Syntax and semantics in a word-sequence recognition system

A recognizer of meaningful sequences of isolated words spoken in the Italian language is presented. The system has been designed in a modular fashion and the current version has been obtained by adding the syntactic and semantic levels to the isolated-word recognizer previously developed by the same authors. The lexical, syntactic and semantic levels are integrated into a hierarchical knowledge source represented by a transition network grammar. The parsing is directed by the control unit and is performed by means of a combined strategy of bottom-up and top-down techniques, using a modified version of the Earley algorithm. Lexical hypotheses are verified at the phonemic level assigning them a score based on a distance measure evaluated by an error-correcting parsing algorithm. The protocol used in the preliminary experiments is a robot command language.