,
Leroy Chew
,
Vaibhav Krishan
,
Anil Shukla
Creative Commons Attribution 4.0 International license
For a quantified Boolean formula (QBF), the problem of computing the number of winning strategies is known as the #QBF problem. This problem is considered harder than the analogous #SAT problem. Recently, important proof systems for QBFs and #SAT have been studied. By extending the ideas from both fields, we show that it is possible to design proof systems for #QBF. Such proof systems are important not only for advancing the theory of #QBF but also for certifying and designing better #QBF solvers, an area that is still in its early stages. In this paper, we explore #QBF proof systems to count the number of Skolem functions. In addition to a naive system, we study #QBF systems based on the ∀-expansion rule of QBFs. We observe that these systems have inherent structural weaknesses that lead to lower bounds. As an alternative, we propose a #QBF proof system that we call Q-MICE, which consists of sound inference rules for computing and certifying the #QBF solution, similar to the line-based #SAT proof system MICE. To demonstrate the strength of Q-MICE, we present various upper bounds, such as the quantified version of the propositional XOR-PAIRS formula, which are known to be hard for MICE. Consequently, we also separate Q-MICE from ∀-expansion based #QBF proof systems.
@InProceedings{chede_et_al:LIPIcs.SAT.2026.32,
author = {Chede, Sravanthi and Chew, Leroy and Krishan, Vaibhav and Shukla, Anil},
title = {{On Proof Systems for #QBF}},
booktitle = {29th International Conference on Theory and Applications of Satisfiability Testing (SAT 2026)},
pages = {32:1--32:12},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-431-4},
ISSN = {1868-8969},
year = {2026},
volume = {377},
editor = {Ignatiev, Alexey and Szeider, Stefan},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.SAT.2026.32},
URN = {urn:nbn:de:0030-drops-263380},
doi = {10.4230/LIPIcs.SAT.2026.32},
annote = {Keywords: QBF, Model Counting, Proof Systems, #QBF}
}