1. MACMERL Mixed-Initiative Scheduling with Coincident Problem Spaces M.J. Prietula, W.L. Hsu, P.S.Ow

2. Scheduling is an important aspect of manufacturing! -No schedule means no output, bad schedule means high costs! Distinct difference between the theory and the practice of scheduling! -In theory, solution to an abstractly specified scheduling problem. -look for stable and correct solution -In practice, solution to an actual organizational problem with many different considerations and constraints. -relatively good solution is OK.

3. The text presents a solution technique created by the authors. The problem is: - Manual scheduling. - Increased competetion, scheduling is important. - Need to use computers in scheduling. - No documentation! - Schedulers are near retirement! Solution: Embody the organizational knowledge in a computer program, MACMERL

4. MACMERL: an interactive scheduler Using a “cognitive perspective”, Focuses experience of human expert scheduler, Computational power of the machine, Machine and human operate in “coincident problem spaces”, Mixed-initiative approach: both human and the machine offer schedule alternatives.

5. The plant; Producing windshields for trucks, Using vinyl and glass, Glass is heated in large ovens to be shaped. It is the bottleneck activity, Scheduling Task: Determine - which type of windshield glass, - on which oven, - when and for what duration?

6. DESIGN APPROACH - System and scheduler should be problem solving in coincident (identical) problem spaces. Components of coincident problem space: - expert’s problem solving methods, - underlying causal model of these methods, - generic problem solving methods to support expert’s methods. - Coordinate the efforts of human and machine.

7. Creating the coincident problem space: 1. Analysis of expert’s methods. - interview the expert - collect information 2. Development of computational analogs. - design data structure (part lists, etc.), - generate codes for methods. 3. Expert-based iterative refinement. - interactive review of generated schedules.

8. TaskHuman Expert’s GoalsMacMerl’s Operators Problem Specification and Goal Recognition 1.Review Starting Conditions 2.Determine critical constraints and preferences 3. Determine scheduling goals 1.Display schedule and parts list. 2.Set constraint/preference switches. 3.Adjust weights on terms in the objective function. Schedule Generation 1.Devise rough-cut capacity plan 2.Generate reservation groups 3.Generate detailed schedule 1.Generate schedule. 2.Construct family and compatibility lists for each part. 3. Execute scheduling algorithm. Schedule Evaluation 1.Evaluate schedule quality1. Display Critiquer and other supporting reports, charts. Schedule Modification 1.Address special cases 2.Adjust schedule 1. Pin parts to schedule and reinvoke scheduler to schedule around them. 2. Manually add/modify/delete jobs.

9. Scheduling Kernel Generative Scheduler Reactive/ Manual Scheduler Support Functions Constraint Checker Critiquer Interface Human Scheduler

10. Generative Scheduler The expert’s approach to forming schedules is incorporated in the Generative Scheduler. Problems Solved: 1.Selecting a lehr (oven) to schedule. -select the earliest available lehr. 2.Selecting a part to schedule on the lehr. -select the one with highest priority(stockout) cost 3.Scheduling additional parts along with the selected parts in the same reservation group. - parts that can be processed in the same lehr setting

11. Constraint Checker Check the feasibility of a given schedule. Returns information on: -type of constraint violated, -the time location in the schedule of the violation, -the lehr on which the violation occured, -the part that caused the violation. The human scheduler has the option of selecting specific constraints to enforce or ignore when invoking the Constraint Checker.

12. Reactive Scheduler -Resolves the conflicts when constraint violation occurs. Manual Scheduler -All the components can operate. -Mixed initiative approach between the human and the machine. Interface and Manipulation Routines In the Manual Scheduler, user has options to affect the schedule. - add, delete, modify jobs. - select parts....

13. Critiquer - Generate critique of a schedule proposed. - Present a discussion of its important and possibly erroneous aspects. - Checks if constraints, preferences are satisfied, etc.

14. Deployment Issues - communication is essential, - interface with existing systems in the company, - system is fine-tuned with the expert, - Macmerl is being used in scheduling, - Also as a training device for new staff, - But, it is specific to organizational context, - Must be updated and continously developed.

15. Conclusion - Actual scheduling problems are too complex to yield analytical solutions. - Need to rely on experience of human schedulers. - Integrating operations research, artificial intelligence and human computer ınteraction techniques can be valuable for some scheduling problems. - Theory of scheduling can not attack too complex scheduling problems with optimal procedures yet. - Heuristics can save us!