1.The input to each step in the pipeline is an XML document or documents, and the output from a nonterminal step is also an XML document.
管道中每一步的输入是单个或多个XML文档，中间步骤的输出也是XML文档。
2.The syntax analyzer has one recursive procedure for each nonterminal U.
对于每个非终结符号U，语法分析程序都有一个递归过程。