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We extend Angluin's (1980) theorem to characterize identiiability of indexed families of r.e. languages, as opposed to indexed families of recursive languages. We also prove some variants characterizing conservativity a n d t wo other similar restrictions, paralleling Zeug-mann, Lange, and Kapur's (1992, 1995) results for indexed families of recursive(More)
We show that the problems of parsing and surface realization for grammar formalisms with " context-free " derivations, coupled with Mon-tague semantics (under a certain restriction) can be reduced in a uniform way to Datalog query evaluation. As well as giving a polynomial-time algorithm for computing all derivation trees (in the form of a shared forest)(More)
Families of Abstract Categorial Languages Abstract We show that the class of string languages generated by abstract categorial grammars is a substitution-closed full AFL. The result also holds of each class G(m, n) in de Groote's hierarchy. We also show that the class of string languages generated by lexicalized ACGs is a substitution-closed AFL, and that(More)
1 Multiple context-free grammars yield = tuple of strings derivation tree S A B a m b n c m d n b n d n c m a m S(x 1 y 1 x 2 y 2) :! A(x 1 , x 2),B(y 1 , y 2). A(","). A(ax 1 ,cx 2) :! A(x 1 , x 2). MCFGs have the same kind of derivation tree as CFGs, but the object produced by a derivation tree is a tuple of strings, rather than a string. A nonterminal is(More)
Second-order abstract categorial grammars (de Groote 2001) and hyperedge replacement grammars (see Engelfriet 1997) are two natural ways of generalizing " context-free " grammar formalisms for string and tree languages. It is known that the string generating power of both formalisms is equivalent to (non-erasing) multiple context-free grammars (Seki et al.(More)