${\sc np-spec}$
is a logic-based executable specification language developed primarily by Marco Cadoli, with the collaboration of these and other authors. This paper describes, by means of several examples, the core language of
${\sc np-spec}$
, along with its semantics and expressive power. Finally, we briefly discuss the translation of
${\sc np-spec}$
specifications into SAT formulae, which provides an efficient implementation of its execution engine.
