【正文】 we have already noted, knowledge is information in a relevant context. 上午 4時 12分 2022 SYSTEMS ENGINEERING 10 2 SITUATION ASSESSMENT But you need more than just knowledge about the specific problem or issue at hand. Familiarity with the environment into which the specific issue or problem is embedded is also crucial to an understanding of context. For example, the design of a successful information system for airline reservation agents is made much easier by someone with an indepth knowledge of the various tasks that such agents perform and the environment that agents must cope with as they perform these tasks. You could learn a lot about designing such a system from someone who is an expert at developing humanputer interfaces. But you can also appreciate how helpful it would be to interview some experienced ticket agents and to find out about the difficulties they experience when talking to customers and booking their flights. It is the job of systems engineers to make sure that the relevant knowledge of experienced people is brought into a project and used in issue formulation. Capturing this knowledge often requires the systems engineer to skillfully conduct both individual interviews and group meetings. 上午 4時 12分 2022 SYSTEMS ENGINEERING 11 2 SITUATION ASSESSMENT A normative scenario describes how the stakeholders want the system to be in the future. This is not as easy to acplish as it might appear to be. ? We will often need to distinguish between realistic needs and frivolous wants. ? Often also, important stakeholders have conflicting opinions on what the future should be, or on b. ? Some have unrealistic expectations of what technology can deliver in the time frame（ 期限 ） under consideration. ? Others are reluctant to see any changes because they think their job or relationship to a system may be put in jeopardy（ 危險 ） . A skilled systems engineer must broker these various interests to create enthusiasm and support for a technically feasible, trustworthy project. One way of gaining support for an improvement to an existing system or for a pletely new system is to involve stakeholders in the process. Helping people visualize the future in meaningful ways will go a long way toward creating a useful normative scenario. 上午 4時 12分 2022 SYSTEMS ENGINEERING 12 2 SITUATION ASSESSMENT But how can you see into the future? Besides talking to key people, another way of acplishing a situation assessment is to observe the current system, if one exists. An objective appraisal of the problems with the current system can be very helpful. A simple listing of these observations in a log book by date and time is often worthwhile. Be sure to note the main ideas of people managing and working with the system. Often, problems will not be evident on the first visit. Subsequent visits will reveal more. People also are more open with you after they get to know you and feel fortable with you. Information gained by observing the current system and talking to people involved with it is most valuable for writing a descriptive scenario. A descriptive scenario tells why the current system came into being, how it works, and what problems are associated with it. You should include the main actors or stakeholders involved with the current system in your descriptive scenario. These stakeholders will usually be owners, users, customers, clients, managers, maintainers, administrators, and regulators of the current system. But, for a plete situation assessment you will also need a normative scenario. 上午 4時 12分 2022 SYSTEMS ENGINEERING 13 2 SITUATION ASSESSMENT If there is not a current system to observe, then you need to create a way of seeing how an entirely new system might work. A number of useful ways exist for this. A group of people with relevant knowledge can meet and talk through how a new system might work. 上午 4時 12分 2022 SYSTEMS ENGINEERING 14 2 SITUATION ASSESSMENT Many other ways exist for examining possibilities for new systems. Prototypes [3,4] can be built and potential users can experiment with them through simulation. A prototype is a firstcut approximation of what a new system might be. The purpose of a prototype is to quickly gain information from the user about what seems to work and what is needed. For example, a prototype of a new information system might be a set of screens that a user could view and ment as to how useful the screens are in helping provide needed information. 上午 4時 12分 2022 SYSTEMS ENGINEERING 15 2 SITUATION ASSESSMENT A model of the situation, and the resulting simulation of operations using the model, can emulate the operation of a new system. To build a simulation requires a model or some representation of the new system. The usual purpose of a simulation is to get an idea of how the new system might actually work if it were put into operation. For example, a city wanting to build an airport at a new location might like to know if the land available can acmodate the number of planes that they anticipate will be landing and takingoff from their new facility. A simulation of an airport that fits within the city39。 ? if it is not benign, we may decide to react to it or continue to observe it. A reasonably good illustration of this is the situation assessment of temperature of the human body. One of the potential difficulties relative to observing a situation is that we wish to be able to interactively and proactively deal with issues and not simply to react to difficulties after they have eventuated. 上午 4時 12分 2022 SYSTEMS ENGINEERING 18 3 APPROACHES TO SITUATION ASSESSMENT