the circumstances under which m- toring context into the design and use of m-com commerc ications are used can be significantly merce applications can be resolved in various ways different those for their desktop e-commerce Increased demands on users' attention in dynam counterpart environments can be addressed through interfaces Furthermore, in the m-commerce environment, that require less attention. Pascoe, Ryan, and Morse users and applications must deal with a diversity of 6] formulated the concept of Minimal Attention devices(phones, handhelds, telematics) that continue User Interfaces, which seek to minimize the amount to shrink in size and weight. While this achieves high of attention required to operate a device device portability, usability They developed a PDA of the devices can suffer.Categ ry Representative Characteristics application, used by Mice and keyboards are Emvironment bocation. Orientation (of objects) field workers ing replace giraffes in Kenya, which tons and keypads. Smaller Availability, quality(of devices and communications) allowed the user to screens can be more diffi- erties ( for example age gender, education, count the number o cult to read. devices bites taken from tree leaves without looking only one hand. Changing Activities away from the animal environmental conditions Tasks and goals (of participants) Events in the environment(for example, weather) (bright Interactions Co-location telescope). The applica weather) can also affect the used two existin use of mobile devices. Dif- ficulty using devices can Seascorkxplargrenwironment relationships (for example, worker! PDA buttons(for incre- me-of-day, day-of-the-week menting and decre translate into wasted time menting the count) and errors, and user frustration Table 1. Representative ould be operated with Security is another significant challenge in the one hand commerce environment [3]. There are potential Devices and applie benefits in storing sensitive data, including medical, tions can also adapt themselves automatically to personal, and financial information, on mobile changing contexts. Context-aware systems [2] assist devices for use by m-commerce applications. But the users based on knowledge of the environment. As an mobility of devices increases the risk of losing the example, messages typed on a mobile device are vir- device and its data. Furthermore, the risk of data tually attached to their current location when using a access by unauthorized context-aware applica sitive user called“ stick-e identification a priority. Increased demands on attention limal-attention interfaces 16. The notes also arise when the loca- Mobile device limitations and×人ma Potential safety issues Dyamic emvironment New and flexible v/o modalities ear if the user approaches the same ion and activities of the location again. Other user can vary widely. For Social conc example, when designing Societal norms and written laws context characteristics, such as time of day and m-commerce systems for automobiles, serious conse- Table 2. M-commerce challenges temperature, can be used quences can result if the application diverts too much and potential solutio in addition to location ttention from the primary task of driving. Web access New or modified in cars creates potential problems associated with interaction techniques may be necessary to overcome browsing while driving the physical limitations of mobile devices. In addi- Finally, m-commerce and its technologies smobile tion,flexibility of input and output modalities can new social concerns to prominence. Ringing allow adaptation to changing contexts phones and keyboard-tapping users are already needs. For example, text entry using a stylus or resented by many people in public locations such as miniature keyboard on a PDA might be most effi- theaters and restaurants. Mobility of devices and cient when both hands are free, but one-handed text applications raises the issue of their appropriateness entry using a thumbwheel [9] might be better when of use under certain circumstances one hand is occupied. Speech input is a viable alter native for devices too small for buttons or for those Addressing the Challenges of Context without a screen but may not be appropriate for The problems and difficulties that occur when fac- noisy environments or where noise is restricted, such COMMUNICATIONS OF THE ACM December 2003/Vol 46, No 12 59dictably. Thus, the circumstances under which m￾commerce applications are used can be significantly different from those for their desktop e-commerce counterparts. Furthermore, in the m-commerce environment, users and applications must deal with a diversity of devices (phones, handhelds, telematics) that continue to shrink in size and weight. While this achieves high device portability, usability of the devices can suffer. Mice and keyboards are being replaced with but￾tons and keypads. Smaller screens can be more diffi￾cult to read. Devices can be difficult to use with only one hand. Changing environmental conditions (brightness, noise levels, weather) can also affect the use of mobile devices. Dif￾ficulty using devices can translate into wasted time, errors, and user frustration. Security is another significant challenge in the m￾commerce environment [3]. There are potential benefits in storing sensitive data, including medical, personal, and financial information, on mobile devices for use by m-commerce applications. But the mobility of devices increases the risk of losing the device and its data. Furthermore, the risk of data access by unauthorized parties makes positive user identification a priority. Potential safety issues also arise when the loca￾tion and activities of the user can vary widely. For example, when designing m-commerce systems for automobiles, serious conse￾quences can result if the application diverts too much attention from the primary task of driving. Web access in cars creates potential problems associated with browsing while driving. Finally, m-commerce and its technologies bring new social concerns to prominence. Ringing mobile phones and keyboard-tapping users are already resented by many people in public locations such as theaters and restaurants. Mobility of devices and applications raises the issue of their appropriateness of use under certain circumstances. Addressing the Challenges of Context The problems and difficulties that occur when fac￾toring context into the design and use of m-com￾merce applications can be resolved in various ways. Increased demands on users’ attention in dynamic environments can be addressed through interfaces that require less attention. Pascoe, Ryan, and Morse [6] formulated the concept of Minimal Attention User Interfaces, which seek to minimize the amount of attention required to operate a device. They developed a PDA application, used by field workers studying giraffes in Kenya, which allowed the user to count the number of bites taken from tree leaves without looking away from the animal (observed through a telescope). The applica￾tion used two existing PDA buttons (for incre￾menting and decre￾menting the count) and could be operated with one hand. Devices and applica￾tions can also adapt themselves automatically to changing contexts. Context-aware systems [2] assist users based on knowledge of the environment. As an example, messages typed on a mobile device are vir￾tually attached to their current location when using a context-aware applica￾tion called “stick-e notes” [6]. The notes reappear if the user approaches the same location again. Other context characteristics, such as time of day and temperature, can be used in addition to location. New or modified interaction techniques may be necessary to overcome the physical limitations of mobile devices. In addi￾tion, flexibility of input and output modalities can allow adaptation to changing contexts and user needs. For example, text entry using a stylus or miniature keyboard on a PDA might be most effi￾cient when both hands are free, but one-handed text entry using a thumbwheel [9] might be better when one hand is occupied. Speech input is a viable alter￾native for devices too small for buttons or for those without a screen but may not be appropriate for noisy environments or where noise is restricted, such COMMUNICATIONS OF THE ACM December 2003/Vol. 46, No. 12 59 Category Environment Participants Activities Interactions Representative Characteristics Location, Orientation (of objects) Physical properties Brightness and noise levels Availability, quality (of devices and communications) Location, Orientation Personal properties (for example, age, gender, education, preferences) Mental state Physical health Expectations Tasks and goals (of participants) Events in the environment (for example, weather) Co-location Group dynamics Social situations Participant/environment relationships (for example, worker/ workplace) Season, time-of-day, day-of-the-week Table 1. Representative characteristics for the context model. Challenges Increased demands on attention Dynamic environment Mobile device limitations and usability Security Safety Social concerns Potential Solutions Minimal-attention interfaces Context awareness New and flexible I/O modalities Biometrics Commonsense design and legislation Societal norms and written laws Table 2. M-commerce challenges and potential solutions