## 3 A Decision Support System for Detailed Scheduling
### DSS Functionality for the Scheduling Process
The final stages of the detailed scheduling process include a what-if-analysis conducted by the planner by trying out different scheduling scenarios among different functional groups and the validation of the final schedule by updating the PPC and ERP databases via ODBC. The planner performs the entire process at the beginning of each week using the production order data updated at the end of the previous week. Rescheduling takes place when necessary, during the planning period. Figure 1 summarizes the above process through an activity-based view. The scheduling process is presented as a series of activities, where specific DSS functions support each activity. The complete functionality of the G-DSS is presented in Table 3. Every function is categorized according to its decision support contribution as \"core\" or \"supplementary\". For example, order releasing and dispatching are core decision support functions that assist the planner in performing detailed production scheduling. At the same time, schedule representation and reports are supplementary since they aim to present and validate the decision-making process's outcome. Furthermore, the various methods and algorithms incorporated by every function are presented in Table 3.  
Figure 2 provides a method/algorithmic-oriented view where the sequence of algorithms is provided for each system function of Figure 1. For example, the second-level dispatching function utilizes the prioritized orders of the previous step using an assortment  
Figure 1: Scheduling process and functionality of the decision support system. of different priority rules in order to create the dispatched orders. Additionally, from a decision support view, during the second-level dispatching, the planner reaches a node and is called to choose a specific priority dispatching rule while taking into account the area of effect of these heuristics, which in that case, is a single work center. It should be noted that for the final step, i.e., BOM precedence constraint satisfaction, the compound TS/VNS-ATM algorithm has a functional group breadth, whereas the impact analysis heuristic considers the entire shop floor (all the functional groups). The next section thoroughly describes these heuristics and algorithms for the core functionality of the DSS. Finally, Figure 3 presents a framework for the G-DSS system that is based on all the operations that were analyzed in Sections 2 and 3. More specifically, the figure presents the interactions of the three enterprise systems. The production scheduling process starts at the PPC planning module with the MPS calculations that are fed to the MRP. These calculations are based on forecasting and sales data. The ERP provides inventory information (used in MRP) and then receives production and purchase orders (as output from the MRP). It can also provide cost estimates for the orders. The MRP sends orders and order backlog (from the PPC production order issuing module) to the G-DSS for use in detailed scheduling. The G-DSS generates detailed schedules based on the aforementioned data and commands from the planner. The PPC production order releasing/dispatching module helps by releasing and dispatching production orders to the shop floor. This detailed schedule is handed to the shop floor to start production. The PPC shop floor control module aids the process by receiving necessary data from the production and sending them to the planner for