diff --git a/src/globals.cpp b/src/globals.cpp
index d1e3686..6962fbc 100644
--- a/src/globals.cpp
+++ b/src/globals.cpp
@@ -7,10 +7,10 @@ std::map<std::string,ObjectBase*> G_vars;
 std::multimap<std::string,Func> G_funcs;
 
 // List of objects to save
-std::list<ObjectList*> G_tosave;
+std::vector<ObjectList*> G_tosave;
 
 // List of objects to print
-std::list<ObjectList*> G_toprint;
+std::vector<ObjectList*> G_toprint;
 
 void ClearGlobals()
 {
@@ -26,4 +26,105 @@ void ClearGlobals()
 void RegisterFunction(const std::string& name, Func func)
 {
  G_funcs.emplace(name,func);
-}
\ No newline at end of file
+}
+
+int DepTree::CreateNodeFromVar(const std::string& var, std::set<std::string>& used)
+{
+ if(G_vars.count(var)==0)
+ {
+  COUT(ERROR)<<"Definition of variable "<<var<<" not found."<<std::endl;
+  return 1;
+ }
+
+ std::vector<std::string> ids;
+
+ used.insert(var);
+ G_vars[var]->UsedIdents(ids);
+ type=DepTree::VAR;
+ name=var;
+ nchild=ids.size();
+ COUT(DEBUG)<<ids.size()<<std::endl;
+ if(nchild!=0)
+ {
+  childrens=new DepTree*[nchild];
+  for(unsigned int i=0;i<nchild;i++) {childrens[i]=new DepTree; childrens[i]->parent=this;}
+  for(unsigned int i=0;i<nchild;i++)
+  {
+   int ret;
+   ret=childrens[i]->CreateNodeFromVar(ids[i],used);
+   if(ret!=0)
+   {
+    COUT(ERROR)<<" in definition of variable "<<var<<"."<<std::endl;
+    return ret;
+   }
+  }
+ }
+ return 0;
+}
+
+
+int DepTree::CreateNodeFromSP(DepTree::NodeType list, std::vector<ObjectList*>::size_type ind, std::set<std::string>& used)
+{
+ if(list!=DepTree::SAVE && list!=DepTree::PRINT)
+ {
+  COUT(ERROR)<<"Internal error, incorrect NodeType in DepTree::CreateNodeFromSP()."<<std::endl;
+  return 2;
+ }
+
+ std::vector<std::string> ids;
+
+ type=list;
+ index=ind;
+
+ if(type==DepTree::SAVE) G_tosave[index]->UsedIdents(ids);
+ else if(type==DepTree::PRINT) G_toprint[index]->UsedIdents(ids);
+ nchild=ids.size();
+ if(nchild!=0)
+ {
+  childrens=new DepTree*[nchild];
+  for(unsigned int i=0;i<nchild;i++) {childrens[i]=new DepTree; childrens[i]->parent=this;}
+  for(unsigned int i=0;i<nchild;i++)
+  {
+   int ret;
+   ret=childrens[i]->CreateNodeFromVar(ids[i],used);
+   if(ret!=0)
+   {
+    COUT(ERROR)<<" in print/save directive "<<G_toprint[index]->Dump()<<"."<<std::endl;
+    return ret;
+   }
+  }
+ }
+
+ return 0;
+}
+
+
+int DepTree::CreateGlobalTree(std::set<std::string>& used)
+{
+ if(parent!=0)
+ {
+  COUT(ERROR)<<"Internal error, DepTree::CreateGlobalTree() call for non-root node."<<std::endl;
+  return 2;
+ }
+
+ unsigned int i,j;
+ int ret;
+
+ type=DepTree::ROOT;
+ nchild=G_toprint.size()+G_tosave.size();
+ if(nchild!=0) childrens=new DepTree*[nchild];
+ for(i=0;i<nchild;i++) {childrens[i]=new DepTree; childrens[i]->parent=this;}
+ i=0;
+ for(j=0;j<G_tosave.size();j++)
+ {
+  ret=childrens[i++]->CreateNodeFromSP(DepTree::SAVE,j,used);
+  if(ret!=0) return ret;
+ }
+ for(j=0;j<G_toprint.size();j++)
+ {
+  ret=childrens[i++]->CreateNodeFromSP(DepTree::PRINT,j,used);
+  if(ret!=0) return ret;
+ }
+
+ return 0;
+}
diff --git a/src/globals.h b/src/globals.h
index 0b8c5c1..395fd81 100644
--- a/src/globals.h
+++ b/src/globals.h
@@ -1,7 +1,7 @@
 #ifndef GLOBALS_H
 #define GLOBALS_H
 #include <map>
-#include <list>
+#include <vector>
 #include <string>
 #include "object.h"
 
@@ -13,14 +13,39 @@ typedef ObjectBase* (*Func)(ObjectList*);
 extern EXPORT std::multimap<std::string,Func> G_funcs;
 
 // List of objects to save
-extern EXPORT std::list<ObjectList*> EXPORT G_tosave;
+extern EXPORT std::vector<ObjectList*> EXPORT G_tosave;
 
 // List of objects to print
-extern EXPORT std::list<ObjectList*> EXPORT G_toprint;
+extern EXPORT std::vector<ObjectList*> EXPORT G_toprint;
 
 void ClearGlobals();
 
 extern "C" {
 EXPORT void RegisterFunction(const std::string& name, Func func);
 }
+
+class DepTree
+{
+ enum NodeType {NOTDEF,ROOT,SAVE,PRINT,VAR};
+
+ DepTree* parent;
+ unsigned int nchild;
+ DepTree** childrens;
+ NodeType type;
+ std::vector<ObjectList*>::size_type index;
+ std::string name;
+
+ int CreateNodeFromVar(const std::string& var, std::set<std::string>& used);
+ int CreateNodeFromSP(NodeType list, std::vector<ObjectList*>::size_type ind, std::set<std::string>& used);
+public:
+ DepTree():parent(0),nchild(0),childrens(0),type(DepTree::NOTDEF) {}
+ DepTree(const DepTree&) = delete;
+ ~DepTree()
+ {
+  if(childrens!=0) for(unsigned int i=0; i<nchild; i++) delete childrens[i];
+  delete[] childrens;
+ }
+
+ int CreateGlobalTree(std::set<std::string>& used);
+};
 #endif
diff --git a/src/init.cpp b/src/init.cpp
index 4a7ae58..44b96c9 100644
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -47,3 +47,9 @@ int RegisterArifmeticFunctions()
  RegisterFunction("NEG",Arifm_Neg);
  return 0;
 }
+
+
+int BuildDepTree(DepTree* deptree,std::set<std::string>& used)
+{
+ return deptree->CreateGlobalTree(used);
+}
diff --git a/src/init.h b/src/init.h
index 10b2e51..df124d2 100644
--- a/src/init.h
+++ b/src/init.h
@@ -4,8 +4,10 @@
 #define YY_TYPEDEF_YY_SCANNER_T
 typedef void* yyscan_t;
 #endif
+#include "globals.h"
 
 int ParseConfigFile(char* config);
 int RegisterArifmeticFunctions();
+int BuildDepTree(DepTree* deptree, std::set<std::string>& used);
 
 #endif
diff --git a/src/main.cpp b/src/main.cpp
index ac754ee..2a83dda 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -6,18 +6,43 @@ int main(int argc, char** argv)
 {
  if(argc!=2) return 1;
  int ret;
+ DepTree* DPTree;
 
  SetDebugLevel(INFO);
 
  COUT(INFO)<<"Parse config file "<<argv[1]<<" ";
  ret=ParseConfigFile(argv[1]); if(ret!=0) { ClearGlobals(); return 1;}
  COUT(INFO)<<"Ok"<<std::endl;
+ if(G_tosave.size()==0 && G_toprint.size()==0)
+ {
+  COUT(INFO)<<"No actions needed, exiting"<<std::endl;
+  ClearGlobals();
+  return 0;
+ }
+
+ {
+  std::set<std::string> used, all;
+  for(auto& i:G_vars) all.insert(i.first);
+  unsigned int tot=G_vars.size();
+
+  DPTree=new DepTree;
+  COUT(INFO)<<"Building dependency tree ";
+  ret=BuildDepTree(DPTree,used); if(ret!=0) { ClearGlobals(); delete DPTree; return 1;}
+  COUT(INFO)<<"Ok"<<std::endl;
+
+  COUT(INFO)<<"Remove unneeded definitions: ";
+  for(auto& i:all) if(used.count(i)==0) { delete G_vars[i]; G_vars.erase(i);};
+  COUT(INFO)<<(tot-G_vars.size())<<" removed, "<<G_vars.size()<<" remains."<<std::endl;
+ }
+
 
  RegisterArifmeticFunctions();
 
+
  COUT(INFO)<<G_vars.size()<<std::endl;
  for(auto& i: G_vars) COUT(INFO)<<i.first<<"="+i.second->Dump()<<";"<<std::endl;
 
  ClearGlobals();
+ delete DPTree;
  return 0;
 }
diff --git a/src/object.h b/src/object.h
index bde6f5d..270f746 100644
--- a/src/object.h
+++ b/src/object.h
@@ -6,6 +6,7 @@
 #include <inttypes.h>
 #include <vector>
 #include <sstream>
+#include <set>
 #include <typeinfo>
 #include <typeindex>
 #include "debug.h"
@@ -64,6 +65,8 @@ public:
   return true;
  }
  virtual std::string Dump() const {return "%"+Type()+"%";}
+ virtual void UsedFuncs(std::vector<std::string>& funcs) const {}
+ virtual void UsedIdents(std::vector<std::string>& ids) const {}
 };
 
 // Template for objects without specific constructor/destructor
@@ -148,6 +151,8 @@ public:
  const ObjectBase* Value() const {return val;}
  void SetPair(const std::string& n, ObjectBase* v) {if(!Exist()) {name=n; val=v;}}
  std::string Dump() const override { return Name()+"="+val->Dump(); }
+ void UsedFuncs(std::vector<std::string>& funcs) const override {return val->UsedFuncs(funcs);}
+ void UsedIdents(std::vector<std::string>& ids) const override {return val->UsedIdents(ids);}
 };
 
 // Class for objects list
@@ -184,20 +189,30 @@ public:
   if(vals.size()!=0) s.resize(s.length()-2);
   return s+")";
  }
+ void UsedFuncs(std::vector<std::string>& funcs) const override {for(auto& i: vals) i->UsedFuncs(funcs);}
+ void UsedIdents(std::vector<std::string>& ids) const override {for(auto& i: vals) i->UsedIdents(ids);}
 };
 
 // Class for storing identifiers
 class OId: public ObjectBase
 {
  std::string name;
+ std::string fullname;
+
+ void ParseName(const std::string& s)
+ {
+  fullname=s;
+  name=s.substr(0,s.find_first_of('.'));
+ }
 public:
- OId(const std::string* t):name(*t) {}
+ OId(const std::string* t) {ParseName(*t);}
  ~OId() {}
  bool Print() const override {return false;}
  std::string Type() const override {return "IDENT";}
  std::string Name() const {return name;}
- void SetName(std::string s) {name=s;}
- std::string Dump() const override {return Name();};
+ void SetName(std::string s) {ParseName(s);}
+ std::string Dump() const override {return fullname;};
+ void UsedIdents(std::vector<std::string>& ids) const override {ids.push_back(name);}
 };
 
 // Class for storing functions
@@ -222,6 +237,8 @@ public:
  std::string Name() const {return name;}
  void SetName(std::string s) {name=s;}
  std::string Dump() const override {return Name()+args->Dump();};
+ void UsedFuncs(std::vector<std::string>& funcs) const override {funcs.push_back(name); args->UsedFuncs(funcs);}
+ void UsedIdents(std::vector<std::string>& ids) const override {args->UsedIdents(ids);}
 };
 
 #endif