Serge Abiteboul Sophie Cluet Tova Milo ACM SIGMOD Conference 1995 24 2 386 397 1045 KB Database systems are concerned with structured data. Unfortunately, data is still often available in an unstructured manner (e.g., in files) even when it does have a strong internal structure (e.g., electronic documents or programs). In a previous paper Information Systems, DATABASE MANAGEMENT, Logical Design, Data models. Theory of Computation, MATHEMATICAL LOGIC AND FORMAL LANGUAGES, Grammars and Other Rewriting Systems, Parsing. Information Systems, DATABASE MANAGEMENT, Systems. Information Systems, DATABASE MANAGEMENT, Languages, Data manipulation languages (DML). Mathematics of Computing, DISCRETE MATHEMATICS, Graph Theory, Trees. G.2.2 Mathematics of Computing, DISCRETE MATHEMATICS, Graph Theory, Trees. H.2.4 Information Systems, DATABASE MANAGEMENT, Systems. H.2.1 Information Systems, DATABASE MANAGEMENT, Logical Design, Data models. F.4.2 Theory of Computation, MATHEMATICAL LOGIC AND FORMAL LANGUAGES, Grammars and Other Rewriting Systems, Parsing. H.2.3 Information Systems, DATABASE MANAGEMENT, Languages, Data manipulation languages (DML).