diff --git a/changelog.md b/changelog.md
--- a/changelog.md
+++ b/changelog.md
@@ -1,5 +1,9 @@
 # Changelog
 
+## 0.1.5.6
+
+- [??]
+
 ## 0.1.5.5
 
 - [compatibility] GHC 7.10 compatibility: sortOn has become more strict, addition of a sortOnLazy
diff --git a/src/UHC/Util/FPath.hs b/src/UHC/Util/FPath.hs
--- a/src/UHC/Util/FPath.hs
+++ b/src/UHC/Util/FPath.hs
@@ -252,8 +252,8 @@
 
 -- | Make FPath from FilePath, setting the suffix when absent
 mkTopLevelFPath
-  :: String		-- ^ suffix
-  -> FilePath	-- ^ file name
+  :: String     -- ^ suffix
+  -> FilePath   -- ^ file name
   -> FPath
 mkTopLevelFPath suff fn
   = let fpNoSuff = mkFPath fn
diff --git a/src/UHC/Util/RelMap.hs b/src/UHC/Util/RelMap.hs
--- a/src/UHC/Util/RelMap.hs
+++ b/src/UHC/Util/RelMap.hs
@@ -4,6 +4,7 @@
 module UHC.Util.RelMap
   ( Rel
   , empty
+  , toDomList, toRngList
   , toList, fromList
   , singleton
   , dom, rng
@@ -13,6 +14,8 @@
   -- , intersection, difference
   , union, unions
   , insert
+  , deleteDom, delete
+  , deleteRng
   
   , applyDomMbSet, applyRngMbSet
   , applyDomSet, applyRngSet
@@ -36,12 +39,23 @@
 import           UHC.Util.Serialize
 
 -------------------------------------------------------------------------
--- Relation
+-- Relation map
 -------------------------------------------------------------------------
 
 -- | Map used in a relation
 type RelMap a b = Map.Map a (Set.Set b)
 
+-- | Delete key in range of RelMap
+relmapDeleteRng :: Ord b => b -> RelMap a b -> RelMap a b
+relmapDeleteRng x r = snd $ Map.mapEither (eith x) r
+  where eith x ds = if Set.null ds' then Left ds else Right ds'
+          where (ds1,ds2) = Set.split x ds
+                ds' = Set.union ds1 ds2
+
+-------------------------------------------------------------------------
+-- Relation
+-------------------------------------------------------------------------
+
 -- | Relation, represented as 2 maps from domain to range and the inverse, thus allowing faster lookup at the expense of some set like operations more expensive.
 data Rel a b
   = Rel
@@ -49,9 +63,17 @@
      , relRngMp :: RelMap b a       -- ^ from range to domain
      }
 
+-- | As assocation list where each domain value only occurs once and the range as list
+toDomList :: Rel a b -> [(a,[b])]
+toDomList (Rel m _) = [ (d, Set.toList rs) | (d,rs) <- Map.toList m ]
+
+-- | As assocation list where each range value only occurs once and the domain as list
+toRngList :: Rel a b -> [([a],b)]
+toRngList (Rel _ m) = [ (Set.toList ds, r) | (r,ds) <- Map.toList m ]
+
 -- | As assocation list
 toList :: Rel a b -> [(a,b)]
-toList (Rel m _) = [ (d,r) | (d,rs) <- Map.toList m, r <- Set.toList rs ]
+toList rel = [ (d,r) | (d,rs) <- toDomList rel, r <- rs ]
 
 -- | From association list
 fromList :: (Ord a, Ord b) => [(a,b)] -> Rel a b
@@ -124,6 +146,16 @@
 -- | Insert
 insert :: (Ord a, Ord b) => a -> b -> Rel a b -> Rel a b
 insert x y r = singleton x y `union` r
+
+-- | Delete at domain
+deleteDom, delete :: (Ord a, Ord b) => a -> Rel a b -> Rel a b
+deleteDom x (Rel d r) = Rel (Map.delete x d) (relmapDeleteRng x r)
+delete = deleteDom
+{-# INLINE delete #-}
+
+-- | Delete at range
+deleteRng :: (Ord a, Ord b) => b -> Rel a b -> Rel a b
+deleteRng x (Rel d r) = Rel (relmapDeleteRng x d) (Map.delete x r)
 
 -- | Apply relation as a function, possible yielding a non empty set
 applyDomMbSet :: (Ord a) => Rel a b -> a -> Maybe (Set.Set b)
diff --git a/uhc-util.cabal b/uhc-util.cabal
--- a/uhc-util.cabal
+++ b/uhc-util.cabal
@@ -1,5 +1,5 @@
 Name:				uhc-util
-Version:			0.1.5.5
+Version:			0.1.5.6
 cabal-version:      >= 1.6
 License:			BSD3
 Copyright:			Utrecht University, Department of Information and Computing Sciences, Software Technology group