Ошибка правил Optaplanner Drools

У меня в Optaplanner есть следующее правило Drools:

rule "oneShiftPerDay"
when
    $leftAssignment : ShiftAssignment($leftId : id, $employee : employee, $shiftDate : shiftDate, employee != null)
    $rightAssignment : ShiftAssignment(employee == $employee, shiftDate == $shiftDate, id > $leftId)
then
    scoreHolder.addHardConstraintMatch(kcontext, -1); end

Но когда я запускаю решатель, я получаю следующую ошибку:

09:02:46.128 [main] ERROR o.d.c.k.b.impl.AbstractKieModule - Unable to build     KieBaseModel:defaultKieBase Error                      importing : 'be.comp.permanenties.domain.solver.EmployeeAssignmentTotal'
Error importing : 'be.comp.permanenties.domain.solver.EmployeeWorkSequence'
Rule Compilation error : [Rule name='oneShiftPerDay']
        be/comp/permanenties/solver/Rule_oneShiftPerDay544009415.java (2:220) : Only a type can be imported. be.comp.permanenties.domain.solver.EmployeeWorkSequence resolves to a package
        be/comp/permanenties/solver/Rule_oneShiftPerDay544009415.java (2:978) : Only a type can be imported. be.comp.permanenties.domain.solver.EmployeeAssignmentTotal resolves to a package

Как я могу решить эту ошибку? Спасибо.

С уважением,

Ник