Engineering Wireless Mobile Applications
Contents
1. e Sensitive data When transmitting sensitive data over the network verify that the data is being masked or encrypted e Error handling Make sure that error mes sages concerning network error conditions such as no network coverage are displayed properly and that when an error message box is dismissed the application regains control e Interruptions Verify that when the device receives system alerts Short Message Ser vice SMS messages and so on while the application is running messages are prop erly displayed Also make sure that when the message box is dismissed the application continues to function properly PROVISIONING WIRELESS APPLICATIONS Developers usually build test and evaluate an application on a platform similar to the one on which it will be deployed and run Development of wireless applications is more challenging be cause they typically are developed on one platform such as Solaris or MS Windows but deployed on a totally different one such as a cell phone or PDA One consequence is that while emulators enable developers to do some oftheir testing on the development platform ultimately they must test and evaluate the application in the very different environment of a live wireless network Wireless applications fall into two broad categories Local applications also called stand alone applications perform all their operations on a handheld wireless device and need no access to external d2. Figure 2 Combining WAP and J2ME applications and over the air distribution models Therefore WAP and MIDP shouldn t be viewed as competing but rather as complementing technolo gies In order to facilitate downloading wireless applications over the air there is a need for some kind of an environment on the handset that allows the user to enter a URL for a MIDlet Suite for example This environment could very well be a WAP browser as shown in Figure 2 Similar to Java Applets that are integrated into HTML MIDlets can be integrated into a WML or an XHTML page Such a page can then be called from a WAP browser and the embedded MIDlet gets downloaded and installed on the device In order to enable this a WAP browser is needed on the device Another alternative ap proach for over the air provisioning is the use of Short Message Service SMS as have been done by Siemens where the installation of MIDIlets is accomplished by sending a corresponding SMS If the SMS contains a URL to a Java Descriptor JAD file specifying a MIDlet Suite then the recipient can install the application simply by confirming the SMS DESIGN CHALLENGES AND POSSIBLE SOLUTIONS In this paper we are more concerned with native interactive applications that can be developed using the J2ME platform or a similar technology J2M2 based wireless applications can be classified into local stand alone and network applications Local applications or st
3. Nikkanen M 2004 User centered development of a browser agnostic mobile e mail application Proceedings of the third Nordic conference on Human computer interaction Tampere Finland pp 53 56 Ocampo A Boggio D Munch J amp Palladino G 2003 Towards a Reference Process for Developing Wireless Internet Services EEE Transactions on Software Engineering Vol 29 No 12 pp 1122 1134 Open Mobile Alliance http www wapforum org Pressman R S 2005 Software Engineering A Practitioner s Approach Sixth Edition McGraw Hill Satoh I 2003 A Testing Framework for Mo bile Computing Software IEEE Transactions on Software Engineering Vol 29 No 12 pp 1112 1121 Sun Microsystems J2ME http Java sun com j2me Sun Microsystems J2ME Wireless Toolkit http java sun com products j2mewtoolkit This work was previously published in Int Journal of Information Technology and Web Engineering Vol 1 Issue 1 edited by G Alkhatib and D Rine pp 59 75 copyright 2006 by IGI Publishing an imprint of IGI Global 112
4. application and the environment in which it will operate As an example if the application is a wireless network aware application such as a multi player game the study will include the users of the application and how they plan to use it Engineering Wireless Mobile Applications The output at the end of this phase is a wire less application plan document that serves as the mobile end user requirement Scenario Analysis This phase is similar to conventional software requirements analy sis and therefore concepts and principles of requirements analysis can be applied here Pressman 2005 In this phase the mobile end user an interaction designer and a developer sit together to come up with a complete scenario analysis model that takes into account the following types of scenario analysis Screen and Interaction Analysis The basic unit of interaction between the user and the mobile device is the screen which is an object that encap sulates device specific graphic user Engineering Wireless Mobile Applications input Therefore the content to be displayed on the screen is identified Content may include text fields menus lists and graphics Interaction analysis specifies how the user interacts with the application In order to find out how the user will interact with the application UML Booch et al 2000 use cases are developed Usage Analysis The use case model de veloped during screen and interaction an
5. is an activity for finding errors in the software system and fixing them so users can be confident that they can depend on the software Errors in software are generally introduced by people involved in software development includ ing analysts architects designers programmers and the testers themselves Examples of errors include mismatch between requirements and implementation Many developers view the subject of software testing as not fashionable and as a result too few of them really understand the job software testers do Testing is an iterative process and should start from the beginning of the project Software developers need to get used to the idea of designing software with testing in mind Some of the new software development methodologies such as eXtreme Programming XP Beck 1999 stress incremental development and testing XP is ideally suited for some types of applications depending on their size scope and nature User interface design for example benefits highly from rapid prototyping and testing usability with actual users Wireless applications like all other types of software must be tested to ensure functionality and usability under all working conditions Test ing is even more important in the wireless world Engineering Wireless Mobile Applications because working conditions vary a lot more than they do for most software For example wireless applications are developed on high end desktop mac
6. of amessage They can occur after a request has been initiated in the middle of the transaction or after a reply has been sent While wireless network protocols may be able to detect and correct some errors error handling strategies that address all kinds of transmission errors that are likely to occur are still needed Message Latency Message latency or the time it takes to deliver a message is primarily affected by the nature of each system that handles the message and by the processing time needed and delays that may occur at each node from origin to destination Mes sage latency should be taken into account and users of wireless applications should be kept informed of processing delays It is especially important to remember that a message may be delivered to auser long after the time it is sent A long delay might be due to coverage problems or transmission errors or the user s device might be switched off or have a dead battery Some systems keep trying at different times to transmit the mes sage until itis delivered Other systems store the message then deliver it when the device is reconnected to the network Therefore it is important to design applications that avoid sending stale information or at least to make sure that users are aware it is not up to date Imagine the possible consequences of sending a stock quote that is three days old without warning the user Security Any information transmitted over wirel
7. 98 Chapter VII Engineering Wireless Mobile Applications Qusay H Mahmoud University of Guelph Canada Zakaria Maamar Zayed University UAE ABSTRACT Conventional desktop software applications are usually designed built and tested on a platform similar to the one on which they will be deployed and run Wireless mobile application development on the other hand is more challenging because applications are developed on one platform like UNIX or Windows and deployed on a totally different platform like a cellular phone While wireless applications can be much smaller than conventional desktop applications developers should think in the small in terms of the devices on which the applications will run and the environment in which they will operate instead of the amount of code to be written This paper presents a systematic approach to engineering wireless application and offers practical guidelines for testing them What is unique about this approach is that it takes into account the special features of the new medium mobile devices and wireless networks the operational environment and the multiplicity of user backgrounds all of which pose new challenges to wireless application development INTRODUCTION Figure 1 Mobile Clients MCs and fixed hosts Some of the fixed hosts called Mobile Support The general mobile computing model ina wireless Stations MSSs are enhanced with wireless in environment consists of two distinct sets o
8. alysis is mainly related to how users interact with the application through the screen The whole functionality of the application should be described with use cases Environment Analysis The environ ment in which the application will operate should be described in details This includes the different wireless networks and backend systems used In addition target mobile devices such as cellular phones and PDAs on which the application willrun should be described in details The output of this phase is an information analysis model document produced by the inter action designer and developer that outlines the functional requirements of the application and the constraints of the environment This document is reviewed by developers and other stakeholders and modified as required e Architectural Design This phase is con cerned with the overall architecture or structure of the wireless application Archi tecture is very important for any application and no optimization techniques will make up for an ill considered architecture Design patterns can be used in this phase to reuse experience in order to come up with an extensible high performance architecture Some of the most important design goals should be to minimize the amount of data transmitted over the wireless link and to anticipate errors and handle them intelli gently Other design and architecture issues include Application partitioning Designers need to
9. and alone perform all their operations ona handheld wireless device and need no access to external data sources through a wireless network Examples include calculators and single player games Network applications on the other hand consist of some components running on a wireless device and others running on a network and thus depend on access to ex ternal resources An example would be an email application with a client residing on a wireless phone interacting with a Simple Mail Transfer Protocol SMTP server to send receive e mail messages A major difference between local and networked applications is in the way they are tested Local applications are easier to test than network applications For example a calculator application can run on a wireless device even when it is not connected to any network but an email client will not work without a connection to mail servers Challenges The constraints discussed earlier pose several crucial challenges which must be faced in order for wireless applications to function correctly in the target environment 101 102 Transmission Errors Messages sent over wireless links are exposed to interference and varying delays that can alter the content received by the user the target device or the server Applications must be prepared to handle these problems Transmission errors may occur at any point ina wireless transac tion and at any point during the sending or receiving
10. ata sources through a wireless network Examples include calculators and single player games Network applications consist of some com ponents running on a wireless device and others runningonanetwork and thus dependon access to externalresources An example would be an email application with a client residing on a wireless phone that interacts with a Simple Mail Transfer Protocol SMTP server to send messages Although these two types of applications are different they are deployed in the same way The big difference shows up later Local applications are easier to test than network applications For example a calculator application can run on a wireless phone even when it is not connected to any network but an email client won t work without a connection to the SMTP server that actually transmits the messages 109 Figure 5 Over the air provisioning Over the Air Provisioning For some time wireless portals in Europe such as Midletcentral have allowed customers to download applications directly to their phones over the air Over the air provisioning of wire less applications OTA is finally available in North America Nextel customers for example can download network aware wireless applica tions without an update data cable OTA 1s the deployment of wireless Java applications MIDlet suites from the Internet to wireless devices over a wireless network Users need not connect their devices to the desktop
11. ations an initial reference process for developing wire less Internet applications which does not differ significantly from traditional iterative process models but includes domain specific guidance on the level of engineering processes Satoh 2003 developed a framework for building and testing networked applications for mobile computing The framework is aimed to emulate the physical mobility of portable computing devices through the logical mobility of applications designed to run on them an agent based emulator is used to perform application level emulation of its target device More recently Chen 2004 proposed a meth odology to help enterprises develop business strategies and architectures for mobile applica tions It is an attempt to formulate a life cycle approach to assisting enterprises in planning and developing enterprise wide mobile strategies and applications This methodology is more concerned with business strategies rather than technical details and thus it is targeted at managers rather than developers And finally Nikkanen 2004 presented the development work of a browser agnostic mobile e mail application It reports on experiences porting a legacy WAP product to a new XHTML based browser application and offers guidelines for developing mobile ap plications Our work is different in the sense that we provide a detailed treatment of the impact of the characteristics of mobile devices and the wire less envir
12. culations and display informa tion locally This approach can dramatically reduce costly interaction over the wireless link but it is feasible only if the device can handle the processing the application needs to perform Use compact data representation Data can be represented in many forms some more Engineering Wireless Mobile Applications compact than others Consider the avail able representations and select the one that requires fewer bits to be transmitted For example numbers will usually be much more compact if transmitted in binary rather than string forms e Manage message latency In some applica tions it may be possible to do other work while a message is being processed If the delay in appreciable and especially if the information is likely to go stale it is impor tant to keep the user informed of progress Design the user interface of your applications to handle message latency appropriately e Simplify the interface Keepthe application s interface simple enough that the user seldom needs to refer to a user manual to perform a task To do so reduce the amount of infor mation displayed on the device make input sequences concise so the user can accomplish tasks with the minimum number of button clicks and offer the user selection lists AD HOC DEVELOPMENT PROCESS An ad hoc development process for wireless ap plications comprises three steps 1l Write the application Several In
13. d in the design process throughout the full development lifecycle We have put forward a systematic ap proach to developing wireless applications which is compatible with the Rational Unified Process or RUP Jacobsen et al 2000 in the sense that it is iterative and responsibility driven We have developed this systematic approach based on our experience designing and building wireless ap plications We recognized that the development of a wireless application is not a one shot task and testing wireless applications is more challenging than testing conventional desktop software ap plications and therefore an ad hoc development process cannot be used Development Activities Our software engineering approach to wireless application development consists of a set of 103 Figure 3 Wireless application development activities Ms oy Se va ae o g aS 2l cy ah ge 3 manageable activities that if followed properly leads to reliable and maintainable wireless ap plications The activities of our approach are shown in Figure 3 104 Planning This iterative process begins with a planning phase which is an activity that identifies the objectives of the wireless application and specifies the scope of the first increment In addition the costs of the overall project are estimated the risks are evaluated and a tentative schedule is set Mobile User Analysis First we must un derstand the audience of the
14. does the user log in but sign out Now enter an invalid user name or password The program should display a mean ingful message box with an OK button Does it Press the OK button Does the application return to the Login screen Youneed to test the GUI navigation of the entire system making notes about usability along the way If for example the user must traverse several screens to perform a function that s likely to be very popular you may wish to consider moving that particular function up the screen layers Some of the questions you should ask during usability testing include is the navigation depth the number of screens the user must go through appropriate for each particular function does the application minimize text entry painful on a wireless phone or should it provide more selection menus can screens ofall supported devices display the content without truncating it and if you expect to deploy the application on foreign devices does it support international character sets Network Performance Testing The goal of this type of testing is to verify that the application performs well in the hardest of conditions for example when the battery is low or the phone is passing through a tunnel Testing performance in an emulated wireless network is very impor tant The drawback with testing in a live wireless 108 Engineering Wireless Mobile Applications network is that so many factors affect the per
15. ess links is subject to interception Engineering Wireless Mobile Applications Some of that information could be sensitive like credit card numbers and other personal information The solution needed really de pends on the level of sensitivity To provide acomplete end to end security solution you must implement it on both ends the client and the server and assure yourself that intermediary systems are secure as well Possible Solutions Here are some practical hints useful to consider when developing mobile applications e Understand the environment Do some research up front As with developing any other software application we must under stand the needs of the potential users and the requirements imposed by all networks and systems the service will rely on Choose an appropriate architecture The architecture of the mobile application 1s very important No optimization techniques will make up for an ill considered architecture The two most important design goals should be to minimize the amount of data transmit ted over the wireless link and to anticipate errors and handle them intelligently e Partition the application Think carefully when deciding which operations should be performed on the server and which on the handheld device Downloadable wireless applications allow locating much of an ap plication s functionality ofthe device it can retrieve data from the server efficiently then perform cal
16. f entities terfaces A MSS can communicate with the MCs Copyright 2009 IGI Global distributing in print or electronic forms without written permission of IGI Global is prohibited Engineering Wireless Mobile Applications Figure 1 Mobile Computing Model Mobile support station A tt client within its radio coverage area called wireless cell A MC can communicate with a fixed host server via a MSS over a wireless channel The wireless channel is logically separated into two sub chan nels an uplink channel and a downlink channel The uplink channel is used by MCs to submit queries to the server via an MSS whereas the downlink channel is used by MSSs to disseminate information or to forward the responses from the server to a target client Each cell has an identi fier CID for identification purposes A CID is periodically broadcasted to all the MCs residing in a corresponding cell A wireless mobile application is defined as a software application a wireless service or amobile service that can be either pushed to users handheld wireless devices or downloaded and installed over the air on these devices Such applications must work within the daunting constraints of the devices themselves Memory Wireless devices such as cellular phones and two way pagers have limited amounts of memory obliging developers to consider memory management most care fully when designing application objects Wireless _ 7 ce
17. for mance of the network itself that you can t repeat the exact test scenarios In an emulated network environment it is easy to record the result of a test and repeat it later after you have modified the application to verify that the performance of the application has improved Server Side Testing Itis very likely that wire less applications communicate with server side applications If your application communicates with servers you control you have a free hand to test both ends of the application Ifit communicates with servers beyond your control such as quotes yahoo com youjust need to find the prerequisites of use and make the best of them You can test server side applications that communicate over HTTP connections using testing frameworks such as HttpUnit http httpunit sourceforge net and measure a Web site s performance using httperf http citeseer nj nec com mosberger98httperf html a tool designed for measuring the perfor mance of Web servers Testing Checklists Here we provide checklists that are useful when testing your application in both emulation and live environments These checklists include tests that are usually performed by certification pro grams offered by Nokia and Motorola Motorola Application Certification Program Navigation Checklist Here are some items to check for when testing the navigational paths of wireless applications e Successful startup and exit Verify that your app
18. ftware project success as it is to that of a large one In this paper we have presented and discussed a systematic approach to wireless application development and presented practi cal guidelines for testing wireless applications The proposed approach takes into account the special features of the wireless environment We have successfully used the approach presented to develop various wireless applications ranging from a stock portfolio management application to a mobile agent platform for mobile devices Mah moud 2002 Our future work includes evaluating the effectiveness of the proposed methodology documenting wireless software design patterns and building tools to automate the task of testing wireless applications There are several interesting research prob lems in the emerging area of wireless mobile applications and services Some of these research issues include Novel mobile services in the area of m commerce and health care Security and privacy issues Mobile agents for mobile services Discovery and interaction of mobile services 111 Enabling roaming of applications and profiles between different wireless standards Location aware and context aware mobile services We are currently addressing some of these research problems and research results will be presented in future articles ACKNOWLEDGMENT The authors would like to thank the anonymous reviewers for the many helpful suggestions for improving th
19. hines but deployed on handheld wireless devices with very different characteristics One way to make testing simple is to design applications with testing in mind Organizing the system in a certain way can make it much easier to test Another implication is that the system must have enough functionality and enough output information to distinguish among the system s different functional features In our approach and similar to many others the system s functional requirements features that the system must pro vide are described using the Unified Modeling Language Booch etal 2000 to create a use case model then detailing the use cases in a consistent written form Documenting the various uses of the system in this way simplifies the task of test ing the system by allowing the tester to generate test scenarios from the use cases The scenarios represent all expected paths users will traverse when they use the features that the system must provide Deployment Deploying and running applica tions in an emulation environment is a very good way to test the logic and flow of your applica tion generally but you won t be certain it will satisfy users until you test it on a real physical device connected to a wireless network Your application s performance may be stunning in the emulator which has all the processing power and memory of your desktop machine at its com mand but will it perform well on the handheld device with it
20. is paper This work was supported in part by the Natural Sciences and Engineering Research Council of Canada NSERC Discovery Grant No 045635 REFERENCES Beaulieu M 2002 Wireless Internet Applica tions and Architecture Addison Wesley Beck K 1999 Extreme Programming Ex plained Embrace Change Addison Wesley Booch G Rumbaugh J amp Jacobsen I 2000 The Unified Modeling Language User Guide Addison Wesley Burkhardt J Henn H Hepper S Rintdorff K amp Schack T 2002 Pervasive Computing Technology and Architecture of Mobile Internet Applications Addison Wesley Chen M 2004 A methodology for building mobile computing applications International Journal of Electronic Business Vol 2 No 3 pp 229 243 Jacobsen I Booch G amp Rumbaugh J 2000 The Unified Software Development Process Addison Wesley Httperf citeseer nj nec com mosberger98httperf html Engineering Wireless Mobile Applications HttpUnit http httpunit sourceforge net Mahmoud Q 2002 MobiAgent An Agent based Approach to the Wireless Internet Journal of Internet Computing special issue on Wireless Internet pp 156 162 Morisio M amp Oivo M 2003 Guest Editors Introduction Software Engineering forthe Wire less Internet IEEE Transactions on Software Engineering Vol 29 No 12 pp 1057 1058 Motorola Application Certification Program http qpqa com motorola iden
21. lication starts up properly and its entry point is consistent Also make sure that the application exits properly e Application name Make sure your applica tion displays a name in the title bar e Keep the user informed If your application does not start up within a few seconds it should alert the user Engineering Wireless Mobile Applications e For large applications it is a good idea to have a progress bar e Readable text Ensure that all kinds of content are readable on both grayscale and color devices Also make sure the text does not contain any misspelled words e Repainting screens Verify that screens are properly painted and that the application does not cause unnecessary screen repaints e Soft buttons Verify that the functionality of soft buttons is consistent throughout the application Verify that the whole layout of screens and buttons is consistent e Screen Navigation Verify that the most commonly used screens are easily acces sible e Portability Verify that the application will have the same friendly user interface on all devices it is likely to be deployed on Network Checklist Some of the items that should be inspected when testing wireless ap plications are e Sending Receiving data For network aware applications verify that the application sends and receives data properly e Nameresolution Ensure that the application resolves IP addresses correctly and sends and receives data properly
22. ll Information server Processing power Wireless devices also have limited processing power 16 bit pro cessors are typical Input Input capabilities are limited Most cell phones provide only a one hand keypad with twelve buttons the ten numerals an asterisk and a pound sign Screen The display might be as small as 96 pixels wide by 54 pixels high and 1 bit deep black and white The amount of informa tion that can be squeezed into such a tight screen is severely limited In addition the wireless environment imposes further constraints 1 wireless networks are unreliable and expensive and bandwidth is low 11 they tend to experience more network errors than wired networks and 111 the very mobility of wireless devices increases the risk that a con nection will be lost or degraded In order to design and build reliable wireless applications designers need to keep these constraints in mind and ask themselves what impact do wireless devices with limited resources have on application design The motivation for this paper is provided in part by the above characteristics that form 99 some of the foundations for pervasive comput ing environments Such characteristics pose several challenges in designing wireless mobile applications for mobile computing This paper provides a detailed treatment of the impact of these characteristics on engineering wireless mobile applications and presents a systematic a
23. n iterative process that you must go through during the implementation phase of the project Part of the validation process can be done in an emulation environment such as the J2ME Wireless Toolkit Sun Microsystems 2005 which provides sev eral phone skins and standard input mechanisms The toolkit s emulation environment does not support all devices and platform extensions but it allows making sure that the application looks appealing and offers a user friendly interface on a wide range of devices Once the application has been tested on an emulator you can move on to the next step and test it on a real device and in a live network Usability Testing In usability testing the focus 1s on the external interface and the relation 107 ships among the screens of the application As an example consider an email application that supports entry and validation of a user name and password enables the user to read compose and send messages and allows maintenance of related settings using the screens shown in Figure 3 among others In this example start the test at the Login window Enter a user name and a password and press the soft button labeled Login Enter a valid user name and password The application should display the main menu Does it The main menu should display a SignOut button Does it Press the SignOut button Does the application return to the Login screen Write yourself a note to raise the question Why
24. onment on engineering wireless mobile applications we discuss the challenges and offer practical solutions for developing mobile applica tions We present a systematic approach for de signing wireless mobile application Our approach is iterative just like in Ocampo et al 2003 but differs in the sense that our process has more focus on requirements elicitation and more importantly scenario analysis We do not provide a testing framework but our testing strategy and check list is more practical than using just an emulated environment Finally unlike the work reported in Chen 2004 our methodology is targeted at developers and researchers rather than managers And unlike the work in Nikkanen 2004 our guidelines and systematic approach is not limited to WAP based applications but can be applied to engineering any wireless application CONCLUSION AND FUTURE WORK As the wireless Internet becomes a reality and software developers become comfortable with the methods and processes required to build software we recognize that the methods devel oped for conventional systems are not optimal for wireless applications In particular wireless application development doesn t always fit into the development model originated to cope with conventional large software systems Most wire less application systems will be smaller than any medium size project however a software development method can be just as critical to a small so
25. pproach for designing them In addition it offers practical design techniques for wireless application design and development WIRELESS APPLICATIONS Wireless applications can be classified into two streams Beaulieu 2002 Burkhardt et al 2002 l Browser based Applications developed using a markup language This is similar to the current desktop browser model where the device is equipped with a browser The Wireless Application Protocol or WAP http www wapforum org follows this approach Open Mobile Alliance 2005 2 Native applications Compiled applications where the device has aruntime environment to execute applications Highly interactive wireless applications are only possible with the latter model Interactive applications such as mobile computer games are a good example Such applications can be developed using the fast growing Java 2 Micro Edition J2ME platform http java sun com and they are known as MIDlets Another stream is the hybrid application model that aims at incorporating the best aspects of both streams above The browser is used to allow the user to enter URLs to download native ap plications from remote servers and the runtime environment is used to let these applications run on the device 100 Engineering Wireless Mobile Applications WAP Might be Dead But What Did We Learn WAP and J2ME MIDP solve similar problems but each can learn a couple of things from the othe
26. r There are special features that are available in WAP but not in MIDP and vice versa These features are summarized as follows e MIDP provides a low level graphics APIs that enable the programmer to have control over every pixel ofthe device s display This is important for entertainment applications such as games in a wireless environ ment e MIDP 1s the way to go for games The nature of MIDlets they exist on the device until they are explicitly removed allows users to run them even when the server becomes unavailable support for disconnected opera tions e WML provides tags and possible presenta tion attributes but it doesn t define an inter action model For example WML defines a SELECT tag for providing a list Some WAP enabled devices interpret the SE LECT tag as a popup menu list while others interpret it as a menu that can be used for navigation Therefore there is no standard interaction model defined for this element If a developer uses it the application may run well on some devices and poorly on others MIDlets on the other hand provide a clearly defined standard for interaction using commands A Micro Browser is Needed MIDlets combine excellent online and offline capabilities that are useful for the wireless envi ronment which suffers from low bandwidth and network disconnection Integrating WAP and MIDP opens up possibilities for new wireless Engineering Wireless Mobile Applications
27. s limited memory and processing power low bandwidth and other constraints In this phase the application is deployed on a live network and evaluated Customer Evaluation Once the application has been deployed it is ready to be downloaded by users for evaluation and usage In this phase users start using the deployed application and report any problems they may experience to the service provider Maintenance Software maintenance encom passes four activities error correction adaptation enhancement and reengineering Pressman 2005 The application will evolve over time as errors are fixed and customers request new features In this phase users report errors to and request new features from the service provider and developers fix errors and enhance the ap plication TESTING ISSUES AND TESTING ACTIVITIES The wide variety of mobile devices such as wireless phones and PDAs results 1n each device running a different implementation of the J2ME environment Varying display sizes add to the complexity of the testing process In addition some vendors provide proprietary API extensions As an example some J2ME vendors may support only the HTTP protocol which the MIDP 1 0 specification requires while others support TCP sockets and UDP datagrams which are optional Here are some guidelines for testing wireless applications Validating the Implementation Ensuring that the application does what it is supposed to be 1s a
28. t impression and improves the user s perception of the services of fered by the application The user interface must be well structured and easy to use Here are some guidelines that can help in designing simple but yet effective user interfaces for mobile devices with tiny screens e Keep the application s interface simple enough that the user seldom needs to refer to a user manual to perform a task e Reduce the amountofinformation displayed on the device e Make input sequences concise so the user can accomplish tasks with the minimum number of button clicks e Offer the user selection lists e Do not depend on any specific screen size The output of this phase is a user manual that describes the screen mockups and the navigational paths Implementation In this phase development tools are used to implement the wireless applica tion There are several tools available for building wireless applications such as Sun s J2ME Wireless Toolkit We would recommend using a tool that allows installing the application in various emula tion environments Conventional implementation strategies and techniques such as coding standards and code reviews can be used in this phase 106 Engineering Wireless Mobile Applications Testing Software testing is a systemic process to find differences between the expected behavior of the system specified in the software require ments document and its observed behavior In other words it
29. tegrated Development Environments IDEs are available for developing Java based wire less applications e g Sun s J2ME Wireless Toolkit and Metrowerks CodeWarrior 2 Testthe application in an emulation environ ment Once the application compiles nicely it can be tested in an emulator 3 Download the application to a physical device and test it Once application s per formance is satisfactory on one or more emulators it can be downloaded to a real device and tested it there If it is a network application it 1s tested on a live wireless network to ensure that its performance is acceptable It is clear that many important software engi neering activities are missing from this ad hoc development process For example there is no formal requirements analysis phase and so fol lowing an ad hoc development process may lead to building a product different from the one the customers want and also testing an application without knowing its requirements is not an easy task In addition issues related to the operating environment such as network bandwidth should be considered during the design so that the per formance of the application will be satisfactory WIRELESS SOFTWARE ENGINEERING While wireless application development might appear to have less need for the coordination that a process provides aspects of development test ing evaluation deployment and maintenance of a wireless application have to be integrate
30. think carefully when deciding which operations should be performed on the server and which on the wireless device J2ME allows designers to locate much of an application s functionality on the device it can retrieve data from the server efficiently then perform calculations and display information locally This approach can dramatically reduce costly interaction over the wire less link but it is feasible only if the device can handle the processing your application needs to perform Message latency Insome applications itmay be possible to do other work while a message is being processed If the delay is appreciable and especially if the information is likely to go stale it is important to keep the user informed of progress The outcome of the architectural design phase is a design document that details the system architecture Navigation and User Interface Design Once the application architecture has been established and its components identified the interaction designer prepares screen mockups and naviga tion paths that show how the user moves from one screen to another to access services Figure 4 shows asimple example where the user will have to login before she is able to check her messages The user interface is the face of the application to users A poorly designed user interface will 105 Figure 4 Screen Mockups scare the user away and a well designed user interface will give a good firs
31. with a data cable or visit a service center to install or upgrade software To take advantage of OTA you must equip your handheld device with a mechanism to discover MIDlet suites available for download using the device s browser such as a WAP browser or a resident application written specifically to iden tify downloadable MIDlet suites The process of 110 1 Get URL from WAP Gateway or HTTP Server 3 Retrieve and Read Java descriptor file jad 4 Download JAE file jar 5 Store JAR file Cae Launch EVM and Application Engineering Wireless Mobile Applications downloading MIDlets over the air is illustrated in Figure 5 RELATED WORK The explosive growth of the wireless mobile appli cation market raises new engineering challenges Morisio amp Oivo 2003 what is the impact of the wireless Internet on engineering wireless mobile applications for the new wireless infrastructure and wireless handheld devices Due to the limited experience with wireless technologies and devel oping wireless applications little work has been in the area of wireless software engineering We found a special issue in the IEEE Transactions on Software Engineering on Software Engineering for the Wireless Internet Morisio amp Oivo 2003 However out of the six papers accepted in the special issue only two papers deal with the devel opment process Ocampo et al 2003 provided Engineering Wireless Mobile Applic
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