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Within the context of the sample application, this requirement is defined in "BPR12: Track Vehicle Disposal" in the Developer Guide and the implementation is described in "About the Data Quality Design in for the Developer GuideSample Application.
The full text of the script for the DateDisposed field appears below. The field validation fails if the Disposal Method is set to a value other than N/A and the DateDisposed is either blank or NULL. Also, the script prevents a user from marking a vehicle as Disposed while it is Rented. (Note that since this validation appears for both fields, a user will receive a validation prompt with two duplicate messages if trying to dispose of a rented vehicle.)
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