In some computer applications of linguistics (such as maximum-likelihood decoding of speech or handwriting), the purpose of the language-handling component (Language Model) is to estimate the linguistic (a priori) probability of arbitrary natural-language sentences. This paper discusses theoretical and practical issues regarding an approach to building such a language model based on any equivalence criterion defined on incomplete sentences, and experimental results and measurements performed on such a model of the Italian language, which is a part of the prototype for the recognition of spoken Italian built at the IBM Rome Scintific Center. .