Reference Data, or lookup tables are things like CustomerType, ProductType and so on. They change infrequently, occasionally a new type is added or an old one retired. In code they're often reproduced as enums/constants, and also used to populate combo boxes. Adding a new Type shouldn't break existing applications, and more often than not those new types are only required to support a feature of a new application, the legacy app(s) should ignore it.Reference Data, or lookup tables are things lik