Following the 23nd International Conference on Database and Expert Systems Applications (DEXA 2012, proceedings published in LNCS vol. 7446 & 7447) the programme chairs invited the authors of 10 selected papers plus the keynote speakers to submit original, extended and revised papers to a special issue of the Transactions on Large-Scale Data- and Knowledge-Centered Sys- tems (TLDKS). Following these invitations ten papers were submitted, each of which was carefully reviewed by two experts in the field. Finally, seven papers were accepted for this special issue.