Frame Relay - for Faster and More Efficient Data Communications ...

23Box 3User interfacesUser interfaces can be defined as the boundarybetween the user and the system and wheresome task is performed. Interfaces can be- dialogues with computers and other products- presentation of information on a display and/orother medium- entry of data/commands from keyboard or otherinput device- physical design of products and workplaces- sight and sound characteristics- procedures, rules and routines- icons, symbols and pictograms- systems for marking cables and connectors- instructions, manuals and training materialFig. 4Two generations of Ericsson mobiletelephonesMobile telephony will be a major part of futuretelecom services. Human Factors will play an integralrole in designing services based on userrequirements and interfaces with regard to cognitiveand physical issuesExamples of task factors are-ease- complexity- novelty- time limits-whether tasks are repetitive, overlapping,monitoring- what skills a task requires- whether a task is performed by a groupor by an individual.Define evaluation criteriaWhen usability testing is integrated into thedesign cycle, it should be quantitativelyspecified in advance. Performance goalsfor usability should be measurable. Keyfactors in usability testing are- learnability- or ease of learning - is thetime and effort required to reach a predefinedlevel of user performance- performance - or ease of use - is thenumber of tasks accomplished by experiencedusers, the speed of task executionand the number of mistakes made- flexibility, the extent to which users canadapt a system to new ways of interactionas they become more experienced- attitude, subjective assessment engenderedin users by the system and the interface.Test and evaluateTesting and evaluation should be carriedout with users early in the design processto ensure that products and interfaces aredesigned to meet user needs and requirements.The conceptual design of an interface maystart with the creation of sketches of the interfacewhich demonstrate surface features.These can be tested for appropriateness;for example, the design of ametaphor or symbol can be checked withrespect to how well it is understood by users.As design develops it will be transformedthrough simple models and simulations toprototypes, full-scale models and, eventually,the final product (implementation).There are many computer-based designtools which permit quick and easy evaluationof user-interface options. Applicationof these tools is essential if interface designis to be cost-effective. Well conductedtrials ensure that the design matchesthe users' mental model of the system andthe tasks.Trials should be conducted in environmentswhich are as realistic as possible;preferably the real situation. It is importantto establish whether the product is reallyusable or not. The principle rule is to designiteratively, with many cycles of "design- test with users - redesign". The aimis not to produce one correct solution whichis subsequently not changed, but an evolvingsystem which - with each iteration - isfurther tailored to users' needs.Experience gained from evaluating theproducts, especially in the real situation,will provide input when planning futuregenerations of the product, or completelynew products. "Future-proofness" is of keyimportance, and interface design guidelinesprovide a consistent approach toproduct and system uppgrades.Variation in the development processThe development process is seldom simpleand regular. The process rarely startsfrom square one, i.e. the development ofa completely new product or system.There is invariably some form of historyfrom existing products which must be takeninto account. This means that HumanFactors efforts in each phase will vary fromproduct to product.When a new product is created, based onnew technology, it is important to identifyuser attitudes and requirements so that theproduct is used, understood and acceptedby users once the novelty value wears off.When combining products from severalvendors into a new and unique configuration,qualities such as homogeneity andcontinuity in use are important. In general,the primary Human Factors considerationis consistency of operation of all componentsrather than optimisation of a singlecomponent.Manufacturers sometimes buy productsfrom another vendor. Human Factors effortwill depend on several factors, such asthe quantity purchased, the importance ofthe product to the corporate strategy, andthe ease with which usability can be improved.There is a golden opportunity to improveusability when redesigning an existingproduct: by obtaining usability data fromthe users of the existing product. Featuresand functions that have been well receivedERICSSON REVIEW No. 1-2. 1992