《计算机网络》课程教学资源（学习资料）design mobile application

BY PETER taRaSeWICh DESIGNING MOBILE COMMERCE APPLICATIONS EXPLORING THE IMPORTANCE A USABLE INTERFACE TO ANY AND UNTANGLING THE APPLICATION IS CRITICAL FOR COMPLEXITY OF THE NOTION EXAMPLE, PROPERLY DESIGNED OF CONTEXT. WEB SITES HELP ENSURE USERS FIND WHAT THEY ARE LOOKING FOR AND SUCCESSFULLY PERFORM ONLINE TRANSACTIONS GIVEN THE UNIQUENESS OF THE M-COMMERCE ENVIRON- MENT II, GOOD INTERFACE DESIGN IS ESPECIALLY DIFFI- CULT TO ACHIEVE [IO. MOBILE DEVICES ARE TYPICALLY SMALLER THAN THEIR DESKTOP COUNTERPARTS, HAVE LESS PROCESSING POWER. AND COMMUNICATE IN LOW- BANDWIDTH ENVIRONMENTS. MOBILE APPLICATIONS MUST BE CAREFULLY DESIGNED TO ACCOUNT FOR THESE LIMITA- tions. But an even greater challenge to I ing dock or in a moving automobile designing successful m-commerce Before mobile devices, computer applications, and their interfaces, is applications had to consider only dealing with context. People can now fairly limited set of contextual con- conceivably be anywhere at anytime cerns. These might include organiza and use a mobile application, unlike tional culture, user characteristics the traditional(wired)Web where a(skills, education), system goals,and Internet connection is the working environment(lighting, required. Applications designed for a noise). But users performed tasks on relatively stable office or home envi- computers that remained stationary. ronment may not work well on a load- Context concerns could be taken into COMMUNICATIONS OF THE ACM December 2003/Vo. 46. No 12 57

COMMUNICATIONS OF THE ACM December 2003/Vol. 46, No. 12 57 A usable interface to any application is critical. For example, properly designed Web sites help ensure users find what they are looking for and successfully perform online transactions. Given the uniqueness of the m-commerce environ￾ment [11], good interface design is especially diffi￾cult to achieve [10]. Mobile devices are typically smaller than their desktop counterparts, have less processing power, and communicate in low￾bandwidth environments. Mobile applications must be carefully designed to account for these limita￾tions. But an even greater challenge to designing successful m-commerce applications, and their interfaces, is dealing with context. People can now conceivably be anywhere at anytime and use a mobile application, unlike the traditional (wired) Web where a physical Internet connection is required. Applications designed for a relatively stable office or home envi￾ronment may not work well on a load￾ing dock or in a moving automobile. Before mobile devices, computer applications had to consider only a fairly limited set of contextual con￾cerns. These might include organiza￾tional culture, user characteristics (skills, education), system goals, and the working environment (lighting, noise). But users performed tasks on computers that remained stationary. Context concerns could be taken into EXPLORING THE IMPORTANCE AND UNTANGLING THE COMPLEXITY OF THE NOTION OF CONTEXT. DESIGNING MOBILE COMMERCE APPLICATIONS BY PETER TARASEWICH

Ⅰ NCREASED DEMANDS attention in dynamic environments can be addressed tbrough interfaces that requre less attention account during the commerce applications design process and within the boundaries of Context hanged slowly (if at all) this context model will be after system completion presented here, followed With the advent of Environment by ways to address them noble an vices, context is a less pre How Context Affects dictable influence on the ommerce actual design and use of Many activiti omputer systems. People for a user's attention on Participants|← Activities the Web. There are set environments that are rel- vices sending news sto- tively unstable from one moment to the next Future prices, and notific In mobile and ubie of email messages uitous computing, the Past least with wired e-com notion of context is merce. the environment often equated simpl outside of the Web is with location but is actually more complex. Mobile Graphical representation of fairly stable from day to application use can vary continuously because day. Most offices and changing circumstances and differing user needs. A homes function with a context model, depicted in the figure here, can be good amount of predictability, even if they experi created using three broad categories of context: envi- ence a great amount of activity, and relatively consis- ronment, participants, and activities. The environ- tent amounts of attention can be devoted to mentcategory is concerned with the properties of performing tasks on the computer. objects in the physical environment. Participants" In the realm of m-commerce, conversely, there us of the user(s) and other partici- can be a significant number of additional people pants in the environment. Activities" covers user, objects, and activities vying for a user's attention participant, and environmental activities. Addition- aside from the application itself. Furthermore, ally, the model includes any interactions or relation- since devices are completely mobile, this outside ships that may exist among participants, activities, environment can change rapidly from moment to ncorporated into this model, allowing for a context user may be trying to juggle history that can be used for predicting future context. mobile device along with other elements in the This context model builds on the strengths of previ- environment. The amount of attention a user can ously proposed models [1, 7, 8]. Severa al challenges give to a mobile application will vary over time, (summarized in Table 2)that arise when designing m- and a user's priorities can also change unpre 58 December 2003/Vol 46, No 12 COMMUNICATIONS OF THE ACM

58 December 2003/Vol. 46, No. 12 COMMUNICATIONS OF THE ACM account during the design process and changed slowly (if at all) after system completion. With the advent of mobile and wireless de￾vices, context is a less pre￾dictable influence on the actual design and use of computer systems. People are using applications in environments that are rel￾atively unstable from one moment to the next. In mobile and ubiq￾uitous computing, the notion of context is often equated simply with location but is actually more complex. Mobile application use can vary continuously because of changing circumstances and differing user needs. A context model, depicted in the figure here, can be created using three broad categories of context: envi￾ronment, participants, and activities. The “environ￾ment” category is concerned with the properties of objects in the physical environment. “Participants” includes the status of the user(s) and other partici￾pants in the environment. “Activities” covers user, participant, and environmental activities. Addition￾ally, the model includes any interactions or relation￾ships that may exist among participants, activities, and the environment. Table 1 summarizes several con￾text characteristics for each category. Time is also incorporated into this model, allowing for a context history that can be used for predicting future context. This context model builds on the strengths of previ￾ously proposed models [1, 7, 8]. Several challenges (summarized in Table 2) that arise when designing m￾commerce applications within the boundaries of this context model will be presented here, followed by ways to address them. How Context Affects M-Commerce Many activities compete for a user’s attention on the Web. There are ser￾vices sending news sto￾ries, alerts about stock prices, and notifications of email messages. But at least with wired e-com￾merce, the environment outside of the Web is fairly stable from day to day. Most offices and homes function with a good amount of predictability, even if they experi￾ence a great amount of activity, and relatively consis￾tent amounts of attention can be devoted to performing tasks on the computer. In the realm of m-commerce, conversely, there can be a significant number of additional people, objects, and activities vying for a user’s attention aside from the application itself. Furthermore, since devices are completely mobile, this outside environment can change rapidly from moment to moment. An m-commerce application may not be the focal point of the user’s current activities, as the user may be trying to juggle interaction with a mobile device along with other elements in the environment. The amount of attention a user can give to a mobile application will vary over time, and a user’s priorities can also change unpre￾INCREASED DEMANDS on users’ attention in dynamic environments can be addressed through interfaces that require less attention. Context Environment Interactions Participants Activities Future Present Past Graphical representation of context model

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 59

dictably. 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

TAKING THE complexities of conteat unto account during the dedign and ude of m-commerce applications id a challenging task but one that must be undertaken deriouoly to achieve long-term duccedd as libraries. Sound can also be used for output, tak- acteristics that are relevant will benefit from ing the place of text or graphics. Holland and Morse increased functionality and usability. c [4] investigated an audio interface for a navigation system that leaves a user's eyes and hands free for REFERENCES other purposes. The application used tones pro 1. Abowd, G.D. and Mynatt, E.D. Charting past, present, and future jected through headphones at locations relative to Human Interaction 7. 1(Mar2000),29-58 the user(left, right, forward)to indicate direction. 2. Chen, G. and Kotz, D. A Survey of Context-Aduare Mobile Computing Security of mobile commerce applications can be Research. Dartmouth Computer Science Tech. Rep. TR2000-381 of Com increased through the use of biometrics. Future 3. Ghosh, A K and Swaminatha, T.M. Softw wireless devices may include thumbprint identifica risks in mobile e-commerce Comm. ACM 44, 2(Feb. 2001), 51-5 tion or smart cards for user authentication. Safety 4. Holland, S. and Morse, D.R. Audio GPS: Spatial audio in a minimal attention interface. In Proceedings of Mobile HCl 2001: Third Intend- concerns can hopef efully be resolved through the tional Workshop on Human-Computer Interaction with Mobile Devices, ommon sen nse of users and designers, but legislation 5. Pascoe, ] Ryan, N. and Morse, D. Using while moving: HCI issue may be needed to enforce the safe use of m-com- fieldwork environments. ACM Transactions on Human-Computer merce devices and applications. Several states already teraction, 3(Sept. 2000),417-437. have laws regulating cell phone use in vehicles. Like 6. Pascoe,J, Ryan, N, and Morse, D. Issues in de omputing. In Proceedings of the First International Symposium on appropriate use of m-commerce applications Handheld and Ubiquitous Computing(HUC 99),H.W.Gellersen,Ed be dictated through laws and societal norms. 7. Schin a' /om santa Cruz, CA, Dec 1994), IEEE Computing Soci- Technology(cell phone jammers, for example) can cations In Procedings of the Workshop on Mobile Computing Systems also be used to enforce what is considered appropri- ate behavior 8. Schmidt, A, Beigl, M, and Gellersen, H -W. There is more to context than location. Computers and Graphics 23, 6(Dec. 1999), 893-901 Implications for 9. Tarasewich, P. Evaluation of thumbwheel text entry methods In Pro- Taking the complexities of context into account dur. 10. Tarasewich, pmapuwfireless devices for mobile commerce: User interface M-Commerce Design lesign and usability In B.E. Mennecke and T ]. Strader, Eds, Mobi ing the design and use of m-commerce applications Commerce T paolo Theory, and Applicatiom. Idea Group Publish- is ke n naerionugsing ac cve lone team musee peser the sues in mobile erom erce dowamken ins 4. 2002).0413-6i4n of guidelines and usability methods that work with wired systems do not necessarily work with mobile PETER TARASEWICH (tarase @ccs. neu. edu)is an assistant systems. Systems must function well even as environ- professor in the College of Computer and Information Science a mental conditions, circumstances, and user priorities how they interact with their surroundings. Realisti- profit or commercial advantage and that copies bear this notice and the full citation on cally, all context characteristics presented in our the first page. To copy otherwise, io republish, te post on servers or to redistribute to merce application or its user at a given time. But applications that do account for those context char- o2003 AC 60 December 2003/Vol 46, No 12 COMMUNICATIONS OF THE ACM

as libraries. Sound can also be used for output, tak￾ing the place of text or graphics. Holland and Morse [4] investigated an audio interface for a navigation system that leaves a user’s eyes and hands free for other purposes. The application used tones pro￾jected through headphones at locations relative to the user (left, right, forward) to indicate direction. Security of mobile commerce applications can be increased through the use of biometrics. Future wireless devices may include thumbprint identifica￾tion or smart cards for user authentication. Safety concerns can hopefully be resolved through the common sense of users and designers, but legislation may be needed to enforce the safe use of m-com￾merce devices and applications. Several states already have laws regulating cell phone use in vehicles. Like￾wise, appropriate use of m-commerce applications will be dictated through laws and societal norms. Technology (cell phone jammers, for example) can also be used to enforce what is considered appropri￾ate behavior. Implications for M-Commerce Design Taking the complexities of context into account dur￾ing the design and use of m-commerce applications is a challenging task, but one that must be under￾taken seriously to achieve long-term success. Design guidelines and usability methods that work with wired systems do not necessarily work with mobile systems. Systems must function well even as environ￾mental conditions, circumstances, and user priorities change. Developers need to understand people and how they interact with their surroundings. Realisti￾cally, all context characteristics presented in our model are not relevant (or important) to an m-com￾merce application or its user at a given time. But applications that do account for those context char￾acteristics that are relevant will benefit from increased functionality and usability. References 1. Abowd, G.D. and Mynatt, E.D. Charting past, present, and future research in ubiquitous computing. ACM Transactions on Computer￾Human Interaction 7, 1 (Mar. 2000), 29–58. 2. Chen, G. and Kotz, D. A Survey of Context-Aware Mobile Computing Research. Dartmouth Computer Science Tech. Rep. TR2000-381, Department of Computer Science, Dartmouth College, 2000. 3. Ghosh, A.K. and Swaminatha, T.M. Software security and privacy risks in mobile e-commerce. Comm. ACM 44, 2 (Feb. 2001), 51–57. 4. Holland, S. and Morse, D.R. Audio GPS: Spatial audio in a minimal attention interface. In Proceedings of Mobile HCI 2001: Third Interna￾tional Workshop on Human-Computer Interaction with Mobile Devices, M.D. Dunlop and S.A. Brewster, Eds., 2001. 5. Pascoe, J., Ryan, N., and Morse, D. Using while moving: HCI issues in fieldwork environments. ACM Transactions on Human-Computer Interaction 7, 3 (Sept. 2000), 417–437. 6. Pascoe, J., Ryan, N., and Morse, D. Issues in developing context-aware computing. In Proceedings of the First International Symposium on Handheld and Ubiquitous Computing (HUC ’99), H.-W. Gellersen, Ed. Springer-Verlag, Berlin, 1999, 208–221. 7. Schilit, B., Adams, N., and Want, R. Context-aware computing appli￾cations. In Proceedings of the Workshop on Mobile Computing Systems and Applications (Santa Cruz, CA, Dec. 1994), IEEE Computing Soci￾ety, 85–90. 8. Schmidt, A., Beigl, M., and Gellersen, H.-W. There is more to context than location. Computers and Graphics 23, 6 (Dec. 1999), 893–901. 9. Tarasewich, P. Evaluation of thumbwheel text entry methods. In Pro￾ceedings of Computer-Human Interaction Conference (CHI 2003). 10. Tarasewich, P. Wireless devices for mobile commerce: User interface design and usability. In B.E. Mennecke and T.J. Strader, Eds., Mobile Commerce: Technology, Theory, and Applications. Idea Group Publish￾ing, Hershey, PA, 2002. 11. Tarasewich, P., Nickerson, R., and Warkentin, M. An examination of the issues in mobile e-commerce. Commun. AIS 8, (2002), 41–64. Peter Tarasewich (tarase@ccs.neu.edu) is an assistant professor in the College of Computer and Information Science at Northeastern University in Boston, MA. Permission to make digital or hard copies of all or part of this work for personal or class￾room use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, to republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. © 2003 ACM 0002-0782/03/1200 $5.00 c 60 December 2003/Vol. 46, No. 12 COMMUNICATIONS OF THE ACM TAKING THE complexities of context into account during the design and use of m-commerce applications is a challenging task, but one that must be undertaken seriously to achieve long-term success