Automated Query Formulation Using an Entity–Relationship Conceptual Schema

  • Authors:

  • Ralph D. Semmel;James Mayfield

  • Affiliations:

  • The Johns Hopkins University Applied Physics Laboratory. E-mail: ralph.semmel@jhuapl.edu;University of Maryland Baltimore County. E-mail: mayfield@cs.umbc.edu

  • Venue:
  • Journal of Intelligent Information Systems
  • Year:
  • 1997

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Abstract

Significant effort is expended in developing a high–level conceptual schema for a relational database. However, criticalknowledge is often discarded when the conceptual schema is mapped to aset of relation schemas. As a result, designers and users must employsparser logical–level knowledge to access data. Unfortunately, naiveusers do not possess the detailed logical–level knowledge required toformulate queries corresponding to ad hoc requests. Auniversal relation interface can shield users from underlyingdesign details. However, most universal relation systems have beenbased on abstractions not typically used by database designers.Consequently, the usefulness of these interfaces has been limited.This article demonstrates how an Entity–Relationship (ER) conceptualschema can be used by a high–level interface to formulate queriesautomatically. The notion of contextsis introduced to describethe segmentation of an ER conceptual schema into overlapping subgraphsthat correspond to sets of relations that can be joined in a losslessmanner. Given a set of contexts, natural join query formulation isstraightforward. As demonstrated with a case study using theprototype QUICK system, the techniques presented facilitate theconstruction of high–level, intelligent interfaces.