Analogy-based morphology: The Kasem number system

This paper presents a formalization of proportional analogy using typed feature structures, which retains all key elements of analogical models of morphology. With the Kasem number system as an example, I show that using this model it is possible to express partial analogies which are unified into complete analogies. The analysis presented is accompanied by a complete TRALE implementation.

The information structure of Danish grammar constructions

This paper addresses the issue of how information structure can be accounted for in a formal grammar of Danish. Three information structure features – topic, focus and background – are discussed, and it is shown how they are instantiated in a number of different grammatical constructions from a corpus of spoken Danish. Prosodic, syntactic and information structure constraints characterising the various constructions are represented as typed feature structures following Head-driven Phrase Structure Grammar (HPSG), and the constructions themselves are ordered in a type hierarchy. The proposed approach modifies and extends earlier HPSG-based accounts by integrating information structure as a dimension of phrasal and clausal grammar constructions.

Memory management for unification-based processing of typed feature structures

We consider two alternatives for memory management in typed-feature-structure-based parsers by identifying structural properties of grammar signatures that may be of some predictive value in determining the consequences of those alternatives. We define these properties, summarize the results of a number of experiments on artificially constructed signatures with respect to the relative rank of their asymptotic cost at parse-time, and experimentally consider how they impact memory management.

Feature Forest Models for Probabilistic HPSG Parsing

Probabilistic modeling of lexicalized grammars is difficult because these grammars exploit complicated data structures, such as typed feature structures. This prevents us from applying common methods of probabilistic modeling in which a complete structure is divided into sub-structures under the assumption of statistical independence among sub-structures. For example, part-of-speech tagging of a sentence is decomposed into tagging of each word, and CFG parsing is split into applications of CFG rules. These methods have relied on the structure of the target problem, namely lattices or trees, and cannot be applied to graph structures including typed feature structures. This article proposes the feature forest model as a solution to the problem of probabilistic modeling of complex data structures including typed feature structures. The feature forest model provides a method for probabilistic modeling without the independence assumption when probabilistic events are represented with feature forests. Feature forests are generic data structures that represent ambiguous trees in a packed forest structure. Feature forest models are maximum entropy models defined over feature forests. A dynamic programming algorithm is proposed for maximum entropy estimation without unpacking feature forests. Thus probabilistic modeling of any data structures is possible when they are represented by feature forests. This article also describes methods for representing HPSG syntactic structures and predicate-argument structures with feature forests. Hence, we describe a complete strategy for developing probabilistic models for HPSG parsing. The effectiveness of the proposed methods is empirically evaluated through parsing experiments on the Penn Treebank, and the promise of applicability to parsing of real-world sentences is discussed.

Design space and typed feature logic

The logic of typed feature structures is a sorted description logic that has enjoyed widespread usage in grammar design for the last 20 years. Woodbury and Burrow have faithfully preserved its strengths in adapting it to design space navigation research, although the weaknesses it has exhibited in the context of natural language grammar design are likely to surface here as well.

A typology of design space explorers

The act of design is a complex of actions and abilities that is evolving and often highly individual. Given the context of human–computer interaction, and a commitment to the model of design space exploration, we identify two axes that help position efforts to realize this model: the spectrum of strengths and needs that stretches from the machine to the human, and the time scale of events in design. Considering a section of each reveals a landscape that prefers certain activities and gives rise to particular emphases. This paper places the other authors in this Special Issue upon this map, and argues the value of typed feature structures and information orderings to the endeavor of realizing design space explorers.