VEL: A Formally Verified Reasoner for OWL2 EL Profile
This addresses reliability issues in high-stakes domains like healthcare by providing a verified tool for ontology reasoning, though it is incremental as it builds on an existing algorithm.
The paper tackled the problem of unreliable deductive reasoning in OWL2 EL ontologies by developing VEL, a formally verified reasoner with machine-checkable proofs, which identified and corrected errors in existing completeness proofs.
Over the past two decades, the Web Ontology Language (OWL) has been instrumental in advancing the development of ontologies and knowledge graphs, providing a structured framework that enhances the semantic integration of data. However, the reliability of deductive reasoning within these systems remains challenging, as evidenced by inconsistencies among popular reasoners in recent competitions. This evidence underscores the limitations of current testing-based methodologies, particularly in high-stakes domains such as healthcare. To mitigate these issues, in this paper, we have developed VEL, a formally verified EL++ reasoner equipped with machine-checkable correctness proofs that ensure the validity of outputs across all possible inputs. This formalization, based on the algorithm of Baader et al., has been transformed into executable OCaml code using the Coq proof assistant's extraction capabilities. Our formalization revealed several errors in the original completeness proofs, which led to changes to the algorithm to ensure its completeness. Our work demonstrates the necessity of mechanization of reasoning algorithms to ensure their correctness at theoretical and implementation levels.