Each element can be viewed as either a sub-hierarchy or as raw markup.
每个元素都可以作为子层次结构或原始标记查看。
2
One can add or remove departments and sub-departments which compose a hierarchy.
我们可以添加或者移除层次结构中的部门和子部门。
3
This is common with retailers where you can navigate through a hierarchy on their Web site to see the products within various categories and sub-categories.