Cochrane, Roberta J.Mark, LeoContext-free grammars provide the basis for many useful tools such as parsergenerators, compiler-compilers and syntax-directed editors. This paper demonstrates the potential benefits obtained when context-free grammars are used to define complex objects in the relational model. The grammar formalism facilitates relational queries on the hierarchical structure of these objects and promotes the use of grammar-based tools as front ends to relational database systems.en-USadvanced application data modelsquery languagescomplex objectsdatabasesdata structuresManufacturing SystemsTechnical Report