Users with existing data:

When importing data from an existing data source, IMW does three things.  First, it reads the data from the source ASCII delimited file.  Second, if required, it converts the values of the data to numbers.  Third, it writes the converted data to its own database.  In this stage it also adds any unknown street names to the streets database.

As a user, you see this happening in one action: IMPORT.  But you have control over how it takes place.  There is an Import definition file (.IML or .IMP) which describes how to read the ASCII delimited file.  There is also a Changes definition file (.CNG) which describes how to convert the data it reads, if a conversion is required.