AN EXTENDED SQL AND QBE WITH SEAMLESS INCORPORATION OF GENITIVE RELATION AND NATURAL QUANTIFIER CONSTRUCTS

Abstract

An extended SQL, called E-SQL, is described, for use with an extended relational data model. The data model allows for restricted unnormalized relations; sets or lists of atomic attributes are allowed but not attributes that are relations, and there is support for both inheritance and composite entities. E-SQL permits the constructs of conventional SQL, but also permits use of genitive relations to model containment relationships and facilitate application of natural quantifiers to containment sets. A genitive relation is a relation that is the equivalent to the genitive case grammatical construct in natural language. The genitive relation construct and the conventional constructs of SQL can be mixed in a seamless manner. For example, the condition within a conventional SQL-IN-construct could contain a condition that is a quantified genitive relational condition, and vice versa. Use of conditions that involve comparison of a quantified genitive relation with a quantified base table is also permitted. E-SQL can also manipulate a set of composite entity instances modelled as a group of relations. E-SQL is essentially a seamless merger of conventional SQL and an experimental genitive relation language, called COOL, designed for efficient manipulation of containment sets. It is shown that an Extended Relational Algebra (ERA) can be used to reduce E-SQL expressions. E-SQL expressions are much more concise and much less error-prone than conventional SQL expressions. It is also shown how the quantified genitive relation concept can be used in an extension of the graphical query language QBE that greatly increases both its retrieval power and simplicity of use.