To model an OWL-2 ontology, the World Wide Web Consortium (W3C) recommends the use of the following five concrete syntax: Manchester, functional, RDF/XML, OWL/XML and Turtle. All of these syntax have the characteristic of being textual. It is accepted in cognitive science that the use of notation based on visual syntax is also a form of symbolization of thought that facilitates the expression of knowledge held by the modeler in addition to being a form of communication that facilitates the conceptualization of a message interpreted by a reader. This talk will present the Graphical Ontology Web Language (G-OWL) a visual syntax for OWL-2 ontology modeling for the semantic web. In addition to presenting the main language elements of G-OWL, we will discuss the cognitive principles of visual notation design that are the principles of: Semiotic Clarity, Perceptual Discriminability, Perceptual Immediacy, Visual Expressiveness and which are at the foundation of G-OWL design. The presentation of the principles will be supported by the demonstration of concrete cases presented in G-OWL compared to other visual notations in use.