Testable and untestable classes of first-order formulae

  • Authors:
  • Charles Jordan;Thomas Zeugmann

  • Affiliations:
  • Division of Computer Science, Hokkaido University, N-14, W-9, Sapporo 060-0814, Japan;Division of Computer Science, Hokkaido University, N-14, W-9, Sapporo 060-0814, Japan

  • Venue:
  • Journal of Computer and System Sciences
  • Year:
  • 2012

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Abstract

In property testing, the goal is to distinguish structures that have some desired property from those that are far from having the property, based on only a small, random sample of the structure. We focus on the classification of first-order sentences according to their testability. This classification was initiated by Alon et al. (2000) [2], who showed that graph properties expressible with prefix @?^@?@?^@? are testable but that there is an untestable graph property expressible with quantifier prefix @?^@?@?^@?. The main results of the present paper are as follows. We prove that all (relational) properties expressible with quantifier prefix @?^@?@?@?^@? (Ackermann@?s class with equality) are testable and also extend the positive result of Alon et al. (2000) [2] to relational structures using a recent result by Austin and Tao (2010) [8]. Finally, we simplify the untestable property of Alon et al. (2000) [2] and show that prefixes @?^3@?, @?^2@?@?, @?@?@?^2 and @?@?@?@? can express untestable graph properties when equality is allowed.