Abstract
Ontology matching and alignment is a key mechanism for linking the diverse datasets and ontologies arising in the Semantic Web. We show that category theory provides the powerful abstractions needed for a uniform treatment at various levels: semantics, language design, reasoning and tools. The Distributed Ontology Language DOL is extended in a natural way with constructs for networks of ontologies. We in particular show how the three semantics of Zimmermann and Euzenat can be uniformly and faithfully represented using these DOL language constructs. Finally, we summarise how the DOL alignment features are currently being implemented in the Ontohub/ Hets ecosystem, including support for the OWL and Alignment APIs.