Diagrams can be an effective means of communicating complex ideas and can aid ontology engineering. Indeed, domain experts often do not have the expertise required to understand or create the complex logical statements of an ontology in description logic (DL). This paper presents a visualisation method, concept diagrams, geared toward expressing assertions and class expression axioms alongside providing support for literals, datatypes and data properties. Property diagrams are introduced, targeted at object property and data property expression axioms. We demonstrate that concept diagrams and property diagrams provide a large coverage of OWL 2 axioms and are, thus, closely aligned in expressive power.