A universal relation database system implemented via the network model

Abstract

We describe a network schema design algorithm that uses a well-designed relational schema as input. The resulting network database handles incomplete information, since we use only the modified foreign-key constraint and not the universal instance assumption. We believe that the repreaentative instance is a correct representation of information stored in the database. We show how to map the representative instance to the network database. We give two algorithms for translating a relational query to a network application program. The first algorithm is confined to relational queries that express selections and projections over the universal relation scheme. The second algorithm includes all relational queries over select, project and (natural) join. Optimization techniques are discussed for both types of trans'lation.

Database states and their tableaux

“…Our notion of equivalence makes abstraction of which relations are actually stored, and we assume this information is not visible to the user. The user interface is instead a universal relation scheme (as in [2,13,19,21]), and QR is interpreted as the projection of this scheme on R. If we were willing to accept the pure universal relation assumption, then Qs could be obtained by simply projecting the appropriate universal relation on R. Instead, under the weak instance model, we are representing a set of possible universal relations rather than a single one. Conceptually, a correct answer to QR is then the result of projecting on R each one of the infinitely many weak instances for the state and then intersecting all such projections.…”

A Universal Relation Approach For Natural Query In Logic Database System

“…In this section, we will discussed the concept of universal relation and demonstrate how it may be used as an interface in an attempt to offer the users a new version of query called a natural query. A lot of research have been conducted on the application of universal relation assumptions to relational database system [Fagin 1982, Kent 1981, Kuck 1982, Maier 1984, Ullman 1989]. There are positive and negative issues such as described in [Kent 1981, Brady 1985].…”

“…The universal relation model is first introduced as a means to free the users fnom the need to know the logical navigation of the database. The major objective is to achieve complete access-path independence, whereby data retrieval only requires the names of the attributes [Maier 1984, Ullman 1989, Korh 1984, Brady 1985, Kent 1981, Maier 1983b, Fagin 1982, Kuck 1982, Beeri 1982, ]. There are positive and negative views on the assumptions [Codd 1990a, Kent 1981].…”