Constraint propagation

Step 2. The qualitative value of the desired change is propagated through the steady-state model equations of the plant equipment, following the constraint propagation procedure of Steele (1980). Manipulations that cause the desired change and that are feasible are identified as White Knights and are constrained to lie before the situation of interest s, in accordance with the truth criterion. 

Whereas the propagation of conditions through the modeling relationships always produces consistent completions in the definition of the initial state, this may not be true with the user-driven specifications. It is possible that a valve specified by the user to be OPEN, is found by the propagation of other conditions to be CLOSED. To detect such potential inconsistencies, we have developed a dependency network (Steele, 1980) to keep track of the flow of computations during constraint propagation. The dependency network is built on the undirected graph that represents the... 

Constraint propagation also reduces the search space size. This method looks at the problem from every view conceivable and, in each of these views, develops and propagates constraints on the solution space. In a separation system synthesis problem, one might look at the mixture and decide that the species D and E should be separated alone and by using distillation. This constraint dramatically reduces the search space size. Decisions not leading to D and E being isolated into a stream that will then be separated by distillation need not be considered in any enumeration scheme. 

R. H. Lathrop. Constrained (Closed-Loop) Robot Simulation by Local Constraint Propagation. In Proceedings of the 1986 IEEE International Coitference on Robotics and Automation, pages 689-694, San Francisco, CA, Aiwil 1986. 

Where J represents a job that required the failed resource and ended after 7, but ended before Tg in the original scheduling solution. This formula means that in the rescheduled solution, either the job is delayed to start after the failure period or the job selects another suitable resource if there is one. The decision is made by the system according to constraint propagation. If the job is delayed, the exact start time TV, will be determined by the system as well. 5q represents another suitable resource for the job. 

This formula means that if a job ended after Tg in the original solution, in the rescheduled solution either its start time remains unchanged or it is delayed, which is also possible. In the meantime either the selected resource will remain unchanged or the job selects another suitable one. These decisions are made by the system according to constraint propagation. 

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