diff --git a/haskell-experiments/src/Datalog/NaiveDatabase.hs b/haskell-experiments/src/Datalog/NaiveDatabase.hs
index e88c2f9..c0fdbd1 100644
--- a/haskell-experiments/src/Datalog/NaiveDatabase.hs
+++ b/haskell-experiments/src/Datalog/NaiveDatabase.hs
@@ -108,12 +108,6 @@ withFactsAndRules :: [Text] -> [Text] -> NaiveDatabase
 withFactsAndRules facts = foldr (addRule . extractRule) (withFacts facts)
  where
 
-extractRule :: Text -> (Literal, [Literal])
-extractRule ruleText =
-  case parseDatalog ruleText of
-    Right (Rule (HeadSingle lhs) rhs) -> (lhs, rhs)
-    Right otherStatement -> throw $ NonRuleException ruleText otherStatement
-    Left ex -> throw $ CannotParseStatementException ruleText ex
 digestHead :: NaiveDatabase -> Relation -> Literal -> RuleContext
 digestHead db relation (Literal neg relationName terms) =
   RuleContext
@@ -186,12 +180,6 @@ addRule (ruleHead, body) db  =
     relationMap' = Map.insert relationName relation' relationMap
     constants' = constants db'
 
-extractVariableNames :: [Term] -> [Text]
-extractVariableNames = mapMaybe extractVariableName where
-  extractVariableName :: Term -> Maybe Text
-  extractVariableName (Var name) = Just name
-  extractVariableName _ = Nothing
-
 query :: NaiveDatabase -> Text -> Text
 query db qText =
   case parseDatalog qText of
@@ -199,14 +187,3 @@ query db qText =
     Right otherStatement -> throw $ NonQueryException qText otherStatement
     Left ex -> throw $ CannotParseStatementException qText ex
 
-data NaiveDatabaseException
-  = CannotParseStatementException Text (ParseErrorBundle Text Void)
-  | NonFactException Text Statement
-  | NonRuleException Text Statement
-  | NonQueryException Text Statement
-  | BadArityException Text Int
-  | VariableLookupException Text [Text]
-  | UnexpectedConstantException Constant
-  deriving (Show)
-
-instance Exception NaiveDatabaseException
\ No newline at end of file
diff --git a/haskell-experiments/src/Datalog/Rules.hs b/haskell-experiments/src/Datalog/Rules.hs
index 5104ad7..5b244f1 100644
--- a/haskell-experiments/src/Datalog/Rules.hs
+++ b/haskell-experiments/src/Datalog/Rules.hs
@@ -52,6 +52,13 @@ data BodyConstraint = BodyConstraint
   , _elements :: [RuleElement]
   }
 
+extractRule :: Text -> (Literal, [Literal])
+extractRule ruleText =
+  case parseDatalog ruleText of
+    Right (Rule (HeadSingle lhs) rhs) -> (lhs, rhs)
+    Right otherStatement -> throw $ NonRuleException ruleText otherStatement
+    Left ex -> throw $ CannotParseStatementException ruleText ex
+
 appendRule :: Relation -> RelationRule -> Relation
 appendRule relation rule =
   relation {
@@ -65,3 +72,20 @@ toRuleBodyElement (BodyConstraint subRelation elements) =
     , _ruleElements = elements
     }
 
+extractVariableNames :: [Term] -> [Text]
+extractVariableNames = mapMaybe extractVariableName where
+  extractVariableName :: Term -> Maybe Text
+  extractVariableName (Var name) = Just name
+  extractVariableName _ = Nothing
+
+data DatalogDBException
+  = CannotParseStatementException Text (ParseErrorBundle Text Void)
+  | NonFactException Text Statement
+  | NonRuleException Text Statement
+  | NonQueryException Text Statement
+  | BadArityException Text Int
+  | VariableLookupException Text [Text]
+  | UnexpectedConstantException Constant
+  deriving (Show)
+
+instance Exception DatalogDBException