Hi Vishwas,
i have created a document for your requirement,kindly go follow the steps to update multiple records to a tuple field.
http://scn.sap.com/docs/DOC-52237
please let me know if you require any more information. Reagrding webservices you can give grant to teh tuple field to update records in third party or EP front end of MDM.
Thank you
Rahul Pandey