Joerg Schoenfisch

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In this paper we present our implementation of an OWL 2 QL reasoner using query rewriting to answer SPARQL queries in a relational database. To answer queries in the database through rewriting, ontolo-gies are limited to the OWL 2 QL profile. The rewriting algorithm internally produces a non-recursive Datalog program from the given SPARQL query. This(More)
We present a solution for modeling the dependencies of an IT infrastructure and determine the availability of components and services therein using Markov logic networks (MLN). MLNs offer a single representation of probability and first-order logic and are well suited to model dependencies and threats. We identify different kinds of dependency and show how(More)
Most current approaches to matchmaking of semantic Web services utilize hybrid strategies consisting of logic-and non-logic-based similarity measures (or even no logic-based similarity at all). This is mainly due to pure logic-based matchers achieving a good precision, but very low recall values. We present a purely logic-based matcher implementation based(More)
In recent years a lot of efforts was put into the field of Semantic Web research to specify knowledge as precisely as possible. However, optimizing for precision alone is not sufficient. The handling of uncertain or incomplete information is getting more and more important and it promises to significantly improve the quality of query answering in Semantic(More)
In this paper we propose an approach for calculating the most probable root cause for an observed failure in an IT infrastructure. Our approach is based on Markov Logic Networks. While Markov Logic supports a special type of deductive inference, known as maximum a posteriori inference, the computation of the most probable cause requires abductive reasoning.(More)
Handling uncertain knowledge – like information extracted from un-structured text, with some probability of being correct – is crucial for modeling many real world domains. Ontologies and ontology-based data access (OBDA) have proven to be versatile methods to capture this knowledge. Multiple systems for OBDA have been developed and there is theoretical(More)
Pneumatic nail guns have a safety device (workpiece contact, nose, yoke, tip) at the end of the gun muzzle that must be depressed before the fastener can be discharged. Two types of trigger systems define how the nail gun fires in response to a trigger press: 1) The sequential actuation trigger requires that each nail can only be discharged when the safety(More)
IT infrastructure is a crucial part in most of today''s business operations. High availability and reliability, and short response times to outages are essential. Thus a high amount of tool support and automation in risk management is desirable to decrease outages. We propose a new approach for calculating the root cause for an observed failure in an IT(More)