Mandos: A User Interaction Method in Embedded ...

Mandos: A User Interaction Method in Embedded Applications for Mobile Telephony Mauro Te´ofilo1,3 , Lucas Cordeiro1 , Raimundo Barreto1 , Jos´e Raimundo Pereira2 Ayres Mardem1 , and Pedro Freitas3 1

Departamento de Ciˆencia da Computac¸a˜ o - Universidade Federal do Amazonas (UFAM), Brazil {lcc, rbarreto, }@dcc.ufam.edu.br and [email protected] 2

Departamento de Estat´ıstica - Universidade Federal do Amazonas (UFAM), Brazil [email protected] 3

Instituto Nokia de Tecnologia (INdT), Brazil {mauro.teof ilo, pedro.f reitas}@indt.org.br

Abstract With the intense use of applicative in mobile device, the question “usability” begins to invigorate strongly as a study object, it is being considered a determinant factor of the success of this segment of the mobile computation. This article proposes an improvement way in the usability of the embedded applicative in mobile devices, considering a new method of user interaction. The Mandos interaction method is based on task idea, which consists in a possible operation that could be executed in an applicative by the user and probabilities between task changes. The cited probabilities will be used for construction of the user interface to interact dynamically with the user. To validate the considered method was developed a framework, called Mandos, which propitiates functionalities to the applicative developer that uses Java technology. A case study will be presented where some prototypes of embedded applicative mobile was developed, using Mandos framework for the interaction method evaluation. The evaluation was established in order to identify any relation of usability gain or loss of applicative, having like approvers the own users of the embedded applicative in mobile telephones.

1

Introduction

The technology advances and the processing capacity increasing of electronic components has been permitted the appearance of new conceptions in the mobile telephony, creating the possibility of such telephony to act as a hand computer, which can carry and to execute embedded appli-

cations. Besides the usefulness, availability and cost, one of the main elements for the acceptance of an embedded application by users is the interface usability [9]. The usability of the equipments and applications for the mobile telephony are a decisive factor of the success of this segment of the mobile computation [5]. In this case, the usability should be considered as one of the main project requirements so that applications and services to take care of mobile user’s needs, allowing him to be effective, productive in the use of the time and of the resources and at the same time be satisfied related to system attributes [3, 2]. The subject to be discussed in this paper is if the current interaction form with the user is the most effective. What we propose is a new interaction form based on the fact that the way of using a cellular phone varies in accordance with culture, age, geographical location, user’s intrinsic characteristics, besides that, several other factors. Putting in other words, there is a variation of used functions, as well as variations in the options more used. This makes it difficult to develop an embedded application that has a good usability in its general form. People from different cultures are different in their perceptions, cognition, thinking styles, and values. Therefore, it is important to thoroughly understand different cultural traits in designing interfaces for international users [6]. In order to have different user interfaces to each culture using the current development way, it is necessary to rewrite the source code which can be Attenuated using Mandos conception. Another inherent problem in the current way of program the code is that embedded applications’ menus are static,

that is, they do not modify or are restructured in order to adapt himself to the user’s needs. The main aim of this paper is to present a solution in such a way that the usability can be improved, without any modification in the source code of an application. In this way, with only one version of an application there will be generated several forms of presentation of the user’s interface in accordance with the current audience. Another intention of this paper is to modify the interaction form with the user. Therefore, after the use of an action, the next action to be presented will be the one with larger probability to be executed next. The main aim of this approach is to reduce the amount of buttons to be pressed to reach the desired functionality. The Mandos method of interaction intends to help the usability of an application through a new user interaction form, based on a matrix of transition probabilities among tasks, and presenting the task in which the user has more probability in executing it in accordance with the current state. For the best understanding of the proposal there is the need of explanation of some basic concepts. The name Mandos is a reference to a fictitious literature character of Tolkien. Mandos is immortal and never forgets anything and he always knows what is coming.

2

Basic Concepts

The Mandos interaction method is based on the concept of tasks. A task is a complete operation started by the user and executed by the application. The user awaits an answer or action that starts when the user begins the execution process, where this process may change screens. A task is always activated through a command emitted by the user. This concept is fundamental since the intention is that the user navigates for tasks, where the amount of buttons to be pressed to execute a certain task is inversely proportional to its frequency. As example of tasks we may mention (i) to leave of application; (ii) to activate the alarm of an application alarm clock; (iii) to save the result in the application memory that simulates a calculator; (iv) to leave any application; and so on. We may say that the transition between tasks represents a Markov process, where future states just depend on the present state and not of past states. After executing a given task there will be a probability of executing another task. Therefore, there will be a list of probabilities that joins the executing task with all other tasks that can be executed later. Such list of probability will be used to mount the user interface. All information about the state transitions between the tasks is in the matrix of transition probabilities. As one of the transition of the matrix of probability is the exit, there is no more probability of another task to be executed, in other words, the process ceases when reaching this condi-

tion (state). Therefore, we have a special case of the Chain of Markov known as Markov Absorbent Chain. The matrix of probabilities is stored as a XML file. In this matrix, the information represents for each task the transition probabilities for the other ones. When there is no transition possibility among two tasks, the probability it will be zero, where the interface that represents such task will not be exhibited. There will be two kinds of matrices: static and dynamic. The static matrix will just make it possible to read the information, not insert captured information of the application, that is, once filled out the matrix, the application will always obey such probabilities. The dynamic matrix will allow the transition probability between tasks will be modified in accordance with the use of the application by the user. In this case, if we have more data about utilization of the application, more accurate will be the relative frequency. The dynamic matrix will offer the functionality of adaptability of the application in accordance with the tasks more used by the user, making it possible that more usual tasks will be easier of activation and, at the same time, offering to the user a more agile and appropriate application to your style. It is not our intention to define precisely how to obtain the exact value of the time of learning of a given application, but the framework Mandos, that it will be implemented to validate the Mandos interaction method will already anticipate this situation. This time can be measured by the amount of pressed buttons, for the time in seconds of use of the application or amount of accessed tasks. This value will be contained in the file text where the head office of transition probabilities will be contained among tasks of a die application. Let us suppose, as an example, the matrix of transition probabilities for a simple alarm clock. In this case, the list of tasks is: Task 01: To activate an alarm clock, Task 02: To disable an alarm clock, Task 03: To adjust the hour, and Task 04: To exit of the application. We can generate a matrix that will contain the change probability between tasks. The probabilities used at this matrix are fictitious. However, in order to obtain such values is necessary to use of a specific group of users that represents a certain target audience.

Table 1. Matrix of Probabilities of Transitions Between Tasks (fictitious values) Tasks Activate Disable Adjust Hour Exit Activate 0 0.1 0.4 0.5 Disable 0.1 0 0.1 0.8 Adjust Hour 0.5 0.1 0.2 0.2 Exit 0 0 0 1

In Table 1, we may observe that the probability of activate the alarm clock and after that adjust the hour is 0.5. When the probability is equal to zero the interface that represents the task will not be available for the user, in other words, the probability of activate such task will be null. We opted to store this matrix in a XML file, since it is a simple format,easy of understanding, in such a way that non specialist in programming may alter the interface with the user.

2.1

Use Levels of the matrix of transition probabilities between tasks

There are three levels of use of the matrix of transition probabilities between tasks listed in the following: 1. Static Initialization (First Level). In this level, the application will just consult the matrix of transition probabilities between tasks in the initialization of the application and the tasks in the application will not be adapted anymore. The presentation of options will stay static, in other words, they will maintain your original positions. This level maintains the navigation style and traditional usability. However, this level solves the problem of code version, in other words, the interface of a certain application will just be able to be altered modifying the data of an external file, facilitating the creation of several versions in accordance with the target audience of a cellular phone. 2. Initialization with dynamic transition of tasks (Second Level). In this level the matrix will just be consulted in the initialization of the application, but all your data will be used. The application will adapt dynamically in accordance with the current state, altering all the accesses of the tasks, privileging the tasks that have, at a particular time instant, the largest probability of access. 3. Adaptation of the transition matrix (Third Level). With the capture of information originating from the use of an application and by the insertion of these data turned into probabilities, the application maybe adapted to a specific style, which gives privilege to more usual tasks starting from the personal use.

2.2

Framework Mandos

In order to validate the Mandos interaction method, it has been developed a Mandos framework that adopts the interaction method shown before to implement some applications and measure the application’s usability. The proposed Mandos framework is of the type black box, that is, the application that will use him uses the existent functionalities

in the framework, without the possibility of the architecture to be seen or altered. The Mandos framework is a kind of application framework, which deals with matters that involve the project of construction of specific applications. The Mandos framework was projected to be used together with J2ME architecture. As the main aim of the proposed Mandos interaction method is the improvement on the applications’ usability, the analysis of the success or failure will be checked through the analysis of the improvements considering only usability aspects. Therefore, the usability concept proposed by Nielson [7] was chosen since it presents a larger number of aspects that defines the usability, what helps in the analysis of the interaction method. The main hypothesis to be verified is if the use of the Mandos interaction method in embedded mobile phone applications will result in improvements on the usability. Generally, if 4 or 5 requirements of the applications that use the respective method of interaction present a superior evaluation, the main hypothesis is considered as true.

3

Experiment Description

This section describes the experiment carried out in order to investigate the Mandos interaction method in terms of usability in mobile phone embedded software. The calculator and alarm embedded applications were evaluated in this experiment. We used essentially two different versions of each application. One version was developed using the proposed Mandos framework in level 3 and contains all functionalities from the original version. In this experiment, it was used the Nokia and BenQ-Siemens mobile phones manufactures in order to prove framework compability and consequently it doesn’t associate the results with only one manufacturer. In order to evaluate the Mandos interaction method, the embedded applications will be used by different mobile phone users. All these users are considered as a potential customer on our evaluation. Twenty people were considered in this experiment and their profile is described as follows: (i) We selected 10 men and 10 women. Each user took part in just one interaction test with each software version, (ii) We chose the users based on the their representativeness as real users of the system, (iii) We did not consider real users of the mobile phone under observation. As proposed by Nielsen, it avoids different experience levels of handling the mobile phone [7]. (iv) User’s age was between 16 and 40 years old. This age-group was chosen due to the fact that they represent the major concentration of mobile phone users in Brazil. This age-group corresponds to 65% of all mobile phone users according to [1], (v) The users should have different occupations and academic background. As described by Rocha, “it is not recommended to test a user

interface against a general group of people and use computer science students as a test group: they do not represent the target user” [8]. Table 2 shows the participants distributions according to the age-group and sex. The tasks were created with the purpose of simulating the user’s behavior during a long time using the mobile phone. Therefore, it allows the embedded application to adapt to the user’s preferences as established in the tasks list. With this goal in mind, all tasks were created in the embedded application with and without the Mandos interaction method (level 3) in order to evaluate the difference between both interaction methods. Table 2. Participants distribution Age-group masculine Feminine Total 16-20 1 3 4 21-25 3 4 7 26-30 4 2 6 30-40 2 1 3 Total 10 10 20

The usability definition adopted in this work was proposed by Nielsen which defines the usability through five different aspects such as: learnability, efficiency, memorability, errors and satisfaction. Based on these usability items, we will evaluate the usability improvement level in mobile phone embedded applications that adopt Mandos interaction method. The usability items will be evaluated by the participants that will carry out the interaction test by using the Likert scale (this scale is recommended to the documents that contain a list of questions to be answered) [10]. The grade will be assigned to an application version that uses the Mandos interaction method and to another application that does not use the proposed method. The evaluations were fulfilled during one week, being the author the only evaluator responsible for conducting all interaction tests. Each interaction test, running both applications (with and without the Mandos interaction methods) took approximately forty minutes. All tests followed the same rigorous guidelines [4]. This guideline is described as follows. The evaluation method was explained to each participant as well as what he/she should do and how long time each session should take. It is of utmost importance that the evaluator provides the needed information to each participant in order for him to feel comfortable. It is strongly recommended that the evaluator explains clearly for each participant that he/she is not being evaluated. The aim of this method is to evaluate the embedded application, in this case the Mandos interaction method. We showed to each participant all equipments that were used in the tests. In addition, we also explained that his/her face would not be

taken a picture and we also emphasized that the procedure would be anonymous. We also asked for each participant to fill in the questionnaire according to his/her profile. After filling in this questionnaire, the participant receives the test guidelines. The participant was introduced into the Mandos interaction method by observing the main difference when compared to the method currently used in the mobile phone. After providing the necessary instructions, the evaluator informed each participant that he/she could use the system freely during five minutes. After training the participant, a list of tasks to be executed was delivered to the participant. The events observed by the evaluator should be registered in the data collection form. After finishing all tasks, the system evaluation questionnaire should be filled in by the participant. At the end of the evaluation phase, we talked with each participant in order to obtain general information about the evaluation method and clarify about the possible difficulties that he/she could face during the experiment. After this talk, the evaluation method was considered as finished. After carrying out all interaction tests, we quantified all data of the applied questionnaires. With these data at hand, we fulfilled statistical tests with the purpose of verifying if the application usability was really improved or not by using the Mandos interaction method. In order to calculate the p-value, we initially thought in using the Paired t-Test. The Shapiro-Wilk test found that some sets were not distributed inside a normal which contradicts the use of Paired t-Test. Therefore, for the determination of the p-value we used the Wilcoxon signed-rank test. According to Wainer, it must be used if the test T conditions are not true (in this case no normality) [10]. This test is not parametric. It means that for the test conditions there is no assumption that the data have any fix distribution. For this reason, it is considered weaker than the parametric test. In order to calculate the statistics we used the Analyse-it software.

4

Results

In order to prove the hypothesis that the use of Mandos interaction method would result on a usability improvement of a mobile phone embedded application, we split the usability in different items and then we measured if it was improved in some item. With this information at hand, we could infer the usability improvement in general. From the five usability items that include learnability, efficiency, memorability, errors, satisfaction, we concluded that the embedded applications that used the proposed method obtained better results in four items which are: learnability, efficiency, memorability and satisfaction, while the other item, errors, did not present improvement statistics evidence neither disapproval. Table 3 shows the p-value that

we found during the analysis. Table 3. Participants distribution Item p-value Learnability 0.0028 Efficiency < 0.0001 Memorability 0.0075 Errors 0.0520 Satisfaction 0.0003

In order to prove the main hypothesis which mentions that the Mandos interaction method improves the mobile phone embedded applications usability, we established that at least four items should reach superior evaluation. This was achieved and the main hypothesis is considered as true. In order to evaluate precisely the improvements caused by the use of Mandos interaction method for each item, we collected at the end of the experiments important data that are described as follows: (i) 90% of interviewed people demonstrated interest in using the Mandos interaction method on his/her mobile phone, (ii) 5% of interviewed people demonstrated interest in using the Mandos interaction method, but they think that all mobile phones should include this method, (iii) 5% of interviewed people would not like to have the Mando’s interaction method in any application installed in the mobile phone, and (iv) 40% of interviewed people state that they felt a little bit confused with the Mando’s interaction method. One of the main objectives to use the Mandos interaction method is to present a way for the embedded applications to adapt to the user’s preferences. Another way to use this idea is to have an embedded application that could define transition matrix values of the tasks in a straightforward and feasible way to the mobile phone’s user. In this way, the mentioned operations could be fulfilled on a PC desktop application and after that user could load the data to the mobile phone. Based on this idea presented to each interviewer, we found that 85% of interviewed people would use an application developed on the PC in order to customize all other applications installed in the mobile phone. During the interviews we took note of many comments. One of them is that the Mandos interaction method could assist in his/her daily use of the mobile phone, not only in embedded application that is the aim of this work, but also in the design of general user interface of mobile phones. Another important suggestion of a participant was that “all innovations are well-come since it does not lead to an additional cost in the final product. We did not evaluate how much the Mando’s framework could increase the final price of the mobile phone, but we are just restricted to the software and the proposed development framework. This framework aims to make the embedded application

adaptation easier and we believe that the impact is as low as possible especially if its conception is applied in the beginning of the software development. Another relevant suggestion issued by a participant was that after the application adapts to a given user and this mobile phone changes to another user then this new user might find the task arrangement terrible. For this situation, the application will continue adapt to the new user and we will plan an approach to update the transition matrix of tasks with the initial standard values. However, our work does not provide yet a solution to this kind of problem.

4.1

Experiment Limitations

The results presented in this work may contain some variation of the reality due to the experiment limitations. One of these limitations includes the time spent to use the embedded application, i.e. the ideal would be that each participant could make use of the evaluated application in his/her day by day. In this case, an evaluation in long term could probably obtain different results. The type of the application used in the experiment was also a limitation, the evaluation result can be changed according to the application under observation. We also mention the expectation effect of a given person (Placebo and Hawthorne effect) and the expectation effect of the experimentalist as factors that can influence the experiment participant evaluation [10].

4.2

Illustrating the Mandos Interaction Method

The calculator application used in this experiment presents some options that can be explored by the user, as we can visualize in Figure 1. The options presented in this application will always stay static, in other words, the order will always be the same. The Mandos interaction method proposes a new way to interface with the user. For instance, after using the application, the function “save in memory”, which is the next function to be used, should hypothetically be replaced by the option “open the memory”. Therefore, this option should be the first one to be presented in the list of options, as shown in Figure 2. It is worth noticing that in Figure 2, the presentation order of functions in the calculator is dynamic, in other words, they change in accordance with the current state. As the state is changed every time a function is used, the proposed method always present a list of options in such a way that the user has to spend smaller efforts to reach what he wants.

5

Conclusion

In recent days, usability in mobile phone area is synonymous of intense researching in order to improve the meth-

Figure 1. Calculator Options

ing the Mandos framework. These applications must be used on a daily basis such as business and enterprise applications, (ii) reduce the limitation of the Mandos interaction method, that in this work is restricted to the embedded applications scope, developed using Java technologies. We also aim to use the interaction method in the development of all mobile phone user interface and with other technologies like Symbian and Brew, (iii) create a product in which the user can determine the desired values of the transitions probability matrix of the tasks. This product could be an application running on the PC desktop where the user should be able to choose the order of the main tasks, and (iv) carry out experiments which allow each participant to use for a long time the application that is under observation.

References

Figure 2. Calculator Using the Mandos Interaction Method

ods and techniques. This paper proposed a technique to interact with mobile phone users by improving the embedded application usability. We developed the Mandos framework that enables the software engineer to develop embedded applications by using the methods provided in the Mandos. The main hypothesis proved in this work was that the usability evaluation in embedded applications that used the Mandos interaction method would be improved. After carrying out the experiment, we concluded that embedded application usability developed by using the Mandos interaction method improved significantly the usability of the mobile phone applications. We proved it by evaluating the superior statistics evidence in four of five usability items evaluated, that include: intuitiveness, efficiency, memory, error reduction, and satisfaction. Therefore, the main contribution of our work is an interaction method that improves substantially the embedded applications usability in mobile phone area. Nevertheless, there are still many topics of research that may be carried out in this knowledge area. Moreover, there is still the need for performing a more detailed experiment with the purpose of confirming that the Mandos interaction method improves substantially the mobile phone embedded application usability. With these goals in mind, we intend to (i) develop and evaluate other mobile phone embedded applications by us-

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