Notation primer

Graffoo, a Graphical Framework for OWL Ontologies, is an open source tool that can be used to present the classes, properties and restrictions within OWL ontologies, or sub-sections of them, as clear and easy-to-understand diagrams. In sum, yellow rounded boxes denote classes, blue and green arrows are object and datatype properties respectively, purple circles denote individuals, and green polygons are datatypes.

For more info on the Graffoo notation, please find the illustration below from this link.