外文文献：
Arrangement system
University teachers arrangement system is a combination of problems, which consist of scheduling a t of cours within a given number of rooms and time periods. Solving a real world timetabling problem manually often requires a significant amount of time, sometimes veral days or even weeks. Therefore, a lot of rearch has been invested in order to provide automated support for human timetablers. Contributions come from the fields of operations rearch and artificial Intelligence. This paper refers to terms and methods from constraint satisfaction. The methods prented were developed using constraint logic programming. Constraint logic programming combines the declarativity of logic programming with the efficiency of methods from operations rearch and artificial intelligence. It has recently become a promising approach for solving timetabling problems.
Applying classical methods from constraint satisfaction requires to model the problem as a constraint satisfaction problem, a t of variables, each associated with a domain of values
it can take on, and a t of constraints among the variables. Constraints are relations that specify the space of solutions by forbidding combinations of values.
bellowsMethods include arch, heuristics, and constraint propagation. Typically, systematic arch assigns values to variables quentially following some arch order. If the procedure fails to extend a partial solution, decisions are undone and alternatives explored. Systematic arch often relies on heuristics, which define the order in which variables and values are chon. Constraint propagation is complementary; it simplifies a problem by identifying values that cannot participate in a solution. This way the arch space gets pruned and arch becomes easier. www voanews com
In practice, most constraint-bad timetabling systems either do not support soft constraints or u a branch and bound arch instead of chronological backtracking. Branch and bound starts out from a solution and requires the next solution to be better. Quality is measured by a suitable cost function that depends on the t of violated soft constraints. With this approach, however, soft constraints play no role in lecting variables and values.
After collecting wishes of teacher and information on the new cours, a first proposal is developed with the timetable of the previous year as a starting point. This is done by using free slots in the timetable left by cours not taking place again for new cours offered by the same people, whereas wishes of teachers take precedence over the timetable of the previous year. After handing out the proposal to all teachers, evaluations and new wishes are collected.
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fqWith the current proposal as a starting point, a new proposal is developed incorporating the respons on the current proposal, again changing as little as possible, and so on. Creating a new timetable is thus a multistage, incremental process. Relying on the timetable of the previous year and changing as little as possible by incremental scheduling drastically reduces the amount of work necessary for creating a new timetable and ensures acceptance of the new timetable by keeping the weekly cour of events people are accustomed to. bootycall
Note that the assignment of rooms is done elwhere. Nevertheless, conflicting requirements for space or certain equipment may be a cau for changing the timetable.
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The general constraints are due to physical laws, academic reasons, and personal preferences of teachers:
A teacher cannot be in two places at the same time, so avoid clashing the cours of a teacher. There should be at least a one hour break between two cours of a teacher.
Some teachers prefer certain times or days for teaching.
Monday afternoon is rerved for professors’ meetings: Do not schedule professors’ cours for Monday afternoon.
扫帚拼音>ghs是什么意思trycatchThe department consists of five units, each dedicated to a certain area of rearch. Most cours are held by members of a single unit while only a few cours are held by members of different units. Cours held by members of a certain unit must not clash with cours held by other members of the same unit.
razorAn offering typically consists of two lectures and a tutorial per week. There should be a day break between the lectures of an offering. The tutorial should not take place on a day,
on which a lecture of the same offering takes place. All cours should be scheduled No lectures should be scheduled for Friday afternoon. No tutorials should be scheduled for late Friday afternoon.
