What should be passed from data element to XDM Object of "value" and "id" property combo, when no values need to be passed?

Hi,

In the XDM schema there are commonly objects that contain a value/id combination, where "value" is a number which acts as a counter and "id" is a string which contains the actual value or identifier being passed. I'm using a data element to populate both these fields. The thing I'm trying to figure out is what values to pass when I don't need to populate these properties, under specific conditions. If I'm not supposed to populate the fields, what do I return for the 'id" and value? I'm assuming undefined for "id" or should I pass null instead. I'm thinking null may cause issues with data ingestion. Same situation for "value", do I pass 0, undefined or null? 

Thanks!