“constraint”的概念、定义、翻译、参考文献-科学参考

constraint

Physics

A limitation imposed on a dynamical system that limits the possible dynamics of that system. An example of a constraint is found in the definition of a rigid body, namely that the distances between all the particles that make up the system must remain constant throughout the motion of the body. The problem of constraints in dynamical systems has been studied systematically. The constraints of invariance under symmetry transformations mean that fundamental theories, such as gauge theories and the general theory of relativity, can be analysed as systems with constraints.

Mathematics

A condition that causes a restriction. For example, if f(t) describes the motion of a pendulum which is released at t = 0, then f(t) is only valid when t≥0. In a probability distribution if p_i = Pr{X = x_i} then the values p_i are subject to two axiomatic constraints: p_i≥0 for each i and ∑p_i = 1.

Computer

A condition that data held in a relational database must satisfy in order to be valid. Constraints are enforced by the database management system, and any attempted changes to data that would violate a constraint are rejected. Types of constraint include: primary keys; referential integrity; forbidding null values in a field; specifying that a field’s values must be different in every row of a table; and arbitrary logical expressions, constructed from the values of one or more fields in the same row, that must evaluate to true.

Philosophy

One proposal for solving the problem of free will and determinism is that we distinguish between acting when caused to do so, which if determinism is correct always happens, and acting under constraint, i.e. when restrictions on our options exist. The suggestion is that while constraint interferes with freedom, causation does not, and should not be regarded as a kind of constraint.

Economics

In economics, a condition which has to be satisfied for any economic activity to be feasible. Constraints may arise from facts of nature: for example, a country has only a certain amount of land available. They may arise from human actions in the past: a country’s capital stock is predetermined by its past investment, and its working population by its past demographic and immigration policies. Such resource constraints can be gradually changed by human action. Technological constraints may arise from the limits on available technology; this again can be gradually improved on by research and development. Incentive compatibility constraints are imposed on human agents by the need to motivate others. Constraints are usually expressed in terms of inequalities, since while the economy cannot use more of a resource than there is, some can be left unused. Economic problems typically take the form of maximizing or minimizing some objective function subject to satisfying a number of constraints, each of which may or may not be effective. See also budget constraint; liquidity constraint.

单词	constraint
释义	constraint Physics A limitation imposed on a dynamical system that limits the possible dynamics of that system. An example of a constraint is found in the definition of a rigid body, namely that the distances between all the particles that make up the system must remain constant throughout the motion of the body. The problem of constraints in dynamical systems has been studied systematically. The constraints of invariance under symmetry transformations mean that fundamental theories, such as gauge theories and the general theory of relativity, can be analysed as systems with constraints. Mathematics A condition that causes a restriction. For example, if f(t) describes the motion of a pendulum which is released at t = 0, then f(t) is only valid when t≥0. In a probability distribution if p_i = Pr{X = x_i} then the values p_i are subject to two axiomatic constraints: p_i≥0 for each i and ∑p_i = 1. Computer A condition that data held in a relational database must satisfy in order to be valid. Constraints are enforced by the database management system, and any attempted changes to data that would violate a constraint are rejected. Types of constraint include: primary keys; referential integrity; forbidding null values in a field; specifying that a field’s values must be different in every row of a table; and arbitrary logical expressions, constructed from the values of one or more fields in the same row, that must evaluate to true. Philosophy One proposal for solving the problem of free will and determinism is that we distinguish between acting when caused to do so, which if determinism is correct always happens, and acting under constraint, i.e. when restrictions on our options exist. The suggestion is that while constraint interferes with freedom, causation does not, and should not be regarded as a kind of constraint. Economics In economics, a condition which has to be satisfied for any economic activity to be feasible. Constraints may arise from facts of nature: for example, a country has only a certain amount of land available. They may arise from human actions in the past: a country’s capital stock is predetermined by its past investment, and its working population by its past demographic and immigration policies. Such resource constraints can be gradually changed by human action. Technological constraints may arise from the limits on available technology; this again can be gradually improved on by research and development. Incentive compatibility constraints are imposed on human agents by the need to motivate others. Constraints are usually expressed in terms of inequalities, since while the economy cannot use more of a resource than there is, some can be left unused. Economic problems typically take the form of maximizing or minimizing some objective function subject to satisfying a number of constraints, each of which may or may not be effective. See also budget constraint; liquidity constraint.
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