François Bry Paula-Lavinia Patranjan Sebastian Schaffert Xcerpt and XChange: Deductive Languages for Data Retrieval and Evolution on the Web. 562-568 2004 conf/gi/2004-2 GI Jahrestagung (2) db/conf/gi/gi2004-2.html#BryPS04 http://subs.emis.de/LNI/Proceedings/Proceedings51/article3312.html