 Parameter estimation can also be used as a technique to capture the influence of effects that are not explicitly modeled, in which case parameters may need to take on values that differ from text-book or table values.An online model as defined here has the useful property that it closely resembles the real plant, and for this reason the online model can at any time by used to assess planned changes in operations, either for control, for optimization and for different operational tasks to be performed.It can then be used amongst other things for real-time monitoring, de-bottlenecking or plant redesign, or for "what-if" analysis.