Conditionally Include a Field

Is there a way to use the blank input to conditionally not include the field at all? Instead of having an empty value, I’d like the field to not exist some percentage of the time.

Is there a way to do that with a field?

My specific use case is that I have XML data that only exists if the value is “true”

<dataField>true<dataField>

But that dataField only exists in 90% of the data, in the other 10% of the records I don’t want the element to exist at all.