This paper describes the application of a new model to learn probabilistic context-free grammars (PCFGs) from a tree bank corpus. The model estimates the probabilities according to a generalized -gram scheme for trees. It allows for faster parsing, decreases considerably the perplexity of the test samples and tends to give more structured and refined parses. In addition, it also allows several ...

The simultaneously phonological and syntactic grammar of second position clitics is an instance of the broader problem of applying constraints across multiple levels of linguistic analysis. Syntax frameworks extended with simple tree transductions can make efficient use of these necessary additional forms of structure. An analysis of Sahidic Coptic second position clitics in a context-free gram...

In this paper we prove the Chomsky Conjecture (all languages recognized by the Lambek calculus are context-free) for both the full Lambek calculus and its product-free fragment. For the latter case we present a construction of context-free grammars involving only product-free types.

We develop a new method for placing a given context-free grammar into Greibach normal form with only polynomial increase of its size. Starting with an arbitrary "-free context-free grammar G, we transform G into an equivalent context-free grammar H in extended Greibach normal form; i.e., in addition to rules, fulllling the Greibach normal form properties, the grammar can have chain rules. The s...

We present a method for automatic program inversion of functional programs based on methods of LR parsing. We formalize the transformation and illustrate it with the inversion of a program for runlength encoding. We solve one of the main problems of automatic program inversion—the elimination of nondeterminism—by viewing an inverse program as a context-free grammar and applying to it methods of...

Current context-aware services make the assumption that the context they are dealing with is correct. However, in reality, both sensed and interpreted context is often imperfect. In this paper, we describe an architecture that supports the building of context-aware services that assume context is imperfect and allows for the refinement of this imperfect context by mobile users in aware-environm...

The way we represent intentions, behaviors, and the spatial context, is crucial for any approach to mobile intention recognition. Formal grammars are cognitively comprehensible and make expressiveness properties explicit. By adding spatial domain knowledge to a grammar we can reduce parsing ambiguities. We argue that there are a number of mobile intention recognition problems which require the ...

Lambek [13] introduces pregroups as a new framework for syntactic structure. In this paper we prove some new theorems on pregroups and study grammars based on the calculus of free pregroups. We prove that these grammars are equivalent to context-free grammars. We also discuss the relation of pregroups to the Lambek calculus.