提供预先存在的业务服务的业务级别抽象。

Provide a business-level abstraction for the composition of preexisting business services.

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您的特定安装可能有也可能没有预先存在的缓存实例。

Your particular install may or may not have pre-existing cache instances.

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然而，预先存在的属性有时不能充分描述某一给定的关系。

However, pre-existing properties sometimes do not adequately describe a given relationship.

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