diff --git a/What is rule file and how to write one.md b/What is rule file and how to write one.md
index 863a883..fc94e95 100644
--- a/What is rule file and how to write one.md	
+++ b/What is rule file and how to write one.md	
@@ -94,7 +94,8 @@ These interface can be grouped into the following phases
 
 Tips about rule file
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-
+* for a specific request, function from phase 1 to 3 will be called in order. For the same request, the parameter `req` is always the same. With this feature, you could set your flag in `req` object in one function and fetch it from another function. 
+* the source code with rule file can be found in [./lib/requestHandler.js](https://github.com/alibaba/anyproxy/blob/master/lib/requestHandler.js). Reading it when you want to learn anyproxy further.
 
 
 To invoke a rule file