Based on the provided DECLARE constraints, the underlying process can be described as a sequence of activities related to the submission, approval, and payment handling of a declaration. Here's a step-by-step breakdown of the process:

1. **Initialization**: The process starts with the activity 'Declaration SUBMITTED by EMPLOYEE'.

2. **Submission and Approval**:
   - After submission, the declaration must be finally approved by a supervisor ('Declaration FINAL_APPROVED by SUPERVISOR'). This approval must occur exactly once and cannot happen without the declaration being submitted first (alternate precedence and response constraints).
   - The submission and final approval activities co-exist and succeed each other without repetitions (alternate succession and co-existence constraints).

3. **Payment Request and Handling**:
   - After the declaration is submitted and finally approved, a payment request can be made ('Request Payment'). This activity must occur exactly once and cannot happen without the declaration being submitted and finally approved first (alternate precedence and response constraints).
   - Once a payment is requested, it must be handled ('Payment Handled'). This activity must also occur exactly once and cannot happen without a payment request being made first (alternate precedence and response constraints).
   - The payment request and handling activities co-exist and succeed each other without repetitions (alternate succession and co-existence constraints). Additionally, they follow a directly-follows relation (chain succession).

4. **Absence of other activities**: Several activities related to rejection, saving, and intermediate approval steps by different roles are constrained to be absent from the process. This implies that the process does not involve any rejections, intermediate approvals, or saving of declarations.

5. **Responded Existence**: Several responded existence constraints ensure that if certain activities occur, others must also occur. For example:
   - If a payment is requested, it must be handled.
   - If a declaration is finally approved by a supervisor, it must have been submitted by an employee.
   - If a payment is handled, the declaration must have been finally approved by a supervisor and a payment must have been requested.

In summary, the process involves the submission of a declaration by an employee, which is then finally approved by a supervisor. After approval, a payment is requested and subsequently handled. The process follows a strict sequence with no repetitions or intermediate rejections and approvals. All mentioned activities, except the absent ones, must occur exactly once.