A collection of violations of a particular constraint for an individual employee. These are the constraints such as those specified in an employee's contract. For example, shift length constraints, shift start time constraints etc.
A collection of violations for an individual employee. The constraints are from the employee's contract and day on/off and shift on/off requests.
A violation of a constraint other than the constraints which apply to employees' individual schedules. For example a violation of a cover constraint.
A violation which occurs in an individual employee's schedule (for example violations of contract constraints). It contains the date, penalty etc for this violation.
Represents a change of a shift. It contains an original shift (if there was one) assigned to an employee and a new shift (if there is one) that has replaced it on this day.
The differences between two solutions. The differences include the changes in shifts in the new solution and the violations added to and removed from the new solution.