GraphLog: a visual formalism for real life recursion

  • Authors:

  • Mariano P. Consens;Alberto O. Mendelzon

  • Affiliations:

  • Computer Systems Research Institute, University of Toronto, Toronto, Canada M5S 1A4;Computer Systems Research Institute, University of Toronto, Toronto, Canada M5S 1A4

  • Venue:
  • PODS '90 Proceedings of the ninth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
  • Year:
  • 1990

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Abstract

We present a query language called GraphLog, based on a graph representation of both data and queries. Queries are graph patterns. Edges in queries represent edges or paths in the database. Regular expressions are used to qualify these paths. We characterize the expressive power of the language and show that it is equivalent to stratified linear Datalog, first order logic with transitive closure, and non-deterministic logarithmic space (assuming ordering on the domain). The fact that the latter three classes coincide was not previously known. We show how GraphLog can be extended to incorporate aggregates and path summarization, and describe briefly our current prototype implementation.