Hootation: A GUI and API library for ontology validation and verbalization

Ontology verbalization refers to the process of translating formal axioms into natural language expressions. The primary objective is to facilitate the review and validation of ontology content by subject matter experts without requiring extensive technical expertise. While previous approaches based on templates or controlled grammar have been effective, they often face limitations in scalability, fluency, and adaptability. To address these issues, we developed Hootation, an open-source software system that supports ontology verbalization through both a graphical user interface and an API library. The tool implements rule-based translation of OWL2 axioms and further incorporates optional Large Language Model (LLM) components for refinement and fact-checking. Hootation allows users to export results for review in common formats such as CSV and Excel. We conducted a usability evaluation using the System Usability Scale (SUS) and achieved an average score of 78.89(S D=10.39), which reflects strong ratings and good usability. A one-sample t-test showed that this score was significantly higher than the standard benchmark of 68 (p=0.014). These results suggest that Hootation can support ontology engineers and domain experts by providing a practical and user-friendly environment for ontology validation and exploration.