A chain is a special handler that represents a sequence of other handlers.
链是一个特殊的处理程序，它代表了其他处理程序的顺序。
2
A sequence of extension generators or extension handlers is referred to as an extension chain.
扩展生成器或扩展处理程序的序列称为扩展链。
3
This example creates a single chain to render a resume XML document, resume.xml, into an HTML page through a sequence of three stylesheet transformations.