Context-free grammars are widely used for the simple form of their rules. A derivation step consists of the choice of a nonterminal of the sentential form and of an application of a rule rewriting it. Several regulations of the derivation process have been studied to increase the power of context-free grammars. In the resulting grammars, however, not only the symbols to be rewritten are restric...

Latent-variable probabilistic context-free grammars are latent-variable models that are based on context-free grammars. Nonterminals are associated with latent states that provide contextual information during the top-down rewriting process of the grammar. We survey a few of the techniques used to estimate such grammars and to parse text with them. We also give an overview of what the latent st...

In this paper, we present techniques for characterizing complex, multi-tasked activities that require both exemplars and models. Exemplars are used to represent object context, image features, and motion appearances to label domainspecific events. Then, by representing each event with a unique symbol, a sequence of interactions can be described as an ordered symbolic string. A model of stochast...

We develop a language model using probabilistic context-free grammars (PCFGs) that is “pseudo context-sensitive” in that the probability that a nonterminal N expands using a rule T depends on N’s parent. We give the equations for estimating the necessary probabilities using a variant of the inside-outside algorithm. We give experimental results showing that, beginning with a high-performance PC...

In the present paper a generalization of ZX(A:)-grammars is given, the notion of the switching function for such grammars is introduced and the model of the Parsing Machine using the switch­ ing function is given. We introduce the necessary notions and notation, mainly according to D. E. Knuth: An alphabet X is a finite nonempty set of symbols, and X* denotes the set of all strings on the alpha...

We present Expressionist, an authoring tool for in-game text generation that combines the raw generative power of context-free grammars (CFGs) with the expressive power of free-text markup. Specifically, authors use the tool to define CFGs whose nonterminal symbols may be annotated using arbitrary author-defined tagsets. Any content generated by the CFG comes packaged with explicit metadata in ...

We continue the investigation of delay games, infinite games in which one player may postpone her moves for some time to obtain a lookahead on her opponent’s moves. We show that the problem of determining the winner of such a game is undecidable for deterministic context-free winning conditions. Furthermore, we show that the necessary lookahead to win a deterministic context-free delay game can...

Collage grammars generate picture languages in a context-free way. The generating process is based on the replacement of atomic nonterminal items and can be seen as an adaptation of the notion of hyperedge replacement known from the area of context-free graph generation. While a pumping lemma holds for hyperedge replacement graph grammars and is quite useful to show that certain graph languages...

This paper describes a system that performs hierarchical error repair for illformed sentences, with heterarchical control of chart items produced at the lexical, syntactic, and semantic levels. The system uses an augmented context-free grammar and employs a bidirectional chart parsing algorithm. The system is composed of four subsystems: for lexical, syntactic, surface case, and semantic proces...

The close relationship between Petri nets and language theory has been extensively studied for a long time [1, 2]. Results from the theory of Petri nets have been applied successfully to provide elegant solutions to complicated problems from language theory [4, 7]. A context-free grammar can be associated with a context-free (communica-tion-free) Petri net, whose places and transitions, corresp...