ABSTRACT
Considerthesetofdisjunctiveformulasofafirst-orderlanguage,L.To determinewhetheragivenL-formulaq,isanelementofthisset,we wouldjustneedtocheckwhetherthefirstsymbolinq,isaleft-hand bracket,andwhetherq,containsanoccurrenceofvwiththenumberof left-handbracketstoitsleftexceedingbyonethenumberofright-hand brackets.Devisingthisproceduremayrequiresomeingenuity,butnone isrequiredforapplyingit.PerformingthesechecksonanL-formulaisa purelymechanicaltask.
