THE 18 TH EUROPEAN CONFERENCE ON MACHINE LEARNING AND THE 11 TH EUROPEAN CONFERENCE ON PRINCIPLES AND PRACTICE OF KNOWLEDGE DISCOVERY IN DATABASES P ROCEEDINGS OF THE WORKSHOPS : P RIOR C ONCEPTUAL K NOWLEDGE IN M ACHINE L EARNING AND DATA M INING AND W EB M INING 2.0 PriCKL’07 & Web Mining 2.0 September 21, 2007 Warsaw, Poland