Ontologies are a formal tool for expressing knowledge. They are based on providing a logic theory about some selected universe of discourse, which defines a decomposition of a topic of interest into its basic elements and formally describes certain restrictions and constraints that need to be met. In the modern days, users cannot expect that ontologies in their initial states will be resistant to changes and remain static throughout the lifespan of their particular application. In this paper we want to focus on expressing alterations, that can be applied to ontologies in time, due to changing business requirements, emerging new knowledge or modification of the scope that an ontology needs to cover.