diff --git a/spot/twaalgos/Makefile.am b/spot/twaalgos/Makefile.am
index 02734f892..9ce9c2750 100644
--- a/spot/twaalgos/Makefile.am
+++ b/spot/twaalgos/Makefile.am
@@ -66,6 +66,7 @@ twaalgos_HEADERS = \
   remfin.hh \
   remprop.hh \
   strength.hh \
+  safra.hh \
   sbacc.hh \
   sccfilter.hh \
   sccinfo.hh \
@@ -121,6 +122,7 @@ libtwaalgos_la_SOURCES = \
   remprop.cc \
   relabel.cc \
   strength.cc \
+  safra.cc \
   sbacc.cc \
   sccinfo.cc \
   sccfilter.cc \
diff --git a/src/twaalgos/safra.cc b/src/twaalgos/safra.cc
new file mode 100644
index 000000000..7a3d63a18
--- /dev/null
+++ b/src/twaalgos/safra.cc
@@ -0,0 +1,210 @@
+// -*- coding: utf-8 -*-
+// Copyright (C) 2015 Laboratoire de Recherche et
+// Développement de l'Epita.
+//
+// This file is part of Spot, a model checking library.
+//
+// Spot is free software; you can redistribute it and/or modify it
+// under the terms of the GNU General Public License as published by
+// the Free Software Foundation; either version 3 of the License, or
+// (at your option) any later version.
+//
+// Spot is distributed in the hope that it will be useful, but WITHOUT
+// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+// or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
+// License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+#include <deque>
+
+#include "safra.hh"
+
+namespace spot
+{
+  auto
+  safra_state::compute_succs(const const_twa_graph_ptr& aut) const -> succs_t
+  {
+    succs_t res;
+    // Given a bdd returns index of associated safra_state in res
+    std::map<bdd, unsigned, bdd_less_than> bdd2num;
+    for (auto& node: nodes_)
+      {
+        for (auto& t: aut->out(node.id_))
+          {
+            auto i = bdd2num.insert(std::make_pair(t.cond, res.size()));
+            unsigned idx;
+	    if (!i.second)
+              idx = i.first->second;
+	    else
+	      {
+                // Each new node starts out with same number of nodes as src
+                safra_state empty_state = safra_state(nb_braces_.size());
+                idx = res.size();
+                res.push_back(std::make_pair(empty_state, t.cond));
+                std::cerr << "Created inner node: " << idx << std::endl;
+              }
+            safra_state& ss = res[idx].first;
+            ss.update_succ(node, t.dst, t.acc);
+          }
+      }
+    for (auto& s: res)
+      {
+        safra_state& tmp = s.first;
+        tmp.finalize_construction();
+      }
+    return res;
+  }
+
+  void safra_state::finalize_construction()
+  {
+    // TODO this is a dirty hack to have two comparision functions depending on
+    // wether or not we are still construction the safra_stata
+    // Ideally I'd like to have this done statically but not sure how to do it
+    for (unsigned i = 0; i < nb_braces_.size(); ++i)
+      {
+        if (nb_braces_[i] == 0)
+          {
+            // TODO We also emit Red = min(red, i)
+            is_green_[i] = false;
+          }
+      }
+    for (auto& n: nodes_)
+      {
+        node& nn = const_cast<node&>(n);
+        nn.disable_construction();
+      }
+  }
+
+  void safra_state::update_succ(const node& src, unsigned dst,
+                                const acc_cond::mark_t acc)
+  {
+    (void) acc; // TODO
+    auto i = nodes_.find(node(dst));
+    if (i != nodes_.end())
+      {
+        // Todo need to handle acc and create new braces
+        if (src.braces_ > i->braces_)
+          {
+            std::cerr << "Replacing braces of: " << dst << std::endl;
+            node& dst = const_cast<node&>(*i);
+            for (auto b: dst.braces_)
+              nb_braces_[b]--;
+            dst.braces_ = src.braces_;
+          }
+        // Node already exists and has bigger values
+        else
+          return;
+      }
+    else
+      {
+        // Todo need to handle acc and create new braces
+        nodes_.emplace(dst, src.braces_);
+      }
+    for (auto b: src.braces_)
+      nb_braces_[b]++;
+    // If brace has no right-hand-side brace than it cannot emit any green color
+    is_green_[src.braces_[src.braces_.size() - 1]] = false;
+  }
+
+  // Comparison is needed when for a set of safra_state
+  bool
+  safra_state::operator<(const safra_state& other) const
+  {
+    return nodes_ < other.nodes_;
+  }
+
+  // Called only to initialize first state
+  safra_state::safra_state(unsigned val, bool init_state)
+  {
+    if (init_state)
+      {
+        unsigned state_num = val;
+        // One brace set
+        is_green_.push_back(true);
+        // First brace has init_state hence one state inside the first braces.
+        nb_braces_.push_back(1);
+        nodes_.emplace(state_num, 0);
+      }
+    else
+      {
+        unsigned nb_braces = val;
+        // One brace set
+        is_green_.assign(true, nb_braces);
+        // First brace has init_state hence one state inside the first braces.
+        nb_braces_.assign(nb_braces, 0);
+      }
+  }
+
+
+  bool
+  safra_state::node::operator<(const node& other) const
+  {
+    if (id_ == other.id_)
+      return in_construction_ ? false : braces_ < other.braces_;
+    else
+      return id_ < other.id_;
+  }
+
+  bool
+  safra_state::node::operator==(const node& other) const
+  {
+    if (id_ == other.id_)
+      return in_construction_ ? true : braces_ == other.braces_;
+    else
+      return false;
+  }
+
+  twa_graph_ptr
+  tgba_determinisation(const const_twa_graph_ptr& aut)
+  {
+    auto res = make_twa_graph(aut->get_dict());
+    res->copy_ap_of(aut);
+    res->prop_copy(aut,
+                   { true, // state based
+                   true, // inherently_weak
+                   true, // deterministic
+                   false // stutter inv
+                   });
+
+    // Given a safra_state get its associated state in output automata.
+    // Required to create new transitions from 2 safra-state
+    typedef std::map<safra_state, int> power_set;
+    power_set seen;
+    safra_state init(aut->get_init_state_number(), true);
+    unsigned num = res->new_state();
+    res->set_init_state(num);
+    seen.insert(std::make_pair(init, num));
+    std::deque<safra_state> todo;
+    todo.push_back(init);
+    while (!todo.empty())
+      {
+        using succs_t = safra_state::succs_t;
+        safra_state curr = todo.front();
+        unsigned src_num = seen.find(curr)->second;
+        todo.pop_front();
+        succs_t succs = curr.compute_succs(aut);
+        for (auto s: succs)
+          {
+            auto i = seen.find(s.first);
+	    unsigned dst_num;
+	    if (i != seen.end())
+	      {
+		dst_num = i->second;
+	      }
+	    else
+	      {
+                dst_num = res->new_state();
+                std::cerr << "New state " << dst_num << std::endl;
+                todo.push_back(s.first);
+                seen.insert(std::make_pair(s.first, dst_num));
+              }
+            std::cerr << "Tr: " << src_num << " -> " << dst_num << "["
+                      << s.second << "]" << std::endl;
+	    res->new_transition(src_num, dst_num, s.second);
+          }
+      }
+    return res;
+  }
+}
diff --git a/src/twaalgos/safra.hh b/src/twaalgos/safra.hh
new file mode 100644
index 000000000..5de34bed8
--- /dev/null
+++ b/src/twaalgos/safra.hh
@@ -0,0 +1,80 @@
+// -*- coding: utf-8 -*-
+// Copyright (C) 2015 Laboratoire de Recherche et Développement
+// de l'Epita.
+//
+// This file is part of Spot, a model checking library.
+//
+// Spot is free software; you can redistribute it and/or modify it
+// under the terms of the GNU General Public License as published by
+// the Free Software Foundation; either version 3 of the License, or
+// (at your option) any later version.
+//
+// Spot is distributed in the hope that it will be useful, but WITHOUT
+// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+// or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
+// License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+#pragma once
+
+#include <set>
+
+#include "misc/bddlt.hh"
+#include "twa/twagraph.hh"
+
+namespace spot
+{
+  class safra_state
+  {
+    class node
+    {
+    public:
+      using brace_t = size_t;
+
+      bool operator==(const node& other) const;
+      bool operator<(const node& other) const;
+      void disable_construction() { in_construction_ = false; }
+      node(unsigned id)
+        : id_(id), in_construction_(true) {}
+      node(unsigned id, brace_t b_id, bool in_construction = true)
+        : id_(id), braces_(1, b_id), in_construction_(in_construction) {}
+      node(unsigned id, std::vector<brace_t> b, bool in_construction = true)
+        : id_(id), braces_(b), in_construction_(in_construction) {}
+      // The name used to identify a state
+      unsigned id_;
+      // The list of braces the state is nested in.
+      std::vector<brace_t> braces_;
+      // Hack to have two comparision functions during construction and after
+      // construction
+      // During construction only the nodes id matterns as the braces are under
+      // construction. After construction (id, braces) is what distinguishes a
+      // node.
+      bool in_construction_;
+    };
+
+  public:
+    typedef std::vector<std::pair<safra_state, bdd>> succs_t;
+    bool operator<(const safra_state& other) const;
+    safra_state(unsigned state_number, bool init_state = false);
+    // Given a certain transition_label, compute all the successors of that
+    // label, and return that new node.
+    succs_t compute_succs(const const_twa_graph_ptr& aut) const;
+    // Used when creating the list of successors
+    void update_succ(const node& src, unsigned dst, const acc_cond::mark_t);
+    void finalize_construction();
+    // A list of nodes similar to the ones of a
+    // safra tree.  These are constructed in the same way as the powerset
+    // algorithm.
+    std::set<node> nodes_;
+    // A counter that indicates the nomber of states within a brace.
+    // This enables us to compute the red value
+    std::vector<size_t> nb_braces_;
+    // A bitfield to know if a brace can emit green.
+    std::vector<bool> is_green_;
+  };
+
+  SPOT_API twa_graph_ptr
+  tgba_determinisation(const const_twa_graph_ptr& aut);
+}