Hii,
Which version of NWGW you are using ??? for doing this things without segw i.e. - SE80
you can refer this link-
But if you are on >=sp05 than i would suggest use SEGW - create one entity set for you - BAPI_MATERIAL_GETLIST
than for query operation ( Based on single material MD_STOCK_REQUIREMENTS_LIST ) create association with different entity set so that your query performance will be better .