A conceptual graph (CG) is a notation for logic based on the existential graphs of Charles Sanders Peirce and the semantic networks of artificial intelligence. In the first published paper on conceptual graphs, John F. Sowa used them to represent the conceptual schemas used in database systems. His first book applied them to a wide range of topics in artificial intelligence, computer science, and cognitive science. A linear notation, called the "Conceptual Graph Interchange Format (CGIF)", has been standardized in the ISO standard for Common Logic.