Understanding OWL/XML structure is essential because implementations vary significantly. Some developers fully embed upper ontologies (like BFO) into their domain ontologies, altering or even destroying the overall structure. Others reference upper ontology classes only through annotations, maintaining clearer separation. This appendix presents one coherent approach whilst acknowledging that alternative structures exist.
Note that only the first and last components are fixed in their positions. Apart from these, a completely randomised sequence of OWL lexemes is also syntactically acceptable (although it is not customary to publish a domain ontology in this way). The generally accepted and usual structure is as follows: Read what interests you, skip what doesn't :)