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

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

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

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

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

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

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

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 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

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