Hi Bharath,
SAP GDS will not import records through MDIS, likewise the syndication will not happen via MDSS.
The complete import and export of the files happen via Java Proxy in GDS. There requires a GDS specific adapter installation in PI (AS2 is one such example) which facilitates the data flow from and out of GDS. Please see that the XSD structure will come as a part of standard structure in case of GDS for mapping in PI.
Hence the mapping have to be done in PI. There is a specific mapping technique that you have to follow for this. GDS/MDM folks have to provide the mapping details to the PI team according the tables and fields that are being used. This can be understood from the standard structure.
Kind Regards,
Thamizharasi N