APPLICATION OF SQL/N AND ASSOCIATION MODES TO DATA BASES CONTAINING RECURSIVE ASSOCIATIONS
Modes of association are defined for the recursive associations that occur in bill of materials data bases and data bases for the family tree of corporations. It is shown that a series of useful modes may be defined. Modes of association may be schema defined to enable a relational data base system capture more meaning about an association. When used with natural quantifiers and SQL/N, an upward-compatible extension of SQL, they permit construction of concise expressions for complex retrievals involving explosions and implosions of entities described in the data base. A mode of association is a set of propositions, each describing a pair of associated entities.