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 Mr ∩ Ms ≥ 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 ¦jk ∩ Mr¦≥ 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).