但是如果说有任何必要的好，这些令人沮丧的数据则是一种提醒，警示着人们经济复苏的道路是不平坦的。
But the gloomier figures are a reminder, if any were needed, that the road to recovery is not a smooth one.
然而由于复杂的树形XML文档和简单平坦的关系型数据库表结构之间固有的不匹配，使得XML到关系型数据库的映射实现十分困难，因此成为当前的一个热门研究课题。
However, due to the mismatch between the XML's tree structure and flat relational tables, mapping XML document to relational database is an involved problem. So it becomes a pop research direction.
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