Martin G. Skjæveland's publications

[JKZ+15a] Ernesto Jiménez-Ruiz, Evgeny Kharlamov, Dmitriy Zheleznyakov, Ian Horrocks, Christoph Pinkel, Martin G. Skjæveland, Evgenij Thorstensen, and José Mora. Bootox: Bootstrapping OWL 2 ontologies and R2RML mappings from relational databases. In Proceedings of the ISWC 2015 Posters & Demonstrations Track co-located with the 14th International Semantic Web Conference (ISWC-2015), Bethlehem, PA, USA, October 11, 2015., 2015. [ bib | .pdf ]
In this demo paper we present BOOTOX, a system facilitating ontology and mapping development by their automatic extraction (i.e., bootstrapping) from relational databases. BOOTOX has a number of advantages: it allows to control the OWL 2 profile of the output ontologies, and to bootstrap complex and provenance mappings, which are beyond the W3C direct mapping specification. Moreover, BOOTOX allows to import pre-existing ontologies.

[KJP+15] Evgeny Kharlamov, Ernesto Jiménez-Ruiz, Christoph Pinkel, Martin Rezk, Martin G. Skjæveland, Ahmet Soylu, Guohui Xiao, Dmitriy Zheleznyakov, Martin Giese, Ian Horrocks, and Arild Waaler. Optique: Ontology-based data access platform. In Proceedings of the ISWC 2015 Posters & Demonstrations Track co-located with the 14th International Semantic Web Conference (ISWC-2015), Bethlehem, PA, USA, October 11, 2015., 2015. [ bib | .pdf ]
Ontology-Based Data Access (OBDA) is an approach to query relational 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 system deployment, an intuitive interface to pose queries over a deployed system, and a query processing and optimisation module that allows to efficiently answer user queries. In this demonstration attendees will be able to experience OPTIQUE with data from the oil and gas industry and data from the music domain.

[KHJ+15] Evgeny Kharlamov, Dag Hovland, Ernesto Jiménez-Ruiz, Davide Lanti, Hallstein Lie, Christoph Pinkel, Martín Rezk, Martin G. Skjæveland, Evgenij Thorstensen, Guohui Xiao, Dmitriy Zheleznyakov, and Ian Horrocks. Ontology based access to exploration data at statoil. In The Semantic Web - ISWC 2015 - 14th International Semantic Web Conference, Bethlehem, PA, USA, October 11-15, 2015, Proceedings, Part II, pages 93–112, 2015. [ bib | DOI | .pdf ]
Ontology Based Data Access (OBDA) is a prominent approach to query databases which uses an ontology to expose data in a conceptually clear manner by abstracting away from the technical schema-level details of the underlying data. The ontology is ‘connected’ to the data via mappings that allow to automatically translate queries posed over the ontology into data-level queries that can be executed by the underlying database management system. Despite a lot of attention from the research community, there are still few instances of real world industrial use of OBDA systems. In this work we present data access challenges in the data-intensive petroleum company Statoil and our experience in addressing these challenges with OBDA technology. In particular, we have developed a deployment module to create ontologies and mappings from relational databases in a semi-automatic fashion, and a query processing module to perform and optimise the process of translating ontological queries into data queries and their execution. Our modules have been successfully deployed and evaluated for an OBDA solution in Statoil.

[JKZ+15b] Ernesto Jiménez-Ruiz, Evgeny Kharlamov, Dmitriy Zheleznyakov, Ian Horrocks, Christoph Pinkel, Martin G. Skjæveland, Evgenij Thorstensen, and José Mora. Bootox: Practical mapping of rdbs to OWL 2. In The Semantic Web - ISWC 2015 - 14th International Semantic Web Conference, Bethlehem, PA, USA, October 11-15, 2015, Proceedings, Part II, pages 113–132, 2015. [ bib | DOI | .pdf ]
Ontologies have recently became a popular mechanism to expose relational 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 queries to ontological terms. Developing appropriate ontologies and mappings for given RDBs is a challenging and time consuming task. In this work we present BOOTOX, a system that aims at fa- cilitating ontology and mapping development by their automatic extraction (i.e., bootstrapping) from RDBs, and our experience with the use of BOOTOX in industrial and research contexts. BOOTOX has a number of advantages: it allows to control the OWL 2 profile of the output ontologies, bootstrap complex and provenance mappings, which are beyond the W3C direct mapping specification. Moreover, BOOTOX allows to import pre-existing ontologies via alignment

[Skj15b] Martin G. Skjæveland. Engineering Semantic Data. PhD thesis, University of Oslo, 2015. [ bib | http ]
[PBJR+15] Christoph Pinkel, Carsten Binnig, Ernesto Jiménez-Ruiz, Wolfgang May, Dominique Ritze, Martin G. Skjæveland, Alessandro Solimando, and Evgeny Kharlamov. Rodi: A benchmark for automatic mapping generation in relational-to-ontology data integration. In Fabien Gandon, Marta Sabou, Harald Sack, Claudia d’Amato, Philippe Cudré-Mauroux, and Antoine Zimmermann, editors, The Semantic Web. Latest Advances and New Domains, volume 9088 of LNCS, pages 21–37. Springer International Publishing, 2015. [ bib | DOI | http ]
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 natively born using these ontologies. Instead, much data resides in legacy relational databases. Therefore, mappings that relate the legacy relational data sources to the ontology need to be constructed. Recent techniques and systems that automatically construct such mappings have been developed. The quality metrics of these systems are, however, often only based on self-designed benchmarks. This paper introduces a new publicly available benchmarking suite called RODI, which is designed to cover a wide range of mapping challenges in Relational-to-Ontology Data Integration scenarios. RODI provides a set of different relational data sources and ontologies (representing a wide range of mapping challenges) as well as a scoring function with which the performance of relational-to-ontology mapping construction systems may be evaluated.

[SGH+15] Martin G. Skjæveland, Martin Giese, Dag Hovland, Espen H. Lian, and Arild Waaler. Engineering ontology-based access to real-world data sources. Web Semantics: Science, Services and Agents on the World Wide Web, 33:112–140, 2015. [ bib | DOI | http ]
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 and data transformation. We argue that to achieve a robust and flexible transformation process, a high-level declarative description is needed, that can be used to drive the entire tool chain. We have implemented this idea for the deployment of ontology-based data access (OBDA) solutions, where semantically annotated views that integrate multiple data sources on different formats are created, based on an ontology and a collection of mappings. Furthermore, we exemplify our approach and show how a single declarative description helps to orchestrate a complete tool chain, beginning with the download of datasets, and through to the installation of the datasets for a variety of tool applications, including data and query transformation processes and reasoning services. Our case study is based on several publicly available tabular and relational datasets concerning the operations of the petroleum industry in Norway. We include a discussion of the relative performance of the used tools on our case study, and an overview of lessons learnt for practical deployment of OBDA on real-world datasets.

[Skj15a] Martin G. Skjæveland. Sgvizler: A JavaScript Wrapper for Easy Visualization of SPARQL Result Sets. In Elena Simperl, Barry Norton, Dunja Mladenic, Emanuele Della Valle, Irini Fundulaki, Alexandre Passant, and Raphaël Troncy, editors, The Semantic Web: ESWC 2012 Satellite Events, volume 7540 of LNCS, pages 361–365. Springer Berlin Heidelberg, 2015. [ bib | poster | .pdf ]
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 specifed visualization type on page load or on function call. Sgvizler supports a vast number of visualization types, most notably all of the major charts available in the Google Chart Tools, but also by allowing users to easily modify and extend the set of rendering functions, e.g., specifed using direct DOM manipulation or external JavaScript visualization tool-kits. Sgvizler is compatible with all modern web browsers.

[SL13] Martin G. Skjæveland and Espen H. Lian. Benefits of Publishing the Norwegian Petroleum Directorate's FactPages as Linked Open Data. In Norsk informatikkonferanse (NIK 2013). Tapir, 2013. [ bib | presentation | .pdf ]
This paper presents the benefits from publishing the Norwegian Petroleum Directorate’s FactPages, a public and popular, freely available dataset, into semantically annotated and query enabled five star linked open data. We discuss and illustrate the added value of publishing open datasets on the Web using web standards, semantic web technologies and best practices—contrasted to the lesser suited, but more traditional methods—and offer advice to data providers on how to achieve these benefits.

Keywords: optique-project
[KGJR+13] Evgeny Kharlamov, Martin Giese, Ernesto Jiménez-Ruiz, Martin G. Skjæveland, Ahmet Soylu, Dmitriy Zheleznyakov, Timea Bagosi, Marco Console, Peter Haase, Ian Horrocks, Sarunas Marciuska, Christoph Pinkel, Mariano Rodriguez-Muro, Marco Ruzzi, Valerio Santarelli, Domenico Fabio Savo, Kunal Sengupta, Michael Schmidt, Evgenij Thorstensen, Johannes Trame, and Arild Waaler. Optique 1.0: Semantic Access to Big Data: The Case of Norwegian Petroleum Directorate's FactPages. In International Semantic Web Conference (Posters & Demos), volume 1035 of CEUR Workshop Proceedings, pages 65–68. CEUR-WS.org, 2013. [ bib | poster | .pdf ]
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 system provides different options, including visual, to formulate queries over ontologies and to display query answers. Optique 1.0 offers installation wizards that allow to extract ontologies from relational schemata, extract and define mappings connecting ontologies and schemata, and align and approximate ontologies. Moreover, the system offers highly optimised techniques for query answering.

[SSG+13] Ahmet Soylu, Martin G. Skjæveland, Martin Giese, Ian Horrocks, Ernesto Jiménez-Ruiz, Evgeny Kharlamov, and Dmitriy Zheleznyakov. A Preliminary Approach on Ontology-based Visual Query Formulation for Big Data. In Emmanouel Garoufallou and Jane Greenberg, editors, Metadata and Semantics Research—7th Research Conference, MTSR 2013, Thessaloniki, Greece, November 19-22, 2013. Proceedings, volume 390, pages 201–212. Springer-Verlag, 2013. [ bib | .pdf ]
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 extract data from databases, could substantially increase competitiveness and profitability. However, the ever increasing volume, complexity, velocity, and variety of data, known as the Big Data phenomenon, renders the end-user data access problem even more challenging. Optique, an ongoing European project with a strong industrial perspective, aims to countervail the Big Data effect, and to enable scalable end-user data access to traditional relational databases by using an ontology-based approach. In this paper, we specifically present the preliminary design and development of our ontology-based visual query system and discuss directions for addressing the Big Data effect.

[SS13a] Martin G. Skjæveland and Audun Stolpe. Bounds: Expressing Reservations about Incoming Data. In Olaf Hartig, Juan Sequeda, Aidan Hogan, and Takahide Matsutsuka, editors, Proceedings of the Fourth International Workshop on Consuming Linked Data, COLD 2013, Sydney, Australia, October 22, 2013, volume 1034 of CEUR Workshop Proceedings. CEUR-WS.org, 2013. [ bib | presentation | .pdf ]
This paper introduces the Boundz vocabulary, an RDF vocabulary for expressing reservations about incoming data. We argue that the need for such a vocabulary is real and pressing, and that it is a useful validation tool for any recipient of RDF data that wishes to formulate restrictions on amendments in terms of the data it is already holding. The Boundz vocabulary has a simple mathematical theory that can be expressed in terms of bounded homomorphisms between RDF graphs. We present the basics of this theory, and show that bounded homomorphisms implement conservative extensions over a restricted class of ontology languages, but can also prevent cases of ontology hijacking. We additionally present a prototype implementation with promising evaluation results.

[SLH13] Martin G. Skjæveland, Espen H. Lian, and Ian Horrocks. Publishing the Norwegian Petroleum Directorate's FactPages as Semantic Web Data. In Harith Alani, Lalana Kagal, Achille Fokoue, Paul Groth, Chris Biemann, JosianeXavier Parreira, Lora Aroyo, Natasha Noy, Chris Welty, and Krzysztof Janowicz, editors, The Semantic Web – ISWC 2013, volume 8219 of LNCS, pages 162–177. Springer Berlin Heidelberg, 2013. [ bib | presentation | .pdf ]
This paper motivates, documents and evaluates the process and results of converting the Norwegian Petroleum Directorate's FactPages, 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 consider are a regular relational database, a linked open data dataset, and an ontology. For each conversion step we explain and discuss necessary design choices which are due to the specific shape of the dataset, but also those due to the characteristics and idiosyncrasies of the representation formats. We additionally evaluate the output, performance and cost of querying the different formats using questions provided by users of the FactPages.

[SS13b] Martin G. Skjæveland and Audun Stolpe. Bounds: Expressing Reservations about Incoming Data, 2013. Position paper for W3C's RDF Validation Workshop—Practical Assurances for Quality RDF Data, 10–11 September 2013, Cambridge, MA, USA. [ bib | presentation | .pdf ]
This position paper presents generic constraints useful for expressing dependencies between source and target datasets in situations where the source is to be merged into the target and the target is particular with what data it is willing to accept. These constraints, which we call bounds, are based only on the graph-like triple structure of RDF graphs and draws ideas from of bisimulation from modal logic, conservative extensions of ontologies, and relational peer database exchange. Although simple and generic, bounds still have powerful and practical natural interpretations, and favorable computational properties. An RDF vocabulary for expressing, publishing, and re-using bounds is available, together with an evaluated prototype implementation for checking such constraints.

[SS12a] Martin G. Skjæveland and Audun Stolpe. Bounded RDF Data Transformations. Technical report, University of Oslo, 2012. [ bib | http ]
RDF data transformations are transformations of RDF graphs to RDF graphs which preserve in different degree the data content in the source to the target. These transformation therefore give special attention to the data elements in such graphs—under the assumption that data elements reside in the subjects and objects of RDF triples, and the peculiar fact that the set of vertices and set of edges in an RDF graph are not necessarily disjoint. Bounded homomorphisms are used to define these transformations, which not only ensure that data from the source is structurally preserved in the target, but also require, in various ways, the target data to be related back to the source. The result of this paper is a theoretical toolkit of transformation characteristics with which detailed control over the transformation target may be exercised. We explore these characteristics in two different RDF graph representations, and give an algorithm for checking existence of transformations.

[SS12b] Audun Stolpe and Martin G. Skjæveland. Preserving Information Content in RDF Using Bounded Homomorphisms. In Elena Simperl, Philipp Cimiano, Axel Polleres, Óscar Corcho, and Valentina Presutti, editors, ESWC, volume 7295 of LNCS, pages 72–86. Springer, 2012. [ bib | presentation ]
The topic of study in the present paper is the class of RDF homomorphisms 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 such they are very useful e.g. for migrating data from one RDF vocabulary to another. In this paper we address a particular instance of this problem and try to provide an answer to the question of when we are licensed to say that data is being transformed, reused or merged in a non-distortive manner. We place this problem in the context of RDF and Linked Data, and study the problem in relation to SPARQL construct queries.

[SS12c] Audun Stolpe and Martin G. Skjæveland. Preserving Information Content in RDF using Bounded Homomorphisms (Extended Version), 2012. Extended version of paper published in proceedings of ESWC 2012. [ bib | .pdf ]
[SS11b] Audun Stolpe and Martin G. Skjæveland. From Spreadsheets to 5-star Linked Data in the Cultural Heritage Domain: A Case Study of the Yellow List. In Norsk informatikkonferanse (NIK 2011), pages 13–24. Tapir, 2011. [ bib | .pdf ]
This paper presents the results and lessons learnt from converting the Cultural Heritage Management Office in Oslo's Yellow List of architecturally and culturally valuable buildings into a Linked Data server. The study was performed in the context of the Semicolon II project, as a foray into the more general problem of lifting public sector information. The paper argues, that whilst the benefits of adopting the Linked Data distribution model are many and important, the required transformation to RDF is not unproblematic. Specifically, one needs to ensure that the information content of a dataset is preserved undistorted despite the change of representation. This can not be assumed to be the case by default, since a transformation will often alter the very structure of the dataset. The paper draws attention to the concept of a bounded RDF homomorphism as a means to address this problem.

[SS11a] Audun Stolpe and Martin G. Skjæveland. Conservative Repurposing of RDF Data. 10th Int. Semantic Web Conference, published on conference website, 2011. Poster paper. [ bib | presentation | poster | .pdf ]
The dawning of the age of the data oriented Web presents us with the challenge of assessing and ensuring the integrity of data across repeated cycles of reuse. Public sector information is a case in point: Whilst the political pressure for reusable public sector information is building momentum, governments as authoritative sources of information on the Web need to take steps to ensure that the primary nature of its information is maintained by consumers. The present paper is concerned with one aspect of this problem, namely the question of when we are licensed to say that data is being transformed, reused or merged in a non-distortive manner. Although inherently more general, we shall place this problem in the context of RDF and Linked Data, and study the problem in relation to the principal means of data repurposing that this stack of technologies offers, i.e. SPARQL construct queries.

[KSVS08] Johan W. Klüwer, Martin G. Skjæveland, and Magne Valen-Sendstad. ISO 15926 templates and the Semantic Web, 2008. Position paper for W3C Workshop on Semantic Web in Energy Industries; Part I: Oil and Gas. [ bib | .pdf ]
[Skj06] Martin G. Skjæveland. Free-Variable Calculi for the Modal Logics K45 and S5 — Extended to the Logic of Only Knowing. Master's thesis, University of Oslo, 2006. [ bib | http ]
This thesis presents a free-variable sequent calculi for the modal logics K45, S5 and the logic of Only Knowing. Labels act as placeholders for points in models, using label variables to postpone the choice of point until more knowledge of a putative satisfying model is gathered, allowing a least commitment search. The relation of contextually equivalents is used to obtain variable-sharing derivations baring tight connections to matrix systems and the goal directed Connection calculus. A system of indexed formulae is employed to enforce reuse of label parameters, establishing an upper bound for the search space. The calculus of the logic of Only Knowing is defined by combining the calculi established for K45 and S5, and utilizing an auxiliary derivation to test models for maximality.


This file was generated by bibtex2html 1.97.