To help insure that all categories and symbols are kept unique, one technique is to prefix them with your company name. For example, since US already exists, Widgets Incorporated may call their new series WID.US. For a Futures category, use WidgetsFutures. The following is a good example of proper symbology for proprietary data loads:

All of the category names used in this example are unique as well as the symbol names. You do not have to create a unique category name but any symbol names that you add to a MIM must be unique.