A Bayesian network (or a belief network ) is a probabilistic graphical model that represents a set of variables and their probabilistic independencies. For example, a Bayesian network could represent the probabilistic relationships between diseases and symptoms. Given symptoms, the network can be used to compute the probabilities of the presence of various diseases.
http://en.wikipedia.org/wiki/Bayesian_network
3
WordNet® is a large lexical database of English, developed under the direction of George A. Miller . Nouns, verbs, adjectives and adverbs are grouped into sets of cognitive synonyms (synsets), each expressing a distinct concept. Synsets are interlinked by means of conceptual-semantic and lexical relations. The resulting network of meaningfully related words and concepts can be navigated with the browser.
http://wordnet.princeton.edu/
7