Next, we see a set of enumerated types:
enum LetterStatus {
o AWAITING_APPROVAL
o APPROVED
o SHIPPED
o RECEIVED
o READY_FOR_PAYMENT
o CLOSED
o REJECTED
}
These are the states through which the letter is going to transition. When we access a letter, we're going to be able to identify where the business process is using this enumeration. All the names are fairly self explanatory.