 Starting with the innovative LMSS95 paper (Levy, Mendelzon, Sagiv, and Srivastava, PODS 1995) that introduced the problem of answering queries using views, Alberto Mendelzon made several important contributions to the emerging area of view-based modeling and processing.His research was central to the development of many areas of database research such as database design, semantic query optimization, graphical query languages, and querying web data.In addition, he also made important contributions to recursive query languages, on-line analytic processing, similarity-based queries, data warehouses and view maintenance, algorithms for computing web page reputations, and indexing of XML data.