diff --git a/lib/data/Internals.hs b/lib/data/Internals.hs
new file mode 100644
index 0000000..68f1a8d
--- /dev/null
+++ b/lib/data/Internals.hs
@@ -0,0 +1,61 @@
+-- Represents an item in the game.
+
+module Internals
+( Action(..)
+, Object(..)
+) where
+
+----------------------------- Constants ------------------------------
+
+data Object = 
+    Item { -- All fields are required
+        -- Easy way to identify items
+        id          :: String,
+        -- Horizontal coördinate in the level
+        x           :: Int,
+        -- Vertical coördinate in the level
+        y           :: Int,
+        name        :: String,
+        -- Short description of the object
+        description :: String,
+        -- Counts how often the object can be used by the player. Either 
+        -- infinite or a natural number
+        useTimes    :: Maybe Int,
+        -- List of conditional actions when the player is standing on this object
+        actions     :: [Action],
+        -- Interpretation depends on action with this object.
+        value       :: Maybe Int
+    }
+    | Entity {
+    -- Required fields
+        -- Easy way to identify items
+        id          :: String,
+        -- Horizontal coördinate in the level
+        x           :: Int,
+        -- Vertical coördinate in the level
+        y           :: Int,
+        name        :: String,
+        -- Short description of the object
+        description :: String,
+        -- List of conditional actions when the player is standing on this object
+        actions     :: [Action],
+    -- Optional fields
+        -- The direction of the item. e.g. a door has a direction.
+        direction   :: Maybe Direction,
+        -- Some entities have health points.
+        hp          :: Maybe Int,
+        -- Interpretation depends on action with this object.
+        value       :: Maybe Int
+    }
+
+data Direction = North 
+               | East 
+               | South 
+               | West
+               deriving (Show)
+
+type Action = ([Condition], Event)
+
+type Condition = Bool
+
+type Event = *
\ No newline at end of file
diff --git a/lib/data/Player.hs b/lib/data/Player.hs
new file mode 100644
index 0000000..642a6c3
--- /dev/null
+++ b/lib/data/Player.hs
@@ -0,0 +1,15 @@
+-- Represents a player in the game. This player can move around, pick
+-- up items and interact with the world.
+
+module Player
+( Player(..)
+) where
+
+import Internals
+
+----------------------------- Constants ------------------------------
+
+data Player = Player {
+    hp :: Int,
+    inventory :: [Object]
+}
\ No newline at end of file
diff --git a/rpg-engine.cabal b/rpg-engine.cabal
index 28aea68..cf4a6f8 100644
--- a/rpg-engine.cabal
+++ b/rpg-engine.cabal
@@ -11,8 +11,11 @@ library
     gloss >= 1.11 && < 1.14, gloss-juicy >= 0.2.3
   exposed-modules:
     RPGEngine,
+    -- Control
     Input, InputHandling,
-    Game, State,
+    -- Data
+    Game, Internals, Player, State,
+    -- Render
     Render
 
 executable rpg-engine