The LinGO (Linguistic Grammars Online) project's English Resource Grammar and the LKB grammar development environment are language resources which are freely available for download for any purpose, including commercial use (see http://lingo.stanford.edu). Executable programs and source code are both included. In this paper, we give an outline of the LinGO English grammar and LKB system, and discuss the ways in which they are currently being used. The grammar and processing system can be used independently or combined to give a central component which can be exploited in a variety of ways. Our intention in writing this paper is to encourage more people to use the technology, which supports collaborative development on many levels.

This paper presents a new bottom-up chart parsing algorithm for Prolog along with a compilation procedure that reduces the amount of copying at run-time to a constant number (2) per edge. It has applications to unification-based grammars with very large partially ordered categories, in which copying is expensive, and can facilitate the use of more sophisticated indexing strategies for retrieving such categories that may otherwise be overwhelmed by the cost of such copying. It also provides a new perspective on “quick-checking ” and related heuristics, which seems to confirm that forcing an early failure (as opposed to seeking an early guarantee of success) is in fact the best approach to use. A preliminary empirical evaluation of its performance is also provided.

Over the past few years significant progress was accomplished in efficient processing with wide-coverage hpsg grammars. hpsg-based parsing systems are now available that can process medium-complexity sentences (of ten to twenty words, say) in average parse times equivalent to real (i.e. human reading) time. A large number of engineering improvements in current hpsg systems were achieved through collaboration of multiple research centers and mutual exchange of experience, encoding techniques, algorithms, and even pieces of software. This article presents an approach to grammar and system engineering, termed competence & performance profiling, that makes systematic experimentation and the precise empirical study of system properties a focal point in development. Adapting the profiling metaphor familiar from software engineering to constraint-based grammars and parsers, enables developers to maintain an accurate record of system evolution, identify grammar and system deficiencies quickl...

HPSG parsing

We present a framework for efficient parsing with probabilistic Head-driven Phrase Structure Grammars (HPSG). The parser can integrate semantic and syntactic preference into figures-of-merit (FOMs) with the equivalence class function during parsing, and reduce the search space by using the integrated FOMs. This paper presents a CKY algorithm with this function and experimental results of beam thresholding. We also present an iterative CKY parsing for HPSG, which should further speed up parsing in runtime.

feature structures (ISTFS), which is an efficient retrieval engine for typed feature structures. Given a set of typed feature structures, the ISTFS efficiently retrieves its subset whose elements are unifiable or in a subsumption relation with a query feature structure. The efficiency of the ISTFS is achieved by calculating a unifiability checking table prior to retrieval and finding the best index paths dynamically.

Licenser rules have originally been introduced in Müller (1999) as a part of a grammar based on discontinuous constituents. We propose licenser rules as a means to avoid underspecified empty elements in grammars with continuous constituents. We applied them to a verb movement analysis of the German main clause with right sentence bracket and to complement extraposition. To reduce the number of unnecessary hypotheses, we extended the licenser rule concept with a licenser binding technique. We compared the licenser rule approach to an approach based on underspecified traces with respect to processing performance. In our experiment, the use of licenser rules reduced the parse time by a factor of 13.5.

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ABC Light is a compiler that implements Light, a simple CLP(OSF) language characterised by the fact that the control level above the OSF-theory unification [Aït-Kaci et al., 1993] [Aït-Kaci et al., 1997] of feature structures (OSF-terms) is achieving head-corner chart-based parsing [Kay, 1989] [Sikkel, 1997] [Shieber et al., 1995]. The system was tested and tuned on LinGO, [Copestake et al., 1999] the large-scale HPSG [Pollard and Sag, 1994] grammar for English developed at CSLI, University of Stanford. In the Light framework, the LinGO grammar is viewed as a Light logic grammar. The aim of this paper is to give the reader the main insights on how we proceeded to prepare the LinGO grammar for the parsing with the ABC Light system, by obtaining an equivalent order- and type-consistent form, via (off-line/partial) expansion, and determine automatically the grammar's "canonical" appropriateness constraints, not explicitly stated by the grammar writer, but used further on [C...

This paper considers three assumptions conventionally made about signatures in typed feature logic that are in potential disagreement with current practice among grammar developers and linguists working within feature-based frameworks such as HPSG: meet-semi-latticehood, unique feature introduction, and the absence of subtype covering. It also