Analysis Techniques For Man-Machine Systems Design

NATO UNCLASSIFIEDAC/243(Panel-8Y)1=Volume I- 50 -further development of the systems analysis approach that has been developed over the last twodecades (Yourdon, 1989). To summarize, CASE tools offer several possible benefits to systemsengineering:(1) A database representation of the system description (e.g., elements, attributes andrelationships) where specifications can be traced to user requirements and designdecisions.(2) A uniform description for all development phases which can be modified easily.(3) Rapid analysis of the impact of potential changes.(4) Automatic consistency and completeness checks according to a selected level.Engineers are not forced to produce "complete" specifications, but are encouragedto consider all parts of the system and their interface in a systematic way.(5) Automatic production of documentation according to standards or some user'sindividual requirement(6) A formal description makes it possible to automate to a large extent the generationof simulation models and prototypes.93. Available tools do not provide all of these features. The growing emplhasis ontaking a truly integrated approach to project development, including an integrated project database, argues for finding a common approach to the definition of system functional andperformance requirements in order to include human factors in system performance.4.3.2 Rapid Prototyping and User Interface ManagementSystems (UIMS)94. In the computer science and human-computer interaction communities there is agrowing emphasis on the use of rapid prototyping and user interface management systems(UIMS). These tools permit the rapid creation and modification of the human-machine interfacewithout the need to realize the underlying application software or hardware. The prototypeinterfaces primarily serve to enhance communications and feedback between designers and users(see for example, Wilson & Rosenberg, 1988). This overall approach parallels onerecommended for software code development (Pressman, 1987). A report of the US DefenseScience Board Task Force on Military Software (1987) recommended strongly that rapidprototyping be applied early in projects to validate the specifications. The more effectiveprototyping tools permit the prototype software code to be transferred to the system developmentmodel (Nordwall, 1991). Most rapid prototyping tools require support facilities and applicationspecific software to represent mission scenarios and operation dependent aspects of the humanmachineinterface, such as maps and mission event generators.95. The rationale for rapid prototyping is that system interactions and user requirementscannot be predicted completely. It is argued that it is more effective to produce the equivalent of adynamic mockup and study how prospective users interact with the system. then modify it andthus develop it iteratively, than to analyse all requirements exhaustively. User evaluation isessential to evolutionary development. Human engineering test and evaluation tends toemphasize subjective measures, apparently because objective measures require more effort toimplement (Meister, 1986). A review of rapid prototyping applications confirms that there is arisk that evaluations may be reduced to little more than judgments of appearance, rather than anevaluation of functionality (St. Denis, Bouchard, & Bergeron, 1990). Some human factorsspecialists have reservations about the importance placed on user opinion in the evaluation ofrapid prototypes (see, for example, NATO RSG.12, 1990). Their reservations are based on thepossibility of "negative transfer" of existing skills and knowledge, resulting in design whichincorporates obsolete or obsolescent features. This is because some users find difficulty inNATO UNCLASSIFIED- 50 -