diff --git a/README.md b/README.md
index c85e0bc..f2157ca 100644
--- a/README.md
+++ b/README.md
@@ -6,7 +6,7 @@ documentation can be found on [pursuit](https://pursuit.purescript.org/packages/
 define your model like this:
 
 ```purescript
-DiGraph [
+digraph [
     node "a" [ Shape Diamond, Style Filled,  Node.FillColor red ],
     node "b" [],
     "a" ==> "b",
@@ -68,9 +68,16 @@ bower i purescript-dotlang
 Changelog
 =========
 
+v4.0.0
+------
+
+Breaking Changes:
+
+- Strictness behaviour of the graph is now supported: To **migrate** replace old calls to `DiGraph` with `digraph`
+
 v3.0.0
 ------
 
 Breaking Changes:
 
-- `Label` of `Edge` and `Node` now support HTML and no formatting: To **migrate** replace old calls to `Label` with calls to `label`
\ No newline at end of file
+- `Label` of `Edge` and `Node` now support HTML and no formatting: To **migrate** replace old calls to `Label` with calls to `label`
diff --git a/src/Data/DotLang.purs b/src/Data/DotLang.purs
index dc6c7e7..fd12038 100644
--- a/src/Data/DotLang.purs
+++ b/src/Data/DotLang.purs
@@ -167,20 +167,40 @@ instance definitionDotlang :: DotLang Definition where
   toText (EdgeDef e) = toText e <> "; "
   toText (Subgraph defs) = "subgraph { " <> (joinWith "" $ toText <$> defs) <> "}"
 
+-- | A graph can either be strict or non-strict
+data Strict
+  = Strict
+  | NonStrict
+
+instance strictDotLang :: DotLang Strict where
+  toText Strict = "strict "
+  toText NonStrict = ""
+
 -- | graph can either be a graph or digraph
 data Graph
-  = Graph (Array Definition)
-  | DiGraph (Array Definition)
-
+  = Graph Strict (Array Definition)
+  | DiGraph Strict (Array Definition)
 
 instance graphDotLang :: DotLang Graph where
-  toText (Graph defs) = "graph {" <> (joinWith "" $ toText <$> defs) <> "}"
-  toText (DiGraph defs) = "digraph {" <> (joinWith "" $ toText <$> defs) <> "}"
+  toText (Graph strict defs) = toText strict <> "graph {" <> (joinWith "" $ toText <$> defs) <> "}"
+  toText (DiGraph strict defs) = toText strict <> "digraph {" <> (joinWith "" $ toText <$> defs) <> "}"
+
+digraph :: Array Definition -> Graph
+digraph = DiGraph NonStrict
+
+graph :: Array Definition -> Graph
+graph = Graph NonStrict
+
+strictDigraph :: Array Definition -> Graph
+strictDigraph = DiGraph Strict
+
+strictGraph :: Array Definition -> Graph
+strictGraph = Graph Strict
 
 -- | create graph from Nodes and Edges
 -- | example: `graphFromElements [Node "e" [], Node "d" []] [Edge "e" "f"]`
 graphFromElements :: Array (Node) -> Array (Edge) -> Graph
-graphFromElements n e = DiGraph $ (NodeDef <$> n) <> (EdgeDef <$> e)
+graphFromElements n e = digraph $ (NodeDef <$> n) <> (EdgeDef <$> e)
 
 -- | `a` is a type that can be represented by a Dot-Graph
 class GraphRepr a where
diff --git a/src/Data/DotLang/Attr/Global.purs b/src/Data/DotLang/Attr/Global.purs
index 0db342d..df85262 100644
--- a/src/Data/DotLang/Attr/Global.purs
+++ b/src/Data/DotLang/Attr/Global.purs
@@ -45,6 +45,7 @@ instance pageDirValueDotLang :: DotLang PageDirValue where
 data Attr
   = RankDir RankDirValue
   | PageDir PageDirValue
+  | Concentrate Boolean
 
 derive instance genericAttr :: Generic Attr _
 
@@ -54,3 +55,4 @@ instance showAttr :: Show Attr where
 instance attrDotLang :: DotLang Attr where
   toText (RankDir dir) = "rankdir=" <> toText dir
   toText (PageDir dir) = "pagedir=" <> toText dir
+  toText (Concentrate concentrate) = "concentrate=" <> show concentrate
diff --git a/test/Main.purs b/test/Main.purs
index b87b311..e0af019 100644
--- a/test/Main.purs
+++ b/test/Main.purs
@@ -3,7 +3,7 @@ module Test.Main where
 import Prelude
 
 import Color.Scheme.MaterialDesign (red)
-import Data.DotLang (Definition(..), Graph(..), Edge(..), EdgeType(..), global, node, (==>), (=*>))
+import Data.DotLang (Definition(..), Edge(..), EdgeType(..), digraph, strictDigraph, global, node, (==>), (=*>))
 import Data.DotLang.Attr (FillStyle(..))
 import Data.DotLang.Attr.Edge as Edge
 import Data.DotLang.Attr.Node (Attr(..), ShapeType(..))
@@ -21,8 +21,8 @@ main = runTest do
   suite "DotLang" do
     test "basic test" do
       let
-        g = DiGraph [
-          global [ Global.RankDir FromLeft ],
+        g = digraph [
+          global [ Global.RankDir FromLeft, Global.Concentrate true ],
           node "a" [ Shape Diamond, Style Filled,  Node.FillColor red ],
           node "b" [],
           "a" ==> "b",
@@ -31,7 +31,20 @@ main = runTest do
             node "d" []
           ]
         ]
-      equal "digraph {rankdir=LR; a [shape=diamond, style=filled, fillcolor=\"#f44336\"]; b []; a -> b; a -> d [fillcolor=\"#f44336\"]; subgraph { d []; }}" (toText g)
+      equal "digraph {rankdir=LR; concentrate=true; a [shape=diamond, style=filled, fillcolor=\"#f44336\"]; b []; a -> b; a -> d [fillcolor=\"#f44336\"]; subgraph { d []; }}" (toText g)
     test "examples from documentation" do
       equal (toText $ Edge Forward "a" "b" []) "a -> b"
       equal (toText $ "a" =*> "b" $ [ Edge.FillColor red ]) "a -> b [fillcolor=\"#f44336\"]; "
+    test "strict graph" do
+      let
+        g = strictDigraph [
+          global [ Global.RankDir FromLeft ],
+          node "a" [ Shape Diamond, Style Filled,  Node.FillColor red ],
+          node "b" [],
+          "a" ==> "b",
+          "a" =*> "d" $ [ Edge.FillColor red ],
+          Subgraph [
+            node "d" []
+          ]
+        ]
+      equal "strict digraph {rankdir=LR; a [shape=diamond, style=filled, fillcolor=\"#f44336\"]; b []; a -> b; a -> d [fillcolor=\"#f44336\"]; subgraph { d []; }}" (toText g)