I agree that semi-colon separated segments (params) can be in PATH portion of the url. I was trying to find out, how a path;params would be useful in wsgiref request_uri's PATH_INFO variable , wherein I assumed PATH_INFO should be a file-system path or a method name.

After doing a bit of study, I find that ';' can be part of PATH_INFO in wsgiref compliant servers. I find a couple of bugs related to issues where ';' in PATH_INFO is not handled properly in other systems - http://bit.ly/g4UHhX

So, I think, we can have ';' as safe character so that it is prevented from quoting.

Also, RFC 3986 in Section 3.3 says that ';' '=' and ',' can be considered safe in the PATH component. Should we include those too?