diff --git a/src/common/mlexception.h b/src/common/mlexception.h
index 7518b5b66..2c452f4d2 100644
--- a/src/common/mlexception.h
+++ b/src/common/mlexception.h
@@ -1,32 +1,45 @@
 #ifndef ML_EXCEPTION
 #define ML_EXCEPTION
 
-class ParsingException : public std::exception
+class MeshLabException : public std::exception
+{
+public:
+	MeshLabException(const QString& text)
+		:std::exception(),excText(text){_ba = excText.toLocal8Bit();}
+
+	~MeshLabException() throw() {}
+	inline const char* what() const throw() {return _ba.constData();}
+
+protected:
+	QString excText;
+	QByteArray _ba;
+
+};
+
+class ParsingException : public MeshLabException
 {
 public:
         ParsingException(const QString& text)
-                :excText(text){excText = QString("Parsing Error: ") + excText;_ba = excText.toLocal8Bit();}
+                :MeshLabException(QString("Parsing Error: ") + text){}
 
         ~ParsingException() throw() {}
-     inline const char* what() const throw() {return _ba.constData();}
-
-private:
-	QString excText;
-	QByteArray _ba;
 };
 
-class ValueNotFoundException : public std::exception
+class ValueNotFoundException : public MeshLabException
 {
 public:
         ValueNotFoundException(const QString& valName)
-                :valNM(valName){valNM = QString("Value Name: ") + valNM +  QString(" has not been found in current environment.");_ba = valNM.toLocal8Bit();}
+                :MeshLabException(QString("Value Name: ") + valName +  QString(" has not been found in current environment.")){}
 
         ~ValueNotFoundException() throw() {}
-    inline const char* what() const throw() { return _ba.constData();}
-		
-private:
-	QString valNM;
-	QByteArray _ba;
 };
 
+class QueryException : public MeshLabException
+{
+public:
+	QueryException(const QString& syntaxError)
+		:MeshLabException(QString("Query Error: ") + syntaxError){}
+
+	~QueryException() throw() {}
+};
 #endif
diff --git a/src/common/pluginmanager.cpp b/src/common/pluginmanager.cpp
index 24c8e31b0..24e222bca 100644
--- a/src/common/pluginmanager.cpp
+++ b/src/common/pluginmanager.cpp
@@ -64,8 +64,7 @@ void PluginManager::loadPlugins(RichParameterSet& defaultGlobal)
 				fc.xmlInfo = XMLFilterInfo::createXMLFileInfo(xmlFile,xmlSchemaFile(),xmlErr);
 				if (fc.xmlInfo != NULL)
 				{
-					XMLMessageHandler errQuery;
-					QStringList fn = fc.xmlInfo->filterNames(errQuery);
+					QStringList fn = fc.xmlInfo->filterNames();
 					foreach(QString filtName,fn)
 					{
 						fc.act = new QAction(filtName,plugin);
@@ -78,7 +77,7 @@ void PluginManager::loadPlugins(RichParameterSet& defaultGlobal)
 				else 
 				{
 					QString err = xmlErr.statusMessage();
-					qDebug("Error in XMLFile: %s - %s",qPrintable(xmlFile),qPrintable(err));
+					qDebug("Error in XMLFile: %s - line: %d, column: %d - %s",qPrintable(xmlFile),xmlErr.line(),xmlErr.column(),qPrintable(err));
 				}
 			}
 
@@ -253,7 +252,7 @@ void PluginManager::LoadFormats(QStringList &filters, QHash<QString, MeshIOInter
 
 void PluginManager::updateDocumentScriptBindings(MeshDocument& doc )
 { 
-	//delete currentDocInterface;
+	//WARNING!
 	//all the currentDocInterface created will be destroyed by QT when the MeshDocument destructor has been called
 	currentDocInterface = new MeshDocumentScriptInterface(&doc);
 	QScriptValue val = env.newQObject(currentDocInterface);
diff --git a/src/common/scriptinterface.h b/src/common/scriptinterface.h
index aeb2761d6..3c10b8ee0 100644
--- a/src/common/scriptinterface.h
+++ b/src/common/scriptinterface.h
@@ -58,6 +58,7 @@ class MeshDocumentScriptInterface : public QObject
 
 public:
 	MeshDocumentScriptInterface(MeshDocument* doc);
+	~MeshDocumentScriptInterface(){}
 
 	Q_INVOKABLE MeshModelScriptInterface* getMesh(const int meshId);
 	Q_INVOKABLE MeshModelScriptInterface* current();
diff --git a/src/common/xmlfilterinfo.cpp b/src/common/xmlfilterinfo.cpp
index 304c60f8a..c55b12ddd 100644
--- a/src/common/xmlfilterinfo.cpp
+++ b/src/common/xmlfilterinfo.cpp
@@ -5,6 +5,7 @@
 #include <QUrl>
 #include <QtXmlPatterns/QXmlQuery>
 #include <QStringList>
+#include "mlexception.h"
 
 XMLFilterInfo* XMLFilterInfo::createXMLFileInfo( const QString& XMLFileName,const QString& XMLSchemaFileName,XMLMessageHandler& errXML)
 {
@@ -33,51 +34,61 @@ XMLFilterInfo* XMLFilterInfo::createXMLFileInfo( const QString& XMLFileName,cons
 		}
 		file.close();
 		validator.setMessageHandler(oldHandler);
+		return new XMLFilterInfo(XMLFileName);
 	}
-	return new XMLFilterInfo(XMLFileName);
+	return NULL;
 }
 
-QStringList XMLFilterInfo::filterNames(XMLMessageHandler& errQuery) const
+QStringList XMLFilterInfo::filterNames() const
 {
 	QString namesQuery = "doc(\"" + this->fileName + "\")/MESHLAB_FILTER_INTERFACE/PLUGIN/FILTER/<p>{data(@name)}</p>/string()";
-	return query(namesQuery,errQuery);
+	try
+	{
+		return query(namesQuery);
+	}
+	catch(QueryException e)
+	{
+		qDebug(e.what());
+	}
+	
 }
 
-QString XMLFilterInfo::filterHelp( const QString& filterName,bool& isValid,XMLMessageHandler& errQuery) const
+QString XMLFilterInfo::filterHelp( const QString& filterName) const
 {
 	QString namesQuery = "doc(\"" + this->fileName + "\")/MESHLAB_FILTER_INTERFACE/PLUGIN/FILTER[@name = \"" + filterName + "\"]/FILTER_HELP/string()";
-	QStringList res = query(namesQuery,errQuery);
-	if (res.size() != 1)
+	try
 	{
-		isValid = false;
-		return QString();
-	}
-	else
-	{
-		isValid = true;
+		QStringList res = query(namesQuery);
+		if (res.size() != 1)
+			throw ParsingException("There is not help tag for filter " + filterName);
 		return res[0];
 	}
+	catch(QueryException q)
+	{
+		qDebug(q.what());
+	}
 }
 
 
-QString XMLFilterInfo::filterAttribute( const QString& filterName,const QString& attribute,bool& isValid,XMLMessageHandler& errQuery) const
+QString XMLFilterInfo::filterAttribute( const QString& filterName,const QString& attribute) const
 {	
 	QString namesQuery = "doc(\"" + this->fileName + "\")/MESHLAB_FILTER_INTERFACE/PLUGIN/FILTER[@name = \"" + filterName + "\"]/@" + attribute + "/string()";
-	QStringList res = query(namesQuery,errQuery);
-	if (res.size() != 1)
+	try
 	{
-		isValid = false;
-		return QString();
-	}
-	else
+		QStringList res = query(namesQuery);
+		if (res.size() != 1)
+			throw ParsingException("Attribute " + attribute + " has not been specified for filter " + filterName);
+		return res[0]; 
+	}	
+	catch (QueryException e)
 	{
-		isValid = true;
-		return res[0];
+		qDebug(e.what());
 	}
 }
 
-QStringList XMLFilterInfo::query( const QString& qry,XMLMessageHandler& errQuery ) const
+QStringList XMLFilterInfo::query( const QString& qry) const
 {
+	XMLMessageHandler errQuery; 
 	QXmlQuery xmlq;
 	xmlq.setQuery(qry);
 	QAbstractMessageHandler * oldHandler = xmlq.messageHandler();
@@ -88,21 +99,83 @@ QStringList XMLFilterInfo::query( const QString& qry,XMLMessageHandler& errQuery
 	{
 		//errQuery = xmlq.messageHandler();
 		xmlq.setMessageHandler(oldHandler);
-		QString mes = errQuery.statusMessage();
-		return result;
+		throw QueryException(QString("line: ") + errQuery.line() + " column: " + errQuery.column() + " - " + errQuery.statusMessage());
+		
 	}
 	xmlq.evaluateTo(&result);
+	QString res;
+	xmlq.evaluateTo(&res);
 	xmlq.setMessageHandler(oldHandler);
 	return result;
 }
 
-QStringList XMLFilterInfo::filterParameters( const QString& filterName,bool& isValid,XMLMessageHandler& errQuery) const
+XMLFilterInfo::MapList XMLFilterInfo::filterParameters( const QString& filterName) const
 {
-	QString namesQuery = "doc(\"" + this->fileName + "\")/MESHLAB_FILTER_INTERFACE/PLUGIN/FILTER[@name = \"" + filterName + "\"]/PARAM/<p>{data(@type)},{data(@name)},{data(@defaultExpression)}</p>/string()";
-	QStringList res = query(namesQuery,errQuery);
-	if (res.size() == 0)
-		isValid = false;
-	else
-		isValid = true;
-	return res;
+	QString namesQuery = "doc(\"" + this->fileName + "\")/MESHLAB_FILTER_INTERFACE/PLUGIN/FILTER[@name = \"" + filterName + "\"]/PARAM/<p>type={data(@type)}|name={data(@name)}|defaultExpression={data(@defaultExpression)}</p>/string()";
+	try
+	{
+		QStringList res = query(namesQuery);
+		return mapListFromStringList(res);
+	}
+	catch (QueryException e)
+	{
+		throw e;
+	}
 }
+
+XMLFilterInfo::MapList XMLFilterInfo::mapListFromStringList( const QStringList& list )
+{
+	MapList result;
+	//"attribute0=value0|attribute1=value1|...|attributeN=valueN" "attribute0=value0|attribute1=value1|...|attributeN=valueN" "attribute0=value0|attribute1=value1|...|attributeN=valueN"
+	foreach(QString st, list)
+	{
+		QStringList coupleList = st.split('|');
+		QMap<QString,QString> attrValue;
+		foreach(QString couple,coupleList)
+		{
+			QStringList cl = couple.split('=');
+			if (cl.size() == 2)
+				attrValue[cl[0]]=cl[1];
+		}
+		result.push_back(attrValue);
+	}
+	return result;
+}
+
+QString XMLFilterInfo::defaultGuiInfo(const QString& guiType,const QString& xmlvariable)
+{
+	return QString("type=" + guiType + "|label={data(" + xmlvariable + "/@label)}");
+}
+
+QString XMLFilterInfo::floatGuiInfo(const QString& guiType,const QString& xmlvariable)
+{
+	return defaultGuiInfo(guiType,xmlvariable) + "|minExpr={data(" + xmlvariable + "/@minExpr)}|maxExpr={data(" + xmlvariable + "/@maxExpr)}";
+}
+
+QMap<QString,QString> XMLFilterInfo::filterParameterGui( const QString& filterName,const QString& parameterName) const
+{ 
+	QString var("$gui");
+	QString queryBase("for " + var + " in doc(\"" + this->fileName + "\")/MESHLAB_FILTER_INTERFACE/PLUGIN/FILTER[@name = " + filterName + "]/PARAM[@name =" + parameterName + "]/(* except PARAM_HELP) return typeswitch($gui)\n");
+	QString caseABS("element (ABSPERC_GUI) return <p>" + defaultGuiInfo("ABSPERC_GUI",var) + "</p>/string()\n");
+	QString caseFLOAT("element (CHECKBOX_GUI) return <p>" + defaultGuiInfo("CHECKBOX_GUI",var) + "</p>/string()\n");
+	QString errorMsg("Error: Unknown GUI widget requested");
+	QString defaultCase("default return " + errorMsg);
+	QString totQuery = queryBase + caseABS + caseFLOAT + defaultCase;
+	QMap<QString,QString> mp;
+	try
+	{
+		QStringList res = query(totQuery);
+		XMLFilterInfo::MapList tmp = mapListFromStringList(res);
+		//MUST BE FOR EACH PARAMETER ONLY ONE GUI DECLARATION
+		if (tmp.size() != 1)
+			throw ParsingException("In filter " + filterName + " more than a single GUI declaration has been found for parameter " + parameterName);
+		else if (res[0] == errorMsg)
+				//GUI NOT DEFINED
+				throw ParsingException("In filter " + filterName + " no valid GUI declaration has been found for parameter " + parameterName);
+			 else return tmp[0];
+	}
+	catch(QueryException e)
+	{
+		qDebug(e.what());
+	}
+}
\ No newline at end of file
diff --git a/src/common/xmlfilterinfo.h b/src/common/xmlfilterinfo.h
index 9da4d2deb..65791d440 100644
--- a/src/common/xmlfilterinfo.h
+++ b/src/common/xmlfilterinfo.h
@@ -47,28 +47,36 @@ private:
 };
 
 
+//Query Exception should be managed by the XMLFilterInfo class (XMLFilterInfo is the class devoted to compose queries)
+//Parsing Exception instead should be managed by the code calling the XMLFilterInfo's functions. 
+//A Parsing Exception is raised every time an unexpected and/or missing tag or attribute in an XML has been encountered. 
+//So this kind of info it's sensible for the plugin's programmer.  
+
+
 class XMLFilterInfo
 {
 private:
 	XMLFilterInfo(const QString& file)
 		:fileName(file){}
 
-
+	static QString defaultGuiInfo(const QString& guiType,const QString& xmlvariable);
+	static QString floatGuiInfo(const QString& guiType,const QString& xmlvariable);
 	QString fileName;
 public:
+	typedef QList< QMap<QString,QString> > MapList;
+	static MapList mapListFromStringList(const QStringList& list);
 	static XMLFilterInfo* createXMLFileInfo(const QString& XMLFileName,const QString& XMLSchemaFileName,XMLMessageHandler& errXML);
 	inline static void deleteXMLFileInfo(XMLFilterInfo* xmlInfo) {delete xmlInfo;}
-	QStringList filterNames(XMLMessageHandler& errXML) const;
-	QString	filterHelp(const QString& filterName,bool& isValid,XMLMessageHandler& errXML) const;
+	QStringList filterNames() const;
+	QString	filterHelp(const QString& filterName) const;
 	
-	//The function returns a string list of all parameters for filterName. Each string in the list is a triple param_type,param_name,param_defaultExpression
-	//In order to parse each triple component is sufficient to call split(',')
-	QStringList filterParameters(const QString& filterName,bool& isValid,XMLMessageHandler& errXML) const;
-	QString filterAttribute(const QString& filterName,const QString& attribute,bool& isValid,XMLMessageHandler& errXML) const;
+	//The function returns a QList<QMap<QString,QString>>. Each map contains "type", "name" and "defaultExpression" of a single parameter.
+	MapList filterParameters(const QString& filterName) const;
 
-	/*QStringList filterParameters(const QString& filter);
-	QStringList filterParametersAndGui(const QString& filter);*/
-	QStringList query(const QString& qry,XMLMessageHandler& errQuery) const;
+	QMap<QString,QString> filterParameterGui(const QString& filter,const QString& parameter) const;
+	QString filterAttribute(const QString& filterName,const QString& attribute) const;
+
+	QStringList query(const QString& qry) const;
 };
 
 struct MeshLabXMLFilterContainer