Ulmo: A system to enable mobile applications ...

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system able to custom the mobile application's user interface and mirror it .... developer can set while doing something more than a simple "text message".
Ulmo: A system to enable mobile applications personalization by binary SMS Mauro Teófilo Nokia Technology Institute [email protected]

Alexandre Martini Nokia Technology Institute [email protected]

Abstract Usability and user interfaces play a huge and important role in today’s mobile application. Besides a good design, acceptable performance, scalability, and robustness, a mobile application needs to be easy to use and, to some extent, customizable. To create a system able to custom the mobile application’s user interface and mirror it immediately to final users is the purpose of this article. Ulmo is such system, which is composed by a web site that enables user to comfortably executes change in mobile application user interface, a mobile application compliant (providing API that facilitates mobile application Ulmo compliance development) and the communication module to mirror web adjustments in mobile phone, which was made using SMS technology. Its availability and low cost are also considered and its high penetration in emergent markets. Some aspects as security, data compression and reliability are taken in account.

1. Introduction This article tries to bring an innovative, cheap, and easy approach to mobile application user interface personalization for mobile devices, based on SMS (Short Message Service) technology. This service aims to provide poor and developing countries with the same kind of possibilities that the rich ones have: access to updated information with low cost. The choice of SMS as the communication channel is obvious, due especially to its popularity – 74% of all mobile phone subscribers are active users, meaning that the worldwide average of messaging use is 2.6 messages per day per person - cost and standardization – it is part of GSM communication system. Besides, SMS is supported by most low-end devices and by almost each existing telecom carrier. This is a very important remark, as one of our purposes is to deliver information to low-income people. According to [1], the success of SMS communication may be upon to 3

Paolo Cruz Nokia Technology Institute [email protected]

main reasons: it is ubiquitous, it has a near real time delivery and it follows the “store and forward” mechanism, with later retransmission in case of failure. Other important SMS characteristic for this system is to be asynchronous, so it’s able to send data for device without mobile device request, and it’s possible to send, for example, an user interface updating without mobile application in question being started or requested it. To fully understand the Ulmo system, a basic comprehension of Vairë tool is needed. The Vairë web application is a tool designed to improve the usability in mobile applications based on user adjustment [2], it was developed based on the fact that people from different cultures are different in their perceptions, cognition, thinking styles, and values [3], so Vairë tool offers a way to individual adjustments. In this article, Vairë tool is joined into Ulmo system, so, through a web interface (Vairë subsystem), the user should adapt the user interface according to its needs, and then use Ulmo system to transfer it to the mobile device. To develop mobile application Ulmo compliance is enough to use Ulmo API based on Mandos framework [4]. The Ulmo system is present in the mobile application and provides a system to integrate web module and mobile application. It was used a SMS broker, which is a kind of virtual network operator for short messages, to intermediate the communication between the server and mobile parts. In order to have a whole system to be able to upgrade and update itself, some relevant aspects should be put together: protocol to be followed to allow interoperability, security, data compression and reliability. Although SMS protocol is a well designed communication protocol that uses GSM networks to information traffic, SMS messages have little security to protect the data being transferred, which can be catch by an unauthorized monitoring agent, besides then, SMS does not guarantee confidentiality and integrity of the message content [5]. Due this fact, some important aspects as authentication and confidentiality must be considered during the project of

Figure 1. Vairë tool snapshot

a SMS-based service to mobile users. By now, cryptography – a branch of mathematics - is the main strategy to achieve security and reliability in transferring sensitive information among mobile phone users by SMS messages. The designed communication protocol must support some basic use cases, such as: i) user registers; ii) user updates personalization data; iii) user updates application and iv) communication system with SMS broker. All these activities have a server response, accordingly. As a SMS message is limited to 160 characters, a data compression algorithm is made necessary and it was also studied in this article. To evaluate Ulmo system was chose the mobile application usability as feature to be improved, in other words, in performed experiment we tried to prove the following hypothesis: the usability evaluation in mobile application after Ulmo system usage would be improved

2. Vairë One of subsystem which composes Ulmo is called Vairë tool, showed in figure 1. Therefore, it is mandatory to have an overview of this tool before proceeding. Vairë is a ubiquitous tool that works as a web application. Its main purpose is to provide the regular user with an easy manner to change user interfaces of mobile applications according to user needs [2], Typically, the user just needs to load for instance an existing menu/ user interface data, modify it – adding, editing or removing items – and then save it back on server. Afterwards, the user can transfer modifications to device – basically in the form of a standard protocol

- which would take effect in the next time the user opens the application. In its first version, Vairë supported Bluetooth and cable transfer modes. Although useful and efficient, this was a huge constraint, due to the proximity demanded for both. This was one of the major motivations to design and create Ulmo system, which enclosing all process using the most simple way achieved and composing a full system. A Vairë adaptation implemented to integrate Ulmo system is about Vairë access. To final user accessing Vairë is necessary some information about final user mobile phone, as mobile phone number, to send personalization data by binary SMS, mobile phone specification, as screen resolution, mobile application version, etc.

3. Ulmo The necessity to have updated information combined with upgraded software versions in the mobile phones made clear that the implementation of a new transfer mode was urgent. More importantly, consolidating all subsystem in one and only unified system creating a standard protocol, although user interface migration has been studied worldwide and even some approaches using Bluetooth and RFID technologies have emerged [6], we suppose that when it comes to communication through mobile devices, SMS is always an alternative. Several key points must be considered before a final decision, though: cost, security and effectiveness. In order to reduce cost, we strived to keep messages small. This can be achieved using compression data algorithms. Though, it is worth pointing out that many times only a few messages are necessary to get all UI modifications. The security requirement, explained in details in the following section. By definition, SMS messages are not guaranteed to be delivered by any GSM operator. Nevertheless, we had very good results, due probably to operator’s service quality. The Experiment section details these figures and shows satisfactory results. To be able to send a SMS message from a mobile phone to a server in Internet, you can use a SMS broker. The core programming language used was Java. Java platform takes place both in server and mobile client. In the former, we have a combination of Servlet and Application Server, while in the latter JME and its WMA (Wireless Message API 1.0, JSR 120) were chosen. The name Ulmo is a reference to a fictitious literature character of Tolkien. The name was used

because Ulmo is Valar that interfered in human changing destiny, a reference to Ulmo system, which intends to change the mobile application. The next sections show all basic features that compose Ulmo system.

interface structure, adding, removing or just reordering the items. This is obviously the largest part of the protocol and must be compressed. This protocol is on the following sense – Ulmo system to mobile application and sent by binary SMS.

3.1 Protocol and Communication

3.1.1 Binary SMS

Three main interfaces must interact so everything can work properly: client application running in mobile device, server application and SMS broker software. Both client and server can start the communication, depending on the type of service. Typically, client may make a request to server for an updated user interface. On the other way around, server can just push user interface modifications to client. In all cases the broker takes action. The protocol to request a service to Ulmo server is as follows: ulmo • ulmo – The main keyword of Ulmo; • – The service name recognized by server: Currently the only service available is update, for an user interface update • – The application name that uses Vairë-Ulmo system; • – The secure code generated based on mobile IMEI. It guarantees that the request was provided by an Ulmo compliant application; • – A code with one character that represents this request instance. This very same code must be returned by server in the response protocol. Example: ulmo update calculator 819EB K This protocol is on the following sense – mobile application to Ulmo system and sent by plain text SMS. To push user interface modifications made in Vairë subsystem to a mobile client software, the following protocol must be used: |||| • – The secure code generated based on mobile IMEI. It guarantees that the content was sent by a proper entity; • – This Id informs the client that the information sent is an UI update. The Id for matrix update service is 1. • – The message code sent in the request. Must be the same as in the request. • – The data with personalization information. Mandos must read and understand this information. The mobile application compliance should create the correspondent user

As Ulmo sends protocol information as binary SMSs, a brief explanation of how a binary SMS works is valid here. Basically, there are two important concepts: ports and body. SMS uses the concept of port just like any internet socket does. A SMS message can be received in a given port and wake up a specific service (in JME this is accomplished through the Push Registry API). The User Data Header (UDH) is what a high level developer can set while doing something more than a simple "text message". It is mainly used to specify what ports our client will send the SMS to. The protocol is sent in binary SMS body. Both are in a hexadecimal representation.

3.2 Cryptography End-to-end security or confidentiality and integrity over the whole path between two parties (e.g., a mobile station to another mobile station) are not provided by mobile systems (such as GSM and UMTS) and therefore they have to be implemented at application level [7]. Due to this fact, some important aspects as authentication and confidentiality must be analyzed during the project of an SMS based service to mobile users. There is a necessity to implement a level of wellknown security such as cryptography: to mess up the original chain of bytes to be sent in an incomprehensive chain of bytes that only can be read if the receiver knows the method to put back everything in its right place. Most of the time, using an HTTPS connection in place of an HTTP connection provides adequate data security. The endpoints of the HTTPS connection agree on a session key that is used to encrypt the remainder of the conversation. After the initial handshake, all data is encrypted. If your application data uses a network mechanism other than sockets or HTTP connections, you'll have to supply your own encryption. Ulmo system deals with two main different kind of data transfer. First of all, the mobile application may need to send some message to the server requesting for some service – today, the only service is an UI update – or it can send directly the UI update, from server, via SMS. During this transfer, it is completely necessary to guarantee that the message received by the server was

plaintext with two different keys, you’ll get two different sets of cipher text. A symmetric cipher uses the same key for encryption and decryption. An asymmetric cipher operates with a key pair—one key is used for encrypting, while the matching key is used for decrypting.

3.3 Data Compression

Figure 2. Menu Ulmo-compliance

sent by a real authorized Ulmo-compliant application and that the UI update really came from the server. Ulmo uses an authentication policy based in password creation, using the IMEI (device serial number) as key, for each connection between server and application; this is a simple and efficient alternative. An automatic generator of password uses information presented in data being transferred, as timestamp, to build the password. Only the application and the server know this generator which makes difficult to a third unauthorized part to break the security. For a future work, an alternative is the creation of a message digest. In this option, the application creates a digest with information that can be seen by an unauthorized part, and the password already known by the server. A message digest push a large part of data into a small piece of data. If a single part of the file has changed, then the messages digest changes completely. The application sends the digest value with the other information and do not send the password. The server receives this information, creates a message digest with the values sent by the application and the password already known. If the digests are equal to each other, then the authentication is valid. Otherwise, the message can be discarded. Besides the authentication, when the application on the client side needs to exchange sensitive messages with the server so that other people do not get access to it, it is necessary to guarantee the data confidentiality. In the current Ulmo system development phase there is no such necessity yet, but for a future work it is considered to use ciphers. Ciphers can either encrypt data or decrypt it. An encrypting cipher accepts your data, called plaintext, and produces an unreadable result, called cipher text. A decrypting cipher takes cipher text and converts it back to plaintext. Ciphers use keys; if you encrypt the same

With a limitation of 160 characters per message, a compression algorithm is mandatory, helping to reduce the consumption of expensive resources, such as transmission bandwidth. On the other hand, the cost of processing for decompressing the information may be harmful to some systems. In our case, as one of our objectives is to reduce the overall cost, we think that the fewer messages are sent, the better. Ulmo uses jZlib library, which is a reimplementation of the Zlib software library [8]. Zlib is a lossless compression mechanism. This kind of compression algorithm is suitable to our purposes because we cannot allow information loss, in contrast to lossy compression algorithms, which are used mostly in audio and video applications. Zlib supports the DEFLATE algorithm.

3.4 Ulmo API for Mobile Application To provide easily the communication between Ulmo web side (Vairë subsystem) and a mobile application by binary SMS, we make available an API to be used by mobile application developer to create mobile application Ulmo compliance. This cited API have already implemented all communication protocol about a specific graphical user interface, in this article, the graphical user interface tested was a grid menu, so using this Ulmo mobile API is lightly possible to create a menu with grid format, showed in figure 2, which can be personalization by Ulmo system. The Ulmo API was developed based on Mandos framework, which is a kind of application framework, which deals with matters that involve specific applications construction project [4]. Mandos framework was designed to be used together with J2ME architecture, so currently Ulmo API, for while, exposes only interface in J2ME. To listen a SMS port to receive a binary SMS in mobile phone is necessary to register it in mobile application installation and inform it to Ulmo system, it is needful for Vairë-Ulmo subsystem to send the personalization data for the correct port, hence, for correct mobile application, for example, a mobile application Ulmo compliance as a Calculator must be registered in one SMS port in mobile phone, as 1D4C,

When the information data arrives in a specific SMS port in mobile phone the mobile application Ulmo compliance is launched presenting the new user interface.

4. Experiment Description

Figure 3. Ulmo system

and the port must be synchronized with Ulmo system, then when a personalization is done so only one port must be registered for one application, this article doesn’t purpose some mechanism to control/manager it.

3.5 Ulmo System: General Vision This section presents a general vision about Ulmo system. The figure 3 shows functionality diagram, illustrating a step by step for final user achieving a mobile application user interface personalization. As pre-condition to apply a mobile application personalization by Ulmo system is that the mobile application mentioned must be Ulmo-compliance (this work exposes an Ulmo API developed in J2ME to facilitate developer work, please see section 3.4). The first step is access Vairë subsystem in Ulmo system (Vairë is designed to be a Ulmo web module responsible for giving a user interface to final user to make mobile application personalization) to execute available changes in mobile application user interface, after it the final user endorses the changes to be applied in mobile application installed in a specified mobile phone. Then, all information data about user interface personalization is compiled by a standard protocol (more details in section 3.1) and sent by SMS broker using HTTP request. The SMS broker receives the HTTP request and sends a binary SMS containing personalization data to mobile phone. To specify the correct mobile application, it is used the SMS port, as described in sections 3.1.1 and 3.4.

This section describes the experiment executed in order to investigate the Ulmo system in terms of improvement in usability in mobile phone’s embedded software. The usability was chosen as property to be evaluated in order to argue the system value. It was used a mobile application shown in figure 2 (which contains a menu in grid format) in this experiment to measure the system capability to improve the usability in mobile phone’s embedded application. The cited menu has as purpose to be service deck, this cited menu can be changed by Ulmo system. In this experiment, it was used Nokia mobile phones manufacture. In order to valuate the Ulmo system, the mobile applications will be used by different mobile phone users, all of these users are considered as a potential customer on our evaluation. This experiment was made in Amazon, Brazil, where SMS technology is broadly disseminated, different from others mobile connection technology, as GPRS. Twenty people we have considered in this experiment and their profiles are described as follows: (i) We selected 10 men and 10 women. Each user took part in just one interaction test with each software version - one without Ulmo system intervention, aiming to execute changes and, consequently, improving usability. The other version uses Ulmo system in order to improve in agreement to user’s needs; (ii) We chose the users based on 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 [9]. (iv) User’s age was between 16 to 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 [18], (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” [15] The usability meaning 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 made use of Ulmo system. 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 for the documents that contain a list of questions to be answered [9]. The grade will be assigned to an application version that does not use the Ulmo system and to another application, which is Ulmo system compliance to perform improvements in user’s interface in agreement with user’s wish. The evaluations were fulfilled during one day, being the authors the only evaluators responsible for conducting all interaction tests. Each interaction test, running both applications with and without Ulmo system took approximately fifty minutes. All tests followed the same rigorous guidelines [12]. These guidelines are described as follows. The evaluation method was explained to each participant as well as what he/she should do and how long each session should take. It is of utmost importance that the evaluator provides the needed information to each participant in order for him/her to feel comfortable; the evaluator explains clearly for each participant that he/she is not being evaluated, only the tool in question. The aim of this method is to evaluate the mobile application usability, before and after Ulmo system usage. 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. Afterwards, the participant received the test guidelines. The participant was invited to use the application to be tested freely during five minutes The participant was introduced into Ulmo system concepts to observe how Ulmo system could bring improvements in usability. After training the participant, a list of tasks to be executed was delivered to the participant. The list contains a set of tasks considered real and stereotyped, as the developed experimental application consists in a menu to achieve services based on SMS, some presented tasks simulate the user to access a sequence of services which are distant from each other, the idea is to force the user identifying improvements based on changes in services position, which compose the menu. Firstly, the participant will execute the list of tasks without access to Ulmo system help. The events

Item p-value Learnability 0.0103 Efficiency < 0.0001 Memorability 0.0004 Errors < 0.0001 Satisfaction < 0.0001 Table 1. Participants Distribution (only p-value below that 1/20, which indicates 95% of assurance, is sufficient to prove that the embedded application is better is some item after Vairë tool usage).

observed by the evaluator should be registered in the data collection form. After the participant has used the mobile application as described previously, the same must use the Ulmo system, which could be accessed by a web browser aiming to improve the application’s usability, based on his/her feeling and preceding experience. When the participant performs all adjustments provided by Ulmo system and intended by him/her, he/she was oriented to transfer the adjustments to mobile phone also through Ulmo system, so they were reflected in the mobile application, the changes are sent by binary SMS, to execute the changes, the user only must press a button in Ulmo website and wait for update in mobile application, which is Ulmo compliance. Therefore, the same list of tasks executed before Ulmo system usage was executed again, but now with new interface based on user’s adjustments. After finishing all tasks for the two cited cases, the system evaluation questionnaire should be filled in by the participant. The measure must take into account the Ulmo system usage, not only the mobile application, and the process of adjustment in Ulmo website executed by the user, which increases the knowledge of application features. At the end of the evaluation phase, we talked to each participant 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. It was not executed any evaluation about Ulmo website (Vairë) usage/usability, the focus is on its results; in other words, only embedded application modified by Ulmo system in agreement with user’s wish will be evaluated and the method that changes it is sent for mobile application, which is binary SMS. After carrying out all interaction tests, we quantified all data of the applied questionnaires. With this data at hand, we fulfilled statistical tests with the purpose of verifying if the application usability was really improved or not by using the Ulmo system. In order to calculate the p-value, we initially thought of using the Paired t-Test. The Shapiro-Wilk test found that some

sets were not distributed inside a normal what 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 [11], it must be used if the test T conditions are not true in the case of no normality. 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.

5. Results In order to prove the hypothesis that the use of Ulmo system 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 and satisfaction, we concluded that the mobile applications after user makes use of the proposed system, obtained better results in all items. Table 1 shows the p-value that we found during the analysis, so this was achieved and the main hypothesis is considered as true. To evaluate precisely the improvements caused by the use of Ulmo system for each item, we collected at the end of the experiments important data that are described as follows: (i) 100% demonstrate some wish of executing changes in mobile phone user interface; (ii) 100% of interviewed people demonstrated interest in using the Ulmo system to improve some software on his/her mobile phone; (iii) 75% demonstrate interest in paying for SMS sent to change some mobile phone UI characteristic; (iv) 35% of interviewed people state that they felt a little bit confused with what is possible to change by Ulmo system; (it was discussed in Experimental Limitations section, the ideal is to give the user more UI changes options) (v) 25% demonstrated some displeasure in Ulmo website usage, but it is not the article focus, only focus on embedded application results; (vi) 30% demonstrated some displeasure due binary SMS delay to apply mobile application personalization; (vii) 65% cited as SMS usage a fair way to sent personalization information, it avoid cable usage.

5.1 Experiment Limitations The results presented in this work may contain some variation of the reality due to the experiment

limitations. One of these limitations include the time spent to use the mobile application, i.e., the best scenario would be that each participant could make use of the evaluated application in his/her day by day and identify what could be improved in agreement with his/her application usage. 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 (only service position in grid was changed in user interface); 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 [11].

6. Conclusion The usability is one of the main requirements to produce a successful application [13, 14]. Design of interactive products has been a challenge for humans since the Antiquity while trying to accomplish even the simplest tasks. The physiological adaptations that made humans more flexible than other primates allowed the development of a wide range of abilities and an incomparable versatility in behavior [15]. The person’s mental model will build internal constructions about each application conceptual model [16], thus, to attend the individual conception versatility in a mobile application usage, this paper proposed a system focused on giving to user the possibility to easily make personalization in user interface aiming to improve the mobile phone’s usability. The Ulmo system acts as a way to execute personalization in a mobile application based on individual user experience and individual cognition. Ulmo system is composed basically by three components: embedded application module, Ulmo web module for user to apply mobile application personalization and the communication module (all personalization information has been sent by binary SMS). The main hypothesis to be proved in this work was that the usability evaluation in mobile application after the Ulmo system usage would be improved. After carrying out the described experiment there are strong statistics evidences that Ulmo system can bring improvements in mobile application’s usability, obtaining good evaluations in all items used to measure usability: learnability, efficiency, errors, memorability and satisfaction. As future works we could mention as development

of a full and compact protocol to execute changes in mobile application, using matrix algebra to design a user interface [17], for example. The compacted data is necessary due channel link communication: SMS, which is popular technology in emergent market, where system is focused on.

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