Designing and Evaluating Interfaces for Mobile Groupware Systems Carla Diacui Medeiros Berkenbrock, Alexandre Parra Carneiro da Silva, Celso Massaki Hirata Instituto Tecnol´ogico de Aeron´autica - ITA, Department of Computer Science, Brazil
[email protected],
[email protected],
[email protected]
Abstract
size means that systems must present only the most important features to display [5]. The system usability is related to efficiency and satisfaction of users’ needs. The system usability is concerned to the development of a mobile groupware system with efficiency and satisfaction in a specified context of use. Usable systems should neither demotivate users nor compromise the cooperative activities. Therefore, it is important to investigate and provide mechanisms to improve the mobile groupware usability. Mobile groups may use either centralized or decentralized information resources, may be technologically connected or disconnected, and may be engaged in synchronous or asynchronous work. Another key issue in cooperative application is awareness. Awareness is a feeling of illusion through which participants in a cooperative system can sense the presence of others and their movements by sharing a workspace [4]. Maintaining awareness of the users working context is crucial to successful cooperation. Therefore mobile cooperation systems can have diverse cooperation requirements. This variety makes difficult to define which design technique works best for a mobile groupware. In our research we investigate a set of features that can be considered in any mobile cooperative scenario. In this paper we present a set of approaches for user interface design and requirements verification that can help developers to improve usability in the development of mobile groupware systems. We also mention some impact of screen size on awareness. The remainder of the paper is organized as follows. Section 2 presents an overview of the related work. Section 3 describes techniques for improving the efficient use of small screen space. Section 4 describes evaluation usability approaches that are proposed to analyze mobile groupware scenarios. Section 5 presents our preliminary experiments. Finally, in Section 6 we present some conclusions and we discuss future work.
Mobile cooperative systems can facilitate cooperation by improving the flexibility of usage. However, mobile devices present some constraints that become the design and implementation of groupware systems harder. Additionally, there is a lack of general interface requirements definition and verification techniques for supporting the development of effective mobile groupware systems. This lack makes it more difficult to develop usable mobile groupware systems. In order to address some of these issues, we present a set of approaches for user interface design and requirements verification that can be used during the elaboration phase in the development of mobile cooperative applications.
1
Introduction
Groupware systems are generally defined as software that allows the creation of cooperative work. The emergence of mobile devices and rapid evolution of wireless communication have created new opportunities for cooperation. As a result, mobile groupware can be an interesting alternative to exploit the anytime and anywhere computing paradigm. Designing groupware systems to include mobile devices can offer great challenges of development. However, little research has been spent in designing and evaluating mobile groupware to help developers to improve the system usability. The main issues include small screen, system usability and collaboration issues. Rekimoto reports in [17] that the most significant difference between personal computers (PCs) and handheld computers is not the computation power, but the size of the screen. This statement still holds nowadays. Small screens make basic tasks such as reading, navigating and selecting operations more difficult in comparison to a large screen. Additionally, straightforward approaches for developing mobile groupware, such as simply applying groupware systems design techniques for desktop computers on handheld computers, fail due to the different nature of mobile devices and wireless networks [18]. The reduced screen
2
Related Work
There are several empirical studies reporting the use of mobile cooperative applications [1, 12, 16]. However, they
978-1-4244-3535-7/09/$25.00 ©2009 IEEE
368
generally consider few and informal aspects to guide the design and evaluation of mobile groupware applications. This situation occurs because the general requirements to support mobile collaboration are still unclear [8]. Some authors have studied the requirements involved in mobile cooperation. Messeguer et al. [15] present a list of design patterns to support communication and coordination, but the study is focused only in mobile ad-hoc scenarios. Herskovic et al. [8] present a framework that specifies a list of general requirements to be considered during the design of mobile shared workspaces. However, their study neither addresses the limitations of small screen devices nor mentions how the proposed requirements can be met. Berkenbrock and Hirata [3] describe a mobile cooperative application design and analyze how aspects of intermittent connectivity, battery life, screen size, and operational system affect the cooperative activities. They point out that the limited interface affects both awareness information and system performance. The limitations were only identified due to the development of a cooperative application in a real mobile scenario. The aim of their study is to examine how the limitations of mobile devices affect the effectiveness of a synchronous mobile cooperative application. Furthermore they also point out that there is a lack of design techniques and usability guidelines for evaluating these mobile groupware systems.
3
we describe four types of menu for designers to draw primary controls in mobile graphical user interfaces. These descriptions highlight the main characteristics and point out the main scenarios for employing them. Marking menus: A marking menu is designed to allow a user to perform a menu selection by either popping-up a radial (or pie) menu, or by making a straight mark in the direction of the desired menu item without popping-up the menu [13]. Marking menus are designed to overcome problems that affect the usability of systems when using accelerator keys or keyboard shortcuts. The research reported in [13] shows that using a mark was on average 3.5 times faster than selection using a menu. In this way, the delays for visualizing of the awareness information updates can be minimized. Adaptive menus: They are constructed based on simplified user model. The model simulates how a user interacts with the menu system and maintains the knowledge of the user’s usage patterns. This type of menu is indicated for mobile applications with its complex rules and highly active interactions context such as games, as investigated in [10]. According to the study and analysis drove in [10], we can have the following conclusions: (i) by making the menu structure flexible and customizable to ever changing conform changes in own awareness information it is able to reduce the menu size and provide faster access to commands and activities of complex applications, (ii) the adaptive structure of the navigation lets an application react quickly and clearly to the user and his decisions, and (iii) by using menu structure based on awareness information to make able to introduce a way to teach functionality and cooperation concepts within groupware systems, while keeping the complex rules and rich graphics that define these systems. Cascading or Hierarchical menus: It uses hierarchies to allow the navigation by the displaying of a sub-menu when an event, like holding a pen on the right hand side within a menu item, occurs. The two general approaches about hierarchical information visualization and navigation are not suitable for mobile devices without proper adaptation. Moreover, when both a desirable display structure and the maximum use of the display area are essential criteria, scaling down the traditional methods designed for desktop displays does not work well. Hao and Zhang in [7] described the technique RELT for visualizing hierarchical data on palm sized devices. RELT have three interesting aspects: (i) it maximizes the screen usage by recursively partitioning the display area, (ii) the non-overlapping regions are arranged in such a way that maintains the explicit hierarchical relationships and (iii) the visual field of hierarchical structure can be configured. With the help from a clear visual structure, people can easily locate where they are. Consequently, the navigation in hierarchical menus for searching
User Interface Design Approaches
The actual generation of mobile devices has higher contrast, easier read displays, and greater storage capacities. However, as foresaw in [11] the mobile devices continue limited by two constraining factors: (i) the dimensions of the displayed text and (ii) the screen on which text is displayed are unlikely to change very much. Reductions in the size of displayed text will be limited by the ability of users to discern small type of size on any display device. The development of mobile groupware interfaces must balance the need for fitting the cooperative objects in small screens and the need to keep these objects sufficiently large to be recognized by the user. Besides it must take into account awareness and performance that mobile groupware systems must address. Therefore some aspects that we present and discuss in this section are related not only to simple interfaces for mobile devices but also to interface requirements for mobile groupware systems.
3.1
Menu Type
Menus are one of the primary controls for issuing commands in graphical user interfaces. Designers must keep attention in organizing the items within each menu, especially on mobile devices with limited screen size. Below,
369
data becomes faster. In addition, it is possible to reserve a mobile device screen piece for showing awareness information. Fisheye menus: They are characterized by their ability to show all of the items in a single view, and by the presentation of the items near the cursor at full size while items further away from the cursor are displayed at a smaller size. The evaluations of fisheye menus let us to conclude that these menus are recommended for use where selection from a long list is required [2]. Another application of fisheye views is presented in [6]. In this research the authors described how fisheye views of shared workspaces can be used as a basis for supporting workspace awareness in groupware. The evaluation these workspace awareness fisheye views was executed on two prototype groupware systems. The result of experiments allows indicating that fisheye views are promising to help to maintain workspace awareness.
3.2
that contains awareness information becoming it opaque. In this way it will avoid unsuccessful cooperation.
3.3
Design Considerations
Users using small devices generally have patterns of collaboration different from users of conventional groupware systems. Thus, due to some mobile devices and environments characteristics mobile groupware requires differentiated design. Next, we list some important design issues to allow for more effectiveness and usability for mobile groupware applications. Hardware and network constraints: The design of mobile groupware system must consider hardware constraints such as device’s weight, screen’s size, resolution, processing power and input availability. Additionally, the design depends on the network resources, where it is necessary to consider that network links can vary significantly in terms of delay, bandwidth and error rate. Shared information availability: Due to frequent disconnections, copies of shared information can be kept in mobile devices in order to improve performance in wireless environments. The replication requirements must be considered for mobile groupware designers. Input methods: The possible methods of data input currently available include keyboard, penbased, touchscreens and voice. Generally, users need high level of visual attention to input new data. However, the input methods should be selected according to the mobile work requirements, for example, if the user needs to use both hands to develop his/her work thus it is important to provide a interface that requires a low level of visual attention during the cooperative work. Extensive scrolling: Because of the limited screen space on handheld devices, many applications use scrolling as a mechanism for accessing information that does not fit on the screen. However, the scroll of screen up and down can be annoying to users. Thus it is important to develop interfaces in a manner that helps avoiding scrolling. Navigation: Small screens can make even basic tasks such as navigation difficult. Then, it is important to select an adequate navigation structure to better present the information on display. It is also important to decrease the number of navigational steps to simplify the navigation required to execute a task by the users.
Interface Design
User interface designers increasingly face the challenge of designing effective interface for a shared context for mobile devices. In what follows we present some user interface design techniques that we believe that are attractive for mobile groupware applications. Flip zooming: This visualization technique allows the presentation of several objects and provides a moveable focus that lets the user select any object. When the object is focused, it receives more screen space so that more of the its content can be displayed. Gestural interfaces: In this technique the user can interact with the displayed content by drawing gestures over the screen with pen. This technique works well in many applications because it frees up valuable screen space. However, one of its limitations is that the user must learn the gestures and be able to reproduce them accurately. Preliminary experiments in [13] shows that gestures in marking menus can be until seven times faster than using linear menus. Eyes-free feedback: We believe that eyes-free feedback is useful in situations where a user’s visual attention must be on something other than the screen device, e.g., in situations where mobile users can not hold the mobile device. In this situation an audio or device vibration is seen as a vehicle for input and feedback of users’ action. Semi-transparent widgets: The objects on the screen are presented with different levels of transparency. So, this technique allows the presentation of several objects at the same time maximizing usable screen space. In [11] it is described techniques for maximizing usable screen space by combining delayed response with semi-transparency of control objects and on-screen text. However, in groupware applications it will be necessary to give priority to the layer
4
Verifying Usability
Usability is an important factor that affects a user’s productivity [14]. Groupware researchers believe that productivity can be improved and user satisfaction can be reached through collaboration. But it has been recognized that verifying and evaluating such claims is difficult [20]. The us-
370
ability is often neglected in the design and development of mobile groupware systems. Different mobile groupware applications result in different usability expectations and usage patterns. The benefit of metrics is the possibility to evaluate how interface requirements can be met, and how to compare and improve usability in mobile cooperative systems. In Table 1 we suggest a set metrics for verifying usability in the development of mobile groupware systems. We claim that most of the metrics can be used in the elaboration phase, more specifically in the design workflow. Table 1. Summary of quantitative metrics I II III IV V VI VII VIII IX
total of awareness aspects identified total of operations (clicked) in each task total of interruptions in each task percentage of activity accuracy average lost time in each task average time to reflect user’s actions average time to understand a pre-determined task average time to complete a pre-determined task average time between user’s request and screen update
We formulated three categories of usability requirements for mobile groupware systems: awareness, interaction and user analysis. In what follows we present a set of requirements for each category and we suggest which metrics presented in Table 1 can be used for evaluating these requirements. These requirements were obtained based on our experiences on developing cooperative applications.
4.1
Awareness
As it was mentioned, awareness is generally relevant for the user of mobile groupware systems, however, considering that mobile users work under resource constraints the information delivered to a mobile device should be restricted so that just the awareness relevant information is passed to the users. In what follows, we list some general awareness requirements and discuss what and how the metrics can be used. R1-Recognition: Tests can be made after or during the cooperation to analyze if the user is recognizing the awareness aspects presenting in the system. These tests can analyze if the user can identify the following aspects: who are the users participating in an activity, what are their location, what are their activities and which changes did they performed. The tests to evaluate awareness-recognition can use metric I. R2-Attention level: One major difference from desktop to handheld interaction is that the attention of users may be split between the mobile device and the real world surrounding them [9]. Using a mobile device, the users need to look at the keyboard or at the other input methods in order to be sure that the data is inputted correctly. Furthermore,
the attention level required to perform some task is related to the current context of the user. So, using mobile devices people are likely to be distracted from their main task by the work environment such as approach of people, traffic of cars, noise level, location and so on. Thus, the attention level can be measured by metrics III and V. R3-Consistency: Maintaining data consistency is one of the main functions and the major challenge in building a groupware system. The problem is increased in mobile groupware systems because when mobile users are involved, we have to deal with loose coupled systems and devices which are often disconnected, thus not accessible to others. In a mobile groupware, a lack of awareness can lead the user to perform inconsistent activities. Consistency can be measured by metric IV. This metric allows analyzing the percentage of activity accuracy after users complete a cooperative task.
4.2
Interaction
Effective interaction is essential to successful groupware. By interaction we mean the communication usersystem-user as well as the communication between usersystem. When designing interaction between mobile users it is generally necessary to consider weak interdependence between users and intermittent communication. R4-Feedback: The user needs perceiving the system state. The feedback can be obtained through visual or audio events. This feedback would allow the group members to take an appropriate course of action. So, the feedback can be measured by the time that user’s actions takes to be reflected to everyone interfaces (metric VI) and by analyzing if the users are able to understand the information provided by the interface (metrics I and VII). R5-Response time: Collaborative groups can vary significantly in terms of number of participants. The measure of system scalability is primarily interactive response time. Interaction between many users engaged in the same task tends to cause performance problem. Additionally, the mobile devices constraints increase interactive response time. We use for measuring the response time the interval between the user request and screen update in the mobile user (metric IX). R6-Management skill: A session manager typically controls and presents an interface to create new conferences, name, delete and locate existing conferences, find out who is in a conference, join users to conferences, allow people to leave them and so on. One of the obstacles in terms of usability to groupware use is the difficulty of start up a groupware session. More specifically in a mobile groupware, we need to simplify the steps to manage sessions allow that the tasks be made in an intuitive way. The management skill can be measured by metrics II and VIII.
371
4.3
User Analysis
The user is a critical factor in a mobile groupware system. Special attention should be paid in examining the users’ characteristics, such as age, gender, languages used, users’ degree of familiarity with mobile devices, and special needs or physical disabilities [19]. Another important criterion that has to be considered in a mobile groupware is the user satisfaction. This user analysis can be made through qualitative interviewing and questionnaires. However, it is important to evaluate some user aspects in terms of quantitative metrics. R7-Learnability: The mobile groupware should be easy for users to both learn and use the interface. The ease of learning to use the application can be used to measure the system learnability. In this way, a set of questions can be made to determine whether users can understand and operate the interface as well as to determine what the approximately time that users can learn to use the interface metrics VII and VIII. R8-Efficiency: The efficiency in task performance is related with the ease of use and the level of productivity attainable by the user. It can be measured by metrics IV and VIII.
5
Our Preliminary Experiments
A prototype application was developed in order to demonstrate some of the design approaches presented in this work. The goal of the collaborative application users is to produce a unique shared document. The document is divided in items where these items can be edited by users. Due to simplicity of implementation, the menu type considered for this application is the marking menu. A menu is displayed when the user holds a pen to the text “WelcomeCooperative Editor” for more than 1 second, then the user can select an item in this menu by pressing it. Additionally, we are adapting the application for providing eyes-free feedback. In this way, we intent to assign a different kind of beep to each of the following user action: user joing/leaving session, user starting/finishing changes. In order to improve performance, each mobile device receives a replica of the cooperative data to be stored locally. The input methods include both keyboard and penbased. Figure 1 shows two interfaces for presenting all data items that the user can initially work in the cooperative group. In the first interface (Figure 1-a) it is showed both the items titles and the full content of each item in a unique screen. In this situation, the users need to use extensive scrolling to see all the items that can be edited. In the second interface (Figure 1-b1/b2), the item content is divided into two screens. The first screen (Figure 1-b1) presents only the items titles. If the item is selected by the user, the
item content is presented in another screen (Figure 1-b2). Then the second interface helps avoiding scrolling, however, it increases the number of navigational steps because users need to select the item to see all of its content. Then it is important to identify the user requirements for establishing a tradeoff between scrolling and navigational steps necessaries to complete a task.
Figure 1. (a) The full item content is presented on a unique screen (b1/b2) Item content is divided into two screens
In our preliminary evaluation, we only use the metrics I, II, IV, VIII and IX. The results are based on the first interface (Figure 1-a). In what follows we summarize our results with respect to the proposed requirements. We identified two awareness aspects in our application for R1: (i) a lock status informing whether each item is being edited by another user and (ii) a notification report with information about the items that were updated. We found that R4 was partially supported by (ii), because this aspect provides a feedback about the data that was changed. However, it is necessary to improve the interface for providing more awareness-recognition and feedback aspects. Further work is needed to understand the impacts of R2 on development of mobile cooperative applications. In this first evaluation we identified that the complexity of keys mapping in the mobile devices impacts on a higher level of visual attention to input data. The percentage of activity accuracy was 80% (used to measure R3 and R8). On average, 2.4 clicks were required to complete operation of editing, deleting and inserting (used to measure R6). The average time to complete a pre-determined task was 38.3 seconds (used to measure R6, R7 and R8). The interval between the user request and screen update in the mobile user for an operation made by user was 3 seconds on average (used to measure R5). Considering a mobile cooperative environment, these preliminary results are considered acceptable. We intend analyze the remaining metrics and improve the requirements by participant observation. For example, through a videotape of cooperation the metrics III, V, VI and VII can be measured in future experiments.
372
6
Conclusions and Future Work
In this paper we present a set of approaches for user interface design and requirements verification that can help developers to improve usability in mobile groupware scenarios. The considerations about the design of interfaces are helpful because they provide some basis for the development of the mobile groupware systems. We believe that the requirements and some of the metrics can be incorporating before starting the implementation of mobile cooperative applications in order to provide a basis for design decisions. Work currently in progress addresses the examination of the designing and evaluating issues proposed in this paper through controlled experiments. So we intend to examine and expand our initial set of considerations in order to refine and improve the design and usability of mobile collaborative applications. We also aim to improve the awareness in our application including context information and information about running sessions. Further experiments will analyze several versions of the cooperative editor presented in this paper. In the versions it will be introduced other menu types that we believe that can improve the usability presented in our preliminary experiment.
Acknowledgements
[7]
[8]
[9]
[10]
[11]
[12]
[13]
[14]
This research was partially supported by CNPQ under grant 141781/2006-8. [15]
References [1] J. E. Bardram and T. R. Hansen. The aware architecture: supporting context-mediated social awareness in mobile cooperation. In Proceedings of the 2004 ACM Conference on CSCW, pages 192–201. ACM Press, 2004. [2] B. B. Bederson. Fisheye menus. In Proceedings of the 13th annual ACM Symposium on User Interface Software and Technology, pages 217–225, 2000. [3] C. D. M. Berkenbrock and C. M. Hirata. Implementac¸a˜ o e an´alise de uso de uma aplicac¸a˜ o para edic¸a˜ o cooperativa em dispositivos m´oveis. In V Simp´osio Brasileiro de Sistemas Colaborativos (SBSC 08), pages 99–110. IEEE, 2008. [4] C. D. M. Berkenbrock and C. M. Hirata. Supporting cache coherence in mobile cooperative systems. The 7th IEEE International Symposium on Network Computing and Applications (IEEE NCA08), pages 240–243, 2008. [5] L. Findlater and J. McGrenere. Impact of screen size on performance, awareness, and user satisfaction with adaptive graphical user interfaces. In Proceeding of the twenty-sixth annual SIGCHI Conference on Human Factors in Computing Systems, pages 1247–1256. ACM Press, 2008. [6] S. Greenberg, C. Gutwin, and A. Cockburn. Awareness Through Fisheye Views in Relaxed-WYSIWIS Groupware.
[16]
[17]
[18] [19]
[20]
373
In Proceedings of the Conference on Graphics Interface ’96, pages 28–38, 1996. J. Hao and K. Zhang. A mobile interface for hierarchical information visualization and navigation. IEEE International Symposium on Consumer Electronics, pages 1–7, 2007. V. Herskovic, S. Ochoa, J. Pino, and A. Neyem. General requirements to design mobile shared workspaces. In 12th International Conference on Computer Supported Cooperative Work in Design, pages 582–587, 2008. P. Holleis, F. Otto, H. Hussmann, and A. Schmidt. Keystroke-level model for advanced mobile phone interaction. In Proceedings of the SIGCHI Conference on Human Factors in Computing Systems, pages 1505–1514, 2007. S. Jahn, A. Liu, M. Dimitrov, M. Mazo, F. Jorgen, and K. Matthias. Context-aware interaction and navigation in mobile games. Information Technology and Control, 35(3):198–202, 2006. T. Kamba, S. A. Elson, T. Harpold, T. Stamper, and P. Sukaviriya. Using small screen space more efficiently. In Proceedings of the SIGCHI Conference on Human Factors In Computing Systems, pages 383–390. ACM Press, 1996. S. Kristoffersen and F. Ljungberg. Making place to make it work: empirical explorations of hci for mobile cscw. In Proceedings of the international ACM SIGGROUP Conference on Supporting group work, pages 276–285, 1999. G. Kurtenbach and W. Buxton. User learning and performance with marking menus. In Proceedings of the SIGCHI Conference on Human Factors in Computing Systems, pages 258–264. ACM Press, 1994. A. Leung, S. Morisson, M. Wringe, and Y. Zou. Developing an adaptive user interface in eclipse. In Proc. the Eclipse Technology Exchange Workshop at European Conference on Object Oriented Programming, 2006. R. Messeguer, S. F. Ochoa, J. A. Pino, L. Navarro, and A. Neyem. Communication and coordination patterns to support mobile collaboration. In 12th International Conference on Computer Supported Cooperative Work in Design, pages 1–10, 2008. D. Pinelle and C. Gutwin. A groupware design framework for loosely-coupled workgroups. In Proceedings of the European Conference on CSCW, 2005. J. Rekimoto. Tilting operations for small screen interfaces. In Proceedings of the 9th annual ACM Symposium on User Interface Software and Technology, pages 167–168, 1996. J. Roth. Seven challenges for developers of mobile groupware. Workshop Mobile Ad Hoc Collaboration, CHI, 2002. D. S. K. Seong. Usability guidelines for designing mobile learning portals. In Proceedings of the 3rd International Conference on Mobile Technology, Applications & Systems, pages 25–32. ACM Press, 2006. J. Wainer and C. Barsottini. Empirical research in CSCW - a review of the ACM/CSCW conferences from 1998 to 2004. In Journal of the Brazilian Computer Society, pages 27–35, 2007.
