When handling null values during extraction, it is important to distinguish whether the NULL value or an empty string is extracted. Not every database system used supports differentiation between NULL and empty strings:
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<attribute type="AT_EXAMPLE"></attribute>
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If you want to use default values such as Not specified instead of extracted null values after import into the PPM system, you can define default values (defaultvalue XML element) in the calculation of the corresponding attribute (see PPM Customizing manual).