The DEAT Business Rule Pattern Language
Russell R. Hurlbut, Ph.D.
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Rule Pattern 32: Interpolation
Problem – Deriving a Point Value from a Range given
Another Point Value and Range
Some business processes rely on calculations that must estimate a value that
falls between two other values that provide an index into this desired value.
This is often the case in lookup tables that are legally mandated or may have
arisen out of traditional industry practice.
An interpolated value can be derived through enumeration of interpolation algorithm
types. This pattern shares similarities with the Interval pattern, except here
a continuous value is desired from provided discrete value rather than vice
versa. Both patterns have floor and ceiling types. However, they are included
only in this pattern for completeness. The same net effect is obtained from
applying the Interval pattern first and then performing a direct lookup. The
primary difference in the type domains is reflected in the opposite orientation
of the two patterns. Instead of nearest, this Interpolation pattern defines
a linear type.
Example – Tax Proration
A real estate contract stipulates that property taxes are to be prorated up to
and including the day of closing based on the most recent tax assessment. A 365
day year is used.
Tax Proration Parameters
||Real Estate Tax Proration
||Day of Year
Example – Early Retirement Factor
A pension benefit is calculated and then reduced for early commencement before
the normal retirement date for an employee. Based on the form of payment, if the
spouse is designed as a surviving beneficiary the reduction amount takes into
consideration both the ages of the employee and the spouse. A table provides lookup
values in years. However, the plan calls for interpolation based on age in completed
months. This example further highlights the similarities between the Interval
and Interpolation patterns, since the age must first be quantitized using a floor
interval rule before performing the linear interpolation on the table lookup.
Early Retirement Factor Parameters
||Early Reduction Factor
|Source Attribute 1
|Source Attribute 2
UML Representation and Related Patterns
. The Interpolation business rule pattern maps to the Operation model element.
This pattern is closely related to the Interval and Derivation Algorithm business rule patterns.
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