Database table structure is stored in universe and cannot be retrieved using Report Engine sdks. Also report engine sdks have deprectaed a ot a functionalities and it is best to move towards restful web services which is the future in terms of web intelligence as of now.
Check the below guide
http://service.sap.com/~sapidb/012002523100011674662015E/sbo41sp6_webi_restws_dg_en.pdf
For any queries relating to restful web services, you can post here
Thanks,
Prithvi