To ensure the success of the semantic web, structures that are implemented, usually ontologies, should maintain their validity well into the future. These ontologies can be very extensive, introducing the problem that only parts (sub-ontologies) of them are needed by applications. A number of rules were established to get from such a base ontology to a derived subontology. This paper explores these rules in a practical way, by giving a realworld scenario, and following it through from initial state to target ontology design. Each step and rule is applied to the scenario, and so the more practical side of the theoretical rules and steps is shown.