BOF stands for Beginning-Of-File and indicates whether the data set is at the beginning of its records.

If BOF returns True then the active record is the first record in the dataset.

If BOF returns False, then the active record is not the first record.

This property is not commonly used. It is more common to check EOF to determine whether you are at the end of the dataset.

Declaration: property BOF: Boolean

Remember, that <DatasetName> in this example is a placeholder, and simply refers to the actual name of your data set as per your Map.

procedure OnMapEvent(var Value:Variant);
begin
if <DatasetName>.BOF then
LogInfo('This is the first record that I am processing from this dataset');
end;