Horn Clauses for Verification and Synthesis

Many Program Verification and Synthesis problems of interest can be modeled directly using Horn clauses and many recent advances in the CLP and CAV communities have centered around efficiently solving problems presented as Horn clauses.

This series of workshops aims to bring together researchers working in the communities of Constraint/Logic Programming (e.g., ICLP and CP), Program Verification (e.g., CAV, TACAS, and VMCAI), and Automated Deduction (e.g., CADE, IJCAR), on the topic of Horn clause based analysis, verification, and synthesis.

Horn clauses for verification and synthesis have been advocated by these communities in different times and from different perspectives and HCVS is organized to stimulate interaction and a fruitful exchange and integration of experiences.

The workshop follows previous meetings: HCVS 2025 in Zagreb, Croatia (CAV 2025), HCVS 2024 in Luxembourg (ETAPS 2024), HCVS 2023 in Paris (ETAPS 2023), HCVS 2022 in Munich (ETAPS 2022), HCVS 2021 in Luxembourg (online, ETAPS 2021), HCVS 2020 in Dublin, Ireland (ETAPS 2020), HCVS 2019 in Prague, Czech Republic (ETAPS 2019), HCVS 2018 in Oxford, UK (CAV, ICLP and IJCAR at FLoC 2018), HCVS 2017 in Gothenburg, Sweden (CADE 2017), HCVS 2016 in Eindhoven, The Netherlands (ETAPS 2016), HCVS 2015 in San Francisco, CA, USA (CAV 2015), and HCVS 2014 in Vienna, Austria (VSL).

Aims and Scope

Topics of interest include, but are not limited to the use of Horn clauses, constraints, and related formalisms in the following areas:

  • Analysis and verification of programs and systems of various kinds (e.g., imperative, object-oriented, functional, logic, higher-order, concurrent, transition systems, petri-nets, smart contracts)
  • Program synthesis
  • Program testing
  • Program transformation
  • Constraint solving
  • Type systems
  • Machine learning and automated reasoning
  • CHC encoding of analysis and verification problems
  • Resource analysis
  • Case studies and tools
  • Challenging problems
We solicit regular papers describing theory and implementation of Horn-clause based analysis and tool descriptions. We also solicit extended abstracts describing work-in-progress, as well as presentations covering previously published results that are of interest to the workshop.

Invited speakers

  • Florian Frohn (RWTH Aachen University, Germany).
    Infinite State Model Checking without Interpolation

    Most state-of-the-art model checking algorithms for infinite state systems are based on Craig Interpolation. These algorithms are very powerful, but also highly sensitive to minor changes of the input or the underlying interpolating SMT solver. In recent years, we developed several non-interpolating model checking algorithms, with the goal of making infinite state model checking more robust and predictable. Their core ingredients are loop acceleration, which is useful for finding deep counterexamples, and recurrence analysis, which is the most important building block of our techniques for proving safety / satisfiability. In this talk, I will give an overview of these non-interpolating model checking algorithms, and highlight their strengths and weaknesses.

  • Natasha Sharygina (University of Lugano, Switzerland).
    CHC-Based Reachability Analysis via Cycle Summarization

    Modern reachability analysis techniques are highly effective when applied to software safety verification. However, they still struggle with certain classes of problems, particularly the verification of programs with complex control flow and deep nested loops. In this talk, I will present Cycle Summarization-based Reachability Analysis (CSRA), a new Constrained Horn Clause (CHC)-based approach for reachability analysis of nested-loop software. Our technique relies on the generation and refinement of cycle summaries within the CHC system. CSRA analyzes cycles in a modular manner, constructing summaries and cycle unrollings. Cycle summaries in our approach are used both to prove safety and detect potential safety violations. This enables more efficient exploration of nested loops. The prototype of CSRA is implemented within the Golem CHC solver. An empirical comparison with other reachability analysis techniques demonstrates that our approach is highly competitive in both proving safety and constructing counterexamples.

Program

TBA

25 July 2026 (All times are in CEST) - Room: TBA

TBA

Program Chairs

Program Committee

  • Nikolaj Bjørner, Microsoft, USA
  • Martin Blicha, Argot Collective, Switzerland
  • Emanuele De Angelis, CNR-IASI, Italy
  • Catherine Dubois, ENSIIE-Samovar, France
  • Gidon Ernst, Ludwig Maximilian University of Munich, Germany
  • Grigory Fedyukovich, Florida State University, USA
  • Florian Frohn, RWTH Aachen University, Germany
  • Carsten Fuhs, Birkbeck, University of London, UK
  • Roberta Gori, University of Pisa, Italy
  • Hossein Hojjat, Tehran Institute for Advanced Studies, Iran
  • Bishoksan Kafle, APS, Australian Government / The University of Melbourne
  • Dale Miller, INRIA and LIX/Institut Polytechnique de Paris, France
  • David Monniaux, CNRS / VERIMAG, France
  • Jose F. Morales, IMDEA Software Research Institute, Spain
  • Gennaro Parlato, University of Molise, Italy
  • Sabina Rossi, Ca' Foscari University of Venice, Italy
  • Wim Vanhoof, University of Namur, Belgium
  • Germán Vidal, MiST, VRAIN, Polytechnic University of Valencia, Spain

Submission

Submission has to be done in one of the following formats:

  • Extended abstracts (from half to 3 pages), which describe work in progress or aim to initiate discussions.
  • Presentation-only papers, i.e., papers already submitted or presented at a conference or another workshop. Such papers can be submitted in any format, and will not be included in the workshop post-proceedings.
  • Regular papers (up to 12 pages plus bibliography in EPTCS format), which should present previously unpublished work (completed or in progress), including descriptions of research, tools, and applications.
  • Tool papers (up to 4 pages in EPTCS format), which can outline the theoretical framework, the architecture, the usage, and experiments of the tool.
All submitted papers will be refereed by the program committee and will be selected for inclusion in the program in accordance with the referee reports. At least one author of each accepted paper will be required to attend the workshop to present the contribution. If enough regular papers are accepted, both regular papers and extended abstracts will be published electronically. The publication of a paper is not intended to preclude later publication. Full versions of extended abstracts, or substantial revisions, may later be published elsewhere.

Papers must be submitted through the FLoC 2026 submission system.