Ontology engineering, universal algebra, and category theory

In this chapter we review a category theoretic approach to ontology engineering. Using ideas from universal algebra, we carefully distinguish presentations of ontologies from the ontologies themselves. This leads to a precise notion of view, and views can be used both to create new ontologies incorporating existing ontologies while recognising their common classes and relations, and to develop interoperating ontologies. Interoperating ontologies are separate but linked ontologies with the property that systems developed under each ontology can interoperate without changing the system and with only a small amount of front-end interoperations code.