The part classification field divides the parts into 10 different classed these classes are as follows
The parts can be aggregated into these 11 groups. These groups can be used as an aid for setting different forecast models to the different groups. Below is a description on how you decide to which group the different parts are going to belong to. The classification is preformed as a job by the forecast server.
Detecting if the time series have trends or not is done by first running a least square regression on the historical demand periods. Then run a F test for overall significance.
Notation
n number of periods
Regression
Line in period i
The
average historical demand
The
historical demand of period i
If the F is bigger than HKEY_LOCAL_MACHINE\SOFTWARE\IFS\ForecastServer\Classification\TrendFTestLimmit then the part has a trend. If the slope is negative then the part has a negative trend if the slope is positive the the part has a positive trend. The default value for TrendLimmit is 3,75. Therefore if F is bigger that 3,75 then the part has a trend, the slope of the regression line determines if the trend is positive or negative.
All parts that never have been classified are set to this ID.
The Brand New Parts class includes all parts that have equal or under a certain number of periods this number can be adjusted in the registry key HKEY_LOCAL_MACHINE\SOFTWARE\IFS\ForecastServer\3.0\Classification\BrandNewLimmit. Default value is 4. The number must be smaller than the New parts number of periods (see New Parts).
The New Parts class includes all parts that have under 1 year and 2 periods of historical demand. This is a fixed number. If months is used as a period length then all parts that have less than 14 periods are treated as a new parts.
The way to determine Intermittent Parts is to count the number of zero’s in the series, if the number of zeros is bigger than the IntermittientZeroPercent limit then the series is intermittent. The IntermittentZeroPercent can be changed from the registry key as follows:
HKEY_LOCAL_MACHINE\SOFTWARE\IFS\ForecastServer\Classification\ IntermittientZeroPercent.
The default value is 20. This means that all parts with 12*0,2=2,4=3 zero periods or more per year are set to intermittent, when monthly period version is assumed.
This is a part that is intermittent, and also has a season. For season detection procedure see Season Profiles (Season Component Detection Algorithm).
If a part only have level then it belongs to this class. See above for level detection procedure.
If a part has level and a season, then it belongs to this class. For season detection procedure see Season Profiles (Season Component Detection Algorithm)
If a part has a positive trend, then it belongs to this class. See above for trend detection procedure.
If a part has a negative trend, then it belongs to this class. See above for trend detection procedure.
If a part has a positive trend and season, then it belongs to this class. See above for trend detection procedure. For season detection procedure see Season Profiles (Season Component Detection Algorithm)
If a part has a negative trend and season, then it belongs to this class. See above for trend detection procedure. For season detection procedure see Season Profiles (Season Component Detection Algorithm)
A part is classified as Terminated If no transactions of the part has occurred for a specified number of periods. The test for terminating parts is as follows.
Assuming that the demand for a part occurs with the intensity l (parts per time interval) according to a Poisson process, then the probability of zero demand in x succeeding periods is:
The arrival intensity can be determined from the more easily interpreted time between succeeding demands, q, as:
, where
If a number of succeeding zero demands occurs and the probability of this is small, then there is reason to believe that the item demanded is terminating. Choose the boundary value for the probability p (0,005 is the default value), then if more than x succeeding zero demands at the end of the time series occur:
The resulting check formula is shown below the probability, p=0,005 (default value). This classifies the part as Terminated when the number of subsequent zero demand periods at the end, SubZeroPeriods, is fulfilling:
The value of p can be changed from the registry key: HKEY_LOCAL_MACHINE\SOFTWARE\IFS\ForecastServer\Classification\TerminatedZeroOccProb.