Hi Muhammed,
SAP does only provide a few standard services as part of the SAP NetWeaver Gateway delivery.
These are described in the Content Guide that can be found in the SAP Online Help
http://help.sap.com/saphelp_gateway20sp06/helpdata/en/d2/3fb0bcecb4477a90457b2b99d5defb/content.htm
For other scenarios we provide tools to either develop or even generate OData Services.
If you know existing business objects on top of either GenIL, SPI or Easy Queries you can use the option to redefine services without writing a single line of code.
Best Regards,
Andre