Xijk 1, if machine k is selected for operation Oij; 0, otherwiseSijk the starting time of operation Oij on machine k Cijk the completion time of operation Oij on machine k Yiji0j0k 1, if operation Oij precedes operation Oi0j0 on machine k; 0, otherwiseCi the completion time of job i Cmax maximum completion time over all jobs (makespan)