【正文】 are called misses or missed problem errors。s land constraint can be tested to see if any airport layouts can successfully meet anticipated passenger and freight demands. 上午 4時(shí) 12分 2022 SYSTEMS ENGINEERING 16 3 APPROACHES TO SITUATION ASSESSMENT Noble says that situation assessment includes the following: ? An estimate of the purpose of activities in the observed situation ? An understanding of the roles of the participants in these activities ? Inferences about pleted or ongoing activities that cannot be directly observed ? Inferences about future activities 上午 4時(shí) 12分 2022 SYSTEMS ENGINEERING 17 3 APPROACHES TO SITUATION ASSESSMENT The notion of a threshold is often very important in situation assessment. We might have a threshold for a situation, and observing this threshold might be all that is required. When the situation descriptor values exceed this threshold, we might then decide to assess it in greater detail. ? If it is benign, we may choose to ignore it。Chapter3 Formulation of Issues 上午 4時(shí) 12分 2022 SYSTEMS ENGINEERING 2 1 INTRODUCTION It is very important, we believe, that texts on systems engineering and problem solving, in general, pay significant attention to issue formulation, as a step in systems engineering that needs to occur in each of the phases of effort. This is so because, in practice, the results of a poor issue formulation effort may be subject to very detailed analysis, and the results of this are carried over into implementation. As a result, we obtain the wrong system! Needless to say, this usually results in a waste of resources and (through engineering) an inferior system, pared to that which might have resulted from a better issue formulation. Issue formulation is critical across the definition, development, and deployment phases of a systems engineering life cycle. This is not a step implemented only as part of the systems definition phase, although it is very important in that phase. 上午 4時(shí) 12分 2022 SYSTEMS ENGINEERING 3 1 INTRODUCTION A problem, or an issue as a generally synonymous term, can usually be viewed from several perspectives, and the solution that results will often be a strong function of the perspectives from which a problem is viewed and formulated. 上午 4時(shí) 12分 2022 SYSTEMS ENGINEERING 4 1 INTRODUCTION Issue formulation begins with a definition of the problem or issue to be resolved. This includes an assessment of the situation surrounding the problem. Situation assessment is important in problem solving and issue resolution. There are many aspects of the environment surrounding an issue that we need to know about in order to be able to generate potentially feasible alternative courses of action that can lead to issue resolution. Many of these factors are dynamic, uncertain, and subject to change with the passage of time. Situation assessment means that we need to make a careful appraisal of the various factors that influence a particular observed state or condition. Generating good alternatives, ones that truly satisfy the needs of our customers in an effective, efficient, equitable, and explicable manner, depends on an indepth situation assessment. 上午 4時(shí) 12分 2022 SYSTEMS ENGINEERING 5 2 SITUATION ASSESSMENT Complete situation assessment consists of three basic steps that are intended to answer the three questions highlighted in Figure . 上午 4時(shí) 12分 2022 SYSTEMS ENGINEERING 6 2 SITUATION ASSESSMENT ? The first part is the identification of the (immediate) past in terms of the question, What was? ? The second part of a situation assessment examines the current status or position of things relative to the goal. It is a descriptive ponent and answers the question, What is? ? The third or normative ponent of a situation assessment answers the question, What ought to be? Understanding of the major, ideally all, factors influencing the past, present, and future is needed for a good situation assessment. There is a horizon ponent of situation assessment and it answers the question, What factors over time matter and when do they matter? 上午 4時(shí) 12分 2022 SYSTEMS ENGINEERING 7 2 SITUATION ASSESSMENT We have a plete situation assessment once we know the following: ? What do we want to acplish? ? What is the past and current state of affairs relative to our goal brought about by the changed situation? ? What are the relevant factors that influence the situation and their associated time frame. 上午 4時(shí) 12分 2022 SYSTEMS ENGINEERING 8 2 SITUATION ASSESSMENT There are a large variety of environments in which various systems must operate. A number of different perspectives— such as technical, economic, legal, political, cultural, and social— can be important for understanding a system39。s environment. When an adequate appreciation of all the important perspectives is achieved, then we say we have preserved the contextual integrity of the issues under consideration. The problem of issue definition, and the resulting identification of worthwhile alternatives, depends on an accurate and timely situation assessment that preserves this contextual integrity. 上午 4時(shí) 12分 2022 SYSTEMS ENGINEERING 9 2 SITUATION ASSESSMENT Acplishing a highquality situation assessment depends on several factors. First, the experiential familiarity with the issues or problem under consideration is very important. For example, it is unlikely that someone with very little background knowledge about nuclear power plants would be able, without considerable study, to develop useful alternatives for ensuring safe operation of such a facility. As