The Functional Data Model as the Basis for an Enriched Database Query Language

  • Authors:

  • Robert Ayres

  • Affiliations:

  • Department of Informatics and Simulation, Cranfield University, Royal Military College of Science, Shrivenham, Swindon, Wiltshire SN6 8LA, UK. r.ayres@rmcs.cranfield.ac.uk

  • Venue:
  • Journal of Intelligent Information Systems - Special issue on functional approach to intelligent information systems
  • Year:
  • 1999

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Abstract

Conventional database languages rely on the userspecifying what relations are to be used when evaluatinga query. Consequently they preclude queries which involvesearching for unspecified connections or associations inthe database. In this paper we present Hydra, a functionallanguage with all the facilities to define, update andquery a database, which also enables users to carry out“associational” queries. Hydra uses a graph-based data model in which nodesrepresent values or entities and arcs the relationshipsbetween them. Associational facilities are made possibleby the provision of built-in functions which find pathsthrough the database graph.The mappings between sets of nodes in the database graphare represented as functions at the Hydra language leveland it is as lists of such functions that associationalresults are returned. The use of a functional language is important since suchlanguages allow functions to be returned as results; suchan approach could not be adopted in alogic-based language which would not permit predicates tobe returned as answers.Hydra also allows users to define general computationalfunctions which are not considered to form part of thedatabase. This use of two sets of functions achieves acomputationally complete system which extends the querypower of previous database systems without compromisingtheir expressive or query power.