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International Journal of Advanced Research in Computer Science and Electronics Engineering
Volume 1, Issue 5, July 2012

Roadmaps for Usability Engineering

Sanjeev Narayan Bal
Asst. Prof. Dept. of Comp.Sc.
Trident Academy of Creative Technology, Bhubaneswar
s_n_bal@yahoo.co.in

Abstract-- Usability engineering is a cost-effective, user of interactive application development, just as are systems
centered process that ensures a high level of effectiveness, engineering and software engineering. Usability engineering
efficiency, and safety in complex interactive systems. A activities can be tailored to allow individualizing as needed
major challenge, and thus opportunity, in the field of for a specific project or product development effort. The
human-computer interaction (HCI) and specifically usability engineering process applies to any interactive
usability engineering (UE) is designing effective user system, ranging from training applications to multimedia CD-
interfaces for emerging technologies that have no ROMs to augmented and virtual environments to simulation
established design guidelines or interaction metaphors, or applications to graphical user interfaces (GUIs). The usability
introduce completely new ways for users to perceive and engineering process is flexible enough to be applied at any
interact with technology and the world around them. This stage of the development life cycle, although early use of the
paper presents a brief description of usability engineering process provides the best opportunity for cost savings.
activities, and discusses our experiences with leading
usability engineering activities for different applications.
we propose a usability engineering approach that employs II. ACTIVITIES IN USABILITY ENGINEERING
user-based studies to inform design, by iteratively
inserting a series of user-based studies into a traditional
usability engineering lifecycle to better inform initial user
interface designs. We will discuss interaction,
visualization, and adaptive user support for maps on
mobile devices. we propose an entangled User Centered
System Design (UCSD) and Feature Driven Development
(FDD) process for MCI ,where a usability engineering
model is used.

Index Terms--Usability engineering, mobile devices, Mass
Casualty Incident, User Centered Design, Feature Driven
Development, virtual environments

I. INTRODUCTION
Usability engineering is a cost-effective, user-centered
process that ensures a high level of effectiveness, efficiency,
and safety in complex interactive systems . Activities in this
process include user analysis, user task analysis, conceptual
and detailed user interface design, quantifiable usability
metrics, rapid prototyping, and various kinds of user-centered
evaluations of the user interface. These activities are further
explained in Section "Activities in Usability Engineering."
Usability engineering produces highly usable user interfaces
that are essential to reduced manning, reduced human error,
and increased productivity. Unfortunately, managers and
developers often have the misconception that usability
engineering activities add costs to a product's development life Fig. 1 Typical user-centered activities associated with our usability
cycle. In fact, usability engineering can reduce costs over the engineering process. Although the usual flow is generally left-to-right from
life of the product, by reducing the need to add missed activity to activity, the arrows indicate the substantial iterations and revisions
that occurs in practice.
functionality later in the development cycle, when such
additions are more expensive. The process is an integral part

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As mentioned in the introduction, usability engineering usability experts rely explicitly and solely on established
consists of numerous activities. Figure 1 shows a simple usability design guidelines to determine whether a user
diagram of the major activities. Usability engineering includes interface design effectively and efficiently supports user task
both design and evaluations with users; it is not just performance (i.e.. usability). But usability experts can also
applicable at the evaluation phase. Usability engineering is not rely more implicitly on design guidelines and work through
typically hypothesis-testing-based experimentation, but user task scenarios during their evaluation. Nielsen
instead is structured, iterative user-centered design and recommends three to five evaluators for an expert evaluation,
evaluation applied during all phases of the interactive system and has shown empirically that fewer evaluators generally
development life cycle. Most existing usability engineering identify only a small subset of problems and that more
methods were spawned by the development of traditional evaluators produce diminishing results at higher costs. Each
desktop graphical user interface (GUIs). evaluator first inspects the design alone, independently of
In the following sections, we discuss several of the major other evaluators' findings. Then the evaluators combine then
usability engineering activities, including domain analysis, data to analyze both common and conflicting usability
expert evaluation (also sometimes called heuristic evaluation findings. Results from an expert evaluation should not only
or usability inspection), formative usability evaluation, and identify problematic user interface components and interaction
summative usability evaluation. techniques, but should also indicate why a particular
Domain Analysis component or technique is problematic. This is arguably the
Domain analysis is the process by which answers to two most cost-effective type of usability evaluation, because it
critical questions about a specific application context are does not involve users.
determined: Formative Usability Evaluation
• Who are the users? Formative evaluation is the process of assessing, refining,
• What tasks will they perform? and improving a user interface design by having
Thus, a key activity in domain analysis is user task representative users perform task-based scenarios, observing
analysis, which produces a complete description of tasks, their performance, and collecting and analyzing data to
subtasks. and actions that an interactive system should provide empirically identify usability problems. This observational
to support its human users, as well as other resources evaluation method can ensure usability of interactive systems
necessary for users and the system to cooperatively perform by including users early and continually throughout user
tasks . While it is preferable that user task analyses be interface development. This method relies heavily on usage
performed early in the development process, like all aspects of context (e.g.. user tasks, user motivation), as well as a solid
user interface development, task analyses also need to be understanding of Formative evaluation produces both
flexible and potentially iterative, allowing for modifications to qualitative and quantitative results collected from
user performance and other user interface requirements during representative users during their performance of task scenarios
any stage of development. In our experience, interviewing an . Qualitative data include critical incidents, a user event that
existing and/or identified user base, along with subject matter has a significant impact, either positive or negative, on users'
experts and application '"visionaries", Provides very useful task performance and/or satisfaction. Quantitative data include
insight into what users need and expect from an application. metrics such as how long it takes a user to perform a given
Observation-based analysis requires a user interaction task, the number of errors encountered during task
prototype, and as such, is used as a last resort. A combination performance, measures of user satisfaction, and so on.
of early analysis of application documentation (when Collected quantitative data are then compared to appropriate
available) and interviews with subject matter experts typically baseline metrics, sometimes initially redefining or altering
provides the most effective user task analysis. Domain evaluators' perceptions of what should be considered baseline.
analysis generates critical information used throughout all Both qualitative and quantitative data are equally important
stages of the usability engineering life cycle. A key result is a since they each provide unique insight into a user interface
top-down, typically hierarchical decomposition of detailed design's strengths and weaknesses.
user task descriptions. This decomposition serves as an Summative Usability Evaluation
enumeration and explanation of desired functionality for use Summative evaluation, in contrast to formative evaluation-
by designers and evaluators, as well as required task is a process that is typically performed after a product or some
sequences. Other key results are one or more detailed part of its design is more or less complete. Its purpose is to
scenarios, describing potential uses of the application, and a statistically compare several different systems or candidate
list of user-centered requirements. Without a clear designs, for example, to determine which one is "better,"
understanding of application domain user tasks and user where better is defined in advance. In practice, summative
requirements, both evaluators and developers are forced to evaluation can take many forms. The most common are the
"best guess" or interpret desired functionality, which comparative, field trial, and more recently, the expert review.
inevitably leads to poor user interface design. While both the field trial and expert review methods are well-
Expert Evaluation suited for design assessment, they typically involve
Expert evaluation (also called heuristic evaluation or assessment of single prototypes or field-delivered designs.
usability inspection) is the process of identifying potential Our experiences have found that the empirical comparative
usability problems by comparing a user interface design to approach employing representative users is very effective for
established usability design guidelines. The identified analyzing strengths and weaknesses of various well-formed,
problems are then used to derive recommendations for candidate designs set within appropriate user scenarios.
improving that design. This method is used by usability However, it is the most costly type of evaluation because it
experts to identify critical usability problems early in the may need large numbers of users to achieve statistical validity
development cycle, so that these design issues can be and reliability, and because data analysis can be complex and
addressed as part of the iterative design process. Often the challenging.
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III. USABILITY ENGINEERING APPROACHES field. Since this methodology assumes the presence of
TO DESIGINING USER INTERFACES guidelines and heuristics to aid in designs to be evaluated
during the "expert guidelines-based evaluation" phase, it is not
To date, numerous approaches to software and user applicable to emerging technologies such as augmented
interface design have been developed and applied. The reality, where user interface design guidelines and heuristics
waterfall model, developed by Royce, was the first widely have not yet been established. When examining many or the
known approach to software engineering. This model takes a approaches described above - and specifically the design and
top-down approach based on functional decomposition. Royce evaluation activities - in most cases, design activities rely on
admitted that while this process was designed to support large leveraging existing metaphors, style guides or standards in the
software development efforts, it was inherently flawed since it field (e.g., drop down menus, a browser's "back" button, etc.).
did not support iteration; a property that he eventually added However, in cases where an application falls within an
the model. The spiral model (Boehm, [1]) was the first widely emerging technological field, designers often have no existing
recognized approach that utilized and promoted iteration. It is metaphors or style guides, much less standards on which to
useful for designing user interfaces (as well as software), base their design. Moreover, in cases where the technology
because it allows the details of user interfaces to emerge over provides novel approaches to user interaction or
time, with iterative feedback from evaluation sessions feeding fundamentally alters the way users perceive the interaction
design and redesign. As with usability engineering space (i.e., where technology and the real world come
approaches, the spiral model first creates a set of user-centered together), designers often have little understanding of the
requirements through a suite of traditional domain analysis perceptual or cognitive ramifications of "best guess" designs.
activities (e.g., structured interviews, participatory design, As a result, a process is needed to help designers of novel user
etc.). Following requirements analysis, the second step simply interfaces iteratively create and evaluate designs, to gain a
states that a "preliminary design is created for the new better understanding of effective design parameters, and to
system". Hix and Hartson [2] describe a star life cycle that is determine under what conditions these parameters are best
explicitly designed to support the creation of user interfaces. applied. Without this process, applications developed using
The points of the star represent typical design/development traditional usability engineering approaches can only improve
activities such as "user analyses", "requirements/ usability incrementally from initial designs which again, are often
specifications", "rapid prototyping", etc, with each activity based on developer's best guesses, given the absences of
connected through a single center "usability evaluation" guidelines, metaphors, and standards.
activity. The points of the start are not ordered, so one can
start at any point in the process, but can only proceed to
another point via usability evaluation. The design activities
focus on moving from a conceptual design to a detailed
design. Mayhew [3] describes a usability engineering lifecycle
that is iterative and centered on integrating users throughout
the entire development process. With respect to design, the
usability engineering lifecycle relies on screen design
standards, which are iteratively evaluated and updated. Both
the screen design standards as well as the detailed user
interface designs rely on style guides that can take the form of
a platform" style guide (e.g., Mac, Windows, etc.),
"corporate" style guide (applying a corporate "look and feel"),
"product family" style guide (e.g., MS Office Suite), etc.
Gabbard, Hix and Swan [4] present a cost-effective,
structured, iterative methodology for user-centered design and
evaluation of virtual environment (VE) user interfaces and
interaction. Fig. 2, depicts the general methodology, which is
based on sequentially performing:
1. user task analysis,
2. expert guidelines-based evaluation,
3. formative user-centered evaluation, and
4. summative comparative evaluations.
While similar methodologies have been applied to
traditional (GUI-based) computer systems, this methodology
is novel because we specifically designed it for —and applied
it to —VEs, and it leverages a set of heuristic guide-
lines specifically designed for VEs. These sets of heuristic
guidelines were derived from Gabbard's taxonomy of
Fig. 2 The user-centered design and evaluation methodology for virtual
usability characteristics for VEs [5,6]. A shortcoming of this environment user interaction described by Gabbard .
approach is that it does not give much guidance for design
activities. The approach does not describe how to engage in User Interface Design Activities for Augmented Reality
design activities, but instead asserts that initial designs can be As shown in Fig. 3, it can be argued that user-based
created using input from task descriptions, sequences, and experiments are critical for driving design activities, usability,
dependencies as well as guidelines and heuristics from the and discovery early in an emerging technology's development

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(such as AR). As a technological field evolves, questions about how different design parameters might
lessons learned from conducting user-based studies are not support user task performance, designers may be able to
only critical for the usability of a particular application, but conduct a user-based study as a starting point. Under this
provide value to the field as a whole in terms of insight into a approach, designers start with experimental design parameters
part of the user interface design space (e.g., of occlusion or as opposed to specific user interface designs. As shown in Fig.
text legibility). As time progresses, contributions to the field 4, user based studies not only identify user interface design
(from many researchers) begin to form a collection of parameters to assist in UI design, but also have the potential to
informal design guidelines and metaphors from which produce UI design guidelines and lessons learned, as well as
researchers and application designers alike can draw from. generate innovation, which provides both tangible
Eventually, the informal design guidelines are shaken down contributions to the field while also improving the usability of
into a collection of tried-and-true guidelines and metaphors a specific application. Ultimately, a set of iteratively refined
that are adopted by the community. Finally, the guidelines and user interface designs are produced that are the basis for the
metaphors become "defacto" standards or at best deemed overall application user interface design. This design can then
"standards" by appropriate panels and committees. The be evaluated using formative user-centered evaluation, as
context of the work reported here, however, falls within the described by Hix, Gabbard, and Swan [4].
application of user-based studies to inform user interface
design; the left-most box of Fig. 3. Based on our experiences
performing usability engineering, and specifically design and
evaluation activities for the Battlefield Augmented Reality
System, we propose an updated approach to user interface
design activities for augmented reality systems. This approach
emphasizes iterative design activities in between the user task
analysis phase (where requirements are gathered and user
tasks understood) and the formative user-centered evaluation
phase (where an application-level user interface prototype has
been developed and is under examination) (Fig. 2). With this
approach, w7e couple the user expert evaluation and user-
based studies to assist in the user interface design activity
(Fig. 3). Expert evaluations can be iteratively combined with
well-designed user-based studies to refine designers'
understanding of the design space, understanding of effective
design parameters (e.g., to identify subsequent user-based
studies), and most importantly to refine user interface designs.
A strength of this approach is that interface design activities
are driven by a number of activities; inputs from the user task
analysis phase (Fig. 2), user interface design parameters
correlated with good user interface performance (derived from Fig. 3 User-based experiments are a critical vehicle for discovery and
usability early in an emerging field's development. Over time, contributions
user-based studies), and expert evaluation results. from the field emerge, leading eventually to adopted user interface design
With this methodology, expert evaluations along with guidelines and standards.
user-based studies are iteratively applied to refine the user
interface design space.
Of the three main activities shown in Fig. 3, there are two
logical starting points: user interface design and user based
studies. An advantage of starting with user interface design
activities is that designers can start exploring the design space
prior to investing time in system development, and moreover,
can explore a number of candidate designs quickly and easily.
In the past, we have successfully used PowerPoint mockups to
examine dozens of AR design alternatives. If mocked up
correctly, the static designs can be presented through an
optical see through display, which allows designers to get an
idea of how the designs may be perceived when viewed
through an AR display in a representative context (e.g.,
indoors versus outdoors). Once a set of designs have been
created, expert evaluations can be applied to assess the static
user interface designs, culling user interface designs that are
likely to be less effective than others. The expert evaluations
are also useful in terms of further understanding the design Fig. 4 We applied the depicted user-centered design activities as part of
space by identifying potential user-based experimental factors our overall usability engineering approach when developing the Battlefield
Augmented Reality System .
and levels. Once identified, user-based studies can be
conducted to further examine those factors and levels to
determine, for example, if the findings of the expert evaluation
match that of user-based studies. In cases where the design
space is somewhat understood and designers have specific
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IV. USABILITY ENGINEERING FOR MOBILE

DEVICES
Usability determines to a major extent the success of
products and services that are based on information and
communication technology. Usability engineering [10] is an
approach to develop software that is easy to use. effective and
efficient, and is in our opinion based on three principles: 1)
Early and continuous focus on user and tasks. 2) empirical
measurement. 3) and iterative design. In UE several
development cycles (Figure 5), with assessments and re-
specifications, are worked through. A complex and interesting
scenario is developed with users, from which user
requirements and features can be derived. The features are
implemented and the quality is assessed by human computer
interaction (HCI) metrics. These metrics are closely related to
the social challenges, regarding comfort and acceptance, but
the technological challenges are also addressed in the metrics.
When taking the user as the center of the design it is also
important to take into account his or her cognitive task load Fig. 5 The Usability engineering method
[9], for which several metrics exist. The assessment of the use which experimental method.
metrics can be done in several different ways, either by We conclude that difficulties for usability testing for
experts or users. mobile devices exist, but several frameworks are available
which can be used for designing usable mobile map
UE is a good design approach for a usable mobile map. applications. Because there are many challenges for mobile
But thorough understanding of the dynamic use context is applications, ease of use and effectiveness are crucial. Using a
crucial for user-centered design of mobile applications [7, 12]. sound usability engineering approach, we decide which
With mobile devices it is necessary to test them eventually interface features for mobile maps help dealing with the
while the user is mobile, which makes evaluation difficult. technological, environmental, and social challenges.
Depending on the task and the application, usability can Example-- Tourist information and navigation support by
highly differ between a sunny day and a rainy day, between a using 3D maps displayed on mobile devices
noisy environment and a silent environment. The choice Laakso, Gjesdal and Sulebak [8] developed 3D maps with
between a lab-experiment or a field experiment is therefore far tourist information and GPS for mobile devices. In this study
from crucial for mobile devices [13]. The use of the mobile there was a strong focus on user requirements and feedback of
map is mostly a secondary task; the primary task (route potential users on the prototypes. The study consisted of three
planning or looking for a nearby restaurant) does have a iterations. In the first iteration the intended user group was
strong influence on the way of use. Not only the device has to asked how they did perform the task which the application
have a high degree of fidelity, but the primary task has to be was going to support, and which functionalities they would
simulated realistic too. Zhang and Adipat [13] give an like to have in the proposed application. With the answers it
overview of challenges in usability testing of mobile devices. was possible to create a prototype which was tested in the
These challenges are the same as the design challenges for second iteration. The application was tested in a usability test
mobile applications: mobile context, connectivity, small and with focus groups. Both the participants of the usability
screen size, different display resolutions, limited processing test and the participants of the focus groups belonged to the
capability and power, and different data entry methods. An group of intended users. The tasks that were performed in the
example is that low screen resolution can have disastrous usability test were typical tasks for the application and
effects on the usability of a mobile application. There are performed in a realistic field environment. There was one
different frameworks for usability testing of mobile devices drawback of the design of the experiment. The 3D map was
[11,13]. In all frameworks, it is an important question whether shown on a mobile device whereas the 2D map was of paper.
to do a usability test in the laboratory or in the field, and Therefore it was difficult to compare the two views. In the
whether experts are used or prospective users. Lab- final iteration another prototype was evaluated with the use of
experiments are appropriate for improvement of the interface usability tests and questionnaires. The 3D map was found fun
design, for which the real device or an emulator can be used. but less usable than the 2D map. for which an explanation
Field-experiments on the other hand are more appropriate could be that participants are used to 2D maps. Furthermore
when the final application is tested [13]. The framework of results showed that location positioning, for example using
Streefkerk et al. [11] extends the framework of Zhang and GPS, is very important for map information on mobile
Adipat by that it not only gives instructions on which devices. The experimental set-up of this study is a sound
experimental method to use , but gives constraints for when to example of usability engineering. All three general approaches
are followed; there is an early and continuous focus on the
user, empirical measurements are used, and it is an iterative
design. In this experiment the technological challenge for

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visualization of the viewpoint was examined and several HCI • Ambulance crews are informed on their way to the area
metrics were used to measure the usability of the design. of operation as well as while waiting at the ambulance
Users were included in both the design and the usability assembly area. Supplying this information to the rescue
testing. workers can help to cope with anxieties and help to prepare
them for the situations they will be confronted with .
V. USABILITY ENGINEERING FOR MASS
CASUALITY INCIDENTS • All relevant information is stored on central servers for
ad-hoc as well as post-hoc analyses. This information can
To design an application system that is usable in case of an be very useful to implement organizational learning and
MCI, we propose an entangled approach of User-Centered gradually improving the whole man-machine-system over
System Design (UCSD) and Feature Driven Development time.
(FDD) [14,15,16,17]. To prepare users to be able to handle a At the moment our project is still in a first prototypical
system in case of an MCI, we propose that the MDGS state. The goal is to integrate the system as a module into
provides training for MCIs within the regular day-to-day the R2-System, an end-to-end solution for regular transport
business . This should be accomplished by using similar and rescue missions, of the DIGITALYS GmbH.
support systems for handling MCIs and regular rescue and
transport missions. Speaking in terms of software engineering,
support for an MCI should be provided by an additional
module of the same MDGS framework that is used for
handling the regular day-to-day business.
Development Process
As already mentioned, we follow an entangled approach
that combines UCSD and FDD to keep the project and
development process focused (Figure 6). Classic elements of
UCSD (e.g. user studies, interviews) will be complemented
by:
•observing MCI exercises;
•accompanying paramedics and emergency physicians
while they are using the MDGS in regular missions;
•evaluating the usability of the MDGS in regular missions; Fig. 6 Process model combining FDD and UCSD .
•attending emergency medical aid and MCI related
workshops.
Combining these and scientific information, features can
be derived. Natural dependencies between these "small, client
valued function[s]" [17] and a prioritization process will lead
to a sorted list of feature sets. To work through the list, we use
the iterative and incremental process of FDD. By using an
entangled FDD/UCSD process as our software
engineering paradigm, we are able to quickly roll out feature-
sets, as well as keeping them close to the users' needs
and expectations through repeated user-feedback.
General Principles for MDGSs
Figure 7, gives an overview of our proposed MDGS. The
overall design is based on the assumption that an MDGS
that follows the principle has to be technically feasible and
suitable for handling day-to-day rescue and transport
missions as well as MCIs. The basic features as shown in the
figure are:
• All rescue workers (paramedics, emergency physicians,
team leader, and incident commander) are using the same
handheld device, most likely a rugged tablet PC.

• All stakeholders (public-safety answering point, crisis
squad, hospital staff, and rescue teams) are kept in the
loop. They are aware of all necessary information. The users
are guided by dialogues that are simple enough to be
still useful even in very demanding situations.

• The location of every patient and rescue worker is made
available by location-based services for the stake holders in Fig. 7 Handling of MCIs as an integrated part of general MDGS.
command.

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VI. CONCLUSION [14] Chu, Y. and Ganz, A. 2007. WISTA: a wireless
telemedicine system for disaster patient care. Mob. Netw.
From these three applications, we have learned many Appl. 12,201-214.
lessons on how to improve the process of usability [15] Demchak, B., Chan, T. C, Griswold, W. G., and Lenert,
engineering. L. A. 2006. Situational awareness during mass-casualty
We have presented a modified usability engineering events: command and control. A MI A Anna Symp Proc, 905.
approach to design that employs a combination of user [16] Norman, D. A. and Draper, S. W. 1986. User centered
interface design, user-based studies and expert evaluation to system design. New perspectives on human-computer
iteratively design a usable user interface as well as refine interaction. Erlbaum, Hillsdale, N.J.
designers' understanding of a specific design space. In this [17] Palmer S. R. and Felsing J. M. 2002. A Practical Guide
paper we looked at the usability of maps on mobile devices. to Feature-Driven Development. Prentice Hall
Different methods of visualization, interaction, and adaptive PTR, Upper Saddle River NJ.
user support to obtain good usability were discussed in the
view of technical, environmental and social challenges. We
have also disclosed a model for Usability Engineering for Author
Mass Casualty Incidents. Sanjeev Narayan Bal
MBA, MCA, MTech (CSE)
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