What problem does it solve? Modeling a domain semantically is error-prone: the Open-World Assumption, inferential domain/range semantics, and OWL 2 profile trade-offs trip up even experienced engineers. This Skill guides the design of well-formed, reusable, reasoner-friendly ontologies and controlled vocabularies that validate consistently. ## Core Features & Use Cases - Ontology & Taxonomy Modeling: Define classes, object/datatype properties, axioms, restrictions, and cardinality in RDFS and OWL 2. - Vocabulary Reuse: Extend standard vocabularies like schema.org, SKOS, Dublin Core, and FOAF instead of minting redundant IRIs. - Profile Selection & Validation: Choose the right OWL 2 profile (EL/QL/RL) and validate consistency with Protégé and reasoners like HermiT, Pellet, or ELK. - Use Case: When asked to build a domain model for a knowledge graph, produce competency questions, a Turtle-serialized model with proper disjointness and cardinality axioms, and a reasoner-verified class hierarchy. ## Quick Start Use the ontology skill to design an OWL 2 ontology for a university domain with classes, properties, and competency questions, serialized in Turtle.