When an input argument of a functional map evaluates to NONE
If any argument of a functional map evaluates to "none", the functional map will not be evaluated for that evaluation set.
For example:
MakeForm ( EntryForm:Input , GroupInfo:Input )
Where the object GroupInfo is optional; it has a component range of (0:3). If there are no occurrences of GroupInfo in the Input data object, the map MakeForm will not be evaluated at all.
Here is another example:
OrderMap ( OrderRecord:Order:Input , SummaryRecord:Order:Input )
If SummaryRecord has a component range of (0:1) and it is missing in a particular Order. The map OrderMap will not be evaluated for that Order.
If you want OrderMap to be evaluated even when SummaryRecord is missing, use the entire Order as an input argument, rather than SummaryRecord. This will ensure that OrderMap will be evaluated, even if SummaryRecord is missing. Then, in the map OrderMap, you can still map from SummaryRecord.
The rule you should use is this:
OrderMap ( OrderRecord:Order:Input , Order:Input )