Hierarchies in Dependence Logic

  • Authors:
  • Arnaud Durand;Juha Kontinen

  • Affiliations:
  • Université Paris Diderot;University of Helsinki

  • Venue:
  • ACM Transactions on Computational Logic (TOCL)
  • Year:
  • 2012

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Abstract

We study fragments D(k∀) and D(k-dep) of dependence logic defined either by restricting the number k of universal quantifiers or the width of dependence atoms in formulas. We find the sublogics of existential second-order logic corresponding to these fragments of dependence logic. We also show that, for any fixed signature, the fragments D(k∀) give rise to an infinite hierarchy with respect to expressive power. On the other hand, for the fragments D(k-dep), a hierarchy theorem is otained only in the case the signature is also allowed to vary. For any fixed signature, this question is open and is related to the so-called Spectrum Arity Hierarchy Conjecture.