diff --git a/comfort-graph.cabal b/comfort-graph.cabal
--- a/comfort-graph.cabal
+++ b/comfort-graph.cabal
@@ -1,5 +1,5 @@
 Name:                comfort-graph
-Version:             0.0.2.1
+Version:             0.0.3
 Synopsis:            Graph structure with type parameters for nodes and edges
 Description:
   This graph structure is based on "Data.Map"
@@ -51,7 +51,7 @@
 Cabal-Version:       >=1.10
 
 Source-Repository this
-  Tag:         0.0.2.1
+  Tag:         0.0.3
   Type:        darcs
   Location:    http://hub.darcs.net/thielema/comfort-graph
 
@@ -70,6 +70,7 @@
     QuickCheck >=2.5 && <3,
     containers >=0.4 && <0.6,
     transformers >=0.5 && <0.6,
+    semigroups >=0.1 && <1.0,
     utility-ht >=0.0.10 && <0.1,
     base >=4.5 && <5
   Hs-Source-Dirs:      src
diff --git a/src/Data/Graph/Comfort.hs b/src/Data/Graph/Comfort.hs
--- a/src/Data/Graph/Comfort.hs
+++ b/src/Data/Graph/Comfort.hs
@@ -1,5 +1,5 @@
 module Data.Graph.Comfort (
-   -- * types
+   -- * Types
    Graph,
    LabeledNode,
    LabeledEdge,
@@ -8,34 +8,35 @@
    UndirEdge(UndirEdge), undirEdge,
    EitherEdge(EDirEdge,EUndirEdge),
 
-   -- * construction
+   -- * Construction
    empty, fromList, fromMap,
 
-   -- * extract large portions of the graph
+   -- * Extract large portions of the graph
    graphMap,
    nodeLabels, nodeSet, nodes, nodeEdges,
    edgeLabels, edgeSet, edges,
 
-   -- * queries
+   -- * Queries
    isEmpty,
    lookupNode, lookupEdge,
-   adjacentEdges,
+   predecessors, successors,
+   adjacentEdgeSet, adjacentEdges,
    isLoop,
    pathExists,
    isConsistent,
 
-   -- * manipulate labels
+   -- * Manipulate labels
    mapNode, mapNodeWithKey,
    mapEdge, mapEdgeWithKey,
    mapNodeWithInOut, InOut,
    filterEdgeWithKey,
    traverseNode, traverseEdge, traverse,
 
-   -- * combine graphs
+   -- * Combine graphs
    checkedZipWith,
    union,
 
-   -- * manipulate indices
+   -- * Manipulate indices
    Reverse,
    reverse,
    reverseEdge,
@@ -43,7 +44,7 @@
    mapMaybeEdgeKeys,
    mapEdgeKeys,
 
-   -- * insertion and removal
+   -- * Insertion and removal
    deleteNode, deleteNodeSet, deleteEdge,
    insertNode, insertEdge, insertEdgeSet,
    ) where
@@ -66,6 +67,7 @@
 import Data.Map (Map)
 import Data.Monoid
          (Monoid, mempty, mappend, All(All), getAll, Endo(Endo), appEndo)
+import Data.Semigroup (Semigroup((<>)), )
 import Data.Tuple.HT (mapFst, fst3, snd3, thd3, mapFst3, mapThd3)
 
 import qualified Test.QuickCheck as QC
@@ -374,6 +376,11 @@
 
 instance
    (Edge edge, Ord node) =>
+      Semigroup (Graph edge node edgeLabel nodeLabel) where
+   (<>) = union
+
+instance
+   (Edge edge, Ord node) =>
       Monoid (Graph edge node edgeLabel nodeLabel) where
    mempty = empty
    mappend = union
@@ -421,23 +428,33 @@
 lookupNode :: (Ord n) => n -> Graph e n el nl -> Maybe nl
 lookupNode n (Graph g) = fmap snd3 $ Map.lookup n g
 
-_pre, suc ::
-   (Edge e, Ord n) =>
-   Graph e n el nl -> n -> [n]
-_pre g n =
+{- |
+Direct predecessors of a node,
+i.e. nodes with an outgoing edge to the queried node.
+-}
+predecessors :: (Edge e, Ord n) => Graph e n el nl -> n -> [n]
+predecessors g n =
    map fromWrap . Map.keys . fst3 .
-   Map.findWithDefault (error "pre: unknown node") n . graphMapWrap $ g
-suc g n =
+   Map.findWithDefault (error "predecessors: unknown node") n . graphMapWrap $ g
+
+{- |
+Direct successors of a node,
+i.e. nodes with an incoming edge from the queried node.
+-}
+successors :: (Edge e, Ord n) => Graph e n el nl -> n -> [n]
+successors g n =
    map toWrap . Map.keys . thd3 .
-   Map.findWithDefault (error "suc: unknown node") n . graphMapWrap $ g
+   Map.findWithDefault (error "successors: unknown node") n . graphMapWrap $ g
 
-adjacentEdges ::
+{-# DEPRECATED adjacentEdges "Use adjacentEdgeSet instead." #-}
+adjacentEdges, adjacentEdgeSet ::
    (Edge e, Ord n) =>
    Graph e n el nl -> n -> Set (e n)
-adjacentEdges g n =
+adjacentEdges = adjacentEdgeSet
+adjacentEdgeSet g n =
    (\(ins,_nl,outs) ->
       unwrapSet $ Map.keysSet ins `Set.union` Map.keysSet outs) $
-   Map.findWithDefault (error "adjacentEdges: unknown node") n $
+   Map.findWithDefault (error "adjacentEdgeSet: unknown node") n $
    graphMapWrap g
 
 {-
@@ -684,7 +701,7 @@
 pathExists src dst =
    let go gr a =
           not (isEmpty gr) &&
-          (a==dst || (any (go (deleteNode a gr)) $ suc gr a))
+          (a==dst || (any (go (deleteNode a gr)) $ successors gr a))
    in  flip go src
 
 
diff --git a/test/Main.hs b/test/Main.hs
--- a/test/Main.hs
+++ b/test/Main.hs
@@ -127,7 +127,7 @@
    let isolated =
          maybe False (const True) (Graph.lookupNode n gr)
          &&
-         Set.null (Graph.adjacentEdges gr n)
+         Set.null (Graph.adjacentEdgeSet gr n)
    in  isolated `implies`
        Graph.insertNode n nl gr
        ==