Hello, Greg Weber asked me to implement a logging system as a WAI middleware. So, I considered it. The typical Apache log format is as follows: 127.0.0.1 - - [10/Aug/2011:11:27:34 +0900] "GET / HTTP/1.1" 200 512 "referer" "agent" where 200 is status and 512 is a response size Response is defined as follows: ResponseFile Status ResponseHeaders FilePath (Maybe FilePart) ResponseBuilder Status ResponseHeaders Builder ResponseEnumerator (forall a. ResponseEnumerator a) We cannot know status from ResponseEnumerator. Also, we cannot directly know size from the all three. Design choices are as follows: 1) Modified the Response type and implement a logging system as a WAI middleware. 2) Giving up implementing a logging system as a WAI middleware and implement a logging system as just a library. Which one is better? --Kazu