diff --git a/C/udi.c b/C/udi.c
index a9a41cd96..b5cdd73ae 100644
--- a/C/udi.c
+++ b/C/udi.c
@@ -3,6 +3,7 @@
 #include "clause.h"
 #include "udi.h"
 
+
 #include "rtree_udi.h"
 
 /* we can have this stactic because it is written once */
@@ -158,3 +159,4 @@ Yap_udi_init(void)
   RtreeCmd.destroy = RtreeUdiDestroy;
   Yap_InitCPred("$udi_init", 2, p_new_udi, 0);
 }
+
diff --git a/include/rtree_udi.h b/include/rtree_udi.h
new file mode 100644
index 000000000..038f7b1c4
--- /dev/null
+++ b/include/rtree_udi.h
@@ -0,0 +1,24 @@
+#ifndef _RTREE_UDI_
+#define _RTREE_UDI_
+
+#ifndef _RTREE_
+typedef void control_t;
+#endif
+
+/*Prolog term from :- udi(a(-,+,+)).
+  User defined index announce
+*/
+extern control_t *RtreeUdiInit (Term spec,
+                                void *pred,
+                                int arity);
+
+/*this is called in each asserted term that was declared to udi_init*/
+extern control_t *RtreeUdiInsert (Term t, /*asserted term*/
+                                  control_t *control,
+                                  void *clausule); /*to store in tree and return
+                                                     in search*/
+
+extern void *RtreeUdiSearch (control_t *control);
+extern int RtreeUdiDestroy(control_t *control);
+
+#endif /* _RTREE_UDI_ */