This, the 13th issue of Transactions on Large-Scale Data and Knowledge-Centered Systems, contains six revised selected regular papers. Topics covered include federated data sources, information filtering, web data clouding, query reformulation, package skyline queries and SPARQL query processing over a LaV (Local-as-View) integration system.

Enabling a Package Query Paradigm on the Semantic Web: Model and Algorithms.- SemLAV: Local-as-View Mediation for SPARQL Queries.- Query Reformulation in PDMS Based on Social Relevance.- Distributed Large-Scale Information Filtering.- RUBIK: Proactive, Entity-Centric and Personalized Situational Web Application Design.- Mining Multiple Related Data Sources Using Object-Oriented Models.