Determining when a structure is a nested relation
Patrick C. Fischer, Dirk Van Gucht · Very Large Data Bases · 1985
Unnormalized relations permit components of tuples to be relation instances themselves instead of atomic values. Such structures do not always represent the restructuring of a flat (1NF) relation. It is shown that for one-level structures (nesting is permitted only over sets of attributes) there is a polynomial time algorithm to determine whether the structure is the result of restructuring a flat relation with a sequence of NEST operations.