Decidability and Complexity of Tree Share Formulas

Authors Xuan Bach Le, Aquinas Hobor, Anthony W. Lin

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Xuan Bach Le
Aquinas Hobor
Anthony W. Lin

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Xuan Bach Le, Aquinas Hobor, and Anthony W. Lin. Decidability and Complexity of Tree Share Formulas. In 36th IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 65, pp. 19:1-19:14, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2016)


Fractional share models are used to reason about how multiple actors share ownership of resources. We examine the decidability and complexity of reasoning over the "tree share" model of Dockins et al. using first-order logic, or fragments thereof. We pinpoint a connection between the basic operations on trees union, intersection, and complement and countable atomless Boolean algebras, allowing us to obtain decidability with the precise complexity of both first-order and existential theories over the tree share model with the aforementioned operations. We establish a connection between the multiplication operation on trees and the theory of word equations, allowing us to derive the decidability of its existential theory and the undecidability of its full first-order theory. We prove that the full first-order theory over the model with both the Boolean operations and the restricted multiplication operation (with constants on the right hand side) is decidable via an embedding to tree-automatic structures.
  • Fractional Share Models
  • Resource Accounting
  • Countable Atomless Boolean Algebras
  • Word Equations
  • Tree Automatic Structures


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