Page 1. Mining in Hepatitis Data by LISp-Miner and SumatraTT Petr Aubrecht1, Martin Kejkula2, Pet... more Page 1. Mining in Hepatitis Data by LISp-Miner and SumatraTT Petr Aubrecht1, Martin Kejkula2, Petr Kremen1, Lenka Nováková1, Jan Rauch2, Milan imunek2, Olga tepánková1, and Monika Záková1 1 Czech Technical University ...
Contemporary product design based on 3D CAD tools aims at improved efficiency using integrated en... more Contemporary product design based on 3D CAD tools aims at improved efficiency using integrated engineering environments with access to databases of existing designs, associated documents and enterprise resource planning. The ultimate goal of this work is to achieve design process improvements by applying state-of-the-art ILP systems for relational data mining of past designs, utilizing commonly agreed design ontologies as background knowledge. This paper demonstrates the utility of relational data mining for virtual engineering of product designs through the detection of frequent design patterns, enabled by the proposed baseline integration of hierarchical background knowledge (a CAD ontology) using sorted refinements.
As the semantic web is becoming more mature, the need for complex, large, formally described onto... more As the semantic web is becoming more mature, the need for complex, large, formally described ontologies grows. Developing such ontologies is rather nontrivial and complex task requiring collaboration among knowledge engineers and domain experts. To support ontology sharing we introduce OWLDiff, an OWL 2 ontology comparison/merge tool, its algorithms, implementation details and usage examples. OWLDiff can be used for syntactic, explanation-based and semantic comparison and merging of OWL 2 ontologies and integrates also a Subversion client for ontology versioning. The system is open-source and is available as a standalone application, Protégé plugin and NeOn toolkit plugin.
Conjunctive query answering is becoming a very important task on the Semantic Web as the adoption... more Conjunctive query answering is becoming a very important task on the Semantic Web as the adoption of SPARQL query language increases. There is considerable work done in the area of optimizing conjunctive query answering for RDF and OWL2-DL ontologies, in the latter case namely for queries without undistinguished variables. However, there has not been much emphasis on how to handle queries with both distinguished and undistinguished variables efficiently. In this paper, we present a novel algorithm for answering conjunctive queries over OWL2-DL ontologies with undistinguished variables efficiently. These optimizations are implemented in the Pellet query engine and our experimental evaluation shows that the new optimization improves the query performance significantly.
Explanations of modeling errors in ontologies are of crucial importance both when creating and ma... more Explanations of modeling errors in ontologies are of crucial importance both when creating and maintaining the ontology. This work presents two novel incremental methods for error explanations in semantic web ontologies and shows their advantages w.r.t. the state of the art black-box techniques. Both promising techniques together with our implementation of a tableau reasoner for an important OWL-DL subset SHIN are used in our semantic annotation tool prototype to explain modeling errors.
IEEE Transactions on Systems, Man, and Cybernetics, 2012
Conventional information systems are built on top of a relational database that requires its data... more Conventional information systems are built on top of a relational database that requires its data model to be stable. This lack of adaptability is very restrictive for systems that manipulate evolving or heterogenous knowledge. The authors of this paper faced this issue at the time of the development of an information system of structural failures. As knowledge on structural failures is very heterogeneous and dynamic, it is practically impossible to define a stable database schema ahead. The widely accepted alternative to relational databases are semantic web ontologies. However, software developers miss adequate frameworks and design methodologies in this area. This paper tries to fill the gap by proposing a methodology for designing ontology-backed software applications that make the ontology possible to evolve while being exploited by one or more applications at the same time. The methodology relies on a contract between the ontology and the application that is formally expressed in terms of integrity constraints. Violation of the contract means either that the ontology evolved in a way that is incompatible with the particular application or the application produced invalid data. In the first case, the ontology change must either be rolled back, or the application needs to be upgraded. In the second case, the user has to modify entered data to fulfill the contract. Furthermore, this paper elaborates an object ontological mapping, transaction management, and efficient querying API. A reference Java implementation of the methodology and the proof-of-concept application in the civil engineering domain is introduced at the end of the paper.
Page 1. Mining in Hepatitis Data by LISp-Miner and SumatraTT Petr Aubrecht1, Martin Kejkula2, Pet... more Page 1. Mining in Hepatitis Data by LISp-Miner and SumatraTT Petr Aubrecht1, Martin Kejkula2, Petr Kremen1, Lenka Nováková1, Jan Rauch2, Milan imunek2, Olga tepánková1, and Monika Záková1 1 Czech Technical University ...
Contemporary product design based on 3D CAD tools aims at improved efficiency using integrated en... more Contemporary product design based on 3D CAD tools aims at improved efficiency using integrated engineering environments with access to databases of existing designs, associated documents and enterprise resource planning. The ultimate goal of this work is to achieve design process improvements by applying state-of-the-art ILP systems for relational data mining of past designs, utilizing commonly agreed design ontologies as background knowledge. This paper demonstrates the utility of relational data mining for virtual engineering of product designs through the detection of frequent design patterns, enabled by the proposed baseline integration of hierarchical background knowledge (a CAD ontology) using sorted refinements.
As the semantic web is becoming more mature, the need for complex, large, formally described onto... more As the semantic web is becoming more mature, the need for complex, large, formally described ontologies grows. Developing such ontologies is rather nontrivial and complex task requiring collaboration among knowledge engineers and domain experts. To support ontology sharing we introduce OWLDiff, an OWL 2 ontology comparison/merge tool, its algorithms, implementation details and usage examples. OWLDiff can be used for syntactic, explanation-based and semantic comparison and merging of OWL 2 ontologies and integrates also a Subversion client for ontology versioning. The system is open-source and is available as a standalone application, Protégé plugin and NeOn toolkit plugin.
Conjunctive query answering is becoming a very important task on the Semantic Web as the adoption... more Conjunctive query answering is becoming a very important task on the Semantic Web as the adoption of SPARQL query language increases. There is considerable work done in the area of optimizing conjunctive query answering for RDF and OWL2-DL ontologies, in the latter case namely for queries without undistinguished variables. However, there has not been much emphasis on how to handle queries with both distinguished and undistinguished variables efficiently. In this paper, we present a novel algorithm for answering conjunctive queries over OWL2-DL ontologies with undistinguished variables efficiently. These optimizations are implemented in the Pellet query engine and our experimental evaluation shows that the new optimization improves the query performance significantly.
Explanations of modeling errors in ontologies are of crucial importance both when creating and ma... more Explanations of modeling errors in ontologies are of crucial importance both when creating and maintaining the ontology. This work presents two novel incremental methods for error explanations in semantic web ontologies and shows their advantages w.r.t. the state of the art black-box techniques. Both promising techniques together with our implementation of a tableau reasoner for an important OWL-DL subset SHIN are used in our semantic annotation tool prototype to explain modeling errors.
IEEE Transactions on Systems, Man, and Cybernetics, 2012
Conventional information systems are built on top of a relational database that requires its data... more Conventional information systems are built on top of a relational database that requires its data model to be stable. This lack of adaptability is very restrictive for systems that manipulate evolving or heterogenous knowledge. The authors of this paper faced this issue at the time of the development of an information system of structural failures. As knowledge on structural failures is very heterogeneous and dynamic, it is practically impossible to define a stable database schema ahead. The widely accepted alternative to relational databases are semantic web ontologies. However, software developers miss adequate frameworks and design methodologies in this area. This paper tries to fill the gap by proposing a methodology for designing ontology-backed software applications that make the ontology possible to evolve while being exploited by one or more applications at the same time. The methodology relies on a contract between the ontology and the application that is formally expressed in terms of integrity constraints. Violation of the contract means either that the ontology evolved in a way that is incompatible with the particular application or the application produced invalid data. In the first case, the ontology change must either be rolled back, or the application needs to be upgraded. In the second case, the user has to modify entered data to fulfill the contract. Furthermore, this paper elaborates an object ontological mapping, transaction management, and efficient querying API. A reference Java implementation of the methodology and the proof-of-concept application in the civil engineering domain is introduced at the end of the paper.
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Papers by Petr Křemen