Hello Anand,
Can you please explain where,when and why you want to read the classification data to get clear picture ?
Anyway,
In Derive and Check BADI you get reference to IO_MODEL instance of type IF_USMD_MODEL_EXT.
This interface has many methods to read the entity values :
You can try methods
IO_model->retrieve_char_value ()
For using the API please refer the below document.
http://scn.sap.com/docs/DOC-45127
Best Regards,
Shivanand