Petr Kremen

Ontology-Driven Information System Design

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.

OWLDiff: A Practical Tool for Comparison and Merge of OWL Ontologies

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.

Expressive OWL Queries: Design, Evaluation, Visualization

Web Ontology Language ontologies become more and more popular in complex domain modeling for their high expressiveness, flexibility and well defined semantics. Although query languages adequate in expressiveness to OWL reasoning capabilities were introduced before, their implementations are rather limited. In this paper, the authors study SPARQL-DLNOT, an extension of one of these query languages, SPARQL-DL, and present novel evaluation and optimization techniques for efficient SPARQL-DLNOT execution. As queries become complex easily, they also present a novel graph-based visualization that simplifies query construction and maintenance. Presented techniques and algorithms were implemented in the Pellet reasoner and in their novel Protege plug-in OWL2Query.

Ontological Foundations of European Coordination Centre for Accident and Incident Reporting Systems

The European Coordination Centre for Accident and Incident Reporting Systems develops an information system for reporting aviation occurrences on the European scale. The system makes use of various...

Object-UOBM: An Ontological Benchmark for Object-Oriented Access

Although many applications built on top of market-ready ontology storages are generic and lack dependence on the particular application domain, most users prefer applications tailored to their particular task. Such applications are typically built using object-oriented paradigm that accesses data differently than generic applications. In this paper, we define a benchmark consisting of an ontology and ontological queries tailored for testing suitability of ontological storages for object-oriented access. We present results of experiments on several state-of-the-art ontological storages and discuss their suitability for the purpose of object-oriented application access.