diff --git a/CHANGELOG.md b/CHANGELOG.md
index 79e258f..499cc7e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,22 @@
 # Change Log
 All notable changes to this project will be documented in this file.
 
+## Unreleased
+### Changed
+- `Language.GraphQL.Encoder` moved to `Language.GraphQL.AST.Encoder`.
+- `Language.GraphQL.Parser` moved to `Language.GraphQL.AST.Parser`.
+- `Language.GraphQL.Lexer` moved to `Language.GraphQL.AST.Lexer`.
+- All `Language.GraphQL.AST.Value` data constructor prefixes were removed. The
+  module should be imported qualified.
+- All `Language.GraphQL.AST.Core.Value` data constructor prefixes were removed.
+  The module should be imported qualified.
+- Make `Language.GraphQL.AST.Core.Object` is now just a HashMap.
+- `Language.GraphQL.AST.Transform` is now isn't exposed publically anymore.
+
+### Fixed
+- (Unsupported) nested fragments doesn't throw a runtime error but return a
+  transformation error.
+
 ## [0.5.1.0] - 2019-10-22
 ### Deprecated
 - `Language.GraphQL.AST.Arguments`. Use `[Language.GraphQL.AST.Argument]`
diff --git a/package.yaml b/package.yaml
index a23dac2..cbb7337 100644
--- a/package.yaml
+++ b/package.yaml
@@ -35,6 +35,8 @@ dependencies:
 
 library:
   source-dirs: src
+  other-modules:
+    - Language.GraphQL.AST.Transform
 
 tests:
   tasty:
diff --git a/src/Language/GraphQL.hs b/src/Language/GraphQL.hs
index c33eb95..afce8aa 100644
--- a/src/Language/GraphQL.hs
+++ b/src/Language/GraphQL.hs
@@ -10,7 +10,7 @@ import Data.List.NonEmpty (NonEmpty)
 import qualified Data.Text as T
 import Language.GraphQL.Error
 import Language.GraphQL.Execute
-import Language.GraphQL.Parser
+import Language.GraphQL.AST.Parser
 import qualified Language.GraphQL.Schema as Schema
 import Text.Megaparsec (parse)
 
diff --git a/src/Language/GraphQL/AST.hs b/src/Language/GraphQL/AST.hs
index 29d7d80..b2feb4d 100644
--- a/src/Language/GraphQL/AST.hs
+++ b/src/Language/GraphQL/AST.hs
@@ -29,16 +29,15 @@ module Language.GraphQL.AST
 import Data.Int (Int32)
 import Data.List.NonEmpty (NonEmpty)
 import Data.Text (Text)
-import Language.GraphQL.AST.Core ( Alias
-                                 , Name
-                                 , TypeCondition
-                                 )
 
 -- * Document
 
 -- | GraphQL document.
 type Document = NonEmpty Definition
 
+-- | Name
+type Name = Text
+
 -- | Directive.
 data Directive = Directive Name [Argument] deriving (Eq, Show)
 
@@ -82,12 +81,56 @@ data Selection
 
 -- * Field
 
--- | GraphQL field.
+-- | Single GraphQL field.
+--
+-- The only required property of a field is its name. Optionally it can also
+-- have an alias, arguments or a list of subfields.
+--
+-- Given the following query:
+--
+-- @
+-- {
+--   zuck: user(id: 4) {
+--     id
+--     name
+--   }
+-- }
+-- @
+--
+-- * "user", "id" and "name" are field names.
+-- * "user" has two subfields, "id" and "name".
+-- * "zuck" is an alias for "user". "id" and "name" have no aliases.
+-- * "id: 4" is an argument for "name". "id" and "name don't have any
+-- arguments.
 data Field
     = Field (Maybe Alias) Name [Argument] [Directive] SelectionSetOpt
     deriving (Eq, Show)
 
--- | Argument.
+-- | Alternative field name.
+--
+-- @
+-- {
+--   smallPic: profilePic(size: 64)
+--   bigPic: profilePic(size: 1024)
+-- }
+-- @
+--
+-- Here "smallPic" and "bigPic" are aliases for the same field, "profilePic",
+-- used to distinquish between profile pictures with different arguments
+-- (sizes).
+type Alias = Name
+
+-- | Single argument.
+--
+-- @
+-- {
+--   user(id: 4) {
+--     name
+--   }
+-- }
+-- @
+--
+--  Here "id" is an argument for the field "user" and its value is 4.
 data Argument = Argument Name Value deriving (Eq,Show)
 
 -- * Fragments
@@ -107,15 +150,15 @@ data FragmentDefinition
 -- * Inputs
 
 -- | Input value.
-data Value = ValueVariable Name
-           | ValueInt Int32
-           | ValueFloat Double
-           | ValueString Text
-           | ValueBoolean Bool
-           | ValueNull
-           | ValueEnum Name
-           | ValueList [Value]
-           | ValueObject [ObjectField]
+data Value = Variable Name
+           | Int Int32
+           | Float Double
+           | String Text
+           | Boolean Bool
+           | Null
+           | Enum Name
+           | List [Value]
+           | Object [ObjectField]
            deriving (Eq, Show)
 
 -- | Key-value pair.
@@ -127,13 +170,15 @@ data ObjectField = ObjectField Name Value deriving (Eq, Show)
 data VariableDefinition = VariableDefinition Name Type (Maybe Value)
                           deriving (Eq, Show)
 
+-- | Type condition.
+type TypeCondition = Name
+
 -- | Type representation.
 data Type = TypeNamed   Name
           | TypeList    Type
           | TypeNonNull NonNullType
             deriving (Eq, Show)
 
-
 -- | Helper type to represent Non-Null types and lists of such types.
 data NonNullType = NonNullTypeNamed Name
                  | NonNullTypeList  Type
diff --git a/src/Language/GraphQL/AST/Core.hs b/src/Language/GraphQL/AST/Core.hs
index a2a53be..2cdb122 100644
--- a/src/Language/GraphQL/AST/Core.hs
+++ b/src/Language/GraphQL/AST/Core.hs
@@ -6,7 +6,6 @@ module Language.GraphQL.AST.Core
     , Field(..)
     , Fragment(..)
     , Name
-    , ObjectField(..)
     , Operation(..)
     , Selection(..)
     , TypeCondition
@@ -14,12 +13,11 @@ module Language.GraphQL.AST.Core
     ) where
 
 import Data.Int (Int32)
+import Data.HashMap.Strict (HashMap)
 import Data.List.NonEmpty (NonEmpty)
-import Data.String
+import Data.String (IsString(..))
 import Data.Text (Text)
-
--- | Name
-type Name = Text
+import Language.GraphQL.AST (Alias, Name, TypeCondition)
 
 -- | GraphQL document is a non-empty list of operations.
 type Document = NonEmpty Operation
@@ -32,80 +30,12 @@ data Operation
     | Mutation (Maybe Text) (NonEmpty Selection)
     deriving (Eq, Show)
 
--- | A single GraphQL field.
---
--- Only required property of a field, is its name. Optionally it can also have
--- an alias, arguments or a list of subfields.
---
--- Given the following query:
---
--- @
--- {
---   zuck: user(id: 4) {
---     id
---     name
---   }
--- }
--- @
---
--- * "user", "id" and "name" are field names.
--- * "user" has two subfields, "id" and "name".
--- * "zuck" is an alias for "user". "id" and "name" have no aliases.
--- * "id: 4" is an argument for "name". "id" and "name don't have any
--- arguments.
+-- | Single GraphQL field.
 data Field = Field (Maybe Alias) Name [Argument] [Selection] deriving (Eq, Show)
 
--- | Alternative field name.
---
--- @
--- {
---   smallPic: profilePic(size: 64)
---   bigPic: profilePic(size: 1024)
--- }
--- @
---
--- Here "smallPic" and "bigPic" are aliases for the same field, "profilePic",
--- used to distinquish between profile pictures with different arguments
--- (sizes).
-type Alias = Name
-
 -- | Single argument.
---
--- @
--- {
---   user(id: 4) {
---     name
---   }
--- }
--- @
---
---  Here "id" is an argument for the field "user" and its value is 4.
 data Argument = Argument Name Value deriving (Eq, Show)
 
--- | Represents accordingly typed GraphQL values.
-data Value
-    = ValueInt Int32
-    -- GraphQL Float is double precision
-    | ValueFloat Double
-    | ValueString Text
-    | ValueBoolean Bool
-    | ValueNull
-    | ValueEnum Name
-    | ValueList [Value]
-    | ValueObject [ObjectField]
-    deriving (Eq, Show)
-
-instance IsString Value where
-  fromString = ValueString . fromString
-
--- | Key-value pair.
---
--- A list of 'ObjectField's represents a GraphQL object type.
-data ObjectField = ObjectField Name Value deriving (Eq, Show)
-
--- | Type condition.
-type TypeCondition = Name
-
 -- | Represents fragments and inline fragments.
 data Fragment
     = Fragment TypeCondition (NonEmpty Selection)
@@ -116,3 +46,18 @@ data Selection
     = SelectionFragment Fragment
     | SelectionField Field
     deriving (Eq, Show)
+
+-- | Represents accordingly typed GraphQL values.
+data Value
+    = Int Int32
+    | Float Double -- ^ GraphQL Float is double precision
+    | String Text
+    | Boolean Bool
+    | Null
+    | Enum Name
+    | List [Value]
+    | Object (HashMap Name Value)
+    deriving (Eq, Show)
+
+instance IsString Value where
+    fromString = String . fromString
diff --git a/src/Language/GraphQL/Encoder.hs b/src/Language/GraphQL/AST/Encoder.hs
similarity index 66%
rename from src/Language/GraphQL/Encoder.hs
rename to src/Language/GraphQL/AST/Encoder.hs
index b3ec655..a8f6ca4 100644
--- a/src/Language/GraphQL/Encoder.hs
+++ b/src/Language/GraphQL/AST/Encoder.hs
@@ -2,7 +2,7 @@
 {-# LANGUAGE ExplicitForAll #-}
 
 -- | This module defines a minifier and a printer for the @GraphQL@ language.
-module Language.GraphQL.Encoder
+module Language.GraphQL.AST.Encoder
     ( Formatter
     , definition
     , directive
@@ -21,7 +21,7 @@ import qualified Data.Text.Lazy as Text.Lazy
 import Data.Text.Lazy.Builder (toLazyText)
 import Data.Text.Lazy.Builder.Int (decimal)
 import Data.Text.Lazy.Builder.RealFloat (realFloat)
-import Language.GraphQL.AST
+import qualified Language.GraphQL.AST as Full
 
 -- | Instructs the encoder whether a GraphQL should be minified or pretty
 --   printed.
@@ -40,7 +40,7 @@ minified :: Formatter
 minified = Minified
 
 -- | Converts a 'Document' into a string.
-document :: Formatter -> Document -> Text
+document :: Formatter -> Full.Document -> Text
 document formatter defs
     | Pretty _ <- formatter = Text.Lazy.intercalate "\n" encodeDocument
     | Minified <-formatter = Text.Lazy.snoc (mconcat encodeDocument) '\n'
@@ -48,29 +48,29 @@ document formatter defs
     encodeDocument = NonEmpty.toList $ definition formatter <$> defs
 
 -- | Converts a 'Definition' into a string.
-definition :: Formatter -> Definition -> Text
+definition :: Formatter -> Full.Definition -> Text
 definition formatter x
     | Pretty _ <- formatter = Text.Lazy.snoc (encodeDefinition x) '\n'
     | Minified <- formatter = encodeDefinition x
   where
-    encodeDefinition (DefinitionOperation operation)
+    encodeDefinition (Full.DefinitionOperation operation)
         = operationDefinition formatter operation
-    encodeDefinition (DefinitionFragment fragment)
+    encodeDefinition (Full.DefinitionFragment fragment)
         = fragmentDefinition formatter fragment
 
-operationDefinition :: Formatter -> OperationDefinition -> Text
-operationDefinition formatter (OperationSelectionSet sels)
+operationDefinition :: Formatter -> Full.OperationDefinition -> Text
+operationDefinition formatter (Full.OperationSelectionSet sels)
     = selectionSet formatter sels
-operationDefinition formatter (OperationDefinition Query name vars dirs sels)
+operationDefinition formatter (Full.OperationDefinition Full.Query name vars dirs sels)
     = "query " <> node formatter name vars dirs sels
-operationDefinition formatter (OperationDefinition Mutation name vars dirs sels)
+operationDefinition formatter (Full.OperationDefinition Full.Mutation name vars dirs sels)
     = "mutation " <> node formatter name vars dirs sels
 
 node :: Formatter
-    -> Maybe Name
-    -> [VariableDefinition]
-    -> [Directive]
-    -> SelectionSet
+    -> Maybe Full.Name
+    -> [Full.VariableDefinition]
+    -> [Full.Directive]
+    -> Full.SelectionSet
     -> Text
 node formatter name vars dirs sels
     = Text.Lazy.fromStrict (fold name)
@@ -79,39 +79,39 @@ node formatter name vars dirs sels
     <> eitherFormat formatter " " mempty
     <> selectionSet formatter sels
 
-variableDefinitions :: Formatter -> [VariableDefinition] -> Text
+variableDefinitions :: Formatter -> [Full.VariableDefinition] -> Text
 variableDefinitions formatter
     = parensCommas formatter $ variableDefinition formatter
 
-variableDefinition :: Formatter -> VariableDefinition -> Text
-variableDefinition formatter (VariableDefinition var ty dv)
+variableDefinition :: Formatter -> Full.VariableDefinition -> Text
+variableDefinition formatter (Full.VariableDefinition var ty dv)
     = variable var
     <> eitherFormat formatter ": " ":"
     <> type' ty
     <> maybe mempty (defaultValue formatter) dv
 
-defaultValue :: Formatter -> Value -> Text
+defaultValue :: Formatter -> Full.Value -> Text
 defaultValue formatter val
     = eitherFormat formatter " = " "="
     <> value formatter val
 
-variable :: Name -> Text
+variable :: Full.Name -> Text
 variable var = "$" <> Text.Lazy.fromStrict var
 
-selectionSet :: Formatter -> SelectionSet -> Text
+selectionSet :: Formatter -> Full.SelectionSet -> Text
 selectionSet formatter
     = bracesList formatter (selection formatter)
     . NonEmpty.toList
 
-selectionSetOpt :: Formatter -> SelectionSetOpt -> Text
+selectionSetOpt :: Formatter -> Full.SelectionSetOpt -> Text
 selectionSetOpt formatter = bracesList formatter $ selection formatter
 
-selection :: Formatter -> Selection -> Text
+selection :: Formatter -> Full.Selection -> Text
 selection formatter = Text.Lazy.append indent . f
   where
-    f (SelectionField x) = field incrementIndent x
-    f (SelectionInlineFragment x) = inlineFragment incrementIndent x
-    f (SelectionFragmentSpread x) = fragmentSpread incrementIndent x
+    f (Full.SelectionField x) = field incrementIndent x
+    f (Full.SelectionInlineFragment x) = inlineFragment incrementIndent x
+    f (Full.SelectionFragmentSpread x) = fragmentSpread incrementIndent x
     incrementIndent
         | Pretty n <- formatter = Pretty $ n + 1
         | otherwise = Minified
@@ -119,8 +119,8 @@ selection formatter = Text.Lazy.append indent . f
         | Pretty n <- formatter = Text.Lazy.replicate (fromIntegral $ n + 1) "  "
         | otherwise = mempty
 
-field :: Formatter -> Field -> Text
-field formatter (Field alias name args dirs selso)
+field :: Formatter -> Full.Field -> Text
+field formatter (Full.Field alias name args dirs selso)
     = optempty (`Text.Lazy.append` colon) (Text.Lazy.fromStrict $ fold alias)
     <> Text.Lazy.fromStrict name
     <> optempty (arguments formatter) args
@@ -132,31 +132,31 @@ field formatter (Field alias name args dirs selso)
         | null selso = mempty
         | otherwise = eitherFormat formatter " " mempty <> selectionSetOpt formatter selso
 
-arguments :: Formatter -> [Argument] -> Text
+arguments :: Formatter -> [Full.Argument] -> Text
 arguments formatter = parensCommas formatter $ argument formatter
 
-argument :: Formatter -> Argument -> Text
-argument formatter (Argument name v)
+argument :: Formatter -> Full.Argument -> Text
+argument formatter (Full.Argument name v)
     = Text.Lazy.fromStrict name
     <> eitherFormat formatter ": " ":"
     <> value formatter v
 
 -- * Fragments
 
-fragmentSpread :: Formatter -> FragmentSpread -> Text
-fragmentSpread formatter (FragmentSpread name ds)
+fragmentSpread :: Formatter -> Full.FragmentSpread -> Text
+fragmentSpread formatter (Full.FragmentSpread name ds)
     = "..." <> Text.Lazy.fromStrict name <> optempty (directives formatter) ds
 
-inlineFragment :: Formatter -> InlineFragment -> Text
-inlineFragment formatter (InlineFragment tc dirs sels)
+inlineFragment :: Formatter -> Full.InlineFragment -> Text
+inlineFragment formatter (Full.InlineFragment tc dirs sels)
     = "... on "
     <> Text.Lazy.fromStrict (fold tc)
     <> directives formatter dirs
     <> eitherFormat formatter " " mempty
     <> selectionSet formatter sels
 
-fragmentDefinition :: Formatter -> FragmentDefinition -> Text
-fragmentDefinition formatter (FragmentDefinition name tc dirs sels)
+fragmentDefinition :: Formatter -> Full.FragmentDefinition -> Text
+fragmentDefinition formatter (Full.FragmentDefinition name tc dirs sels)
     = "fragment " <> Text.Lazy.fromStrict name
     <> " on " <> Text.Lazy.fromStrict tc
     <> optempty (directives formatter) dirs
@@ -166,25 +166,25 @@ fragmentDefinition formatter (FragmentDefinition name tc dirs sels)
 -- * Miscellaneous
 
 -- | Converts a 'Directive' into a string.
-directive :: Formatter -> Directive -> Text
-directive formatter (Directive name args)
+directive :: Formatter -> Full.Directive -> Text
+directive formatter (Full.Directive name args)
     = "@" <> Text.Lazy.fromStrict name <> optempty (arguments formatter) args
 
-directives :: Formatter -> [Directive] -> Text
+directives :: Formatter -> [Full.Directive] -> Text
 directives formatter@(Pretty _) = Text.Lazy.cons ' ' . spaces (directive formatter)
 directives Minified = spaces (directive Minified)
 
 -- | Converts a 'Value' into a string.
-value :: Formatter -> Value -> Text
-value _ (ValueVariable x) = variable x
-value _ (ValueInt x) = toLazyText $ decimal x
-value _ (ValueFloat x) = toLazyText $ realFloat x
-value _ (ValueBoolean  x) = booleanValue x
-value _ ValueNull = mempty
-value _ (ValueString x) = stringValue $ Text.Lazy.fromStrict x
-value _ (ValueEnum x) = Text.Lazy.fromStrict x
-value formatter (ValueList x) = listValue formatter x
-value formatter (ValueObject x) = objectValue formatter x
+value :: Formatter -> Full.Value -> Text
+value _ (Full.Variable x) = variable x
+value _ (Full.Int x) = toLazyText $ decimal x
+value _ (Full.Float x) = toLazyText $ realFloat x
+value _ (Full.Boolean  x) = booleanValue x
+value _ Full.Null = mempty
+value _ (Full.String x) = stringValue $ Text.Lazy.fromStrict x
+value _ (Full.Enum x) = Text.Lazy.fromStrict x
+value formatter (Full.List x) = listValue formatter x
+value formatter (Full.Object x) = objectValue formatter x
 
 booleanValue :: Bool -> Text
 booleanValue True  = "true"
@@ -196,10 +196,10 @@ stringValue
     . Text.Lazy.replace "\"" "\\\""
     . Text.Lazy.replace "\\" "\\\\"
 
-listValue :: Formatter -> [Value] -> Text
+listValue :: Formatter -> [Full.Value] -> Text
 listValue formatter = bracketsCommas formatter $ value formatter
 
-objectValue :: Formatter -> [ObjectField] -> Text
+objectValue :: Formatter -> [Full.ObjectField] -> Text
 objectValue formatter = intercalate $ objectField formatter
   where
     intercalate f
@@ -208,8 +208,8 @@ objectValue formatter = intercalate $ objectField formatter
         . fmap f
 
 
-objectField :: Formatter -> ObjectField -> Text
-objectField formatter (ObjectField name v)
+objectField :: Formatter -> Full.ObjectField -> Text
+objectField formatter (Full.ObjectField name v)
     = Text.Lazy.fromStrict name <> colon <> value formatter v
   where
     colon
@@ -217,17 +217,17 @@ objectField formatter (ObjectField name v)
       | Minified <- formatter = ":"
 
 -- | Converts a 'Type' a type into a string.
-type' :: Type -> Text
-type' (TypeNamed   x) = Text.Lazy.fromStrict x
-type' (TypeList    x) = listType x
-type' (TypeNonNull x) = nonNullType x
+type' :: Full.Type -> Text
+type' (Full.TypeNamed   x) = Text.Lazy.fromStrict x
+type' (Full.TypeList    x) = listType x
+type' (Full.TypeNonNull x) = nonNullType x
 
-listType :: Type -> Text
+listType :: Full.Type -> Text
 listType x = brackets (type' x)
 
-nonNullType :: NonNullType -> Text
-nonNullType (NonNullTypeNamed x) = Text.Lazy.fromStrict x <> "!"
-nonNullType (NonNullTypeList  x) = listType x <> "!"
+nonNullType :: Full.NonNullType -> Text
+nonNullType (Full.NonNullTypeNamed x) = Text.Lazy.fromStrict x <> "!"
+nonNullType (Full.NonNullTypeList  x) = listType x <> "!"
 
 -- * Internal
 
diff --git a/src/Language/GraphQL/Lexer.hs b/src/Language/GraphQL/AST/Lexer.hs
similarity index 99%
rename from src/Language/GraphQL/Lexer.hs
rename to src/Language/GraphQL/AST/Lexer.hs
index dc000b5..97a334c 100644
--- a/src/Language/GraphQL/Lexer.hs
+++ b/src/Language/GraphQL/AST/Lexer.hs
@@ -3,7 +3,7 @@
 
 -- | This module defines a bunch of small parsers used to parse individual
 --   lexemes.
-module Language.GraphQL.Lexer 
+module Language.GraphQL.AST.Lexer 
     ( Parser
     , amp
     , at
diff --git a/src/Language/GraphQL/Parser.hs b/src/Language/GraphQL/AST/Parser.hs
similarity index 92%
rename from src/Language/GraphQL/Parser.hs
rename to src/Language/GraphQL/AST/Parser.hs
index bbe1de7..a5b6681 100644
--- a/src/Language/GraphQL/Parser.hs
+++ b/src/Language/GraphQL/AST/Parser.hs
@@ -2,7 +2,7 @@
 {-# LANGUAGE OverloadedStrings #-}
 
 -- | @GraphQL@ document parser.
-module Language.GraphQL.Parser
+module Language.GraphQL.AST.Parser
     ( document
     ) where
 
@@ -11,7 +11,7 @@ import Control.Applicative ( Alternative(..)
                            )
 import Data.List.NonEmpty (NonEmpty(..))
 import Language.GraphQL.AST
-import Language.GraphQL.Lexer
+import Language.GraphQL.AST.Lexer
 import Text.Megaparsec ( lookAhead
                        , option
                        , try
@@ -105,16 +105,16 @@ typeCondition = symbol "on" *> name
 -- * Input Values
 
 value :: Parser Value
-value = ValueVariable <$> variable
-    <|> ValueFloat    <$> try float
-    <|> ValueInt      <$> integer
-    <|> ValueBoolean  <$> booleanValue
-    <|> ValueNull     <$  symbol "null"
-    <|> ValueString   <$> blockString
-    <|> ValueString   <$> string
-    <|> ValueEnum     <$> try enumValue
-    <|> ValueList     <$> listValue
-    <|> ValueObject   <$> objectValue
+value = Variable <$> variable
+    <|> Float    <$> try float
+    <|> Int      <$> integer
+    <|> Boolean  <$> booleanValue
+    <|> Null     <$  symbol "null"
+    <|> String   <$> blockString
+    <|> String   <$> string
+    <|> Enum     <$> try enumValue
+    <|> List     <$> listValue
+    <|> Object   <$> objectValue
     <?> "value error!"
   where
     booleanValue :: Parser Bool
diff --git a/src/Language/GraphQL/AST/Transform.hs b/src/Language/GraphQL/AST/Transform.hs
index 107e1c6..ea90bab 100644
--- a/src/Language/GraphQL/AST/Transform.hs
+++ b/src/Language/GraphQL/AST/Transform.hs
@@ -1,3 +1,5 @@
+{-# LANGUAGE TupleSections #-}
+
 -- | After the document is parsed, before getting executed the AST is
 --   transformed into a similar, simpler AST. This module is responsible for
 --   this transformation.
@@ -113,20 +115,20 @@ argument :: Schema.Subs -> Full.Argument -> Maybe Core.Argument
 argument subs (Full.Argument n v) = Core.Argument n <$> value subs v
 
 value :: Schema.Subs -> Full.Value -> Maybe Core.Value
-value subs (Full.ValueVariable n) = subs n
-value _    (Full.ValueInt      i) = pure $ Core.ValueInt i
-value _    (Full.ValueFloat    f) = pure $ Core.ValueFloat f
-value _    (Full.ValueString   x) = pure $ Core.ValueString x
-value _    (Full.ValueBoolean  b) = pure $ Core.ValueBoolean b
-value _     Full.ValueNull        = pure   Core.ValueNull
-value _    (Full.ValueEnum     e) = pure $ Core.ValueEnum e
-value subs (Full.ValueList     l) =
-  Core.ValueList   <$> traverse (value subs) l
-value subs (Full.ValueObject   o) =
-  Core.ValueObject <$> traverse (objectField subs) o
+value subs (Full.Variable n) = subs n
+value _    (Full.Int      i) = pure $ Core.Int i
+value _    (Full.Float    f) = pure $ Core.Float f
+value _    (Full.String   x) = pure $ Core.String x
+value _    (Full.Boolean  b) = pure $ Core.Boolean b
+value _     Full.Null        = pure   Core.Null
+value _    (Full.Enum     e) = pure $ Core.Enum e
+value subs (Full.List     l) =
+    Core.List <$> traverse (value subs) l
+value subs (Full.Object   o) =
+    Core.Object . HashMap.fromList <$> traverse (objectField subs) o
 
-objectField :: Schema.Subs -> Full.ObjectField -> Maybe Core.ObjectField
-objectField subs (Full.ObjectField n v) = Core.ObjectField n <$> value subs v
+objectField :: Schema.Subs -> Full.ObjectField -> Maybe (Core.Name, Core.Value)
+objectField subs (Full.ObjectField n v) = (n,) <$> value subs v
 
 appendSelectionOpt ::
     Traversable t =>
diff --git a/src/Language/GraphQL/Schema.hs b/src/Language/GraphQL/Schema.hs
index d7e698b..44e9077 100644
--- a/src/Language/GraphQL/Schema.hs
+++ b/src/Language/GraphQL/Schema.hs
@@ -30,10 +30,10 @@ import Data.HashMap.Strict (HashMap)
 import qualified Data.HashMap.Strict as HashMap
 import Data.Text (Text)
 import qualified Data.Text as T
+import Language.GraphQL.AST.Core
 import Language.GraphQL.Error
 import Language.GraphQL.Trans
-import Language.GraphQL.Type
-import Language.GraphQL.AST.Core
+import qualified Language.GraphQL.Type as Type
 
 -- | Resolves a 'Field' into an @Aeson.@'Data.Aeson.Types.Object' with error
 --   information (if an error has occurred). @m@ is usually expected to be an
@@ -58,7 +58,7 @@ objectA name f = Resolver name $ resolveFieldValue f resolveRight
 
 -- | Like 'object' but also taking 'Argument's and can be null or a list of objects.
 wrappedObjectA :: MonadIO m
-    => Name -> ([Argument] -> ActionT m (Wrapping [Resolver m])) -> Resolver m
+    => Name -> ([Argument] -> ActionT m (Type.Wrapping [Resolver m])) -> Resolver m
 wrappedObjectA name f = Resolver name $ resolveFieldValue f resolveRight
   where
     resolveRight fld@(Field _ _ _ sels) resolver
@@ -66,7 +66,7 @@ wrappedObjectA name f = Resolver name $ resolveFieldValue f resolveRight
 
 -- | Like 'object' but can be null or a list of objects.
 wrappedObject :: MonadIO m
-    => Name -> ActionT m (Wrapping [Resolver m]) -> Resolver m
+    => Name -> ActionT m (Type.Wrapping [Resolver m]) -> Resolver m
 wrappedObject name = wrappedObjectA name . const
 
 -- | A scalar represents a primitive value, like a string or an integer.
@@ -80,19 +80,19 @@ scalarA name f = Resolver name $ resolveFieldValue f resolveRight
   where
     resolveRight fld result = withField (return result) fld
 
--- | Lika 'scalar' but also taking 'Argument's and can be null or a list of scalars.
+-- | Like 'scalar' but also taking 'Argument's and can be null or a list of scalars.
 wrappedScalarA :: (MonadIO m, Aeson.ToJSON a)
-    => Name -> ([Argument] -> ActionT m (Wrapping a)) -> Resolver m
+    => Name -> ([Argument] -> ActionT m (Type.Wrapping a)) -> Resolver m
 wrappedScalarA name f = Resolver name $ resolveFieldValue f resolveRight
   where
-    resolveRight fld (Named result) = withField (return result) fld
-    resolveRight fld Null
+    resolveRight fld (Type.Named result) = withField (return result) fld
+    resolveRight fld Type.Null
         = return $ HashMap.singleton (aliasOrName fld) Aeson.Null
-    resolveRight fld (List result) = withField (return result) fld
+    resolveRight fld (Type.List result) = withField (return result) fld
 
 -- | Like 'scalar' but can be null or a list of scalars.
 wrappedScalar :: (MonadIO m, Aeson.ToJSON a)
-    => Name -> ActionT m (Wrapping a) -> Resolver m
+    => Name -> ActionT m (Type.Wrapping a) -> Resolver m
 wrappedScalar name = wrappedScalarA name . const
 
 resolveFieldValue :: MonadIO m
diff --git a/src/Language/GraphQL/Type.hs b/src/Language/GraphQL/Type.hs
index 3f91e50..c8a9997 100644
--- a/src/Language/GraphQL/Type.hs
+++ b/src/Language/GraphQL/Type.hs
@@ -1,11 +1,9 @@
--- | Definitions for @GraphQL@ type system.
+-- | Definitions for @GraphQL@ input types.
 module Language.GraphQL.Type
     ( Wrapping(..)
     ) where
 
-import Data.Aeson as Aeson ( ToJSON
-                           , toJSON
-                           )
+import Data.Aeson as Aeson (ToJSON, toJSON)
 import qualified Data.Aeson as Aeson
 
 -- | GraphQL distinguishes between "wrapping" and "named" types. Each wrapping
diff --git a/tests/Language/GraphQL/AST/EncoderSpec.hs b/tests/Language/GraphQL/AST/EncoderSpec.hs
new file mode 100644
index 0000000..a418a61
--- /dev/null
+++ b/tests/Language/GraphQL/AST/EncoderSpec.hs
@@ -0,0 +1,19 @@
+{-# LANGUAGE OverloadedStrings #-}
+module Language.GraphQL.AST.EncoderSpec
+    ( spec
+    ) where
+
+import Language.GraphQL.AST (Value(..))
+import Language.GraphQL.AST.Encoder
+import Test.Hspec ( Spec
+                  , describe
+                  , it
+                  , shouldBe
+                  )
+
+spec :: Spec
+spec = describe "value" $ do
+    it "escapes \\" $
+        value minified (String "\\") `shouldBe` "\"\\\\\""
+    it "escapes quotes" $
+        value minified (String "\"") `shouldBe` "\"\\\"\""
diff --git a/tests/Language/GraphQL/LexerSpec.hs b/tests/Language/GraphQL/AST/LexerSpec.hs
similarity index 98%
rename from tests/Language/GraphQL/LexerSpec.hs
rename to tests/Language/GraphQL/AST/LexerSpec.hs
index 274b29a..b1c280f 100644
--- a/tests/Language/GraphQL/LexerSpec.hs
+++ b/tests/Language/GraphQL/AST/LexerSpec.hs
@@ -1,12 +1,12 @@
 {-# LANGUAGE OverloadedStrings #-}
 {-# LANGUAGE QuasiQuotes #-}
-module Language.GraphQL.LexerSpec
+module Language.GraphQL.AST.LexerSpec
     ( spec
     ) where
 
 import Data.Text (Text)
 import Data.Void (Void)
-import Language.GraphQL.Lexer
+import Language.GraphQL.AST.Lexer
 import Test.Hspec (Spec, context, describe, it)
 import Test.Hspec.Megaparsec (shouldParse, shouldSucceedOn)
 import Text.Megaparsec (ParseErrorBundle, parse)
diff --git a/tests/Language/GraphQL/ParserSpec.hs b/tests/Language/GraphQL/AST/ParserSpec.hs
similarity index 89%
rename from tests/Language/GraphQL/ParserSpec.hs
rename to tests/Language/GraphQL/AST/ParserSpec.hs
index 9b71c62..8473d73 100644
--- a/tests/Language/GraphQL/ParserSpec.hs
+++ b/tests/Language/GraphQL/AST/ParserSpec.hs
@@ -1,10 +1,10 @@
 {-# LANGUAGE OverloadedStrings #-}
 {-# LANGUAGE QuasiQuotes #-}
-module Language.GraphQL.ParserSpec
+module Language.GraphQL.AST.ParserSpec
     ( spec
     ) where
 
-import Language.GraphQL.Parser (document)
+import Language.GraphQL.AST.Parser
 import Test.Hspec (Spec, describe, it)
 import Test.Hspec.Megaparsec (shouldSucceedOn)
 import Text.Megaparsec (parse)
diff --git a/tests/Language/GraphQL/EncoderSpec.hs b/tests/Language/GraphQL/EncoderSpec.hs
deleted file mode 100644
index d2d4a00..0000000
--- a/tests/Language/GraphQL/EncoderSpec.hs
+++ /dev/null
@@ -1,21 +0,0 @@
-{-# LANGUAGE OverloadedStrings #-}
-module Language.GraphQL.EncoderSpec
-    ( spec
-    ) where
-
-import Language.GraphQL.AST ( Value(..))
-import Language.GraphQL.Encoder ( value
-                                , minified
-                                )
-import Test.Hspec ( Spec
-                  , describe
-                  , it
-                  , shouldBe
-                  )
-
-spec :: Spec
-spec = describe "value" $ do
-    it "escapes \\" $
-        value minified (ValueString "\\") `shouldBe` "\"\\\\\""
-    it "escapes quotes" $
-        value minified (ValueString "\"") `shouldBe` "\"\\\"\""
diff --git a/tests/Test/KitchenSinkSpec.hs b/tests/Test/KitchenSinkSpec.hs
index 674f85b..9f5a947 100644
--- a/tests/Test/KitchenSinkSpec.hs
+++ b/tests/Test/KitchenSinkSpec.hs
@@ -7,8 +7,8 @@ module Test.KitchenSinkSpec
 import qualified Data.Text.IO as Text.IO
 import qualified Data.Text.Lazy.IO as Text.Lazy.IO
 import qualified Data.Text.Lazy as Lazy (Text)
-import qualified Language.GraphQL.Encoder as Encoder
-import qualified Language.GraphQL.Parser as Parser
+import qualified Language.GraphQL.AST.Encoder as Encoder
+import qualified Language.GraphQL.AST.Parser as Parser
 import Paths_graphql (getDataFileName)
 import Test.Hspec (Spec, describe, it)
 import Test.Hspec.Megaparsec (parseSatisfies)
diff --git a/tests/Test/StarWars/Data.hs b/tests/Test/StarWars/Data.hs
index 6a514c5..4854f8f 100644
--- a/tests/Test/StarWars/Data.hs
+++ b/tests/Test/StarWars/Data.hs
@@ -26,7 +26,7 @@ import Control.Monad.Trans.Except (throwE)
 import Data.Maybe (catMaybes)
 import Data.Text (Text)
 import Language.GraphQL.Trans
-import Language.GraphQL.Type
+import qualified Language.GraphQL.Type as Type
 
 -- * Data
 -- See https://github.com/graphql/graphql-js/blob/master/src/__tests__/starWarsData.js
@@ -191,8 +191,8 @@ getDroid' _      = empty
 getFriends :: Character -> [Character]
 getFriends char = catMaybes $ liftA2 (<|>) getDroid getHuman <$> friends char
 
-getEpisode :: Int -> Maybe (Wrapping Text)
-getEpisode 4 = pure $ Named "NEWHOPE"
-getEpisode 5 = pure $ Named "EMPIRE"
-getEpisode 6 = pure $ Named "JEDI"
+getEpisode :: Int -> Maybe (Type.Wrapping Text)
+getEpisode 4 = pure $ Type.Named "NEWHOPE"
+getEpisode 5 = pure $ Type.Named "EMPIRE"
+getEpisode 6 = pure $ Type.Named "JEDI"
 getEpisode _ = empty
diff --git a/tests/Test/StarWars/Schema.hs b/tests/Test/StarWars/Schema.hs
index f516f2a..7b98747 100644
--- a/tests/Test/StarWars/Schema.hs
+++ b/tests/Test/StarWars/Schema.hs
@@ -15,7 +15,7 @@ import Data.List.NonEmpty (NonEmpty(..))
 import Data.Maybe (catMaybes)
 import qualified Language.GraphQL.Schema as Schema
 import Language.GraphQL.Trans
-import Language.GraphQL.Type
+import qualified Language.GraphQL.Type as Type
 import Test.StarWars.Data
 
 -- See https://github.com/graphql/graphql-js/blob/master/src/__tests__/starWarsSchema.js
@@ -26,23 +26,23 @@ schema = hero :| [human, droid]
 hero :: MonadIO m => Schema.Resolver m
 hero = Schema.objectA "hero" $ \case
   [] -> character artoo
-  [Schema.Argument "episode" (Schema.ValueEnum "NEWHOPE")] -> character $ getHero 4
-  [Schema.Argument "episode" (Schema.ValueEnum "EMPIRE" )] -> character $ getHero 5
-  [Schema.Argument "episode" (Schema.ValueEnum "JEDI"   )] -> character $ getHero 6
+  [Schema.Argument "episode" (Schema.Enum "NEWHOPE")] -> character $ getHero 4
+  [Schema.Argument "episode" (Schema.Enum "EMPIRE" )] -> character $ getHero 5
+  [Schema.Argument "episode" (Schema.Enum "JEDI"   )] -> character $ getHero 6
   _ -> ActionT $ throwE "Invalid arguments."
 
 human :: MonadIO m => Schema.Resolver m
 human = Schema.wrappedObjectA "human" $ \case
-  [Schema.Argument "id" (Schema.ValueString i)] -> do
+  [Schema.Argument "id" (Schema.String i)] -> do
       humanCharacter <- lift $ return $ getHuman i >>= Just
       case humanCharacter of
-        Nothing -> return Null
-        Just e -> Named <$> character e
+        Nothing -> return Type.Null
+        Just e -> Type.Named <$> character e
   _ -> ActionT $ throwE "Invalid arguments."
 
 droid :: MonadIO m => Schema.Resolver m
 droid = Schema.objectA "droid" $ \case
-   [Schema.Argument "id" (Schema.ValueString i)] -> character =<< liftIO (getDroid i)
+   [Schema.Argument "id" (Schema.String i)] -> character =<< liftIO (getDroid i)
    _ -> ActionT $ throwE "Invalid arguments."
 
 character :: MonadIO m => Character -> ActionT m [Schema.Resolver m]
@@ -50,8 +50,8 @@ character char = return
     [ Schema.scalar "id" $ return $ id_ char
     , Schema.scalar "name" $ return $ name char
     , Schema.wrappedObject "friends"
-        $ traverse character $ List $ Named <$> getFriends char
-    , Schema.wrappedScalar "appearsIn" $ return . List
+        $ traverse character $ Type.List $ Type.Named <$> getFriends char
+    , Schema.wrappedScalar "appearsIn" $ return . Type.List
         $ catMaybes (getEpisode <$> appearsIn char)
     , Schema.scalar "secretBackstory" $ secretBackstory char
     , Schema.scalar "homePlanet" $ return $ either mempty homePlanet char