diff --git a/oi.cabal b/oi.cabal
--- a/oi.cabal
+++ b/oi.cabal
@@ -1,11 +1,10 @@
 Name:			oi
-Version:		0.1.1
+Version:		0.2.0.1
 Category:		Data
-Synopsis:		Purely Functional Lazy Interaction with the outer world
-Description:		This package implements a data structure and operations on it 
-			for making interactive program without using explicitly IO monads.
-			
-			Version 0.1.1: APIs are changed!
+Synopsis:		Library for purely functional lazy interactions with the outer world.
+Description:		This package implements a data structure and operations on it for writing interactive program with no imperative flavor of IO monads.
+			.
+			[N.B.] At the moment, APIs maybe change.
 
 Stability:		Experimental
 License:		BSD3
@@ -24,8 +23,14 @@
   Build-Depends:	    base >= 4.5 && < 5, parallel, comonad, filepath
   GHC-Options:		    -Wall -O0
   Exposed-modules:	    Data.OI
-                           ,Data.OI.Base
+                           ,Data.OI.Internal
                            ,Data.OI.Combinator
+                           ,Data.OI.Force
+                           ,Data.OI.IFun
                            ,Data.OI.IO
                            ,Data.OI.Resource
                            ,Data.OI.System
+
+Source-Repository head
+  type:		  darcs
+  location:	  http://darcs.sampou.org/oi/
diff --git a/sample/catsIO.hs b/sample/catsIO.hs
--- a/sample/catsIO.hs
+++ b/sample/catsIO.hs
@@ -1,7 +1,13 @@
 module Main where
 
 import System.Environment
+import System.IO hiding (readFile, writeFile)
+import Prelude hiding (readFile, writeFile)
 
+{-
+ If "files" contains much many files, "./catsIO" throws a resource-exhaused exception."
+-}
+
 main :: IO ()
 main = do
   args     <- getArgs
@@ -15,3 +21,15 @@
 
 textproc :: String -> String
 textproc = unlines . take 1 . lines
+
+readFile :: String -> IO String
+readFile f = do
+  h  <- openFile f ReadMode
+  cs <- hGetContents h
+  return cs
+
+writeFile :: String -> String -> IO ()
+writeFile f cs = do
+  h  <- openFile f WriteMode
+  r  <- hPutStr h cs
+  return r
diff --git a/sample/catsLIO.hs b/sample/catsLIO.hs
--- a/sample/catsLIO.hs
+++ b/sample/catsLIO.hs
@@ -1,9 +1,9 @@
 module Main where
 
 import System.Environment
-import System.IO
+import System.IO hiding (readFile, writeFile)
 import System.IO.Unsafe
-import Prelude
+import Prelude hiding (readFile, writeFile)
 
 main :: IO ()
 main = do
@@ -31,3 +31,15 @@
   r  <- lazy i
   rs <- sequenceLz is
   return (r:rs)
+
+readFile :: String -> IO String
+readFile f = do
+  h  <- openFile f ReadMode
+  cs <- hGetContents h
+  return cs
+
+writeFile :: String -> String -> IO ()
+writeFile f cs = do
+  h  <- openFile f WriteMode
+  r  <- hPutStr h cs
+  return r
diff --git a/sample/catsOI.hs b/sample/catsOI.hs
--- a/sample/catsOI.hs
+++ b/sample/catsOI.hs
@@ -1,24 +1,38 @@
 {-# LANGUAGE TypeOperators #-}
 module Main where
 
-import Data.OI
+import Data.OI hiding (openFile)
+import System.IO (IOMode (..), Handle)
+import qualified System.IO as IO
+import Prelude hiding (readFile, writeFile)
 
 main :: IO ()
-main = run pmain
+main = runInteraction pmain
 
-pmain :: (([String], Either (String, [String]) [String]), ()) :-> ()
+pmain 
+  :: (([String],Either ((Handle, String), [(Handle, String)]) [(Handle, String)]), (Handle, ()))
+  :-> ()
 pmain = args 
-    |/| choiceOIOn (const $ lines . readFile' "files" |/| zipWithOI readFile') 
-                   (zipWithOI readFile')
+    |/| choiceOIOn (const $ lines . readFile "files" |/| zipWithOI readFile) 
+                   (zipWithOI readFile)
                    null
-    |/| writeFile' "output.txt" . concatMap textproc
-
-readFile' :: FilePath -> OI String -> String
-readFile'  = iooi . readFile
-
-writeFile' :: FilePath -> String -> OI () -> ()
-writeFile' = (iooi .) . writeFile
+    |/| writeFile "output.txt" . concatMap textproc
 
 textproc :: String -> String
 textproc = id -- unlines . take 1 . lines
+
+readFile :: FilePath -> (Handle, String) :-> String
+readFile f      = openFile f ReadMode   |/| hGetContents
+
+writeFile :: FilePath -> String -> (Handle, ()) :-> ()
+writeFile f cs  = openFile f WriteMode  |/| flip hPutStr cs
+
+openFile :: FilePath -> IOMode -> Handle :-> Handle
+openFile     = (iooi .) . IO.openFile
+
+hGetContents :: Handle -> String :-> String
+hGetContents = iooi . IO.hGetContents
+
+hPutStr :: Handle -> String -> () :-> ()
+hPutStr      = (iooi .) . IO.hPutStr
 
diff --git a/sample/catsSIO.hs b/sample/catsSIO.hs
--- a/sample/catsSIO.hs
+++ b/sample/catsSIO.hs
@@ -1,9 +1,14 @@
 module Main where
 
 import System.Environment
-import System.IO.Strict
+import qualified System.IO as IO
+import System.IO.Strict hiding (readFile, writeFile)
 import Prelude hiding (readFile, writeFile)
 
+{-
+ If the amount of size of files contained in "files" is too much, "./catsSIO" throws a out-of-memory exception."
+-}
+
 main :: IO ()
 main = do
   args     <- getArgs
@@ -21,3 +26,15 @@
 
 textproc :: String -> String
 textproc = unlines . take 1 . lines
+
+readFile :: String -> SIO String
+readFile f = do
+  h  <- openFile f IO.ReadMode
+  cs <- hGetContents h
+  return cs
+
+writeFile :: String -> String -> SIO ()
+writeFile f cs = do
+  h  <- openFile f IO.WriteMode
+  r  <- hPutStr h cs
+  return r
diff --git a/sample/echo.hs b/sample/echo.hs
--- a/sample/echo.hs
+++ b/sample/echo.hs
@@ -7,10 +7,10 @@
 import System.IO
 
 main :: IO ()
-main = run $ pmain1
+main = runInteraction $ pmain1
 
-pmain0 = forces . mapOI echo
-pmain1 = forces . echos
+pmain0 = forceSeq . mapOI echo
+pmain1 = forceSeq . echos
 
 eof :: Int
 eof = -1
diff --git a/sample/recdircs.hs b/sample/recdircs.hs
--- a/sample/recdircs.hs
+++ b/sample/recdircs.hs
@@ -11,7 +11,7 @@
 import System.Directory
 
 main :: IO ()
-main = run pmain
+main = runInteraction pmain
 
 pmain :: (([String], [(Bool, IOResult [FilePath])]), ()) :-> ()
 pmain = ((args |> head) |/| getDirCsRec) |> snd |/| putStrOI . unlines
diff --git a/sample/talk.hs b/sample/talk.hs
--- a/sample/talk.hs
+++ b/sample/talk.hs
@@ -10,7 +10,7 @@
 
 main :: IO ()
 main = do { kbd1:scr1:kbd2:scr2:_ <- getArgs
-          ; run $ pmain (kbd1,scr1) (kbd2,scr2)
+          ; runInteraction $ pmain (kbd1,scr1) (kbd2,scr2)
           }
 
 pmain ::  (FilePath,FilePath)
@@ -28,10 +28,10 @@
     (is,os,us) = deTriple r
     ins = map ((name ++ ": ")++) $ lines $ readkbd kbd is
 
-readkbd :: FilePath -> OI String -> String
+readkbd :: FilePath -> String :-> String
 readkbd = iooi . readFile
 
-showscr :: FilePath -> [String] -> OI () -> ()
+showscr :: FilePath -> [String] -> () :-> ()
 showscr s = iooi . writeFile s . unlines
 
 mergeOI = (iooi .) . mergeIO
diff --git a/src/Data/OI.hs b/src/Data/OI.hs
--- a/src/Data/OI.hs
+++ b/src/Data/OI.hs
@@ -9,15 +9,19 @@
 module Data.OI 
   (
   -- * Export modules
-   module Data.OI.Base
+   module Data.OI.Internal
   ,module Data.OI.Combinator
+  ,module Data.OI.IFun
   ,module Data.OI.IO
   ,module Data.OI.Resource
   ,module Data.OI.System
+  ,module Data.OI.Force
   ) where
 
-import Data.OI.Base
+import Data.OI.Internal
 import Data.OI.Combinator
+import Data.OI.Force
+import Data.OI.IFun
 import Data.OI.IO
 import Data.OI.Resource
 import Data.OI.System
diff --git a/src/Data/OI/Base.hs b/src/Data/OI/Base.hs
deleted file mode 100644
--- a/src/Data/OI/Base.hs
+++ /dev/null
@@ -1,275 +0,0 @@
-{-# LANGUAGE TypeOperators
-            ,ScopedTypeVariables
-            ,PostfixOperators
-            ,NoMonomorphismRestriction
-            ,BangPatterns
-  #-}
-{-# OPTIONS_GHC -fno-cse #-}
--- |
--- Module      : Data.OI.Base
--- Copyright   : (c) Nobuo Yamashita 2011-2012
--- License     : BSD3
--- Author      : Nobuo Yamashita
--- Maintainer  : nobsun@sampou.org
--- Stability   : experimental
---
-module Data.OI.Base
-  (
-  -- * Interaction datatypes
-   OI
-  ,(:->)
-  -- * Drive an interaction
-  ,run
-  -- * Primitive operators on OI
-  ,(=:)
-  ,(??)
-  -- * Splitter against OI
-  ,dePair
-  ,deList
-  ,deTriple
-  ,deTuple4
-  ,deTuple5
-  ,deTuple6
-  ,deTuple7
-  ,deLeft
-  ,deRight
-  -- * Convert IO to interaction
-  ,IOResult(..)
-  ,iooi
-  ,iooi'
-   -- * Forcing
-  ,forces
-  ,force
-  ,split
-  )
-  where
-
-import Control.Applicative
-import Control.Category
-import Control.Comonad
-import Control.Exception
-import Control.Monad
-import Control.Concurrent
-import Control.Parallel
-import System.IO.Unsafe
-import Prelude hiding ((.),id,catch)
-
--- | Datatype for intermediating interaction
-data OI a = OI (LeftValueOf a) (RightValueOf a)
-
--- | Interaction type
-type a :-> b = OI a -> b
-infixr 0 :->
-
-instance Functor OI where
-  fmap f = (##) . f . (??)
-
-instance Monad OI where
-  return = (##)
-  (>>=)  = flip ($) . (??)
-
-instance Extend OI where
-  duplicate = (##)
-
-instance Comonad OI where
-  extract = (??)
-
--- | Assign operator
-(=:) :: a -> OI a -> a
-(=:) !x (OI var val) = put (return x) var `pseq` val
-
--- | Dereference operator
-(??) :: OI a -> a
-(??) (OI _ val) = val
-
--- | Reference operator
-(##) :: a -> OI a
-(##) x = OI (unsafeNew x) x
-
-
--- | Decomposer for pair
-dePair :: OI (a,b) -> (OI a, OI b)
-dePair (OI vxy ~(x,y)) = put io vxy `pseq` (OI vx x, OI vy y)
-  where
-    vx  = new x
-    vy  = new y
-    io  = (,) <$> lazy (deref vx) <*> lazy (deref vy)
-
--- | Decomposer for list
-deList :: OI [a] -> Maybe (OI a, OI [a])
-deList (OI vxxs xxs) = put io vxxs
-  `pseq` case xxs of
-     x:xs -> Just (OI vx x, OI vxs xs)
-     _    -> Nothing
-  where
-    vx  = new (undefined :: a)
-    vxs = new (undefined :: [a])
-    io = (:) <$> lazy (deref vx) <*> lazy (deref vxs)
-
--- | Decomposer for triple
-deTriple :: OI (a,b,c) -> (OI a, OI b, OI c)
-deTriple (OI vxyz ~(x,y,z)) = put io vxyz
-  `pseq` (OI vx x, OI vy y, OI vz z)
-  where
-    vx  = new x
-    vy  = new y
-    vz  = new z
-    io  = (,,) <$> lazy (deref vx) 
-               <*> lazy (deref vy)
-               <*> lazy (deref vz)
-
--- | Decomposer for 4-tuple
-deTuple4 :: OI (a,b,c,d) -> (OI a, OI b, OI c, OI d)
-deTuple4 (OI vwxyz ~(w,x,y,z)) = put io vwxyz
-  `pseq` (OI vw w, OI vx x, OI vy y, OI vz z)
-  where
-    vw  = new w
-    vx  = new x
-    vy  = new y
-    vz  = new z
-    io  = (,,,) 
-      <$> lazy (deref vw) 
-      <*> lazy (deref vx) 
-      <*> lazy (deref vy)
-      <*> lazy (deref vz)
-
--- | Decomposer for 5-tuple
-deTuple5 :: OI (a,b,c,d,e) -> (OI a, OI b, OI c, OI d, OI e)
-deTuple5 (OI vvwxyz ~(v,w,x,y,z)) = put io vvwxyz
-  `pseq` (OI vv v, OI vw w, OI vx x, OI vy y, OI vz z)
-  where
-    vv  = new v
-    vw  = new w
-    vx  = new x
-    vy  = new y
-    vz  = new z
-    io  = (,,,,) 
-      <$> lazy (deref vv) 
-      <*> lazy (deref vw) 
-      <*> lazy (deref vx) 
-      <*> lazy (deref vy)
-      <*> lazy (deref vz)
-
--- | Decomposer for 6-tuple
-deTuple6 :: OI (a,b,c,d,e,f) -> (OI a, OI b, OI c, OI d, OI e, OI f)
-deTuple6 (OI vuvwxyz ~(u,v,w,x,y,z)) = put io vuvwxyz
-  `pseq` (OI vu u, OI vv v, OI vw w, OI vx x, OI vy y, OI vz z)
-  where
-    vu  = new u
-    vv  = new v
-    vw  = new w
-    vx  = new x
-    vy  = new y
-    vz  = new z
-    io  = (,,,,,) 
-      <$> lazy (deref vu) 
-      <*> lazy (deref vv) 
-      <*> lazy (deref vw) 
-      <*> lazy (deref vx) 
-      <*> lazy (deref vy)
-      <*> lazy (deref vz)
-
--- | Decomposer for 7-tuple
-deTuple7 :: OI (a,b,c,d,e,f,g) -> (OI a, OI b, OI c, OI d, OI e, OI f, OI g)
-deTuple7 (OI vtuvwxyz ~(t,u,v,w,x,y,z)) = put io vtuvwxyz
-  `pseq` (OI vt t, OI vu u, OI vv v, OI vw w, OI vx x, OI vy y, OI vz z)
-  where
-    vt  = new t
-    vu  = new u
-    vv  = new v
-    vw  = new w
-    vx  = new x
-    vy  = new y
-    vz  = new z
-    io  = (,,,,,,) 
-      <$> lazy (deref vt) 
-      <*> lazy (deref vu) 
-      <*> lazy (deref vv) 
-      <*> lazy (deref vw) 
-      <*> lazy (deref vx) 
-      <*> lazy (deref vy)
-      <*> lazy (deref vz)
-
-deLeft  :: OI (Either a b) -> Either (OI a) (OI b)
-deRight :: OI (Either a b) -> Either (OI a) (OI b)
-
-deLeft (OI ve ~(Left a)) = put io ve `pseq` Left (OI vl a)
-  where
-    vl = new a
-    io = Left <$> lazy (deref vl)
-
-deRight (OI ve ~(Right b)) = put io ve `pseq` Right (OI vr b)
-  where
-    vr = new b
-    io = Right <$> lazy (deref vr)
-
--- | Drive interaction
-run :: (OI a -> b) -> IO b
-run pmain = do 
-  { v <- newEmptyMVar
-  ; x <- lazy (deref v)
-  ; return $! pmain (OI v x)
-  }
-
--- | Convert IO to interaction
-iooi :: IO a -> OI a -> a
-iooi io (OI var val) = put io var `pseq` val
-
-data IOResult a = Success a | Failure String
-
-instance Functor IOResult where
-  fmap f (Success x) = Success (f x)
-  fmap _ (Failure s) = Failure s
-
-instance (Show a) => Show (IOResult a) where
-  show (Success x) = show x
-  show (Failure s) = "Failure: "++s
-
-iooi' :: IO a -> OI (IOResult a) -> IOResult a
-iooi' io (OI var val)
-  = put ( do { r <- try io
-             ; case r of { Left  e -> return $ Failure (show (e :: SomeException))
-                         ; Right a -> return $ Success a }}
-        ) var `par` val
-
--- | Forcing utilities
-
-forces :: [a] -> ()
-forces = force . dropWhile (()==) . map force
-
-force :: a -> ()
-force x = x `pseq` ()
-
-split :: a -> (a,())
-split x = x `pseq` (x,())
-
--- Wrapper
-
-type LeftValueOf  a = MVar (IO a)
-type RightValueOf a = a
-
-new :: a -> LeftValueOf a
-new   = unsafeNew
-
-deref :: MVar a -> a
-deref = unsafeDeref
-
-put   :: a -> MVar a -> a
-put   = unsafePut
-
-lazy :: IO a -> IO a
-lazy = unsafeInterleaveIO
-
--- Unsafe primitive
-
-unsafeNew :: a -> LeftValueOf a
-unsafeNew _ = unsafePerformIO newEmptyMVar
-
-unsafeDeref :: MVar a -> a
-unsafeDeref = unsafePerformIO . readMVar
-
-unsafePut :: a -> MVar a -> a
-unsafePut x v = unsafePerformIO $ do
-              { s <- tryPutMVar v x
-              ; if s then return x else readMVar v
-              }
diff --git a/src/Data/OI/Combinator.hs b/src/Data/OI/Combinator.hs
--- a/src/Data/OI/Combinator.hs
+++ b/src/Data/OI/Combinator.hs
@@ -31,7 +31,8 @@
   ,seqsOI'
   ) where
 
-import Data.OI.Base
+import Data.OI.Internal
+import Data.OI.Force
 
 (|>) :: (a -> b) -> (b -> c) -> (a -> c)
 (|>) = flip (.)
@@ -95,11 +96,9 @@
 
 -- | Sequencing
 seqsOI :: [a :-> b] -> ([a] :-> ())
-seqsOI s os =  forces $ zipWithOI ($) s os
-
+seqsOI s os =  forceSeq $ zipWithOI ($) s os
 
 seqsOI' :: [a] :-> ([a :-> b] -> ())
 seqsOI' os is = case dropWhile (()==) $ map force $ zipWithOI id is os of
   [] -> ()
   _  -> error "seqsOI': Impossible!"
-
diff --git a/src/Data/OI/Force.hs b/src/Data/OI/Force.hs
new file mode 100644
--- /dev/null
+++ b/src/Data/OI/Force.hs
@@ -0,0 +1,28 @@
+-- |
+-- Module      : Data.OI.Force
+-- Copyright   : (c) Nobuo Yamashita 2012
+-- License     : BSD3
+-- Author      : Nobuo Yamashita
+-- Maintainer  : nobsun@sampou.org
+-- Stability   : experimental
+--
+module Data.OI.Force (
+  -- * Forcing utility functions
+   force
+  ,force'
+  ,forceSeq
+  ) where
+
+import Control.Parallel
+
+-- | forces sequence
+forceSeq :: [a] -> ()
+forceSeq = force . dropWhile (()==) . map force
+
+-- | forces
+force :: a -> ()
+force x = x `pseq` ()
+
+-- | returns forcing invoker
+force' :: a -> (a,())
+force' x = x `pseq` (x,())
diff --git a/src/Data/OI/IFun.hs b/src/Data/OI/IFun.hs
new file mode 100644
--- /dev/null
+++ b/src/Data/OI/IFun.hs
@@ -0,0 +1,37 @@
+{-# LANGUAGE TypeOperators
+            ,BangPatterns
+  #-}
+-- |
+-- Module      : Data.OI.IFun
+-- Copyright   : (c) Nobuo Yamashita 2012
+-- License     : BSD3
+-- Author      : Nobuo Yamashita
+-- Maintainer  : nobsun@sampou.org
+-- Stability   : experimental
+--
+module Data.OI.IFun
+  (
+  -- * Type of function with interaction
+   IFun
+  -- * IFun combinator
+  ,(|::|)
+  ,(|->|)
+  ,(|<>|)
+  ) where
+
+import Data.OI.Internal
+
+type IFun p a b = a -> p :-> b
+
+(|::|) :: IFun p a c -> IFun q  b d -> IFun (p,q) (a,b) (c,d)
+(f |::| g) (a,b) opq = case dePair opq of
+  (p,q) -> (f a p, g b q)
+
+(|->|) :: IFun p a (b',c) -> IFun q (b',b) d -> IFun (p,q) (a,b) (c,d)
+(f |->| g) (a,b) opq = case dePair opq of
+  (p,q) -> case f a p of
+    (b',c) -> (c, g (b',b) q)
+
+(|<>|) :: IFun p (a',a) (b',c) -> IFun q (b',b) (a',d) -> IFun (p,q) (a,b) (c,d)
+(f |<>| g) (a,b) opq = case dePair opq of
+  (p,q) -> (c,d) where (b',c) = f (a',a) p; (a',d) = g (b',b) q 
diff --git a/src/Data/OI/IO.hs b/src/Data/OI/IO.hs
--- a/src/Data/OI/IO.hs
+++ b/src/Data/OI/IO.hs
@@ -9,8 +9,10 @@
 --
 module Data.OI.IO
   (
+  -- * Interaction enable to handle I/O error
+   (:~>)
   -- * I/O oprations
-   openFile
+  ,openFile
   ,hIsClosed
   ,hIsEOF
   ,hGetLine
@@ -21,37 +23,39 @@
   ,putStrLn
   ) where
 
-import Data.OI.Base
+import Data.OI.Internal
+
 import System.IO (IOMode(..),Handle)
 import qualified System.IO as IO
 import System.FilePath
 import Prelude hiding (getLine,putStrLn)
 
-type a :=> b = OI (IOResult a) -> IOResult b
+type a :~> b = OI (IOResult a) -> IOResult b
+infixr 0 :~>
 
-openFile :: FilePath -> IOMode -> Handle :=> Handle
+openFile :: FilePath -> IOMode -> Handle :~> Handle
 openFile = (iooi' .) . IO.openFile
 
-hIsClosed :: IO.Handle -> Bool :=> Bool
+hIsClosed :: IO.Handle -> Bool :~> Bool
 hIsClosed = iooi' . IO.hIsClosed
 
-hIsEOF :: IO.Handle -> Bool :=> Bool
+hIsEOF :: IO.Handle -> Bool :~> Bool
 hIsEOF = iooi' . IO.hIsEOF
 
-hGetLine :: IO.Handle -> String :=> String
+hGetLine :: IO.Handle -> String :~> String
 hGetLine = iooi' . IO.hGetLine
 
-hClose :: IO.Handle -> () :=> ()
+hClose :: IO.Handle -> () :~> ()
 hClose = iooi' . IO.hClose
 
-hPutStrLn :: IO.Handle -> String -> () :=> ()
+hPutStrLn :: IO.Handle -> String -> () :~> ()
 hPutStrLn = (iooi' .) . IO.hPutStrLn
 
-isEOF :: Bool :=> Bool
+isEOF :: Bool :~> Bool
 isEOF = iooi' IO.isEOF
 
-getLine :: String :=> String
+getLine :: String :~> String
 getLine = iooi' IO.getLine
 
-putStrLn :: String -> () :=> ()
+putStrLn :: String -> () :~> ()
 putStrLn = iooi' . IO.putStrLn
diff --git a/src/Data/OI/Internal.hs b/src/Data/OI/Internal.hs
new file mode 100644
--- /dev/null
+++ b/src/Data/OI/Internal.hs
@@ -0,0 +1,263 @@
+{-# LANGUAGE TypeOperators #-}
+{-# LANGUAGE PostfixOperators #-}
+{-# LANGUAGE BangPatterns #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE NoMonomorphismRestriction #-}
+{-# OPTIONS_GHC -fno-cse #-}
+-- |
+-- Module      : Data.OI.Base
+-- Copyright   : (c) Nobuo Yamashita 2011-2012
+-- License     : BSD3
+-- Author      : Nobuo Yamashita
+-- Maintainer  : nobsun@sampou.org
+-- Stability   : experimental
+--
+module Data.OI.Internal
+  (
+   -- * Types
+   OI
+  ,(:->)
+  -- * Primitive operators on OI
+  ,(??)
+  -- * Splitters against `OI' datatype
+  ,dePair
+  ,deList
+  ,deTriple
+  ,deTuple4
+  ,deTuple5
+  ,deTuple6
+  ,deTuple7
+  ,deLeft
+  ,deRight
+  -- * Interaction driver
+  ,runInteraction
+  -- * IO converters
+  ,IOResult(..)
+  ,iooi
+  ,iooi'
+  ) 
+  where
+
+import Control.Applicative
+import Control.Category
+import Control.Comonad
+import Control.Exception
+import Control.Monad
+import Control.Concurrent
+import Control.Parallel
+import System.IO.Unsafe
+import Prelude hiding ((.),id,catch)
+
+-- | Datatype for intermediating interaction: 
+-- @OI@ has two states, non-expressed and exressed. 
+-- `Non-expressed' indicates that no computation is assigned.
+-- In other words, it's value is never denotated by any expression.
+-- So, if you refer the value then the process will be suspended 
+-- until other process determins the value.
+-- Non-expressed value can be determined to become 'expressed' for a value by a expression at most once.
+-- `Expressed' indicates that some computation is assigned for the value.
+-- And expressed values are never changed.
+data OI a = OI (LeftValueOf a) (RightValueOf a)
+
+-- | Interaction (a function from a intermediating type to another type) type
+type a :-> b = OI a -> b
+infixr 0 :->
+
+instance Functor OI where
+  fmap f = (##) . f . (??)
+
+instance Monad OI where
+  return = (##)
+  (>>=)  = flip ($) . (??)
+
+instance Extend OI where
+  duplicate = (##)
+
+instance Comonad OI where
+  extract = (??)
+
+-- | Dereference operator
+(??) :: OI a -> a
+(??) (OI _ val) = val
+
+-- | Reference operator
+(##) :: a -> OI a
+(##) x = OI (unsafeNew x) x
+
+-- | Decomposer for pair
+dePair :: OI (a,b) -> (OI a, OI b)
+dePair (OI vxy ~(x,y)) = put io vxy `pseq` (OI vx x, OI vy y)
+  where
+    vx  = new x
+    vy  = new y
+    io  = (,) <$> lazy (deref vx) <*> lazy (deref vy)
+
+-- | Decomposer for list
+deList :: OI [a] -> Maybe (OI a, OI [a])
+deList (OI vxxs xxs) = put io vxxs
+  `pseq` case xxs of
+     x:xs -> Just (OI vx x, OI vxs xs)
+     _    -> Nothing
+  where
+    vx  = new (undefined :: a)
+    vxs = new (undefined :: [a])
+    io = (:) <$> lazy (deref vx) <*> lazy (deref vxs)
+
+-- | Decomposer for triple
+deTriple :: OI (a,b,c) -> (OI a, OI b, OI c)
+deTriple (OI vxyz ~(x,y,z)) = put io vxyz
+  `pseq` (OI vx x, OI vy y, OI vz z)
+  where
+    vx  = new x
+    vy  = new y
+    vz  = new z
+    io  = (,,) <$> lazy (deref vx) 
+               <*> lazy (deref vy)
+               <*> lazy (deref vz)
+
+-- | Decomposer for 4-tuple
+deTuple4 :: OI (a,b,c,d) -> (OI a, OI b, OI c, OI d)
+deTuple4 (OI vwxyz ~(w,x,y,z)) = put io vwxyz
+  `pseq` (OI vw w, OI vx x, OI vy y, OI vz z)
+  where
+    vw  = new w
+    vx  = new x
+    vy  = new y
+    vz  = new z
+    io  = (,,,) 
+      <$> lazy (deref vw) 
+      <*> lazy (deref vx) 
+      <*> lazy (deref vy)
+      <*> lazy (deref vz)
+
+-- | Decomposer for 5-tuple
+deTuple5 :: OI (a,b,c,d,e) -> (OI a, OI b, OI c, OI d, OI e)
+deTuple5 (OI vvwxyz ~(v,w,x,y,z)) = put io vvwxyz
+  `pseq` (OI vv v, OI vw w, OI vx x, OI vy y, OI vz z)
+  where
+    vv  = new v
+    vw  = new w
+    vx  = new x
+    vy  = new y
+    vz  = new z
+    io  = (,,,,) 
+      <$> lazy (deref vv) 
+      <*> lazy (deref vw) 
+      <*> lazy (deref vx) 
+      <*> lazy (deref vy)
+      <*> lazy (deref vz)
+
+-- | Decomposer for 6-tuple
+deTuple6 :: OI (a,b,c,d,e,f) -> (OI a, OI b, OI c, OI d, OI e, OI f)
+deTuple6 (OI vuvwxyz ~(u,v,w,x,y,z)) = put io vuvwxyz
+  `pseq` (OI vu u, OI vv v, OI vw w, OI vx x, OI vy y, OI vz z)
+  where
+    vu  = new u
+    vv  = new v
+    vw  = new w
+    vx  = new x
+    vy  = new y
+    vz  = new z
+    io  = (,,,,,) 
+      <$> lazy (deref vu) 
+      <*> lazy (deref vv) 
+      <*> lazy (deref vw) 
+      <*> lazy (deref vx) 
+      <*> lazy (deref vy)
+      <*> lazy (deref vz)
+
+-- | Decomposer for 7-tuple
+deTuple7 :: OI (a,b,c,d,e,f,g) -> (OI a, OI b, OI c, OI d, OI e, OI f, OI g)
+deTuple7 (OI vtuvwxyz ~(t,u,v,w,x,y,z)) = put io vtuvwxyz
+  `pseq` (OI vt t, OI vu u, OI vv v, OI vw w, OI vx x, OI vy y, OI vz z)
+  where
+    vt  = new t
+    vu  = new u
+    vv  = new v
+    vw  = new w
+    vx  = new x
+    vy  = new y
+    vz  = new z
+    io  = (,,,,,,) 
+      <$> lazy (deref vt) 
+      <*> lazy (deref vu) 
+      <*> lazy (deref vv) 
+      <*> lazy (deref vw) 
+      <*> lazy (deref vx) 
+      <*> lazy (deref vy)
+      <*> lazy (deref vz)
+
+deLeft  :: OI (Either a b) -> Either (OI a) (OI b)
+deLeft (OI ve ~(Left a)) = put io ve `pseq` Left (OI vl a)
+  where
+    vl = new a
+    io = Left <$> lazy (deref vl)
+
+deRight :: OI (Either a b) -> Either (OI a) (OI b)
+deRight (OI ve ~(Right b)) = put io ve `pseq` Right (OI vr b)
+  where
+    vr = new b
+    io = Right <$> lazy (deref vr)
+
+-- | Drive interaction
+runInteraction :: (OI a -> b) -> IO b
+runInteraction pmain = do 
+  { v <- newEmptyMVar
+  ; x <- lazy (deref v)
+  ; return $! pmain (OI v x)
+  }
+
+-- | @IOResult@ for error handling
+data IOResult a = Success { result :: a }
+                | Failure { errmsg :: String }
+
+instance (Show a) => Show (IOResult a) where
+  show (Success x) = show x
+  show (Failure e) = e
+
+instance Functor IOResult where
+  fmap f (Success x) = Success (f x)
+  fmap _ (Failure e) = Failure e
+
+-- | Convert IO to interaction
+iooi :: IO a -> OI a -> a
+iooi io (OI var val) = put io var `pseq` val
+
+iooi' :: IO a -> OI (IOResult a) -> IOResult a
+iooi' io (OI var val)
+  = put ( do { r <- try io
+             ; case r of { Left  e -> return $ Failure (show (e :: SomeException))
+                         ; Right a -> return $ Success a }}
+        ) var `par` val
+
+-- Wrapper
+
+type LeftValueOf  a = MVar (IO a)
+type RightValueOf a = a
+
+new :: a -> LeftValueOf a
+new   = unsafeNew
+
+deref :: MVar a -> a
+deref = unsafeDeref
+
+put   :: a -> MVar a -> a
+put   = unsafePut
+
+lazy :: IO a -> IO a
+lazy = unsafeInterleaveIO
+
+-- Unsafe primitive
+
+unsafeNew :: a -> LeftValueOf a
+unsafeNew _ = unsafePerformIO newEmptyMVar
+
+unsafeDeref :: MVar a -> a
+unsafeDeref = unsafePerformIO . readMVar
+
+unsafePut :: a -> MVar a -> a
+unsafePut x v = unsafePerformIO $ do
+              { s <- tryPutMVar v x
+              ; if s then return x else readMVar v
+              }
+
diff --git a/src/Data/OI/Resource.hs b/src/Data/OI/Resource.hs
--- a/src/Data/OI/Resource.hs
+++ b/src/Data/OI/Resource.hs
@@ -18,13 +18,15 @@
   ,mapR
   ,mapR'
   ,filterR
+  ,filterR'
   ,takeR
   ,takeR'
   ,takeWhileR
+  ,takeWhileR'
   ) where
 
 import Control.Exception
-import Data.OI.Base
+import Data.OI.Internal
 import System.IO (IOMode(..))
 import qualified System.IO as IO
 import System.IO.Unsafe
diff --git a/src/Data/OI/System.hs b/src/Data/OI/System.hs
--- a/src/Data/OI/System.hs
+++ b/src/Data/OI/System.hs
@@ -10,7 +10,7 @@
  where
 
 import System.Environment
-import Data.OI.Base
+import Data.OI.Internal
 
 args :: [String] :-> [String]
 args = iooi getArgs