Richard Cyganiak pointed me to this one, perhaps we find something there that can help us doing updates on graphs. but which code snippet? hm

http://rdqlplus.sourceforge.net/doc/ridiql.html

RIDIQL (RDF Insertion Deletion Inspection and Query Language) builds several utility commands on top of RDQL to make working with RDF graphs easy. This reference describes each of the commands and gives examples where appropriate.
Note: All commands may be written on multiple lines and are terminated with a ; character. Command names and tokens are case-insensitive, but when written in this reference, they are capitalized for clarity.

http://rdqlplus.sourceforge.net/doc/ridiql.html