Comments are welcome.
I consider the semantic network formalism due to R. Brachman and the system of existential graph due to C. S. Peirce. The semantic networks of Brachman are very weak. Not all the information expressible in a terminological language can be represented as a semantic network. By contrast, the system of Peirce is very powerful. I show how any information expressed in any terminological language can be transformed and displayed as an existential graph and propose that existential graphs be used to complement the semantic network representations.