Update 18.12.2013
The approach described in this whitepaper is not needed anymore since as of Service Pack 7 SAP NetWeaver Gateway supports a delta query protocol.
Therefore you should rather have a look at the following two more recent documents:
How to Implement Basic Delta Query Support in SAP NetWeaver Gateway
and
How To Enable Delta Queries using Syclo Exchange Framework and SAP NetWeaver Gateway
Additional upcoming whitepapers will be listed in our SCN Wiki:
Development - Technologies - SCN Wiki
Best Regards,
Andre