diff --git a/ChangeLog b/ChangeLog
index fb4e8a348..c20c1869c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,15 @@
 2003-05-26  Alexandre Duret-Lutz  <aduret@src.lip6.fr>
 
+	* src/tgba/tgba.hh: Rename as ...
+	* src/tgba/public.hh: .. this.
+	* src/tgba/tgba.hh: New file.
+	* src/tgba/Makefile.am (libtgba_la_SOURCES): Add public.hh.
+	* src/tgba/tgbabddconcrete.hh (tgba_bdd_concrete): Inherit from tgba.
+	(tgba_bdd_concrete::init_iter): Delete.
+	(tgba_bdd_concrete::succ_iter): Take a state_bdd as argument, 
+	not a bdd.
+	* src/tgba/tgbabddconcrete.cc: Likewise.
+
 	Initial code for TGBA (Transition Generalized Büchi Automata).
 	Contains tgba_bdd, a BDD-encoded TGBA, and ltl_to_tgba,
 	a LTL-to-TGBA translator using Couvreur's algorithm.
diff --git a/src/tgba/Makefile.am b/src/tgba/Makefile.am
index febfde8df..39605da82 100644
--- a/src/tgba/Makefile.am
+++ b/src/tgba/Makefile.am
@@ -9,6 +9,7 @@ libtgba_la_SOURCES = \
   dictunion.hh \
   ltl2tgba.cc \
   ltl2tgba.hh \
+  public.hh \
   state.hh \
   statebdd.cc \
   statebdd.hh \
diff --git a/src/tgba/public.hh b/src/tgba/public.hh
new file mode 100644
index 000000000..011420f60
--- /dev/null
+++ b/src/tgba/public.hh
@@ -0,0 +1,9 @@
+#ifndef SPOT_TGBA_PUBLIC_HH
+# define SPOT_TGBA_PUBLIC_HH
+
+# include "tgba.hh"
+# include "tgbabddconcrete.hh"
+# include "tgbabddconcreteproduct.hh"
+# include "ltl2tgba.hh"
+
+#endif // SPOT_TGBA_PUBLIC_HH
diff --git a/src/tgba/tgba.hh b/src/tgba/tgba.hh
index 7232ea142..43b214b7f 100644
--- a/src/tgba/tgba.hh
+++ b/src/tgba/tgba.hh
@@ -1,8 +1,26 @@
 #ifndef SPOT_TGBA_TGBA_HH
 # define SPOT_TGBA_TGBA_HH
 
-# include "tgbabddconcrete.hh"
-# include "tgbabddconcreteproduct.hh"
-# include "ltl2tgba.hh"
+#include "statebdd.hh"
+#include "succiter.hh"
+#include "tgbabdddict.hh"
+
+namespace spot
+{
+  class tgba
+  {
+  public:
+    virtual
+    ~tgba()
+    {
+    }
+
+    virtual state_bdd get_init_state() const = 0;
+    virtual tgba_succ_iterator* succ_iter(state_bdd state) const = 0;
+
+    virtual const tgba_bdd_dict& get_dict() const = 0;
+  };
+
+}
 
 #endif // SPOT_TGBA_TGBA_HH
diff --git a/src/tgba/tgbabddconcrete.cc b/src/tgba/tgbabddconcrete.cc
index bc3064e6e..39c5b4f20 100644
--- a/src/tgba/tgbabddconcrete.cc
+++ b/src/tgba/tgbabddconcrete.cc
@@ -29,20 +29,14 @@ namespace spot
   }
 
   tgba_succ_iterator_concrete*
-  tgba_bdd_concrete::succ_iter(bdd state) const
+  tgba_bdd_concrete::succ_iter(state_bdd state) const
   {
-    bdd succ_set = bdd_replace(bdd_exist(data_.relation & state,
+    bdd succ_set = bdd_replace(bdd_exist(data_.relation & state.as_bdd(),
 					 data_.now_set),
 			       data_.next_to_now);
     return new tgba_succ_iterator_concrete(data_, succ_set);
   }
 
-  tgba_succ_iterator_concrete*
-  tgba_bdd_concrete::init_iter() const
-  {
-    return new tgba_succ_iterator_concrete(data_, init_);
-  }
-
   const tgba_bdd_dict&
   tgba_bdd_concrete::get_dict() const
   {
diff --git a/src/tgba/tgbabddconcrete.hh b/src/tgba/tgbabddconcrete.hh
index 5417daefd..62e9901c7 100644
--- a/src/tgba/tgbabddconcrete.hh
+++ b/src/tgba/tgbabddconcrete.hh
@@ -1,28 +1,28 @@
 #ifndef SPOT_TGBA_TGBABDDCONCRETE_HH
 # define SPOT_TGBA_TGBABDDCONCRETE_HH
 
+#include "tgba.hh"
 #include "statebdd.hh"
 #include "tgbabddfactory.hh"
 #include "succiterconcrete.hh"
 
 namespace spot
 {
-  class tgba_bdd_concrete
+  class tgba_bdd_concrete: public tgba
   {
   public:
     tgba_bdd_concrete(const tgba_bdd_factory& fact);
     tgba_bdd_concrete(const tgba_bdd_factory& fact, bdd init);
     ~tgba_bdd_concrete();
-  
+
     void set_init_state(bdd s);
     state_bdd get_init_state() const;
-  
-    tgba_succ_iterator_concrete* succ_iter(bdd state) const;
-    tgba_succ_iterator_concrete* init_iter() const;
-  
+
+    tgba_succ_iterator_concrete* succ_iter(state_bdd state) const;
+
     const tgba_bdd_dict& get_dict() const;
     const tgba_bdd_core_data& get_core_data() const;
-  
+
   protected:
     tgba_bdd_core_data data_;
     tgba_bdd_dict dict_;