Abstract
We revisit the notion of deep equality among objects in an object database from a formal point of view. We present three natural formalizations of deep equality: one based on the infinite value-trees associated with objects, one based on the greatest fixpoint of an operator on equivalence relations among objects, and one based on indistinguishability of objects using observations of atomic values reachable from the objects. These three definitions are then shown to be equivalent. The characterization in terms of greatest fixpoints also yields a polynomial-time algorithm for checking deep equality. We also study the expressibility of deep equality in deductive database languages.
Work performed while on leave at INRIA as a research assistant of the Belgian National Fund for Scientific Research (N.F.W.O.).
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Abiteboul, S., Van den Bussche, J. (1995). Deep equality revisited. In: Ling, T.W., Mendelzon, A.O., Vieille, L. (eds) Deductive and Object-Oriented Databases. DOOD 1995. Lecture Notes in Computer Science, vol 1013. Springer, Berlin, Heidelberg. https://doi.org/10.1007/3-540-60608-4_42
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DOI: https://doi.org/10.1007/3-540-60608-4_42
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