1995: image compression, implementation of JPEG progressive operation modes in the Independent JPEG group (IJG) library
1996-1997: quality measures of JPEG compressed images
1998: from image compression to image classification
1999-2002: from image compression to data mining
2001-2006: from image compression to image watermarking and fingerprinting
2002-2003: from data mining to web mining
2003-current: educational data mining and learning analytics
2004-current: from web mining to personalization in virtual learning environments
2006-current: open educational resources, learning object repositories
2010-current: crazy about processing, arduino
2011-current: even more crazy abou...