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Abstract machine for \(\mathcal{L}\mathcal{D}\mathcal{L}\)

  • Danette Chimenti
  • Ruben Gamboa
  • Ravi Krishnamurthy
Session 4: Deductive Database Systems
Part of the Lecture Notes in Computer Science book series (LNCS, volume 416)

Abstract

We propose an abstract machine for \(\mathcal{L}\mathcal{D}\mathcal{L}\) that maintains a high-level view of an \(\mathcal{L}\mathcal{D}\mathcal{L}\) program while incorporating aspects of its execution that make a performance difference. A canonical AND/OR graph corresponding to the \(\mathcal{L}\mathcal{D}\mathcal{L}\) program provides the skeleton of its execution. The nodes in the AND/OR graph are annotated to specify relevant details of the execution, such as access methods, join methods, execution strategies, intelligent backtracking etc. We formalize four execution methods (top-down, bottom-up as well as two hybrid methods that incorporate memoing) and two recursive computations (fixpoint and stack-based). The two computations and four execution methods are combined to cater to a rich variety of recursive techniques. This annotated AND/OR graph represents a declarative program for the abstract machine. The set of all possible annotated AND/OR graphs constitutes the execution space that defines the abstract machine.

To prove the feasibility of this declarative abstract machine, we demonstrate an actual realization by presenting a code generation algorithm that proceeds by translating each node in the annotated AND/OR graph into a sequence of imperative statements that include calls to a tuple-level interface of an underlying DBMS. The \(\mathcal{L}\mathcal{D}\mathcal{L}\) compiler — which supports Datalog, sets, updates, negation, non-deterministic choice and other advanced features — has been implemented using this approach.

Keywords

Abstract Machine Query Form Success Point Node Table Execution Method 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag Berlin Heidelberg 1990

Authors and Affiliations

  • Danette Chimenti
    • 1
  • Ruben Gamboa
    • 1
  • Ravi Krishnamurthy
    • 1
  1. 1.MCC, 3500 West Balcones Center DriveAustin

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