Stephan Oepen

DISCO: an HPSG-based NLP system and its application for appointment scheduling

The natural language system DISCO is described. It combines o a powerful and flexible grammar development system; o linguistic competence for German including morphology, syntax and semantics; o new methods for linguistic performance modelling on the basis of high-level competence grammars; o new methods for modelling multi-agent dialogue competence; o an interesting sample application for appointment scheduling and calendar management.

Parser engineering and performance profiling

We describe and argue for a strategy of performance profiling and comparison in the engineering of parsing systems for wide-coverage linguistic grammars. A performance profile is a precise, rich and structured snapshot of system (and grammar) behaviour at a given development point. The aim is to characterize system performance at a very detailed technical level, but at the same time to abstract away from idiosyncracies of particular processors. Profiles are obtained with minimal effort by applying a specialized profiling tool to a set of structured reference data (taken from both existing test suites and corpora), in conjunction with a uniform format for test data and processing results. The resulting profiles can be analyzed and visualized at various levels of granularity in order to highlight different aspects of system performance, thus providing a solid empirical basis for system refinement and optimization. Since profiles are stored in a database, comparison with earlier versions, different parameter settings, or other processing systems is straightforward. We apply several salient performance metrics in a contrastive discussion of various (one-pass, bottom-up, chart-based) parsing strategies (viz. passive vs. active and uni- vs. bidirectional approaches). Based on insights gained from detailed performance profiles, we outline and evaluate a novel ‘hyper-active’ parsing strategy. We also present preliminary profiles for techniques for ‘packing’ of local ambiguities with respect to (partial) subsumption of feature structures.

Introduction to this Special Issue

This issue of Natural Language Engineering journal reports on recent achievements in the domain of HPSG-based parsing. Research groups at Saarbrucken, CSLI Stanford and the University of Tokyo have worked on grammar development and processing systems that allow the use of HPSG-based processing in practical application contexts. Much of the research reported here has been collaborative, and all of the work shares a commitment to producing comparable results on wide-coverage grammars with substantial test suites. The focus of this special issue is deliberately narrow, to allow detailed technical reports on the results obtained among the collaborating groups. Thus, the volume cannot aim at providing a complete survey on the current state of the field. This introduction summarizes the research background for the work reported in the issue, and puts the major new approaches and results into perspective. Relationships to similar efforts pursued elsewhere are included, along with a brief summary of the research and development efforts reflected in the volume, the joint reference grammar, and the common sets of reference data.

Studien zur performanzorientierten Linguistik

SummaryLooking at relative clause extraposition in German as a concrete example, the paper demonstrates how linguistic model building, corpus study and psycholinguistic experiments combine into an integrational research programme that aims at an improved understanding and linguistically as well as cognitively adequate modelling of human language performance. Starting from the word order theory articulated by (Hawkins, 1994), we formulate hypotheses on the positional distribution of relative clauses and evaluate them on the basis of data drawn from corpus analyses and acceptability experiments. Our empirical studies confirm the expectation that grammatical weight has a significant effect on relative clause distribution; at the same time, there is an interesting asymmetry between language production and perception data.ZusammenfassungAm Beispiel der Relativsatzextraposition im Deutschen zeigt der Beitrag, wie Verfahren der sprachwissenschaftlichen Modellbildung, korpuslinguistischen Untersuchung und des psycholinguistischen Experiments in einem integrativen Forschungsansatz zusammenwirken, der auf ein verbessertes Verständnis und die linguistisch wie kognitiv adäquate Modellierung sprachlicher Performanzprobleme zielt. Ausgehend von der von Hawkins (1994) formulierten Theorie zur Wortstellung werden Hypothesen über die positionelle Verteilung von Relativsätzen formuliert und in Bezug auf Korpusdaten und Akzeptabilitätsmessungen überprüft. Alle beschriebenen empirischen Untersuchungen bestätigen den erwarteten Einfluß von Längenfaktoren auf die Relativsatzdistribution, zeigen gleichzeitig aber eine interessante Asymmetrie zwischen Produktionsund Rezeptionsdaten.

COSMA - multi-participant NL interaction for appointment scheduling

We discuss the use of NL systems in the domain of appointment scheduling. Appointment scheduling is a problem faced daily by many people and organizations, and typically solved using communication in natural language. In general, cooperative interaction between several participants is required whose calendar data are distributed rather than centralized. In this distributed multi-agent environment, the use of NL systems makes it possible for machines and humans to cooperate in solving scheduling problems. We describe the COSMA (Cooperative Schedule Managament Agent) system, a secretarial assistant for appointment scheduling. A central part of COSMA is the reusable NL core system DISCO, which serves, in this application, as an NL interface between an appointment planning system and the human user. COSMA is fully implemented in Common Lisp and runs on Unix Workstations. Our experience with COSMA shows that it is a plausible and useful application for NL systems. However, the appointment planner was not designed for NL communication and thus makes strong assumptions about sequencing of domain actions and about the error-freeness of the communication. We suggest that further improvements of the overall COSMA functionality, especially with regard to flexibility and robustness, be based on a modified architecture.

Studien zur performanzorientierten LinguistikStudies in Performance-Oriented Linguistics: Aspects of German Relative Clause Extraposition

SummaryLooking at relative clause extraposition in German as a concrete example, the paper demonstrates how linguistic model building, corpus study and psycholinguistic experiments combine into an integrational research programme that aims at an improved understanding and linguistically as well as cognitively adequate modelling of human language performance. Starting from the word order theory articulated by (Hawkins, 1994), we formulate hypotheses on the positional distribution of relative clauses and evaluate them on the basis of data drawn from corpus analyses and acceptability experiments. Our empirical studies confirm the expectation that grammatical weight has a significant effect on relative clause distribution; at the same time, there is an interesting asymmetry between language production and perception data.ZusammenfassungAm Beispiel der Relativsatzextraposition im Deutschen zeigt der Beitrag, wie Verfahren der sprachwissenschaftlichen Modellbildung, korpuslinguistischen Untersuchung und des psycholinguistischen Experiments in einem integrativen Forschungsansatz zusammenwirken, der auf ein verbessertes Verständnis und die linguistisch wie kognitiv adäquate Modellierung sprachlicher Performanzprobleme zielt. Ausgehend von der von Hawkins (1994) formulierten Theorie zur Wortstellung werden Hypothesen über die positionelle Verteilung von Relativsätzen formuliert und in Bezug auf Korpusdaten und Akzeptabilitätsmessungen überprüft. Alle beschriebenen empirischen Untersuchungen bestätigen den erwarteten Einfluß von Längenfaktoren auf die Relativsatzdistribution, zeigen gleichzeitig aber eine interessante Asymmetrie zwischen Produktionsund Rezeptionsdaten.