Can we initialize a map field? If yes, how to do so.
Map fields are initialized by the programming objects that invoke the map. They are defined on the map as modifiable, so the user sees the initial value and then can modify it if necessary.
Natural code within the map is executed after the map has been displayed. Field values can be modified by that code, but not initialized prior to display.
(There is a trick where a map is executed twice. Once to “initialize” fields but no be displayed; the second to display the modified fields. I don’t recommend this technique.)
Technically speaking, there is no such thing as a “pre-processing” rule for Natural Maps. However, using layouts, you can create such a facility.
If you are interested, send me an e-mail at firstname.lastname@example.org. I will send you a pdf file which describes what you need to know about layouts and maps to implement pre-processing rules.