Moreover, our parser presupposes a restricted inventory of fragments in the grammar (the ones allowed by an ITSG) as opposed to the general CFG rules allowed by the Earley algorithm.
the Backward Substitution operation is more limited than the corresponding Prediction step of the Earley algorithm: only lex-first fragments can be introduced using Backward Substitution, and therefore left recursion (allowed by the Earley algorithm) is not pos-sible here.