Hi Frank,
DESKI is no longer supported in BOXI 4.x. In earlier 4.x versions DESKI reports were not even stored in CMS. Later versions store DESKI reports but only to support migration from DESKI to webi. Access to those DESKI documents (which are stored in a 4.x CMS) is possible with a special R3 client installation. This X3 client is patched to work with BOXI R4.x servers.
WEBIs have two sdks in BOXI 4.x. The REPENG java sdk still exists but does not support many functionality. You need to check if your application is still working with the java sdk. If it does not you need to check the new WebI RESTFul web services sdk.
Thanks,
bernd