@carmianleslie I think it is important to explain to the business that FIX is a standard and not the superset of all proprietary terminology and representations. FIX tries to avoid redundancies as much as possible, i.e. if a specific business requirement has been covered by FIX in a specific way, there is no desire from a standardization point of view to cover it in additional ways. This reduces standardization and increases cost to the industry by having to implement something multiple times simply because not all counterparties adhere to the same approach. In your example the FIX representation is a) integer field for the unit and b) string field for the period and not a single string field for an acronym. The business should care less about the technical implementation as long as the requirement has been met.
So what is the solution? Your interface specification (aka user manual aka Rules of Engagement) allows you to add your proprietary terminology by showing both in the description, e.g.
- NACA (annually): set frequency period to 1 and frequency unit to Yr = Year
- NACS (semi-annually): set frequency period to 6 and frequency unit to Mo = Month