1. Introduction

This paper describes NUSMV, a new symbolic model checker developed as a joint project between Carnegie Mellon University (CMU) and Istituto per la Ricerca Scientifica e Tecnolgica (IRST). NUSMV is designed to be a well structured, open, flexible and documented platform for model checking. In order to make NUSMV applicable in technology transfer projects, it was designed to be very robust, close to the standards required by industry, and to allow for expressive specification languages.

NUSMV is the result of the reengineering, reimplementation and extension of SMV [6], version 2.4.4 (SMV from now on). With respect to SMV, NUSMV has been extended and upgraded along three dimensions. First, from the point of view of the system functionalities, NUSMV features a textual interaction shell and a graphical interface, extended model partitioning techniques, and allows for LTL model checking. Second, the system architecture of NUSMV has been designed to be highly modular and open. The interdependencies between different modules have been separated, and an external, state of the art BDD package [8] has been integrated in the system kernel. Third, the quality of the implementation has been strongly enhanced. This makes of NUSMV a robust, maintainable and well documented system, with a relatively easy to modify source code. NUSMV is available at http://nusmv.irst.itc.it/.