AN EXTENDED SQL AND QBE WITH SEAMLESS INCORPORATION OF GENITIVE RELATION AND NATURAL QUANTIFIER CONSTRUCTS
Date
1996-12-01
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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.
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Computer Science