We introduce the concept of unavoidability of languages with respect to a language class; this means that every language of the given class shares at least some word with the unavoidable language. Several examples of such unavoidabilities are presented. The most interesting one is that the set of primitive words is unavoidable for context-free languages that are not linear. 1 The Language of Pr...

Group work context involves many more elements than individual work context. Few researchers have tried to identify context for groupware systems. However, such models are limited to certain kind of contextual information such as location, while others more relevant for group-work are neglected. From a review of the work done in groupware, we discuss three main components for considering contex...

This paper investigates adapting a lexicalized probabilistic context-free grammar (PCFG) to a novel domain, using maximum a posteriori (MAP) estimation. The MAP framework is general enough to include some previous model adaptation approaches, such as corpus mixing in Gildea (2001), for example. Other approaches falling within this framework are more effective. In contrast to the results in Gild...

Context aware systems reduce the need for user intervention and provide smarter services by considering a user’s situation. Context models decide how the contextual information is modeled and what type of context should be considered; they are essential in providing the “right” services to the users. Existing surveys of context-aware systems focus heavily on the data structures for modeling con...

This paper introduces adaptor grammars, a class of probabilistic models of language that generalize probabilistic context-free grammars (PCFGs). Adaptor grammars augment the probabilistic rules of PCFGs with “adaptors” that can induce dependencies among successive uses. With a particular choice of adaptor, based on the Pitman-Yor process, nonparametric Bayesian models of language using Dirichle...

We propose the design of deterministic constituent parsers that choose parser actions according to the probabilities of parses of a given probabilistic context-free grammar. Several variants are presented. One of these deterministically constructs a parse structure while postponing commitment to labels. We investigate theoretical time complexities and report experiments.

Propagating scattered context grammars, introduced in [3], represent an important type of semi-parallel rewriting systems. Since their introduction, however, the exact relationship of the family of languages they generate to the family of context-sensitive languages is unknown. The language family generated by these grammars is included in the family of context-sensitive languages; on the other...

We present a hierarchical chunk-to-string translation model, which can be seen as a compromise between the hierarchical phrasebased model and the tree-to-string model, to combine the merits of the two models. With the help of shallow parsing, our model learns rules consisting of words and chunks and meanwhile introduce syntax cohesion. Under the weighed synchronous context-free grammar defined ...