+ InvalidParameterValue(const std::string &w_): Exception(w_) { }
+};
+
+/**
+Thrown when the current object state doesn't allow the requested action.
+*/
+class InvalidState: public Exception
+{
+public:
+ InvalidState(const std::string &w_): Exception(w_) { }
+};
+
+/**
+Thrown when the application is invoked with wrong parameters.
+*/
+class UsageError: public Exception
+{
+public:
+ UsageError(const std::string &r, bool b=true): Exception(r), brief(b) { }