diff --git a/lib/sof/all.rb b/lib/sof/all.rb
index cbdf2ffc..841fa004 100644
--- a/lib/sof/all.rb
+++ b/lib/sof/all.rb
@@ -5,31 +5,30 @@ require_relative "writer"
 require_relative "array"
 require_relative "hash"
 require_relative "occurence"
+require_relative "node"
 
 Symbol.class_eval do
-  def to_sof(io, members)
-    io.write ":#{to_s}"
+  def to_sof()
+    ":#{to_s}"
   end
 end
 TrueClass.class_eval do
-  def to_sof(io , members)
-    io.write "true"
+  def to_sof()
+    "true"
   end
 end
 FalseClass.class_eval do
-  def to_sof(io , members)
-    io.write "false"
+  def to_sof()
+    "false"
   end
 end
 String.class_eval do
-  def to_sof(io, members)
-    io.write "'"
-    io.write self
-    io.write "'"
+  def to_sof()
+    "'" + self + "'"
   end
 end
 Fixnum.class_eval do
-  def to_sof(io , members)
-    io.write to_s
+  def to_sof()
+    to_s
   end
 end
diff --git a/lib/sof/array.rb b/lib/sof/array.rb
index dba030d5..321a517b 100644
--- a/lib/sof/array.rb
+++ b/lib/sof/array.rb
@@ -1,10 +1,9 @@
 Array.class_eval do
-  def to_sof(io , members , level)
-    each_with_index do |object , i|
-      io.write(" " * level) unless i == 0
-      io.write("-")
-      members.output(io , object)
-      io.write("\n")
+  def to_sof_node(members , level)
+    node = Sof::Node.new(nil)
+    each do |object|
+      node.add members.to_sof_node( object )
     end
+    node
   end
 end
diff --git a/lib/sof/hash.rb b/lib/sof/hash.rb
index b90d602b..38d329a6 100644
--- a/lib/sof/hash.rb
+++ b/lib/sof/hash.rb
@@ -1,5 +1,5 @@
 Hash.class_eval do
-  def to_sof(io , members , level)
+  def to_sof_node(members , level)
     each_with_index do |pair , i|
       key , object = pair
       io.write(" " * level) unless i == 0
diff --git a/lib/sof/node.rb b/lib/sof/node.rb
new file mode 100644
index 00000000..4bed1f18
--- /dev/null
+++ b/lib/sof/node.rb
@@ -0,0 +1,30 @@
+# We transform objects into a tree of nodes
+
+module Sof
+  class Node
+    def initialize head
+      @head = head
+    end
+    attr_accessor :head , :children
+    def add child
+      child = Node.new(child) if(child.is_a? String)
+      @children = [] if(@children.nil?)
+      @children << child
+    end
+
+    def out io , level = 0
+      io.write head
+      return unless @children
+      first = @children[0]
+      io.write " "
+      first.out(io , level + 1)
+      indent = " " * level      
+      @children.each do |child|
+        next if child == first  # done already
+        io.write indent
+        io.write "-"
+        child.out(io , level + 1)
+      end
+    end
+  end
+end
diff --git a/lib/sof/writer.rb b/lib/sof/writer.rb
index 1e1490d4..666eff96 100644
--- a/lib/sof/writer.rb
+++ b/lib/sof/writer.rb
@@ -6,47 +6,37 @@ module Sof
     end
 
     def write
+      node = to_sof_node(@members.root)
       io = StringIO.new
-      output io , @members.root
+      node.out( io )
       io.string
     end
 
-    def output io , object
+    def to_sof_node(object)
       if is_value?(object)
-        object.to_sof(io , self)
-        return
+        return Node.new(object.to_sof())
       end
       occurence = @members.objects[object]
       raise "no object #{object}" unless occurence
-      if(object.respond_to? :to_sof) #mainly meant for arrays and hashes
-        object.to_sof(io , self , occurence.level)
+      if(object.respond_to? :to_sof_node) #mainly meant for arrays and hashes
+        object.to_sof_node(self , occurence.level)
       else
-        object_sof(object , io , occurence.level)
+        object_sof_node(object , occurence.level)
       end
     end
 
-    def object_sof( object , io , level)
-      io.write object.class.name
-      io.write "("
+    def object_sof_node( object , level)
+      head = object.class.name + "("
       attributes = attributes_for(object)
-      attributes.each_with_index do |a , i|
+      immediate , extended = attributes.partition {|a| is_value?(get_value(object , a) ) }
+      head += immediate.collect {|a| "#{a}: #{get_value(object , a)}"}.join(", ") + ")"
+
+      node = Node.new(head)
+      extended.each do |a|
         val = get_value(object , a)
-        next unless is_value?(val)
-        io.write( a )
-        io.write( ": " )
-        output( io , val)
-        io.write(" ,") unless i == (attributes.length - 1)
-      end
-      io.write ")"
-      attributes.each_with_index do |a , i|
-        val = get_value(object , a)
-        next if is_value?(val)
-        io.write " " * (level+1)
-        io.write "-"
-        io.write( a )
-        io.write( ": " )
-        output( io , val)
+        node.add to_sof_node(val)
       end
+      node
     end
 
     def self.write object