某电子商务方案（英文）

简　介：

What is a Constraint?
Any element or factor that prevents a system from achieving a higher level of performance with respect to its goal
Constraints can be physical, such as a machine center or a lack of material, but they can also be managerial, such as a policy or procedure.
Defining Constraints
There are three types of constraints:
Material
Capacity
Time
Constraints are modeled as extension selectors available on different models.
Example: Buffer flow policy and Operation process extension selector
Some extension selectors require the use of a calendar model.
What is an Extension Selector?
There is a predefined list of choices
One and only one extension selector can be chosen
Depending on the selection, more fields will be available
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