Analysis Techniques For Man-Machine Systems Design

NATO UNCLASSIFIED- 9 - AC/243(Panel-8)TR/7Volume 2Inputs to the techniqueInformation on the major system functions, theinformation flow, and those functions which modifyinformation. Detailed mission analyses might besufficient to start the analysis.Outputs of the techniqueCharts showing the information flow, and identifying thecritical decision points and information modifiers.Decision/Action diagrams use only two symbols, one fordecisions, and one for other activities.swWhen to useThe technique should be used during concept definition and preliminary design. It should be used for the functionalanalysis of systems where there may be important dichotomous decisions. It is useful for identifying the criticaldecisions made by human operators, and could be a useful input to a cognitive task analysis.h|Ls}Related techniquesThe technique is strongly related to function analysis, to SADTr'/IDEF®, and to flow charts produced for computerprogramming. There is a high level of redundancy between information flow and processing analyses and functionflow diagrams (2.1). It is recommended that only one of the techniques be used on the same project. Meister (1985)recommends that the analyses should be followed by time line analysis (4.1) to investigate the effect of time onsystem performance.ResourcesrequiredThe analyst must have information on the system functions, particularly those which modify information. Notechnical resources are required. but a computer aided production system is desirable.AdvantagesUsers report the technique highly effective and easy touse. It has been found very effective for analysing theoption trees and identifying the "modes" of operation ofmulti-function controls and menu systems ("modinganalysis').DisadvantagesUsers find the technique time consuming. It is difficult todefine many human operator decisions clearly, becausehumans are included as system components to deal withunanticipated events. The Decision/Action Diagram itselfis a cumbersome way to analyse information flows,because it forces decisions into a "Yes/No" dichotomy,thereby creating a large number of decisions.Relative contributionUsers report the technique to make a good contribution Lo detailed analyses. such as the moding analysis mentionedabove.NATO UNCLASSIFIED- 29 -