[SOLVED] Import data error "Impossible to load class AssignmentPlanningElement<br/>"

Hi,
I've successfully imported "Activity" and "Work" elements.
When I try to import "Assignment" no messages are displayed on form (neither errors or some info) and in log file I can see these messages:
2016-03-14 18:10:52.634 ===== TRACE ===== Importation : File type CSV
2016-03-14 18:10:52.634 ===== TRACE ===== File Name : ../files/attach//import/IMPORT_assignment_sample1.csv
2016-03-14 18:10:52.670 ***** ERROR ***** Impossible to load class AssignmentPlanningElement<br/> => Not found in ../model/custom/AssignmentPlanningElement.php <br/> => Not found in ../model/AssignmentPlanningElement.php <br/> => Not found in ../model/persistence/AssignmentPlanningElement.php <br/>

Just for some troubleshooting I try also to import "Task" using a bad file format, same result: no errors on form and log messages recorded.
Atteched the CSV file.

Thank you.
Regards.

Sorry (I didn't click Insert button ) !!!!

Here the file content ...

id;project;type of item;element id;resource;function;comments;assigned work;left work;rate (%);closed
;1;Assignment;8;4;3;"Commento";10;10;100;

With this new version of the file I can import assignments for the actvities.

id;project;type of item;element id;resource;function;comments;assigned work;left work;rate (%);closed
;1;Activity;8;4;3;"Commento";10;10;100;

Thanks!!!