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Unformatted text preview: do not have much information about the real world or we want to obtain some information about it, then it is helpful to describe the system in terms of one single variable through which it interacts with its environment. Such an approach is called “Black Box” approach. Here we simply ignore the inner structure of the RWM. We use input to get an output, e.g. in Soft Drink Problem if we just work with the ‘Sale records of previous months’ to estimate the demand in the next year, then it is a “Black Box” approach. On the other hand if we consider the system in detail, i.e. by considering all possible objects and the relationships in detail, we get a White Box. This may be very close to the RW, but may become unmanageable and so of limited use. In general one should enough and relevant details so as to get a tractable model. It always does not help to include all the details of the RW in the model (Recall Weight Lifting Problem!) but one should also not leave significant details of the RW. One often starts with a simple model (can even be a black box model) and then improve it by adding more complications or one can start with a white box and then keep simplifying it till a tractable model is obtained. Static or Dynamic Model: In case time does not play any role in the various interactions and all the variables are independent of time, we say model is a Static model. However when one or more variables dependent on time we say it is a Dynamic Model. For example, weight lifting system provides a Static Characterization while Rain drop or Rocket launch problem distance, velocity etc. depend on time, so they are dynamic models. How about the ‘Soft drink demand’ and ‘Alloy Selection’ Problems’? In case of Dynamic Model we should see if the dependence on time is continuous or is it discrete (note that the data is available only at discrete time intervals). If the variables are changing continuously with time then we have to describe the system for all times, so making it a detailed description. If it is chosen discrete, the...
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This document was uploaded on 01/25/2014.
 Winter '14

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