Hello Pratish,
First check what partner function do the notification task is mapped to. Is it a vendor, employee or customer. If it is customer you can get the description (List name) from KNA1 and if it is vendor LFA1.
Please note that this can be achieved in BW without doing any enhancement in the data source. If suppose partner that you use in the task ia customer you can map this field to 0Customer( or any info object which is mapped to customer master data) The text of 0customer will take care of your requirement. In the case you are using employee no you can map the parnr field to 0employee.
Regards
Gajesh