AbstractIn this work, we consider the adoption of an OWL 2 ontology for the representation and management of time-varying knowledge. The W3C OWL 2 recommendation lacks explicit support for time-varying OWL ontologies. In previous work, we introduced τOWL which is an infrastructure and suite of tools to support the creation and validation of OWL ontologies with time-varying instances. In this paper, we extend τOWL to also support temporal versioning of the ontology schema. Schema versioning in the τOWL framework means that all the three components of a τOWL schema (i.e. conventional schema, logical and physical annotations) are versioned. In particular, we propose two complete sets of primitives, one for updating the conventional ontology schema and the other for managing the temporal ontology schema, and define their operational semantics. We also illustrate their use, through an example.