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If for a given transformation there are different coefficientSets configured for different periods in time, then the following rule is used. The start of a period is always inclusive. The end of a period is exclusive if another period follows without a gap in between, otherwise the end of the period is inclusive. If for example there are three periodCoefficientSets defined (A, B and C), each with a different period, as in the following block of codexml example. Then at 2002-01-01 00:00:00 periodCoefficientSet A is valid. At 2003-01-01 00:00:00 periodCoefficientSet B is valid since the start of the period is inclusive. At 2004-01-01 00:00:00 periodCoefficientSet B is still valid, since there is a gap after 2004-01-01 00:00:00. At 2011-01-01 00:00:00 periodCoefficientSet C is valid, since no other periods follow (the period of C is the last period in time that is defined). This same rule applies to time-dependent transformations.
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