Normalized Web Distance and Word Similarity Paul M.B. Vitányi and Rudi L. Cilibrasi

Objects can be given literally, like the literal four-letter genome of a mouse, or the literal text of War and Peace by Tolstoy. For simplicity, we take it that all meaning of the object is represented by the literal object itself. Objects can also be given by name, like “the four-letter genome of a mouse,” or “the text of War and Peace by Tolstoy.” There are also objects that cannot be given literally, but only by name, and that acquire their meaning from their contexts in background common knowledge in humankind, like “home” or “red.”