General Resource Models

In  computer  controlled scheduling,    material,  machine handling  equipment,  tooling  and  buffer  space  should  be comprised. The explicit consideration of these resources conclude in additional decisions to be made  in  the  schedule  and  accordingly  the  problem  difficulty  is  raised.  For illustration,  the  general  thing  in  computer  controlled  systems  is  the  simultaneous need of two or more resources for the execution of a particular activity. An instance is the task of loading a part onto a machine by using a robot. At several point of time in loading operation, the robot should hold the part in position for the machine to secure the part in its machining location. Obviously, the robot and the machine are utilized simultaneously in this operation. In case of tooling, the problem is additionally difficult via the fact that tools may be shared among various machines. Thus, in making sequencing decisions one must schedule both tool movement and part movement; that is tools have part attributes as they will also consume material handling resources.

Assumption A1, A2 and A4 that are mentioned in earlier section should be relaxed to capture the nature of computer controlled scheduling. Mostly A1 is relaxed as if several operators need extra than one resource at the time, then M_r ∩ M_s ≥ 1.  A 2 relaxed since when the loading and unloading are disaggregated from the processing time, the result is that more than one operation in a job requires the same machine, or ¦j_k  ∩ M_r¦≥ 1  and A 4 is relaxed since other resources as like: material handlers must be considered. One time the assumption stated above are relaxed, the machine scheduling problem becomes an extra usual Resource-Constrained Scheduling Problem (RCSP).