Model-Based Definition > Geometric Dimensioning and Tolerancing Advisor > Advisor Message Help > Datum Messages > Datum Type Is Unknown
  
Datum Type Is Unknown
The datum type is unknown because the parent feature is not supported as a datum feature.
To fix this problem, you should do one of the following:
1. Delete the parent feature and all its children
2. Delete the datum
3. Edit the parent feature and select valid datum options