Martin G. Skjæveland

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This paper motivates, documents and evaluates the process and results of converting the Norwegian Petroleum Directorate's Fact-Pages, a well-known and diverse set of tabular data, but with little and incomplete schema information, stepwise into other representations where in each step more semantics is added to the dataset. The different representations we(More)
Ontologies have recently became a popular mechanism to expose rela-tional database (RDBs) due to their ability to describe the domain of data in terms of classes and properties that are clear to domain experts. Ontological terms are related to the schema of the underlying databases with the help of mappings, i.e., declarative specifications associating SQL(More)
Sgvizler is a small JavaScript wrapper for visualization of SPARQL results sets. It integrates well with HTML web pages by letting the user specify SPARQL SELECT queries directly into designated HTML elements, which are rendered to contain the specified visualization type on page load or on function call. Sgvizler supports a vast number of visualization(More)
The Optique project aims at developing an end-to-end system for semantic data access to Big Data in industries such as Statoil ASA and Siemens AG. In our demonstration we present the first version of the Optique system customised for the Norwegian Petroleum Directorate's FactPages, a publicly available dataset relevant for engineers at Statoil ASA. The(More)
Data access in an enterprise setting is a determining factor for the potential of value creation processes such as sense-making, decision making, and intelligence analysis. As such, providing friendly data access tools that directly engage domain experts (i.e., end-users) with data, as opposed to the situations where database/IT experts are required to(More)
Ontology-Based Data Access (OBDA) is an approach to query rela-tional data via a unified semantic access point powered by an ontology that is 'connected' to the underlying databases via mappings. OPTIQUE is an end-to-end OBDA platform. It offers support for semi-automatic bootstrapping of ontologies and mappings from relational databases thus facilitating(More)
A major challenge in information management today is the integration of huge amounts of data distributed across multiple data sources. A suggested approach to this problem is ontology-based data integration where legacy data systems are integrated via a common ontology that represents a unified global view over all data sources. However, data is often not(More)
The preparation of existing real-world datasets for publication as high-quality semantic web data is a complex task that requires the concerted execution of a variety of processing steps using a range of different tools. Faced with both changing input data and evolving requirements on the produced output, we face a significant engineering task for schema(More)
The topic of study in the present paper is the class of RDF homomorph-isms that substitute one predicate for another throughout a set of RDF triples, on the condition that the predicate in question is not also a subject or object. These maps turn out to be suitable for reasoning about similarities in information content between two or more RDF graphs. As(More)