An identifier is a column or combination of columns that uniquely defines a specific RAP message.
Identifiers in the RAP Messages model become keys on tables in the RAPCache and RAPStore physical models.
Each RAP message can have at most one primary identifier, which becomes the primary key in the generated table.
When an identifier has multiple attributes, the primary key in the destination table is composed of multiple columns. For example, in the sample model, the Dividend Event message has one identifier. Attributes for this primary identifier are Instrument and Disbursed Date. Thus the primary key for the Dividend Event table is composed of both the Instrument and Disbursed Date columns.