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Loopy belief propagation for approximate inference: An empirical study. In:

by Kevin P Murphy , Yair Weiss , Michael I Jordan - Proceedings of Uncertainty in AI, , 1999
"... Abstract Recently, researchers have demonstrated that "loopy belief propagation" -the use of Pearl's polytree algorithm in a Bayesian network with loops -can perform well in the context of error-correcting codes. The most dramatic instance of this is the near Shannon-limit performanc ..."
Abstract - Cited by 676 (15 self) - Add to MetaCart
to the correct marginals. However, on the QMR network, the loopy be liefs oscillated and had no obvious relation ship to the correct posteriors. We present some initial investigations into the cause of these oscillations, and show that some sim ple methods of preventing them lead to the wrong results

The Determinants of Credit Spread Changes.

by Pierre Collin-Dufresne , Robert S Goldstein , J Spencer Martin , Gurdip Bakshi , Greg Bauer , Dave Brown , Francesca Carrieri , Peter Christoffersen , Susan Christoffersen , Greg Duffee , Darrell Duffie , Vihang Errunza , Gifford Fong , Mike Gallmeyer , Laurent Gauthier , Rick Green , John Griffin , Jean Helwege , Kris Jacobs , Chris Jones , Andrew Karolyi , Dilip Madan , David Mauer , Erwan Morellec , Federico Nardari , N R Prabhala , Tony Sanders , Sergei Sarkissian , Bill Schwert , Ken Singleton , Chester Spatt , René Stulz - Journal of Finance , 2001
"... ABSTRACT Using dealer's quotes and transactions prices on straight industrial bonds, we investigate the determinants of credit spread changes. Variables that should in theory determine credit spread changes have rather limited explanatory power. Further, the residuals from this regression are ..."
Abstract - Cited by 422 (2 self) - Add to MetaCart
from Lehman Brothers via the Fixed Income (or Warga) Database. We use only quotes on non-callable, non-puttable debt of industrial firms; quotes are discarded whenever a bond has less than four years to maturity. Monthly observations are used for the period July 1988 through December 1997. Only

OBDA with the Ontop Framework

by Diego Calvanese, Benjamin Cogrel, Elem Guzel Kalayci, Sarah Komla Ebri, Roman Kontchakov, Davide Lanti, Martin Rezk, Mariano Rodriguez-muro, Guohui Xiao
"... Abstract. Ontology-based data access (OBDA) has become a popular paradigm for accessing data stored in legacy sources using Semantic Web technologies. In the OBDA setting, users access the data through a con-ceptual layer, which provides a convenient query vocabulary abstracting from specific aspect ..."
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aspects related to the data sources. This conceptual layer is typically expressed as an RDF(S) or OWL ontology, and it is con-nected to the underlying relational databases using R2RML mappings. When the ontology is queried in SPARQL, the OBDA system exploits the mappings to retrieve elements from the data

No Relation: The Mixed Blessings of Non-Relational Databases

by Ian Thomas Varley, Ian Thomas Varley, Adnan Aziz, Daniel Miranker Dedication, Ian Thomas Varley, Co-supervisors Adnan Aziz, Daniel Miranker
"... To my wife Jill, without whose unending support I most certainly would not be here today. Acknowledgements I would like to acknowledge the generous support of my many professors at the University of Texas who have given graciously of their time in support of my education and research over the past t ..."
Abstract - Cited by 4 (0 self) - Add to MetaCart
To my wife Jill, without whose unending support I most certainly would not be here today. Acknowledgements I would like to acknowledge the generous support of my many professors at the University of Texas who have given graciously of their time in support of my education and research over the past

On (In)Tractability of OBDA with OWL 2 QL

by S. Kikot, R. Kontchakov, M. Zakharyaschev
"... Abstract. We show that, although conjunctive queries over OWL 2 QL ontologies are reducible to database queries, no algorithm can construct such a reduction in polynomial time without changing the data. On the other hand, we give a polynomial reduction for OWL 2 QL ontologies without role inclusions ..."
Abstract - Cited by 16 (6 self) - Add to MetaCart
Abstract. We show that, although conjunctive queries over OWL 2 QL ontologies are reducible to database queries, no algorithm can construct such a reduction in polynomial time without changing the data. On the other hand, we give a polynomial reduction for OWL 2 QL ontologies without role

D.: The NPD benchmark: reality check for OBDA systems

by Davide Lanti, Martin Rezk, Guohui Xiao, Diego Calvanese - In: Proceedings of the 18th International Conference on Extending Database Technology (EDBT , 2015
"... In the last decades we moved from a world in which an enterprise had one central database—rather small for todays ’ standards—to a world in which many different—and big—databases must interact and operate, providing the user an integrated and understandable view of the data. Ontology-Based Data Acce ..."
Abstract - Cited by 4 (2 self) - Add to MetaCart
specification given in terms of mappings. Although prototype OBDA systems providing the ability to answer SPARQL queries over the ontology are available, a significant challenge re-mains when it comes to use these systems in industrial environ-ments: performance. To properly evaluate OBDA systems, bench

OBDA: Query rewriting or materialization? In practice, both

by Juan F. Sequeda, Marcelo Arenas, Daniel P. Miranker - In Proc. of the 13th Int. Semantic Web Conf. (ISWC), volume 8796 of Lecture Notes in Computer Science , 2014
"... Abstract. Given a source relational database, a target OWL ontology and a map-ping from the source database to the target ontology, Ontology-Based Data Ac-cess (OBDA) concerns answering queries over the target ontology using these three components. This paper presents the development of UltrawrapOBD ..."
Abstract - Cited by 1 (0 self) - Add to MetaCart
Abstract. Given a source relational database, a target OWL ontology and a map-ping from the source database to the target ontology, Ontology-Based Data Ac-cess (OBDA) concerns answering queries over the target ontology using these three components. This paper presents the development of UltrawrapOBDA

The combined approach to OBDA: Taming role hierarchies using filters

by Carsten Lutz , İnanç Seylan , David Toman , Frank Wolter - In SSWS+HPCSW , 2012
"... Abstract. There are several approaches to implementing query answering over instance data in the presence of an ontology that target conventional relational database systems (SQL databases) as their back-end. They all share the limitation that, for ontologies formulated in OWL2 QL or versions of th ..."
Abstract - Cited by 20 (1 self) - Add to MetaCart
Abstract. There are several approaches to implementing query answering over instance data in the presence of an ontology that target conventional relational database systems (SQL databases) as their back-end. They all share the limitation that, for ontologies formulated in OWL2 QL or versions

A Foundation for Representing and Querying Moving Objects

by Ralf Hartmut Güting , Michael H. Böhlen , Martin Erwig , Christian S. Jensen , Nikos A. Lorentzos , Markus Schneider , Michalis Vazirgiannis , 2000
"... Spatio-temporal databases deal with geometries changing over time. The goal of our work is to provide a DBMS data model and query language capable of handling such time-dependent geometries, including those changing continuously which describe moving objects. Two fundamental abstractions are moving ..."
Abstract - Cited by 200 (39 self) - Add to MetaCart
of operations, i.e., operations range over as many types as possible and behave consistently, and (iii) closure and consistency between structure and operations of non-temporal and related temporal types. Satisfying these goals leads to a simple and expressive system of abstract data types that may

Self-determination and persistence in a real-life setting: Toward a motivational model of high school dropout.

by Robert J Vallerand , Michelle S Fbrtier , Frederic Guay - Journal of Personality and Social Psychology, , 1997
"... The purpose of this study was to propose and test a motivational model of high school dropout. The model posits that teachers, parents, and the school administration's behaviors toward students influence students' perceptions of competence and autonomy. The less autonomy supportive the so ..."
Abstract - Cited by 183 (19 self) - Add to MetaCart
that this relationship applies to the dropout situation as well. Not only is the motivational model theoretically sound, it is also in line with the high school dropout literature. First, with respect to the social context, dropout students, relative to persistent students, report that they participate much less
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