When multiple instances of an element exist as children of a single parent element, normal iteration techniques apply.
如果同一个父元素中存在同一元素的多个实例，通常需要使用迭代技术。
2
You can do this by introducing an iteration identifier in the namespace of the subscription header element. Here are some examples.
可以通过在订阅头元素的命名空间中引入反复标识符来实现这一点。
3
We nest an tag inside the first and indicate that within the scope of the iteration, variable name "swimmer" will be associated with the current element.