As an abbreviation, the arguments required for the input and output lists are not written explicitly in a grammar rule, but are added when the rule is translated into an ordinary Prolog clause. In this section we informally describe this translation, which resembles the DCG rules of other Prologs in most particulars. Each grammar rule is translated into a Prolog clause as it is consulted or compiled. Extra conditions expressed as explicit procedure calls naturally translate into themselves. Similarly, a cut is translated literally.
Disjunction has a fairly obvious translation.