Previous research on materialized views has primarily been in the context of flat relational databases-materialized views defined in terms of one or more flat relations.This paper discusses a broader class of view definitions-materialized views defined over a nested data model such as the nested relational model or an object-oriented data model An attibute of a tuple deriving the view cna be a reference (i.e.,a pointer) to a nested relation,with arbitrary levels of nesting ppossible.the extended capability of this netsed data modle,together with materialized views,simplifies dat amodelling and gives more flexibility.
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