  The recognition problem for attribute-value grammars (AVGs) was shown to be
undecidable by Johnson in 1988. Therefore, the general form of AVGs is of no
practical use. In this paper we study a very restricted form of AVG, for which
the recognition problem is decidable (though still NP-complete), the R-AVG. We
show that the R-AVG formalism captures all of the context free languages and
more, and introduce a variation on the so-called `off-line parsability
constraint', the `honest parsability constraint', which lets different types of
R-AVG coincide precisely with well-known time complexity classes.
