The Principles In Usability Engineering

Published Date: 02 Nov 2017

Faulkner (1998) has defined usability engineering as "usability engineering endeavors to solve the problem of ensuring that the system is fit for which it was designing" (Faulkner, 1998). According to Dix et al (2005) usability engineering is "one approach to user-centered design has been introduction of explicit usability engineering goals into the design process" (Dix et al, 2005). As per Faulkner (1998) usability engineering focuses on real users in action and measures the system in terms of pre-defined set of criteria. As described by Faulkner (1998) usability addresses the practical rather than the theoretical. This methodology helps to designed out deficiencies in the system. As said by Faulkner (1998) Usability Engineering is a methodology which helps to make the process of design open and includes different types of measurements that against criteria which were agreed earlier. In this methodology all the decisions relate to the interface design will be taken by the designer. From this it helps to do the interface design in the appropriate manner since the designer has been work on different interface and has knowledge about it. Also since the designer is dealing with the interface design there will not be any misunderstanding about what exactly need to do. From this also has better understanding among the team members.

Principles in Usability Engineering

According to Faulkner (1998) the main objective of usability approach is to identify what success is and decide how it might be measured. Principles that support usability categorized into mainly three categories. They are,

Learnability: - In the category of learnability describes about the effective ways to approach for an appropriate interaction and get the maximum performance from that.

Following principles are has developed to make the learnability much effectively. Below Table 1 describes about the principles evolves with the learnability.

Principle

Definition and Explanation

Related Principles

Predictability

Support for the user to determine the effect of future action based on the past interaction history. From that mistakes can happen when working on system and adding requirements will be reduced. Also user will have clear idea about what really happen in the upcoming functions in the system.

Operation Visibility

Synthesizability

Support for the user to assesses the effect of past operations on the current state.

Immediate Honesty

Familiarity

User can use the knowledge that has working on previous work, in other real world activities to interact with the system.

Guess ability, affordance

Generalizability

Support for the user to extend knowledge or specific interaction within and across the application to other similar situations

-

Consistency

Likeness in input-output behavior arising from similar situations or similar task objectives

-

Source: Author’s Work based on Dix et al, (2005)

As mentioned in above Table1 the principles which are having built up for improve the human interaction towards the system has discussed for the users’ side. These principles explained how a user can use the knowledge that has to have an effective interaction in-order to get the maximum output.

Flexibility: - Flexibility evolves with the multiple ways which end-user and system exchange information.

Principle

Definition and Explanation

Related Principles

Dialog Initiative

Allowing the user freedom from Ability of artificial constraints on the input dialog imposed by the system

System

Multi- threading

Ability of the system to support user interaction pertaining to more than one task at a time.

Concurrent vs. interleaving, multi-modality

Task migratable

The ability to pass control for the execution of a given task that so that it becomes either internalized by the user and the system or shared between them.

-

Substitutivity

Allow equivalent values of input and output to be arbitrarily substituted for each other

Representation multiplicity, equal opportunity

Customizability

Modifiability of the user interface by the user of the system

Adaptively

Source: Author’s Work based on Dix et al, (2005)

Above table2 discuss about the flexibility of the system. How flexible the system should interact with the user. By following these principles can measure the efficiency of the system. This is not discussing straight a way of how the user interaction help to develop a system. But these principles can accomplish if follows the principles in the Table 1 which leads to have an output/system which is into user’s standard.

Robustness

Robustness evolves with interaction covers features which are supporting the successful achievement and assessment of the goals.

Principle

Definition and Explanation

Related Principles

Observability

Ability of the user to evaluate the internal state of the system from its perceivable representation. This helps to customer to see the difference between the current system and the system that is in development stage.

Browsing, static/dynamic/default, reachability, operation, visibility

Recoverability

Ability of the user to take corrective action once an error has been recognized

Reachability, forward/backward recovery

Responsiveness

How the user perceives the rate of communication with the system. In this principle checks how long system will take for respond to user action.

Stability

Task Conformance

The degree to which the system the user to wishes to perform and in the way that the user understands them

Task completeness, task adequacy

Source: Author’s Work based on Dix et al, (2005)

Principles that have described in above Table 3 help user to check the satisfaction level user has towards the system. From these principles user can find out whether system is up to the standard as expected by the user. If these principles are complete which means user is satisfied with the current status of the system and developers can continue the development stages in the system.

Usability Specification

There are various types of features in the usability engineering method, but one of the most important features is usability specification. Under the usability specification includes and describes the requirement specification which helps to focuses on the features of the user system interaction which that evolves with the usability of the product. As described by White et al. (1988) cited in Faulkner (1998) usability specification creates to identify followings,

Performance Criteria

Description

Worst Case

Worst possible scenario for the system and one that make it unacceptable, there can be more errors than the present system.

Lowest Acceptable Level

Lowest level of performance that is acceptable by the user, this consists of same errors as in current system

Planned Case

Level the system is expected to achieve, Few errors can be in the system

Best Case

Best possible scenario, error free

Now level

Current status of the system

Source: White et al. (1988) cited in Faulkner (1998)

Usability specification helps user/client to aware of the status of the system in different levels. From that client can give appropriate feedbacks to the development team, because user has better understand of the system status. Below Figure is sample usability specification table.

Source: Ferre et al, (2001)

There are different levels in usability specification. They are,

An existing system/previous version

Your own prototype

Competitive systems

User’s earlier performance

Carrying out the task without use of a computer system

Each component of a system separately

An absolute scale

A success split of the difference between best and worst values observed in user tests

Source: Whiteside, Bennett and Holtzbaltt (1988) cited in Dix et al (2005)

Also usability specification focuses on above mentioned levels and gathers information. This information leads into have a clear and effective communication between the user and the system. Because the usability specification covers the every single component in the system and the comparison between the current and the developing system help to identify whether new system up to the user’s standard which fulfill all the functional requirements.

Usability Engineering in Software Development

Figure : Usability Process

Source: Ferre et al, (2001)

According to Ferre et al (2001) Above Figure illustrates the usability process which is help when user interaction with designers to have a proper communication during the analysis phase and help the design in design phase. As mentioned in above Figure there is two main phases in the usability process. They are, analysis phase and design phase. In the analysis phase focuses on users and in design phase focuses on user interface.

Phase

Explanation

Analysis Phase

User Analysis

This is the phase of gathering information from users. There are different types of information gathering techniques. Most popular techniques are site visits, focus groups, surveys and derived data. Most of the time first approach is site visit. In the site visit developers analyses the way the users use systems and the processes in the system also in-order to gather more information interview users and find out the problems and needs of them. Contextual Analysis is a structured way of gathering information which can be used during gathering information. In-order to gather view points and experience knowledge uses focus group approach.

Task Analysis

According to Ferre et al (2001) "task analysis describes set of techniques people use to get things done" (Ferre et al, 2001). In usability process task analysis conducted in a way of focuses on smaller tasks which are helps to easy to understand complicated tasks. This approach helps to developers build most appropriate functions in the system. One of the approaches can use in this is user centered design model in this model tasks describe as use-cases. At the end of the task analysis find out the most appropriate task sets. Task sets will be given to the users and from that analyses the performance and identify tasks and sub tasks for the system depend on the user requirements.

Usability Benchmark

Identify quantitative usability goals which are define before the system design. This is important because in-order to have development attributes need to have operationally defined usability benchmarks. Usability attributes are define according to the developers wants, for the functions need to evaluate will be define usability benchmarks. Usability benchmarks need to define in a way of calculable in a usability test or user satisfaction questionnaire. Usability benchmark linked with task analysis.

Design Phase

Phase

Conceptual Design

In the conceptual design defines user system interaction and the objects in the user interface and the context which interaction take place. The information gathered from user and task analysis will be used to draw screen mockups. Conceptual design defines the foundation of the entire system because of that it called as most critical phase. The design in the conceptual design is very creative. There are set of rules need to follow when designing. Principles cover feedback. Reuse, simplicity, structure, tolerance and visibility in UIs. At the end of conceptual design evaluate the results using the drawn prototype and defined tasks.

Visual Design

In this phase defines the user interfaces’ appearance. This includes the layout of screens and dialog boxes, use of widgets and design of graphics and icons. In the visual design also set of rules that need to follow. In this phase designing done by professional designers. This phase focuses on screen design and real specifications of UI appearance. At the end of this phase prototypes must be tested and the final speciation of the UI and specification for new widgets.

Explanation of Usability Process

Source: Ferre, (2003)

Above Figure illustrates how the above mentioned activities has grouped base on the development activities.

Tools and Techniques in Usability Engineering

Write an introduction

Techniques (Inception Methods)

Heuristic Evaluation

According to Holzinger (2005) Heuristic evaluation is a usability inspection methods use as a technique in usability engineering. As per Fortson (2012) in heuristic evaluation usability specialists evaluate interface using set of principles which introduced by Nielsen. According to Dix et al (2005) Heuristic evaluation is a flexible and relatively cheap approach. This consider as a discount usability technique. Heuristic evaluation can use to evaluate the design earlier by creating design specification. This also can use in prototypes, story boards or fully functioning system. In heuristic approach several evaluators evaluate the system and critique the system in-order to come up with a potential usability problem. According to Dix et al (2005) between three to five evaluators are enough to resulting 75% of usability problems in a system. In-order to do evaluation properly Nielsen has set 10 heuristics. They are,

Heuristic

Description

Visibility of system status

Always keep user informed about what is going on, through appropriate feedback within reasonable time.

Match between system and the real world

The system should speak the user’s language, with words, phrases and concepts familiar to the user, rather than system oriented terms.

User control and freedom

User often chooses system functions by mistake and need a clearly marked. Support undo and redo.

Consistency and standards

User should not have to wonder whether words, situations or actions mean the same thing in different contexts. Follow platform conventions and accepted standards.

Error Prevention

Make it difficult to make errors. Even better than good error messages is a careful design that prevents a problem from occurring in the first place.

Recognition rather than recall

Make objects, action and option visible. The user should not have remembered information from one part of the dialog to the other. Instructions for use the system should be visible or easily retrievable whenever appropriate.

Flexibility and efficiency of use

Allow user to tailor frequent actions.

Aesthetic and minimalist design

Dialogs should not contain information that is irrelevant or rarely needed. Every extra unit of information in the dialog competes with the relevant unit of information and diminishes their relatively visibility.

Help users recognize, diagnose and recover from errors

Error messages should be expressed in plain language (no code), precisely indicate the problem and constructively suggest a solution.

Help and documentation

Few systems can be used with no instructions so it may be necessary to provide help and documentation. Any such information should be easy to search, focused on the user’s task, list concrete step to be carried out and not be too large.

Source: Dix et al, (2005)

Above mentioned table consists of Nielsen ten heuristics which are help to do a design to ta system. These principles help to do a very proper design for the system. By following these principles and collect appropriate information from the clients which are align to these principles can do a design will help to do a design fulfill user requirements and standard as required. After gathering requirements from the user can identify the usability problems and requirements can rate the usability problem and from that it helps to identify the required functions need include in the design.

Cognitive Walk through Method

According to Alshboul (2012) "Cognitive walk through is a practical evaluation technique and it is a task oriented method by which the analyst explores the system’s functionalities" (Alshboul, 2012). Cognitive walk through method analyzes user behavior step by step for a given task. In a development team one or two members from team conduct the walk through process and one or more user comment as the walk through proceeds. As per Alshboul (2012) this methods helps development team to detect the usability problems in the interface based on the detail specification, document or screen mock ups. As explained by Alshboul (2012) this method suites to evaluate the design before testing with users becomes difficult or expensive to recruit. Cognitive walk through method has developed for evaluate walk-up-and-use systems and later can apply on complex interfaces. The procedures for this method consist of preparation and execution phases.

In the preparation phase describes the user, chooses the task need to evaluate, and construct correct action sequence for each task. After these being done can start the execution phase. In this phase four questions are asked.

Will the user try to achieve the right effect?

Will the user notice that the correct action is available?

Will the user associate the correct action with the effect trying to be achieved?

If the correct action is performed, will the user see that progress is being made toward solution of the task?

From these question evaluator analyses the design is lead into success or failure. After evaluating actions merge the detected problems into a non-duplicate list.

This method helps to check the correct practicality of the design. By performing tasks in front of the user it helps to get a clear feed-back from the user. Because user is the one has the clear idea about the system. By seeing this it helps user to take the right decisions about the system and give correct feedback and add more requirements as required.

Usability Test Methods

Thinking Aloud Method

As defined by Alshboul (2012) "Thinking aloud is a usability engineering method which is a very efficient approach of getting quantitative data from a user" (Alshboul, 2012). In this method users need to think aloud when performing tasks with the system. From verbalizing users’ thoughts test users enable to understand the view point of the user for the system. As per Alshboul (2012) there is no aim or definition or accepted procedures to follow in thinking loud method. This method can be used in earlier stage or latter part in the development cycle.

The fundamental of thinking loud testing evolves with the small number of users being tested who think aloud while performing a task and the evaluator detect the problem by observing the user and listen to their thoughts. As per Holzinger (2005) depend on the interpretation of the user for each interface item, method facilitates a direct understanding of which part of the dialogue causes the most problems. Time is very important in this method because contents of the users’ working memory contents are desired (Holzinger, 2005).

Observation Method

According to Alshboul (2012) Observation is a method which involves an investigator observes the user and take down note of the activities perform by the users. There are two types of observation methods they are direct and indirect. Direct observation is the investigator present during the task and does observation. Indirect observation means investigator not present during the task but observes it through some other like video recorder. According to Holzinger (2005) can user electronic observation like data logging which is involved with statistical data about the detailed use of system.

Questionnaire Method

As per Holzinger (2005) "Questionnaires are useful for studying how end users use the system and their preferred features, but need some experience to design" (Holzinger, 2005). The simple form of questionnaire is the interview.

Advantages and Disadvantages in Tools and Techniques

Technique/ Tool

Advantages

Disadvantages

Heuristic Evaluation

application of recognized and accepted principles; intuitive; usability early in the development process; effective identification of major and minor problems; rapidity; HE can be used throughout the development process;

disassociation from end users; does not identify or allow for unknown users’ needs; unreliable domain specific problem identification; HE does not necessarily result in evaluating the complete design since there is no mechanism to ensure the entire design is explored, evaluators can focus too much on one section or another; the validity of Nielsen’s guidelines has been questioned 

Cognitive Walk through

independence from end users and a fully functioning prototype, helps designers to take on a potential user’s perspective; effective identification of problems arising from interaction with the system, can help to define users’ goals and assumptions.

Possible tediousness and the danger of an inherent bias due to improper task selection; emphasis on low-level details; non-involvement of the end user.

Thinking Aloud

reveals why users do something; a very close approximation to the individual usage; the provision of a wealth of data, which can be collected from a fairly small number of users; comments of the users often contain vivid and explicit quotes; preference and performance information can be collected simultaneously; helps some users to focus and concentrate; early clues can help to anticipate and trace the source of problems to avoid later misconceptions and confusion in the early stage of design.

a failure to lend itself well to most types of performance measurement; the different learning style is often perceived as unnatural, distracting and strenuous by the users; non-analytical learners generally feel inhibited; time consuming since briefing the end users is a necessary part of the preparation.

Causing users to focus and concentrate is both an advantage and disadvantage since it results in less than natural interactions at times and THA results in being faster due to the users focus.

Observation

simple, examines real-life settings in real workplaces,

applicable rather in the final testing, at least with using prototypes, relatively many users needed (20+), required expertise is high,

Questionnaire

Subjective user preferences, satisfaction and possible anxieties can be easily identified; can be used to compile statistics.

Indirect methods result in low validity (discrepancies between subjective and objective user reactions must be taken into account); needs sufficient response to be significant (we are of the opinion that 30 users is the lower limit for a study); identifies only a low number of problems relative to the other methods.

Source: Author’s Work based on Holzinger, (2010)

OODPM Methodology (Object Oriented Design by Prototype Methodology)

According to Drori (2001) Object Oriented Design by Prototype Methodology (OOPDM) is a system planning and design method that integrates two approaches: object oriented design and prototype" (Drori, 2001). As per Drior (2001) OOPDM focuses mainly on system planning and also focuses on the business specification stage. As the way develop this methodology user needs to study the system which is going to implement and also need to study the current system because need to provide the correct requirements to the development team. In other methodologies one of the main part ignore by the users is the requirements that they have already met, they only include the requirements which are not met to the standard. But OODPM focuses on the ignored part in other methodologies. As described by Drior (2001) the system analysis and the planning begin with the study of the current situation, but mainly identifying the needs/activities, also define a time period for the entire process. As explained by Petkun and Drori (2003) "the activity of the system is defined as a collection of data and process which are strongly interconnected and which handles defined subject" Petkun and Drori (2003). The process ended with the business specification for the new system.

Components in OOPDM

According to Drori (2004) there are six components in the OOPDM methodology.

Source: Drori, (2004)

Above Figure shows the components in the OOPDM methodology. They are,

User Interface – Window/screen of the computer system, depicting the activity of the future system.

Process Description - Verbal description of the process used by the activity (free text or pseudo code).If the process will be automated, this description must be explicit, integral, and unambiguous – in other words, pseudo-code.

Input - Data will be entered to the window/screen of the information system

Output – computer system widow/screen

Data Structure – Data format used in the activity

System State- Common communication area for objects

Source: Drori, (2004)