Example: User demand estimation

Once the function, behaviour type and usage pattern data have been provided the model starts to produce useful information based on its estimations. The most important of this is the daily function usage estimation. This information is presented on the “Estimated Function Demand” sheet within the model, and provides as estimate, by year, of the average daily usage for each function. This is then used to provide an estimate of the average and peak operations per second for the system.

Calculated daily function useCalculated function usage per second

 The first use of this information is often to check the model against other data that has been provided. In this example the bank is likely have provided an idea of their expectation of the daily levels of system usage for key functions. It is unlikely that their values will exactly match those estimated by the model. A serious difference should be considered carefully, however, as it may represent a serious issue in underlying assumptions about system usage.

The next set of usage data that may be of value is on the “Annual Function Demand” sheet. This provides the average daily usage data multiplied up to provide total annual usage, and cumulative annual usage of the different functions. Again, this information is often provided for comparison purposes. If the information hasn’t been previously provided the overall function usage estimates can provide a strong indication of the overall scale of the system being analysed.

This information can be used to support an understanding of the likely levels of technical and business risk in the system before the detailed architecture has been elaborated. It may also be used in the evaluation of the technology needed to produce the system under consideration. The next stage of the modelling, however, will start to provide the basis for architectural part of the estimation process.

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