我们最后将总结何时应用数据联合模式及何时不应用此模式，并将列出重要的约束。
We will conclude by summarizing when to apply and when not to apply the data federation pattern and to list important constraints.
实现了应用程序后，需要了解可伸缩性选项，以确定采用哪个选项以及何时应用。
After you implement an application, you need to understand the scalability options to know which ones to employ and when.
注意声明方法：您指定如何处理元素，处理器(通过其内置的树遍历逻辑)决定何时应用模板。
Note the declarative approach: you specify what to do with the elements and the processor (through its built-in tree walking logic) decides when to apply a template.
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