上下文节点

• The ancestor axis contains the ancestors of the context node ; the ancestors of the context node consist of the parent of context node and the parent s parent and so on ; thus , the ancestor axis will always include the root node , unless the context node is the root node
  Ancestor轴axis包含上下节点的祖先节点,该祖先节点由其上下文节点的父节点以及父节点的父节点等等诸如此类的节点构成,所以ancestor轴总是包含有根节点,除非上下文节点就是根节点本身