Considerations for Multi-Level BOM Roll-up Calculations
This section provides details on the considerations for multi-level BOM roll-up calculations for attributes of type Integer, Real Number, Real Number with Units, and Boolean:
• When calculating the value for an attribute of type Integer, Real Number, or Real Number with Units, for the usage of a specific part in the structure, the value for the part is multiplied by the usage quantity. The individual calculations are then added together for the next higher level part in the structure.
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Quantity and its unit are applicable for attributes of numeric types. Quantity can be Integer or Real Number, which includes zero and negative numbers.
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Consider the following example of parts having attributes of type Real Number:
Consider a part with an attribute of type Real Number that has a value as 2 and a quantity of 3 will have its calculated value = (attribute value * quantity) = (2*3) = 6 where another part with an attribute that has a value of 3 with a quantity of 1 will have its calculated value = (attribute value * quantity) = (3*1) = 3 which summed together for the next higher level part is 6+3=9.
• When calculating the value for an attribute of type Boolean, for the usage of a specific part in the structure, the value for the part is directly used. The individual values are summarized, with a logical operation OR between the attribute values of its usages, for the next higher level part in the structure.
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Quantity and its unit are not applicable for attributes of type Boolean.
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Expanding the mechanics for a single-level calculation to consider multiple levels brings in the possibility that the next higher level may have a defined value that is considered more accurate than the value that might be rolled up from the sum of the individual components used. Here, the definition of the part is critical:
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Part Definition
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Use Defined Value
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Configurable
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No
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Roll-up value from a specific configuration is more likely to be accurate than a static value from an overloaded configuration.
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Collapsible
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No
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Configurable End Item
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No
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End Item
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Yes
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Defined value is more likely to contain more values from product measurements.
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Phantom
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No
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Does not represent a physical part.
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Gathering
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No
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Does not represent a physical part.
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Standard
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Yes
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Defined value is more likely to contain more values from part measurements.
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The exception to the above table is the top-level part which does not use the defined value and, instead, always reports the calculated roll-up value.
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In the event that the roll-up calculation identifies that a required value has not been defined for a selected attribute, an error indicator is displayed for that attribute.
For more information on configurations available for the roll-up calculation, see Properties for Multi-Level BOM Roll-up.
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It is recommended to define values for standard part used at the leaf nodes of the structure.
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