There are numerous modeling languages, each with special characteristics. We are using a knowledge representation tool called LOOM. Our model is a network of concepts and relations, connected to one another with links that show a concept's definition and its subsumption (IS-A) relationship to other concepts.
This kind of model is controversial; there is a high start-up cost, while the design of the concepts and relations is as much art as science. Some semantic models are good, some are bad. Many people think that such models are just fancy forms of data-bases. We will try to address all these issues.