Alvin Cheung Karin Kailing Stefan Schönauer Theseos: A Query Engine for Traceability across Sovereign, Distributed RFID Databases. 1495-1496 2007 conf/icde/2007 ICDE http://dx.doi.org/10.1109/ICDE.2007.369050 db/conf/icde/icde2007.html#CheungKS07