Human-computer interface design 161

User

Form mapping:

perceptualsensitivity;learnedassociations

representationalforms in interface

)

general capa­bilities andlimitations;

specific domainknowledge

Interface

informationcontent ininterface

(

domainbehavior;pragmaticcontext

Content mapping:

Workdomain

relationalinvariants of

work domain

M. C. Rice, Mushrooms for Color, Mad River Press,Eureka, CA, 1980; M. C. Rice, Mushrooms for Dyes,Paper, Pigments & Myco-Stix™, Mushrooms forColor Press, Forestville, CA, 2007.

Human-computer interface designAdvances in computational technology have madecomputerized devices an integral part of our dailylives. Unfortunately, poorly designed interfaces oftenmake these devices difficult and awkward to use.A conceptual ftanlework for the design of effectivehuman-eomputer interfaces will be outlined.

Cognitive Systems Engineering (CSE). CSE providesa systematic approach to interface design. The in­terface is considered a form of decision support: itis used by a person with the goal of completing atask within a work domain. Thus, there are three sys­tem components (domain, user, and interface) thatcontribute a set of mutually interacting "constraints"(Fig. 1). How well these components "fit together"will determine the ease of use and the effectivenessof the device.

Domain constraints. Because the interface is viewedas decision support, the logical starting point for in­terface design is an analysis of the constraints in thework domain. The unfolding events in "law-driven"domains such as process control (for example, apower plant) arise from the physical structure andfunctionality of the system. In the case of a powerplant, the laws of thermodynamics are a fundamen­tal source of regularity. At the opposite end of the

Fig. 1. The Cognitive Systems Engineering ICSE) perspective on interface design: systemcomponents and mappings between them.

~lent-that is, red dyes tend more toward bluees. The quality of the water used influences theas well, especially if cWorine, acids, alkalines,

heavy minerals are present. A weight ratio of 1:1mushroom to fiber is recommended at the start.

'Ome fungi have a lot of pigment, whereas otherse very little. Thus, with experimentation, care­

:aI observation, and note taking, one can decide theproportions on a case-by-ease basis.

ince the First International Mushroom Dyes Tex­Die Show-FUNGI and FIBERS was held in Mendo­000 in the summer of 1980, interest in mushroom

has continued to spread worldwide rapidly,particular enthusiasm from the Scandinavian

countries, Scotland, and Western Australia. In 1985,me International Mushroom Dye Institute (!MOl)

established. The nonprofit research institutefounded to encourage the use of fungal pig­

.ents, to further research on their extraction andanployment, to encourage research on cultivation ofespecially desirable fungi, and to provide financialad to artists and researchers to enable them to par­lIiripate in the international mushroom dye symposiamd exhibitions.

Other developments. In the 1980s, Miriam Rice ex­- red the pOSSibility of making paper out of the

al detritus that is left over from the dyes. Alwayssionate advocate of recycling, she saw this as

me natural solution for disposal of the fungal residue~ the dye process. She tried many mushrooms... polypores (shelf fungi typically lacking stalks),

. g that the polypores that contain chitin as wellcellulose produced the best paper-all colors and

r:nures, and with no additives necessary. Thus, in5, the concept of papermaking from fungi was

IIIli"oduced.further experiments in the 1990s led in another di­

-raion: specifically, making watercolor paints fromof the mushrooms that had also been used for

::-e. By extracting the fungal pigments and combin­o them with a variety of media, a variety of water­

paints have been generated (Fig. 5).In addition, recent researdl into developing the-hroom pigments into some form of medium for

-' to use in drawing and sketching to supple-c8eIlt the watercolor paints has resulted in a drawinglDedi.um called "MycO-Stix™.'' This medium uses pig­c8eIlts extracted from fungi and combines them with

-.uiety of binders to form crayons that can be useddrawing, watercolor, pastel, and encaustic (hot

) media.fur background information see COLOR; DYE; DYE­

'l.Y; FUNGAL ECOLOGY; FUNGI; MORDANT; MUSH­"\1; PAPER; PIGME T (MATERIAL); PRINTING; WOOL

the McGraw-Hill Encydopedia of Science & Tech-lOlogy. Dorothy M. Beebee

Bibliography. A. R. Bessette and A. E. Bessette,"be Rainbow beneath My Feet: A Mushroom Dyer's-i,dd Guide, Syracuse UniversityPress, Syracuse, NY,

1; K. 1. Casselman, Craft of the Dyer: Colourl Plants and Lichens, Dover Publications, New, 1993; M. C. Rice, Let's Try Mushrooms for

• or, Thresh Publications, Santa Rosa, CA, 1974;

162 Human-computer interface design

spectrum are "intent-driven" domains, where the un­folding events arise from the user's intentions, goals,and needs (for example, information retrieval).

User constraints. The capabilities and limitations ofusers constitute another set of constraints. Forexample, humans possess extremely powerful skillsfor perception (obtaining visual information) and ac­tion (manipulating objects), but they have extremelimitations in terms of attention and memory (onlya few items can be maintained in working memory).Additional constraints are introduced by those whowill use the device. Power-plant operators are highlytrained and will have homogeneous (uniform) skillsets; this is in contrast to mobile cell phone users,who do not require this level of training and skill.

Interface constraints. A third set of constraints is intro­duced by the interface. In the early years of com­puter technology, the interface was designed usingan ineffective "conversation" design metaphor: cryp­tic verbal instructions were communicated throughan intermediary (that is, a command line) to th.e com­puter. This imposed a severe set of constraints on in­teraction. Interface technology has evolved consider­ably since then (high-resolution screens, bit-mappedgraphics, precise pointing devices, and so on). Thishas allowed the use of design metaphors that arepredominantly spatial in nature and are far more ef­fective (for example, the desktop metaphor).

Principles of design. The fundamental goal of in­terface design is to build virtual ecologies of workdomains that allow the powerful perception-actionskills of the human to be leveraged (in other words,that do not require the use of limited-capacity re­sources such as working memory). The ease of useand effectiveness of a device will ultimately de­pend upon the relationships (the "fitting together")between these tllfee sets of constraints (Fig. 1).Three principles of interface design can be usedto help these three system components fit togetherwell.

Directperception. The interface should allow the userto comprehend the current (and perhaps the fu­ture) state of the system through powerful visual pro­cesses. The first step is to conduct work domain anal­yses to reveal the domain constraints (physical, func­tional, and goal-related properties). Effective graphi­cal representations (the virtual ecology) then need tobe developed. The visual properties of these repre­sentations must match the perceptual and cognitiveabilities of the observer (for example, is the user sen­sitive to variations in the visual features that werechosen?). They must also match the domain con­straints (for example, do variations in the visual fea­tures accurately reflect variations in, or propertiesof, the domain?).

Direct manipulation. The interface should allow theuser to execute control input trnough powerful ac­tion capabilities applied directly to objects in the in­terface. A good example is file deletion in the Macin­tosh OS X operating system. An object in the workdomain (a computer file) is represented in the in­terface (its icon). The user manipulates this repre­sentation directly (that is, point, click, drag, drop)

to delete it. In contrast, the deletion of a file .command-line interface (for example, "rm klunk.terfaces.doc," where "rm" stands for "remove")even a pull-down menu is not direct manipulation

Perception-action loop. There is a potentially symbi .relationship between direct perception and elimanipulation. The objects in the interface can besigned to support the powerful human skills ofboi;;perception and action simultaneously. When this 0..

curs, the display interface and the control interneare merged into one; the perception-action lac­(the coupling between a human and the world)intact.

Examples of interface design. The applicationthese trnee general principles will require diffedesign strategies for different work domains. Twexamples will be provided.

Law-driven domain. The most effective interfacesign strategy for law-driven domains is to ck:velop spatial analogs (that is, abstract geomemcal forms) that directly reflect the underlyingmain constraints (Fig. 2). This display combineover 100 individual sensor values into an octagon:..form. The octagon is perfectly symmetrical wberpower-plant conditions are normal (Fig. 2a).versely, asymmetrical distortions provide visualidence that there is a fault (Fig. 2b). The opeutors learn to associate particular patterns of disttion in the display with particular types of faultsDirect perception has been achieved: the operator can literally see the state of the plant <trect!y, without the need to gather relevant inform:tion and perform complicated mental calculation:s(Figure 2c illustrates the display in an actual poplant.)

An optimal implementation of direct manipulatioein this interface would involve high-level control: t1koperator would have the capability to point, cliand drag the vertices of tbe octagon to a desired l0­cation, thereby changing the underlying variablesUnfortunately, this is not possible becausetlle complexity, interconnectedness, and potentia.!.t'conflicting goals that characterize a power plant. rn-­rect manipulation must therefore be implementat a lower level. Thus, to change the setting of at:

individual variable, the user might select a visual in­

dicator and drag it to a new location on a graphiscale (rather than typing it in).

Intent-driven domain. The most effective design strat­egy for intent-driven domains is to develop spati:tmetaphors (for example, the desktop metaphor oncomputers) that relate the requirements for interac­tion to more fantiliar objects and activities. The AppleiPhone provides an excellent example.

Direct perception in the iPhone's interface is

achieved prinlarily trnough static spatial metaphorsThese metaphors use physical sinlilarity or symbolicconvention (a stylized phone icon) to provide a se­mantic link between the lIser's intentions (the neto make a phone call) and tbe underlying func­tionality of me iPhone (cell phone). Thus, this de­sign strategy uses graphical representations to lever­age preexisting concepts and knowledge, thereby

Human-computer interface design 163

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An abstract geometrical form display used to represent dynamic values of system variables for a process control(a) The octagon form in a perfectly symmetrical shape represents the values of variables under normal power-plant

. ns. (b) The nonsymmetrical distortion of the octagon form characterizes a particular abnormality in the plant (that is,f-coolant accident). (c) The geometrical form display as it appears in an actual power plant. (Line drawings from W. F.

er et al., Generating an integrated graphic display of the safety status of a complex process plant, United Statesno. 4,675,147, June 23, 1987; photo courtesy of David D. Woods, Cognitive Systems Engineering Laboratory)

. . g casual users in understanding and using thee.

-less obvious that the iPhone uses an overarch­tial metaphor to facilitate navigation among'ous applications and modes. This metaphor

es an array of icons (representing applications)orne" mode, a row of icons at the bottom oflication interface (representing modes of thetion), and a dedicated mechanical button atttom of the phone (return to home mode).atial dedication of these interface componentsnavigation of the iPhone much like naviga­the real world: getting to different applica-

and modes in the interface is somewhat sim­navigating between rooms in a well-knowng.ct manipulation in the iPhone's interface rep­. a true advance in the state of the art. Theremenus, no cursor, no mouse, no stylus; the

fingers are the only pointing device that is re­_The user directly manipulates the objects oft in the interface in a very natural manner: theensitive screen recognizes a number of fairly

complicated gestures, including taps (single and dou­ble), slides, swipes, flicks, and pinches. This gesture­based interaction represents the wave of the futurefor interface design, even for those devices that arenot handheld.

Summary. Designing effective interfaces is a moredifficult problem than it initially seems. CognitiveSystems Engineering (CSE) provides a conceptualperspective and principles of design that pointto successful solutions. Ultimately, interface designshould be driven by tlle nature of the problems tobe solved and by the capabilities and limitations ofproblem olvers.

For background information see COGNITION;

COMPUTER; COMPUTER ARCHITECTURE; COMPUTER

PROGRAMMING; ENGINEERING DESIG; HUMAN­

COMPUTER INTERACTIO ; HUMAN FACTORS E ­

GINEERING; PERCEPTIO ; PSYCHOLOGY in theMcGraw-Hill Encyclopedia of Science & Technology.

Kevin B. Bennett; Shannon M. PoseyBibliography. K. B. Bennett and J. M. Flach, Dis­

play andInterface Design: Subtle Science, ExactArt,Taylor & Francis, London, in preparation; K. Mullet

164 Human papillomavirus: impact of cervical cancer vaccine

and D. Sano, Designing Visual Interfaces: Commu­nication Oriented Techniques, SunSoft Press, Engle­wood Cliffs, N], 1995; ]. Rasmussen, A. M. Pejtersen,and 1. P. Goodstein, Cognitive Systems Engineer­ing, Wiley, New York, 1994; K. ]. Vicente, Cogni­tive Work Analysis: Toward Safe, Productive, andHealtby Computer-Based Work, Lawrence ErlbaumAssociates, Mahwah, N], 1999; D. D. Woods, Thecognitive engineering of problem representations,pp. 169-188, in G. R. S. Weir and]. 1. Aity (eds.),Human-Computer Interaction and Complex Sys­tems, Academic Press, ew York, 1991.