State Of Art In Usability Computer Science Essay

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Usability, originally derived from the term user friendly is one of the characteristics included in all quality standards and definitions. However, each researcher uses in his work different definitions of usability and thus it is not possible to give one, exact definition. In the following paragraph are provided several common definitions and international standards, which have become to be widely accepted by the academic community.

Definition of Usability

Usability, defined as: for people who use the product can do so quickly and easily to accomplish their tasks. It may also consider such factors as cost-effectiveness and usefulness. [Dumas & Redish, 1999.]. The Usability Professionals Association (UPA) definition focuses more on the product development process when usability is an approach to product development that incorporates direct user feedback throughout the development cycle in order to reduce costs and create products and tools that meet user needs. Furthermore, international standards about the usability already exist. For an example, one refers to the extent to which a product can be used by specified users to achieve specified goals with effectiveness, efficiency and satisfaction in a specified context of user [ISO 9241-11, 1998]. Another standard presents a term Human(User)-Oriented Design, which is characterized by: the active involvement of users and a clear understanding of user and task requirements; an appropriate allocation of function between users and technology; the iteration of design solutions; multi-disciplinary design [ISO 13407, 1999]. Third example of an international standard is IEEE-1061 (1998), which describes usability as the ease with which a user can learn to operate, prepare inputs for, and interpret outputs of a system or component. Although these definitions and standards are used across the globe, they are also very general and do not describe precisely neither the methodologies nor frameworks, which could be used for testing developed applications. Thus, eight attributes and later one additional attribute were defined to measure software usability, [Nielsen, 1993; Goldstein, 2002] and they are described below:

Learnability deals with users and their ability to finish tasks for their first time application using.

Efficiency describes how fast users can proceed different tasks during using an application.

Memorability focuses on how users can perform tasks when they return to use an application after some time.

Errors, it is possible to count number of mistakes, which users make while they work with an application and how easily users can correct the mistakes. These mistakes might have different level of importance (severity) or being of different types (e.g. wrong button pressed, input data mistake, misunderstanding of functionality).

User satisfaction reports how users like or dislike tested application and it is based on a personal opinion of each user.

Effectiveness is defined for a certain goal and userâ„¢s ability to achieve this goal with a certain completeness and accuracy.

Simplicity is a level of comfort with which users find a solution for a given tasks.

Comprehensibility ¦.

Learning performance measures ...

Except the general definitions and attributes of usability, there is also a different look on usability. One of it is the type of user working with the application. For the end user, software usability is essential because it measures user performance, satisfaction, and productivity. An application with a good usability will allow the user to perform the tasks more efficiently. For managers, usability is a major decision factor, particularly for selecting a product because it has a direct influence on the organizational productivity and performance. The last group, software developers and users with professional skills in a computer field, see usability from the view, which can be described in terms of internal attributes of a system that affect user performance and productivity [Gafni, 2009]. Moreover, except type of users, there are huge differences between usability for desktop software and for mobile applications. Since desktop software expects using in a standard human-computer interaction way, concepts, approaches and methodologies already made for it are not always usable in mobile applications [Jones et al., 1999].

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After usability testing is performed, output report is automatically the next step. Even if testing is done precisely, wrongly written report can destroy all the work, which has been already made. Avoid such a situation, report should follow several guidelines. It should have appropriate length (no more than 60 problems described), has executive summary included, problems having severity classification, amount of users facing the problems (frequency). Also, there should be some positive findings (not only the negative things) about the tested application and the report should have a professional look and layout [Redish J. G., Bias R. G., Bailey R., Molich R., Dumas J., Spool J. M., 2002].

Usability of Mobile Applications

Subsequent to the given definition of the general usability, the following sections are focused on the usability in devices. Firstly, the definitions of mobile devices and applications are provided; secondly, specific issues in usability of mobile applications are considered and related works and researches are presented.

Definition of Mobile Application

Mobile application is defined as a service that is accessible on mobile devices. A mobile device is anything that can be used on the move, ranging from laptops to mobile phones. In the next sections only the mobile phones with their specific functionality (e.g. making phone calls) and construction issues (small screen, limited keyboard, etc.) will be considered as mobile devices. The first service that was available over mobile devices was that of voice communication [Andersen, 2002]. Nowadays, mobile applications are a rapidly developing segment of the global mobile market. They consist of software that runs on a mobile device and performs certain tasks for the user of the mobile phone [MMA, 2008].

Applications can be run on different types of mobile phones; starting from the low-cost, inexpensive models, over the middle-class phones and finishing with the high-end models equipped with the latest technologies. With over 5,000 phone types in the global market, it is important to narrow down how the project idea (and future application) is to be executed to reach the target audience [Cartman J., Ting R., 2009]. However, not every application can be run on every phone. This depends on the category of application and on its requirements. Here is the basic classification of mobile applications when we consider the runtime environment:

Native platforms and operating systems - Symbian, Windows Mobile, Android, Samsung Touchwiz, etc.

Managed platforms - J2ME, BREW, Flash Lite, etc.

Mobile runtimes applications " Opera Mini, Mobile Firefox, Google Maps, etc.

Another approach is to classify the mobile applications according to their type of usage. Mobile Marketing Association (MMA) divides applications into the six main categories as described below:

Communication " email clients, IM clients, web browsers, social network clients, etc.

Office " calendars, calculators, spreadsheets, text processors, etc.

Games " action, sport, logic, educational, etc.

Multimedia " picture viewers, video / audio players, sound recorders, etc.

Travel " city guides, navigation (GPS), maps, weather forecast, etc.

Utilities " file managers, task managers, address book, etc.

Usability Issues in Mobile Applications

The usability of the mobile devices and their applications is a key factor for the success of mobile computing. The needs and characteristics of the mobile user, the usage context of the mobile devices and the physical limitations of these devices are factors, which can influence the interaction and should be considered in the design of the interfaces, as well as in the usability evaluation [Betiol & Cybis, 2005]. The list and description of the most limitation areas for mobile applications are described in the next paragraphs.

Mobile context can be defined as: any information that characterizes a situation related to the interaction between users, applications, and the surrounding environment [Dey & Abowd, 2001]. Mobile applications are mainly used in a dynamic context where users are in move and under the influence of the surroundings, e.g. colleagues in the office, walking on the street, etc. It means that users do not interact with an application like they are used to do with desktop software. It is a difficult task to choose a methodology that would include all types of mobile context in a single usability test [Smith et al., 2001].

Small screen size is one of the physical constraints of mobile devices. Small screen size can significantly affect the usability of mobile applications. For example using mobile devices with small screen for browsing web pages can be very complicated and uncomfortable. Moreover, most of the users would stop using such an application on their devices after several failures in usability. Other issue closely connected with the small screen size is different display resolutions. At present, the top mobile devices have resolution 800 x 480 pixels. However, the most common resolution is 240 x 320 pixels or even below [DeviceAtlas, 2010]. Low resolution degrades the image / video quality, textsâ„¢ readability and provides less space on display for showing control and navigation buttons.

Providing input to small devices is difficult and requires a certain level of proficiency [Smith et al., 2001]. Small buttons and labels limit usersâ„¢ effectiveness and efficiency in entering data, which may reduce the input speed and increase errors. Results of a usability study can be affected by the use of different data entry methods (e.g., soft versus physical keyboards) (MacKenzie & Zhang, 1999; Soukoreff & MacKenzie, 1995; Zhang, 1998). Different user status (e.g., sitting versus walking; holding a device in hand or putting it on a table) while using a mobile device can further exacerbate the data entry problem. There are also some other challenges. Today, multimodal mobile applications are emerging. Multimodality combines voice and touch (via a keypad or stylus) as input with relevant spoken output (e.g., users are able to hear synthesized, prerecorded streaming or live instructions, sounds and music on their mobile devices) and onscreen visual displays in order to enhance the mobile user experience and expand network operator service offerings. Blending multiple access channels provides new avenues of interaction to users, but it poses dramatic challenges to usability testing as well.

The network connectivity in the mobile devices is rapidly emerging. Different methods of access based on WiFi, 3G and 4G technologies allow connecting devices to the Internet in any time and any place where the signal is available. Unfortunately, the technologies are not always reliable and fast enough and thus it is a common hindrance for mobile applications [Smith et al., 2001]. Strength of signals and data transfer speed in a wireless network may vary at different time and locations, compounded by user mobility [Sears & Jacko, 2000]. This problem mainly affects data downloading time and quality of streaming media (e.g. video clips). For developers it means to develop their applications in a way when the bandwidth has to be used effectively and do not using the connection until it is necessary for the expected application behavior.

Limited computational power of mobile devices lags far behind the present desktop computers. Some applications that require a large amount of memory for graphic support or fast processing speed, such as applications of 3D maps or action games [Rakkolainen & Vainio, 2001], may not be practical for mobile devices. Furthermore, fast processing speed, big screen size as well as network connectivity drain the battery life. The old devices were able to run several weeks on one charge, when most of todayâ„¢s devices have to be charged every few days. This is also very crucial while developing mobile application; considering the power consumption is a marginal issue in order to accomplish a userâ„¢s satisfaction.

The above problems caused by physical restrictions of mobile devices and wireless networks imply that while designing and conducting usability studies for mobile applications, these issues must be carefully examined in order to select an appropriate research methodology and minimize the potential effect of contextual factors on perceived usability when they are not the focus of studies.

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