diff -r f8bbfed86036 -r 6b4e38acef1c lemon/lemon_reader.h
--- a/lemon/lemon_reader.h	Sat Dec 03 18:17:29 2005 +0000
+++ b/lemon/lemon_reader.h	Sat Dec 03 18:30:31 2005 +0000
@@ -425,7 +425,14 @@
     class ValueReaderBase {
     public:
       virtual void read(std::istream&) {};
+      ValueReaderBase() { _touched = false; }
+
+      void touch() { _touched = true; }
+      bool touched() const { return _touched; }
+
       virtual ~ValueReaderBase() {}
+    private:
+      bool _touched;
     };
 
     template <typename _Value, typename _Reader>
@@ -1926,8 +1933,17 @@
 	typename Readers::iterator it = readers.find(id);
 	if (it != readers.end()) {
 	  it->second->read(ls);
+	  it->second->touch();
 	}
       }
+      for (typename Readers::iterator it = readers.begin();
+	   it != readers.end(); ++it) {
+	if (!it->second->touched()) {
+	  ErrorMessage msg;
+	  msg << "Attribute not found in file: " << it->first;
+	  throw IOParameterError(msg.message());
+	}	
+      }
     }    
 
   private: