TDL--- A Type Description Language for Constraint-Based Grammars

This paper presents \tdl, a typed feature-based representation language and inference system. Type definitions in \tdl\ consist of type and feature constraints over the boolean connectives. \tdl\ supports open- and closed-world reasoning over types and allows for partitions and incompatible types. Working with partially as well as with fully expanded types is possible. Efficient reasoning in \tdl\ is accomplished through specialized modules.Comment: Will Appear in Proc. COLING-9

An efficient Algorithm to partition a Sequence of Integers into Subsets with equal Sums

To partition a sequence of n integers into subsets with prescribed sums is an NP-hard problem in general. In this paper we present an efficient solution for the homogeneous version of this problem; i.e. where the elements in each subset add up to the same sum.Comment: 12 page

The stability of simulation based estimation of the multiperiod multinominal probit model with individual specific covariates

The multi-period multinomial Probit model (MMPM) is seen as a flexible tool to explain individual choices among several alternatives over time. There are two versions of this model: a) for each individual the covariates for all alternatives are known and b) for each individual only the parameters of the alternative which was chosen is known. The main difficulty with the MMPM was the calculation of the probability for the individual sequence of chosen alternatives, which requires the computation of the integral over a high dimensional multivariate Normal density. This remedy was removed by the Smooth Recursive Conditional (SRC) simulator. Several simulation studies have investigated the stability of the MMPM estimates with special emphasis to the number of replications of the SRC routine. In contrast to these studies, which use the case of alternative specific covariates, we use the case of the individual specific covariates. We conclude that the MMPM with individual specific covariates is only weakly identified, generalizing Keane's (1992) result for the one period case. As a consequence the maximization of the simulated likelihood often converges to a singular covariance structure so that the SRC-routine stops iterating. This feature cannot be avoided by increasing the number of replications in the SRC-routine. The percentage of these failures rapidly increases with the number of alternatives. --discrete choice models,multi-period multinomial,probit models,simulated maximum likelihood method,smooth recursive conditional simulator,panel data

The DeepThought Core Architecture Framework

The research performed in the DeepThought project aims at demonstrating the potential of deep linguistic processing if combined with shallow methods for robustness. Classical information retrieval is extended by high precision concept indexing and relation detection. On the basis of this approach, the feasibility of three ambitious applications will be demonstrated, namely: precise information extraction for business intelligence; email response management for customer relationship management; creativity support for document production and collective brainstorming. Common to these applications, and the basis for their development is the XML-based, RMRS-enabled core architecture framework that will be described in detail in this paper. The framework is not limited to the applications envisaged in the DeepThought project, but can also be employed e.g. to generate and make use of XML standoff annotation of documents and linguistic corpora, and in general for a wide range of NLP-based applications and research purposes

Physically Embedded Genetic Algorithm Learning in Multi-Robot Scenarios: The PEGA algorithm

We present experiments in which a group of autonomous mobile robots learn to perform fundamental sensor-motor tasks through a collaborative learning process. Behavioural strategies, i.e. motor responses to sensory stimuli, are encoded by means of genetic strings stored on the individual robots, and adapted through a genetic algorithm (Mitchell, 1998) executed by the entire robot collective: robots communicate their own strings and corresponding fitness to each other, and then execute a genetic algorithm to improve their individual behavioural strategy. The robots acquired three different sensormotor competences, as well as the ability to select one of two, or one of three behaviours depending on context ("behaviour management"). Results show that fitness indeed increases with increasing learning time, and the analysis of the acquired behavioural strategies demonstrates that they are effective in accomplishing the desired task

Pollenanalytical studies in NE-Nigeria: preliminary results from the Manga Grasslands and Lake Tilla, Biu Plateau

Two sites situated in the Sahelian and Sudanian zones of NE-Nigeria were chosen for pollen analysis. A sediment core from an interdunal depression in the eastern Manga Grassland provides information on the Holocene vegetation history of the Sahel between c. 9600-3400 B.P. The 3 m pollen record indicates an open savanna during the mid-Holocene. The presence of Sudano-Guinean taxa, which were mainly restricted to the interdunal depressions, points to more humid conditions. Already before c. 4000 B.P., a slow change towards drier conditions and the establishment of the modern Sahelian vegetation is visible in the diagram. This development was accompanied by high fire frequencies. A 16 m core from a crater lake (Lake Tilla) in the Sudanian zone of NE-Nigeria provides a pollen record which can be dated back to approximately 11-12000 B.P. Preliminary pollen spectra show a relatively constant pattern with a dominance of grass pollen even during the middle Holocene.Deux sites situés dans la zone sahélienne et soudanienne du NE-Nigeria ont été choisi pour l'analyse de pollen. L'analyse palynologique d'une carotte provenant d'une dépression interdunaire dans les Manga Grassland de l'Est a mis en évidence de nouvelles informations sur l'histoire de la végétation holocène du Sahel entre ca. 9600 et 3400 B.P. Le profile pollinique de 3 m montre l'existence d'une savane ouverte pendant l'holocène moyen. La présence d'éléments soudano-guinéens dont l'extension était surtout limitée à la dépression interdunaire indique des conditions plus humides. Dès avant ca. 4000 B.P., un lent changement des conditions vers une plus grande sècheresse et l'établissement d'une végétation sahélienne comparable à l'actuelle est visible sur le diagramme. Cette évolution fut accompagnée de fortes fréquences de feu. Une carotte de 16 m d'un lac cratére (Lake Tilla) dans la zone soudanienne du NE-Nigeria proviens une profile de 11-12000 ans environs. Le spèctra polliniques préliminaires sont relativement constante avec une dominance de graminées même pendant l'Holocene moyen

Pointwise differentiability of higher order for sets

The present paper develops two concepts of pointwise differentiability of higher order for arbitrary subsets of Euclidean space defined by comparing their distance functions to those of smooth submanifolds. Results include that differentials are Borel functions, higher order rectifiability of the set of differentiability points, and a Rademacher result. One concept is characterised by a limit procedure involving inhomogeneously dilated sets. The original motivation to formulate the concepts stems from studying the support of stationary integral varifolds. In particular, strong pointwise differentiability of every positive integer order is shown at almost all points of the intersection of the support with a given plane.Comment: Description of subsequent work added to the introduction, references and affiliations updated, typographical corrections made; 34 page