A template rule has two parts: a pattern which is matched against nodes in the source tree and a template which can be instantiated to form part of the result tree.

• 每个模板规则由两部分构成：模式，用于匹配“源树”中的结点；模板，可以被实例化，实例化的结果是生成“结果树中的某个部分”。（用于构造出“结果树”的某个部分）。