Qimin Chen & Abdelkader Hameurlain 
Transactions on Large-Scale Data- and Knowledge-Centered Systems XXVIII 
Special Issue on Database- and Expert-Systems Applications

This, the 28th issue of Transactions on Large-Scale Data- and Knowledge-Centered Systems, contains extended and revised versions of six papers presented at the 26th International Conference on Database- and Expert-Systems Applications, DEXA 2015, held in Valencia, Spain, in September 2015. Topics covered include efficient graph processing, machine learning on big data, multistore big data integration, ontology matching, and the optimization of histograms for the Semantic Web.