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The User Interface

Design Process

Part 2. Step 1.

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Part 2

Part 2 presents an extensive series of

guidelines for the interface design process. It

is organized in the order of the development

steps typically followed in creating a graphical

systems or Web sites screens and pages.

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Designing for People: The Five

Commandments Gain a complete understanding of users and their tasks.

Involving the users in design from the beginning provides a directconduit to the knowledge they possess about jobs, tasks, andneeds.

Perform rapid prototyping and testing. Prototyping and testing the

product will quickly identify problems and allow you to developsolutions.

Modify and iterate the design as much as necessary. While designwill proceed through a series of stages, problems detected in onestage may force the developer to revisit a previous stage.

Integrate the design ofall

the system components. The software,the documentation, the help function, and training needs are allimportant elements of a graphical system or Web site and all shouldbe developed concurrently.

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Usability

Shackel (1991) simply defined usability as the

capability to be used by humans easily and

effectively, where,

easily = to a specified level of subjective

assessment,

effectively = to a specified level of human

performance.

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Some Objective Measures of Usability

Shackel (1991) presents the following more

objective criteria for measuring usability.

How effective is the interface?

How learnable is the interface?

Howflexible is the interface?

What are the attitudes of the users?

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The Design Team

Provide a balanced design team, including

specialists in:

Development

Human factors

Visual design

Usability assessment

Documentation

Training

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STEP 1. Know Your

User or Client

The journey into the world of interface designand the screen design process must begin with anunderstanding of the system user, the most

important part of any computer system. It is theuser whose needs a system is built to serve.

Understanding people and what they do is adifficult and often undervalued process but very

critical because of the gap in knowledge, skills,and attitudes existing between system users anddevelopers that build them.

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STEP 1. Know Your

User or Client

To create a truly usable system, the designer mustalways do the following:

Understand how people interact with computers.

Understand the human characteristics important in design.

Identify the users level of knowledge and experience.

Identify the characteristics of the users needs, tasks, andjobs.

Identify the users psychological characteristics.

Identify the users physical characteristics.

Employ recommended methods for gaining understandingof users.

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Important Human Characteristics in

Design. Perception

Perception is influenced, in part, by experience. We classify stimuli based onmodels stored in our memories and in this way achieve understanding.

Proximity. Our eyes and mind see objects as belonging together if they are near

each other in space.

Similarity. Our eyes and mind see objects as belonging together if they share acommon visual property, such as color, size, shape, brightness, or orientation.

Matching patterns. We respond similarly to the same shape in different sizes. Theletters of the alphabet, for example, possess the same meaning, regardless ofphysical size.

Succinctness (qartesi dhe thjeshtesi). We see an object as having some perfect orsimple shape because perfection or simplicity is easier to remember.

Continuity. Shortened lines may be automatically extended.

Balance. We desire stabilization or equilibrium in our viewing environment.Vertical, horizontal, and right angles are the most visually satisfying and easiest tolook at.

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Design. Memory Today, memory is viewed as consisting of two components, long-

term and short-term (or working) memory.

Short-term, or working, memory receives information from eitherthe senses or long term memory, but usually cannot receive both atonce.

Long-term memory contains the knowledge we possess.Information received in short-term memory is transferred to it andencoded within it, a process we call learning.

Minimize the need for a mighty memory (memorje e fuqishme).

Presenting information in an organized, structured, familiar, and

meaningful way. Placing all required information for task performance in close

physical proximity.

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Design .Visual Acuity

The capacity of the eye to resolve details is called visualacuity. It is the phenomenon that results in an objectbecoming more distinct as we turn our eyes toward itand rapidly losing distinctness as we turn our eyes

awaythat is, as the visual angle from the point offixation increases. It has been shown that relativevisual acuity is approximately halved at a distance of2.5 degrees from the point of eye fixation (Bouma,1970). Therefore, a five-degree diameter circle

centered around an eye fixation character on a displayhas been recommended as the area near thatcharacter (Tullis, 1983). (shih slide pasardhes)

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Design . Foveal and Peripheral Vision Foveal vision is used to focus directly on something;peripheral

vision senses anything in the area surrounding the location we arelooking at, but what is there cannot be clearly resolved because ofthe limitations in visual acuity just described. Foveal and peripheralvision maintain, at the same time, a cooperative and a competitive

relationship. Peripheral vision can aid a visual search, but can alsobe distracting.

Mori and Hayashi (1993) experimentally evaluated the effect ofwindows in both a foveal and peripheral relationship and found thatperformance on a foveal window deteriorates when there areperipheral windows, and the performance degradation is even

greater if the information in the peripheral is dynamic or moving.Care should be exercised in design to utilize peripheral vision in itspositive nature, avoiding its negative aspects.

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Design. Information ProcessingRecent thinking (Lind, Johnson, and Sandblad, 1992) is that there are two levels ofinformation processing going on within us.

One level, the highest level, is identified with consciousness and working memory. It is limited,slow, and sequential, and is used for reading and understanding.

In addition to this higher level, there exists a lower level of information processing, and thelimit of its capacity is unknown. This lower level processes familiar information rapidly, inparallel with the higher level, and without conscious effort. Repetition and learning results in a

shift of control from the higher level to the lower level. Both levels function simultaneously, the higher level performing reasoning and

problem solving, the lower level perceiving the physical form of informationsensed. When a screen is displayed, you usually will want to verify that it is the one you want. If youre

new to a system, or if a screen is new to you, you rely on its concrete elements to make thatdetermination, its title, the controls and information it contains, and so forth. You consciouslylook at the screen and its components using this higher-level processing.

As you become experienced and familiar with screens, however, a newly presented screen canbe identified very quickly with just a momentary glance. Your lower-level informationprocessing has assumed the screen identity task.

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Design. Mental Models

As a result of our experiences and culture, we developmental models of things and people we interact with.

When confronting a new computer system, people willbring their own expectations and preconceptions

based upon mental models they have formed doingthings in their daily life. If the system conforms to themental models a person has developed, the model isreinforced and the systems use feels more intuitive.If not, difficulties in learning to use the system will be

encountered. This is why in design it is critical that a users mental

models be to identified and understood.

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Design. Movement Control

In computer systems, movements include such activities aspressing keyboard keys, moving the screen pointer bypushing a mouse or rotating a trackball, or clicking a mousebutton. Particularly important in screen design is Fitts Law(1954). This law states that:

The time to acquire a target is a function of the distance toand size of the target. This simply means that the bigger thetarget is, or the closer the target is, the faster it will bereached.

The implications in screen design are: Provide large objects for important functions. Big buttons are

better than small buttons.

Take advantage of the pinning actions of the sides, top,bottom, and corners of the screen.

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Design. Learning Learning, as has been said, is the process of encoding in long-term

memory information that is contained in short-term memory. It is acomplex process requiring some effort on our part.

A design developed to minimize human learning time can greatlyaccelerate human performance.

There is evidence that people are very sensitive to even minorchanges in the user interface, and that such changes may lead toproblems in transferring from one system to another.

Learning can be enhanced if it:

Allows skills acquired in one situation to be used in another somewhatlike it. Design consistency accomplishes this.

Provides complete and prompt feedback.

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Design. Skill

The goal of human performance is to perform

skillfully. To do so requires linking inputs and

responses into a sequence of action.

Skills are hierarchical in nature, and many basic

skills may be integrated to form increasingly

complex ones. Lower-order skills tend to become

routine and may drop out of consciousness.System and screen design must permit

development of increasingly skillful performance.

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Design.Individual Differences

In reality, there is no average user. A complicating butvery advantageous human characteristic is that we alldifferin looks, feelings, motor abilities, intellectualabilities, learning abilities and speed, and so on.

Individual differences complicate design because thedesign must permit people with widely varyingcharacteristics to satisfactorily and comfortably learnthe task or job, or use the Web site.

Multiple versions of a system can easily be created.Design must provide for the needs of all potentialusers.

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Human Considerations in Design

The users tasks and needs are also important

in design. The following should be

determined:

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Human Considerations in Design

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Methods for Gaining an

Understanding of Users Gould (1988) suggests using the following kinds of techniques to gain an

understanding of users, their tasks and needs, the organization where theywork, and the environment where the system may be used.

Visit user locations, particularly if they are unfamiliar to you, to gain anunderstanding of the users work environment.

Talk with users about their problems, difficulties, wishes, and what workswell now. Establish direct contact; avoid relying on intermediaries.

Observe users working or performing a task to see what they do, theirdifficulties, and their problems.

Videotape users working or performing a task to illustrate and studyproblems and difficulties.

Learn about the work organization where the system may be installed. Try the job yourself. It may expose difficulties that are not known, or

expressed, by users.

Prepare surveys and questionnaires to obtain a larger sample of useropinions.

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