Publications

Kharlamov, Evgeny; Kotidis, Yannis; Mailis, Theofilos; Neuenstadt, Christian; Nikolaou, Charalampos; Özcep, Özgür; Svingos, Christoforos; Zheleznyakov, Dmitriy; Ioannidis, Yannis; Lamparter, Steffen; Möller, Ralf & Waaler, Arild (2019). An ontologymediated analyticsaware approach to support monitoring and diagnostics of static and streaming data. Journal of Web Semantics.
ISSN 15708268.
56, s 30 55 . doi:
10.1016/j.websem.2019.01.001

Cameron, David B.; Waaler, Arild & Komulainen, Tiina M. (2018). Oil and Gas digital twins after twenty years. How can they be made sustainable, maintainable and useful?. Linköping Electronic Conference Proceedings.
ISSN 16503686.
(153), s 9 16 . doi:
10.3384/ecp181539
Show summary
The digital twin offers a potentially powerful way of using simulation to support business and change the way industrial operations are done. The idea of the digital twin is not new but recent changes in information technology make implementation of digital twins a natural next step in the application of simulation technologies. Simulation practitioners will find that their models are increasingly embedded in complex systems that combine simulations with operational data to solve a business problem. However, the successful adoption of this approach is challenging. This paper asks the question: “How can digital twins be made sustainable, maintainable and useful?”. We focus primarily on the development of twins in the oil and gas industry. Most academic work in this area has been done in the manufacturing industries. We review this literature and propose a simple model of digital twins. This allows us to identify challenges with current implementations and propose a research agenda that will allow future twins to be sustainable, maintainable and usable.

Kharlamov, Evgeny; Skjæveland, Martin G; Hovland, Dag; Mailis, Theofilos; JimenezRuiz, Ernesto; Xiao, Guohui; Soylu, Ahmet; Horrocks, Ian & Waaler, Arild (2018). Finding Data Should be Easier than Finding Oil, In Naoki Abe; Huan Liu; Xiaohua Hu; Nesreen Ahmed; Mu Qiao; Yang Song; Donald Kossmann; Bing Liu; Kisung Lee; Jiliang Tang; Jingrui He & Jeffrey Saltz (ed.),
2018 IEEE International Conference on Big Data (Big Data), Seattle, 1013 Dec. 2018.
IEEE.
ISBN 9781538650356.
artikkel.
Full text in Research Archive.
Show summary
The competitiveness of modern enterprises heavily depends on their ability to make the right business decisions by relying on efficient and timely analysis of the right business critical data. In large and data intensive companies such as Equinor, a Norwegian multinational oil and gas company with more than 20,000 employees, gathering such data is not a trivial task due to the growing size and complexity of corporate information sources. As a result, the data gathering task is often the most timeconsuming part of the decision making process, in particular when it comes to the work processes of Equinor’s Exploration geologists that should find in a timely manner New exploitable accumulations of oil or gas in given areas by analysing data about these areas. In this work we present our experience in addressing this data challenge tast at Equinor. We have developed and deployed at Equinor a semantic data access system that relies on the Ontology Based Data Access (OBDA) approach. Our system is based on our solid theoretical contributions and has been extensively evaluated at Equinor

Klungre, Vidar Norstein; Soylu, Ahmet; Giese, Martin; Waaler, Arild & Kharlamov, Evgeny (2018). On Enhancing Visual Query Building over KGs Using Query Logs. Lecture Notes in Computer Science.
ISSN 03029743.
11341, s 77 85 . doi:
10.1007/9783030042844_6
Full text in Research Archive.
Show summary
Knowledge Graphs have recently gained a lot of attention and have been successfully applied in both academia and industry. Since KGs may be very large: they may contain millions of entities and triples relating them to each other, to classes, and assigning them data values, it is important to provide endusers with effective tools to explore information encapsulated in KGs. In this work we present a visual query system that allows users to explore KGs by intuitively constructing treeshaped conjunctive queries. It is known that systems of this kind suffer from the problem of information overflow: when constructing a query the users have to iteratively choose from a potentially very long list of options, sich as, entities, classes, and data values, where each such choice corresponds to an extension of the query new filters. In order to address this problem we propose an approach to substantially reduce such lists with the help of ranking and by eliminating the socalled deadends, options that yield queries with no answers over a given KG.

Skjæveland, Martin G; Gjerver, Anders; Hansen, Christian Mahesh; Kluwer, Johan Wilhelm; Strand, Morten Rørvik; Waaler, Arild & Øverli, Per Øyvind (2018). Semantic Material Master Data Management at Aibel. CEUR Workshop Proceedings.
ISSN 16130073.
2180

Harrow, Ian; JimenezRuiz, Ernesto; Splendiani, Andrea; Romacker, Martin; Woollard, Peter; Markel, Scott; AlamFaruque, Yasmin; Koch, Martin; Malone, James & Waaler, Arild Torolv Søetorp (2017). Matching disease and phenotype ontologies in the ontology alignment evaluation initiative. Journal of Biomedical Semantics.
ISSN 20411480.
8(1), s 1 13 . doi:
10.1186/s1332601701629
Full text in Research Archive.

Hovland, Dag; Kontchakov, Roman; Skjæveland, Martin G; Waaler, Arild & Zakharyaschev, Michael (2017). OntologyBased Data Access to Slegge. Lecture Notes in Computer Science.
ISSN 03029743.
10588, s 120 129 . doi:
10.1007/9783319682044_12
Full text in Research Archive.

Kharlamov, Evgeny; Hovland, Dag; Skjæveland, Martin G; Bilidas, Dimitris; JimenezRuiz, Ernesto; Xiao, Guohui; Soylu, Ahmet; Lanti, Davide; Rezk, Martin; Zheleznyakov, Dmitriy; Giese, Martin; Lie, Hallstein; Ioannidis, Yannis; Kotidis, Yannis; Koubarakis, Manolis & Waaler, Arild Torolv Søetorp (2017). Ontology Based Data Access in Statoil. Journal of Web Semantics.
ISSN 15708268.
44, s 3 36 . doi:
10.1016/j.websem.2017.05.005
Full text in Research Archive.

Kharlamov, Evgeny; Mailis, Theofilos; Mehdi, Gulnar; Neuenstadt, Christian; Özçep, Özgür Lütfü; Roshchin, Mikhail; Solomakhina, Nina; Soylu, Ahmet; Svingos, Christoforos; Brandt, Sebastian; Giese, Martin; Ioannidis, Yannis; Lamparter, Steffen; Möller, Ralf; Kotidis, Yannis & Waaler, Arild (2017). Semantic access to streaming and static data at Siemens. Journal of Web Semantics.
ISSN 15708268.
44, s 54 74 . doi:
10.1016/j.websem.2017.02.001
Full text in Research Archive.

Skjæveland, Martin G; Forssell, Jon Henrik; Klüwer, Johan W.; Lupp, Daniel Paul; Thorstensen, Evgenij & Waaler, Arild (2017). Reasonable ontology templates: APIs for OWL: Efficient and practical ontology design and maintenance. CEUR Workshop Proceedings.
ISSN 16130073.
1963, s 1 4

Skjæveland, Martin G; Forssell, Jon Henrik; Kluwer, Johan Wilhelm; Lupp, Daniel Paul; Thorstensen, Evgenij & Waaler, Arild (2017). PatternBased Ontology Design and Instantiation with Reasonable Ontology Templates. CEUR Workshop Proceedings.
ISSN 16130073.
2043

Cameron, David B.; Skjæveland, Martin G; Giese, Martin; Hovland, Dag; Waaler, Arild; Bjørge, Eldar & Tungland, Knut Sebastian (2016). Optique: Simple, Oil & Gasoriented access to big data in exploration, In
SPE Intelligent Energy Conference and Exhibition, Aberdeen, Scotland, UK, 68 September 2016  Conference Proceedings.
Society of Petroleum Engineers.
ISBN 9781613994597.
KAPITTEL.

Horrocks, Ian; Giese, Martin; Kharlamov, Evgeny & Waaler, Arild (2016). Using Semantic Technology to Tame the Data Variety Challenge. IEEE Internet Computing.
ISSN 10897801.
20(6), s 62 66 . doi:
10.1109/MIC.2016.121

Kharlamov, Evgeny; Brandt, Sebastian; Giese, Martin; JimenezRuiz, Ernesto; Kotidis, Yannis; Lamparter, Steffen; Mailis, Theofilis P.; Neuenstadt, Christian; Özcep, Özgür; Pinkel, Christoph; Soylu, Ahmet; Svingos, Christoforos; Zheleznyakov, Dmitriy; Horrocks, Ian; Ioannidis, Yannis; Möller, Ralf & Waaler, Arild (2016). Enabling semantic access to static and streaming distributed data with optique: demo, In Avigdor Gal; Matthias Weidlich; Vana Kalogeraki & Nalini Venkasubramanian (ed.),
Proceedings of the 10th ACM International Conference on Distributed and Eventbased Systems, DEBS '16, Irvine, CA,USA, June 20 24.
ACM Publications.
ISBN 9781450340212.
Chapter.
s 350
 353

Kharlamov, Evgeny; Mailis, Theofilis P.; Bereta, Konstantina; Bilidas, Dimitris; Brandt, Sebastian; JimenezRuiz, Ernesto; Lamparter, Steffen; Neuenstadt, Christian; Özcep, Özgür; Soylu, Ahmet; Svingos, Christoforos; Xiao, Guohui; Zheleznyakov, Dmitriy; Calvanese, Diego; Horrocks, Ian; Giese, Martin; Ioannidis, Yannis; Kotidis, Yannis; Möller, Ralf & Waaler, Arild (2016). A Semantic Approach to Polystores, In James Joshi (ed.),
Proceedings 2016 IEEE International Conference on Big Data.
IEEE.
ISBN 9781467390057.
KAPITTEL.
s 2565
 2573

VegaGorgojo, Guillermo; Fjellheim, Roar; Roman, Dumitru; Akerkar, Rajendra & Waaler, Arild (2016). Big data in the oil & gas upstream industry  a case study on the Norwegian continental shelf. Oil, Gas.
ISSN 03425622.
42(II), s 67 77
Show summary
This case study is focused on the impact of big data in exploration and production of oil & gas in the Norwegian Continental Shelf. Overall, the industry is currently transitioning from mere data collection practices to more proactive uses of data, especially in the operations area. Positive economical impacts associated with the use of big data comprise data generation and data analytics business models, commercial partnerships around data, and the embracement of open data by the Norwegian regulator. On the negative side there are concerns regarding the future of existing business models and the reluctance of oil companies to share data. Positive social and ethical impacts include mitigation of safety and environment concerns with big data, personal privacy not really a problem, and creation of new jobs for data scientists; on the other hand cyberthreats are becoming a serious concern and there are trust issues with data.

VegaGorgojo, Guillermo; Giese, Martin; Heggestøyl, Simen; Soylu, Ahmet & Waaler, Arild (2016). PepeSearch: Semantic Data for the masses. PLOS ONE.
ISSN 19326203.
11(3) . doi:
10.1371/journal.pone.0151573
Full text in Research Archive.
Show summary
With the emergence of the Web of Data, there is a need of tools for searching and exploring the growing amount of semantic data. Unfortunately, such tools are scarce and typically require knowledge of SPARQL/RDF. We propose here PepeSearch, a portable tool for searching semantic datasets devised for mainstream users. PepeSearch offers a multiclass search form automatically constructed from a SPARQL endpoint. We have tested PepeSearch with 15 participants searching a Linked Open Data version of the Norwegian Register of Business Enterprises for nontrivial challenges. Retrieval performance was encouragingly high and usability ratings were also very positive, thus suggesting that PepeSearch is effective for searching semantic datasets by mainstream users. We also assessed its portability by configuring PepeSearch to query other SPARQL endpoints.

VegaGorgojo, Guillermo; Slaughter, Laura; Giese, Martin; Heggestøyl, Simen; Kluwer, Johan Wilhelm & Waaler, Arild (2016). Pepesearch: Easy to use and easy to install semantic data search. Lecture Notes in Computer Science.
ISSN 03029743.
9989 LNCS, s 146 150 . doi:
10.1007/9783319476025_29

VegaGorgojo, Guillermo; Slaughter, Laura; Giese, Martin; Heggestøyl, Simen; Soylu, Ahmet & Waaler, Arild (2016). Visual query interfaces for semantic datasets: An evaluation study. Journal of Web Semantics.
ISSN 15708268.
39, s 81 96 . doi:
10.1016/j.websem.2016.01.002

Zheleznyakov, Dmitriy; Kharlamov, Evgeny; Klungre, Vidar Norstein; Skjæveland, Martin G; Hovland, Dag; Giese, Martin; Horrocks, Ian & Waaler, Arild (2016). KeywDB: A system for keyworddriven ontologytoRDB mapping construction. CEUR Workshop Proceedings.
ISSN 16130073.
1690

Giese, Martin; Soylu, Ahmet; Vega, Gorgojo Guillermo; Waaler, Arild; Haase, Peter; JimenezRuiz, Ernesto; Lanti, Davide; Rezk, Martin; Xiao, Guohui; Oezcep, Oezguer & Rosati, Riccardo (2015). Optique: Zooming in on Big Data. Computer.
ISSN 00189162.
48(3), s 60 67 . doi:
10.1109/MC.2015.82

Kharlamov, Evgeny; JiménezRuiz, Ernesto; Pinkel, Christoph; Rezk, Martin; Skjæveland, Martin G; Soylu, Ahmet; Xiao, Guohui; Zheleznyakov, Dmitriy; Giese, Martin; Horrocks, Ian & Waaler, Arild (2015). OPTIQUE: Ontologybased data access platform. CEUR Workshop Proceedings.
ISSN 16130073.
1486

Skjæveland, Martin G; Giese, Martin; Hovland, Dag; Lian, Espen Hallenstvedt & Waaler, Arild (2015). Engineering ontologybased access to realworld data sources. Journal of Web Semantics.
ISSN 15708268.
33, s 112 140 . doi:
10.1016/j.websem.2015.03.002
Full text in Research Archive.

Calvanese, Diego; Giese, Martin; Haase, Peter; Ioannidis, Yannis; Jimenezruiz, Ernesto; Kharlamov, Evgeny; Kllapi, Herald; Koubarakis, Manolis; Lampater, Steffen; Moeller, Ralf; Neuenstadt, Christian; Oezcep, Oezguer; Rodriguezmuro, Mariano; Roshchin, Mikhail; Ruzzi, Marco; Savo, Domenico Fabio; Schmidt, Michael; Soylu, Ahmet; Waaler, Arild & Zheleznyakov, Dmitriy (2013). The Optique Project: Towards OBDA Systems for Industry. CEUR Workshop Proceedings.
ISSN 16130073.
1080

Giese, Martin; Calvanese, Diego; Haase, Peter; Horrocks, Ian; Ioannidis, Yannis; Kllapi, Herald; Koubarakis, Manolis; Lenzerini, Maurizio; Moeller, Ralf; Oezcep, Oezguer; Rodriguezmuro, Mariano; Rosati, Riccardo; Schlatte, Rudolf; Schmidt, Michael; Soylu, Ahmet & Waaler, Arild (2013). Scalable Enduser Access to Big Data, In Rajendra Akerkar (ed.),
Big Data Computing.
Taylor & Francis.
ISBN 9781466578371.
Section II.

Kharlamov, Evgeny; Jimenezruiz, Ernesto; Zheleznyakov, Dmitriy; Bilidas, Dimitris; Giese, Martin; Haase, Peter; Horrocks, Ian; Kllapi, Herald; Koubarakis, Manolis; Oezcep, Oezguer; Rodriguezmuro, Mariano; Rosati, Riccardo; Schmidt, Michael; Schlatte, Rudolf; Soylu, Ahmet & Waaler, Arild (2013). Optique: Towards OBDA Systems for Industry. Lecture Notes in Computer Science.
ISSN 03029743.
7955, s 125 140 . doi:
10.1007/9783642412424_11

Calvanese, Diego; Giese, Martin; Haase, Peter; Horrocks, Ian; Hubauer, Thomas; Ioannidis, Yannis; Jimenezruiz, Ernesto; Kharlamov, Evgeny; Kllapi, Herald; Kluwer, Johan Wilhelm; Koubarakis, Manolis; Lampater, Steffen; Moeller, Ralf; Neuenstadt, Christian; Nordveit, Toralv; Oezcep, Oezguer; Rodriguezmuro, Mariano; Roshchin, Mikhail; Savo, Fabio; Schmidt, Michael; Soylu, Ahmet; Waaler, Arild & Zheleznyakov, Dmitriy (2013). Optique: OBDA Solution for Big Data. Lecture Notes in Computer Science.
ISSN 03029743.
7955, s 293 295 . doi:
10.1007/9783642412424_48

Giese, Martin; Ornæs, Jens I.; Overå, Lars; Svensson, Inge & Waaler, Arild (2012). Using Semantic Technology to Autogenerate Reports: Case Study of Daily Drilling Reports, In Sanjay Kanvinde (ed.),
SPE Intelligent Energy International, 2729 March 2012, Utrecht, The Netherlands.
Society of Petroleum Engineers.
ISBN 9781613991916.
SPE 150225.

Hansen, Christian Mahesh; Antonsen, Roger; Giese, Martin & Waaler, Arild (2012). Incremental variable splitting. Journal of symbolic computation.
ISSN 07477171.
47(9), s 1046 1065 . doi:
10.1016/j.jsc.2011.12.032
Show summary
The variable splitting method for freevariable tableau calculi provides an admissibility condition under which the same free variables can be assigned values independently on different branches. While this has a large potential for automated proof search, a direct implementation of this condition is impractical. We adapt the incremental closure framework for free variables to variable splitting tableaux by recasting the admissibility condition for closing substitutions into a constraint satisfaction problem. The resulting mechanism allows to check the existence of an admissible closing substitution incrementally during the construction of a proof. We specify a rulebased algorithm for testing satisfiability of constraints that accounts for split variables, and present experimental results based on a prototype variable splitting theorem prover implementation measuring the computational overhead of the variable splitting framework.

Lian, Espen Hallenstvedt; Johnsen, Einar Broch & Waaler, Arild (2010). Confluent Term Rewriting for Onlyknowing Logics. Frontiers in Artificial Intelligence and Applications.
ISSN 09226389.
222, s 162 174

Løkke, Håvard & Waaler, Arild (2010). Change, Modal Categories, and Agency, In Jon Stewart & Katalin Nun (ed.),
Kierkegaard and the Greek World: Tome II: Aristotle and other Greek Authors.
Ashgate.
ISBN 9780754669821.
Kapittel.
s 25
 46

Løkke, Håvard & Waaler, Arild (2010). The First Principles of Logic and the Debate about Mediation, In Jon Stewart & Katalin Nun (ed.),
Kierkegaard and the Greek World: Tome II: Aristotle and other Greek Authors.
Ashgate.
ISBN 9780754669821.
Kapittel.
s 3
 24

Holen, Bjarne; Johnsen, Einar Broch & Waaler, Arild (2009). Proof Search for the FirstOrder Connection Calculus in Maude. Electronical Notes in Theoretical Computer Science.
ISSN 15710661.
238, s 173 188

Løkke, Håvard & Waaler, Arild (2009). Traces of Kierkegaard’s Reading of the Theodicy, In Jon Stewart (ed.),
Kierkegaard and the Renaissance and Modern Traditions  Philosophy.
Ashgate.
ISBN 9780754668183.
Kapittel.

Lian, Espen Hallenstvedt & Waaler, Arild (2008). Computing Default Extensions by Reductions on O^R, In Gerhard Brewka & Jérôme Lang (ed.),
Principles of Knowledge Representation and Reasoning: Proceedings of the Eleventh International Conference, KR 2008.
AAAI Press.
ISBN 9781577353843.
Nonmonotonic Reasoning.
s 496
 506

Antonsen, Roger & Waaler, Arild (2007). A Labelled System for IPL with Variable Splitting. Lecture Notes in Computer Science.
ISSN 03029743.
LNAI(4603), s 132 146 . doi:
10.1007/9783540735953_10
Show summary
The paper introduces a free variable, labelled proof system for intuitionistic propositional logic with variable splitting. In this system proofs can be found without backtracking over rules by generating a single, uniform derivation. We prove soundness, introduce a construction that extracts finite countermodels from unprovable sequents, and formulate a branchwise termination condition. This is the first proof system for intuitionistic propositional logic that admits goaldirected search procedures without compromising proof lengths, compared to corresponding tableau calculi.

Antonsen, Roger & Waaler, Arild (2007). Liberalized Variable Splitting. Journal of automated reasoning.
ISSN 01687433.
38, s 3 30 . doi:
10.1007/s1081700690559

Waaler, Arild; Klüwer, Johan W.; Langholm, Tore & Lian, Espen (2007). Only knowing with degrees of confidence. Journal of Applied Logic.
ISSN 15708683.
5(3), s 492 518
Show summary
A new logic of belief (in the "only knowing" family) with confidence levels is presented. The logic allows a natural distinction between explicit and implicit belief representations, where the explicit form directly expresses its models. The explicit form can be found by applying a set of equivalence preserving rewriting rules to the implicit form. The rewriting process is performed entirely within the logic, on the object level, provided we supply an explicit formalization of the logical space. We prove that the problem of deciding whether there exists a consistent explicit form is complete, a complexity class to which many problems of nonmonotonic reasoning belong. The article also contains a conceptual analysis of basic notions like belief, cobelief and degrees of confidence.

Waaler, Arild; Kluwer, Johan Wilhelm; Langholm, Tore & Lian, Espen Hallenstvedt (2007). Only knowing with degrees of confidence. Journal of Applied Logic.
ISSN 15708683.
5(3), s 492 518

Klüwer, Johan W. & Waaler, Arild (2006). Relative trustworthiness. Lecture Notes in Computer Science.
ISSN 03029743.
3866, s 158 170
Show summary
We present a method for trust scenarios with more than one trustee, where sets of trustees are ordered in a relation of relative trustworthiness. We show how a priority structure implicit in a trust relation can be made fully explicit by means of a lattice and how a system of default expectations arises from a systematic interpretation. The default structure lends itself to formal interpretation, but is independent of a particular logical language. The theory is designed to directly extend the analysis of the concept of trust given by Andrew Jones.

Klüwer, Johan W. & Waaler, Arild (2006). Trustworthiness by default. Lecture Notes in Computer Science.
ISSN 03029743.
3900, s 96 111
Show summary
We present a framework for reasoning about trustworthiness, with application to conflict resolution and belief formation at various degrees of reliability. On the basis of an assignment of relative trustworthiness to sets of information sources, a lattice of degrees of trustworthiness is constrructed; from this, a priority structure is derived and applied to the problem of forming the right opinion in the presence of possibly conflicting information. Consolidated with an unquestioned knowledge base, this provides an unambiguous account of what an agent should believe, conditionally on which information sources are trusted. Applications in multiagent doxastic logic are sketched.

Kluwer, JW & Waaler, Arild (2006). Relative trustworthiness. Lecture Notes in Computer Science.
ISSN 03029743.
3866

Kluwer, JW & Waaler, Arild (2006). Trustworthiness by default. Lecture Notes in Computer Science.
ISSN 03029743.
3900, s 96 111

Solhaug, Bjørnar & Waaler, Arild (2006). Logical spaces in multiagent Only knowing systems. Lecture Notes in Computer Science.
ISSN 03029743.
3900, s 77 95
Show summary
We present a weak multiagent system of Only knowing and an analysis of the logical spaces that can be defined in it. The logic complements the approach to generalizing Levesque's All I Know system made by Halpern and Lakemeyer. A novel feature of our approach is that the logic is defined entirely at the object level with no reference to metaconcepts in the definition of the axiom system. We show that the logic of Halpern and Lakemeyer can be encoded in our system in the form of a particular logical space.

Solhaug, Bjørnar & Waaler, Arild (2006). Logical spaces in multiagent Only knowing systems. Lecture Notes in Computer Science.
ISSN 03029743.
3900, s 77 95 . doi:
10.1007/11750734_5
Show summary
Solhaug: Også infomedia, UiB. TØF: Knytter posten til Solhaug kommer på plass./tøf

Antonsen, Roger & Waaler, Arild (2005). Consistency of Variable Splitting in Free Variable Systems of FirstOrder Logic. Lecture Notes in Computer Science.
ISSN 03029743.
LNAI(3702), s 33 47
Show summary
We prove consistency of a sequent calculus for classical logic with explicit splitting of free variables by means of a semantical soundness argument. The free variable system is a mature formulation of the system proposed at TABLEAUX 2003. We also identify some challenging and interesting open research problems.

Engan, Iselin; Langholm, Tore; Lian, Espen Hallenstvedt & Waaler, Arild (2005). Default Reasoning with Preference Within Only Knowing Logic. Lecture Notes in Computer Science.
ISSN 03029743.
3662, s 304 316

Antonsen, Roger & Waaler, Arild (2005). Consistency of Variable Splitting in Free Variable Systems of FirstOrder Logic. Lecture Notes in Computer Science.
ISSN 03029743.
3702, s 33 47
Show summary
We prove consistency of a sequent calculus for classical logic with explicit splitting of free variables by means of a semantical soundness argument. The free variable system is a mature formulation of the system proposed at TABLEAUX 2003 [1]. We also identify some challenging and interesting open research problems.

Engan, Iselin; Langholm, Tore; Lian, Espen & Waaler, Arild (2005). Default Reasoning with Preference within Only Knowing Logic. Lecture Notes in Computer Science.
ISSN 03029743.
3662, s 304 316
Show summary
The main construction in this paper is an encoding of default logic into an ``only knowing'' logic with degrees of confidence. By imposing simple and natural constraints on the encoding we show that the ``only knowing'' logic can accommodate ordered default theories and that the constrained encoding implements a prescriptive interpretation of preference between defaults. An advantage of the encoding is that it provides a transparent formal rendition of such a semantics. A feature of the construction is that the generation of extensions can be carried out within the ``only knowing'' logic, using object level concepts alone.

Waaler, Arild (2005). Consistency Proofs for Systems of Multiagent Only Knowing, In
Advances in modal logic.
King's College Publications.
s 347
 366
Show summary
Various multimodal systems are proposed for the representation of belief states in a multiagent context. We introduce sequent calculi for these systems and prove cutelimination results. A corollary to these results is that a new and natural multimodal extension of Levesque's system of only knowing is consistent.

Waaler, Arild & Solhaug, Bjørnar (2005). Semantics for multiagent only knowing (extended abstract). Proceedings of the conference on Theoretical Aspects of Rationality and Knowledge.
ISSN 15253430.
10, s 109 125
Show summary
This paper presents a Kripke semantics for a multiagent generalization of Levesque's logic of ``only knowing''. We prove soundness and completeness and show that the logic has the finite model property. In addition we prove a Modal reduction theorem which states that complex syntactical representations can be syntactically reduced to a provably equivalent form which directly reflects all the models of the representation.

Waaler, Arild & Solhaug, Bjørnar (2005). Semantics for multiagent only knowing: extended abstract, In Ron van der Meyden (ed.),
TARK X  Proceedings of the 10th Conference on Theoretical Aspects of Rationality and Knowledge.
National University of Singapore.
ISBN 9810534124.
Session 5.
s 109
 125

Lian, Espen Hallenstvedt; Langholm, Tore & Waaler, Arild (2004). Only Knowing with Confidence Levels: Reductions and Complexity. Lecture Notes in Computer Science.
ISSN 03029743.
3229, s 500 512

Tolstrup, Christian & Waaler, Arild (2004). Innledning til Filosofiske smuler, I:
Filosofiske smuler / med innledning av Arild Waaler og Christian Fink Tolstrup.
N.W. Damm & Sønn.
s 9
 69

Waaler, Arild (2004). Begynnelsens problem hos Lequier og Kierkegaard. Kirke og kultur.
ISSN 0023186X.
109(Årg. 109, h. 2), s 205 210

Waaler, Arild & Tolstrup, Christian (2004). Philosophical fragments  in response to the debate between Mynster and Martensen. ?.
s 208 234
Show summary
We provide an interpretation of Kierkegaard's "Philosophical fragments" based on an analysis of the debate between Mynster and Martensen about rationalism and supernaturalism. We argue that the composition of the Fragments in an essential way reflects the manner in which the theological questions under debate were formulated. From this perspective, the Fragments may at first sight seem to bring ample support to Mynster, both in form and in substance. However, we argue that this impression changes radically upon closer examination. Quite to the contrary, we argue that Climacus reformulates the points put forth by Mynster in a way which goes against Mynster's own theological system.

Waaler, Arild & Antonsen, Roger (2003). A Free Variable Sequent Calculus with Uniform Variable Splitting. Lecture Notes in Computer Science.
ISSN 03029743.
2796, s 214 229
Show summary
Abstract: A system with variable splitting is introduced for a sequent calculus with free variables and runtime Skolemization. Derivations in the system are invariant under permutation, so that the order in which rules are applied has no effect on the leaves. Technically this is achieved by means of a simple indexing system for formulae, variables and Skolem functions. Moreover, the way in which variables are split enables us to restrict the term universe branchwise.

Waaler, Arild (2001). Connections in Nonclassical Logics. Handbook of Automated Reasoning.
2, s 1487 1576
Show summary
The article addresses the use of connection methods within nonclassical proof systems. It contains an original presentation of the main ideas in the field and the following new results: (1) a clarification of the relationship between the sequent calculus with free variables, free variable tableaux and the matrix system for classical logic. I have in particular identified a new class of sequent calculus skeletons which corresponds to matrices, (2) a new soundness proof for the free variable systems for classical logic based on permutation. The technique is then applied to the nonclassical systems, (3) a sequent calculus rendition of the matrix system for intuitionistic and normal modal logics up to S4 with new proofs of soundness and completeness, (4) new proof systems for modal logics K45 and S5 with quantifiers.

Waaler, Arild (2001). Connections in nonclassical logics, In
Handbook of Automated Reasoning, eds. A. Robinson and A. Voronkov.
Elsevier Science.
s 1487
 1576
Show summary
The direct use of connection methods within nonclassical proof systems has been limited to matrix characterizations. A main objective for this work has been to present the idea underlying the matrix systems in a simpler way, and in a way which also acc ommodates the related activity within the tableau community. The article contains an original presentation of the main ideas in the field and contains the following new results: (1) a clarification of the relationship between the sequent calculus with f ree variables, free variable tableaux and the matrix system for classical logic. I have in particular identified a new class of sequent calculus skeletons which corresponds to matrices, (2) a new soundness proof for the free variable systems for classic al logic based on permutation. The technique is then applied to the nonclassical systems, (3) a sequent calculus rendition of the matrix system for intuitionistic and normal modal logics up to S4 with new proofs of soundness and completeness, (4) new pr oof systems for modal logics K45 and S5 with quantifiers

Kolstad, Hans; Bjørnstad, Hall & Waaler, Arild (1999). Noen punkter fra Pascals liv og verk, I:
Endelighet og evighet. 15 essays om Blaise Pascal.
Aschehoug forlag.
s 11
 23
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Giese, Martin & Waaler, Arild (ed.) (2009). Automated Reasoning with Analytic Tableaux and Related Methods. 18th International Conference, TABLEAUX 2009, Oslo, Norway, July 610, 2009, Proceedings.
Springer.
ISBN 9783642027154.
341 s.

Kolstad, Hans; Bjørnstad, Hall & Waaler, Arild (1999). Endelighet og evighet. 15 essays om Blaise Pascal.
Aschehoug & Co.
ISBN 8203180507.
299 s.

Kolstad, Hans; Bjørnstad, Hall & Waaler, Arild (1999). Endelighet og evighet. 15 essays om Blaise Pascal.
Aschehoug forlag.
ISBN 8203180507.
299 s.

Kolstad, Hans & Waaler, Arild (red.) (1999). Endelighet og evighet. 15 essays om Blaise Pascal.
Aschehoug & Co.
ISBN 8203180507.
View all works in Cristin

Cameron, David B.; Waaler, Arild & Abel, Mara (2019). Digital Twins as a Platform For Artificial Intelligence in the Petroleum Supply Chain.
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The digital twin offers a potentially powerful way of using simulation to support business and change the way field development and petroleum operations are done. The concept is hyped, being at the very top of the Gartner hype curve. The idea of the digital twin is also not new in the petroleum and process industries. We have been building simulations and linking them to design and operational data for as long as computers have been used. However recent changes in information technology make implementation of digital twins a natural next step in the application of analytical methods of all types to problems in the petroleum supply chain. We argue that a wellstructured digital twin is essential for the scalable, effective implementation of artificial intelligence. Digital twins are complex systems that combine simulations with design and operational data to solve a business problem. However, the successful adoption of this approach is challenging. We need to answer the question: “How can digital twins be made sustainable, maintainable and useful?”. We focus here on the development of twins in the oil and gas industry. Most academic work in this area has been done in the manufacturing industries. We review this literature and propose a simple model of digital twins. This allows us to identify challenges with current implementations and propose a research agenda that will allow future twins to be sustainable, maintainable and usable. We believe that such a digital twin will need the development and use of a semantic backbone – an applicationindependent description of the facility of system to be twinned. This backbone consists of several elements. The first is an asset model that describes the facility, how it is built up and what it is made of. The second element is a set of requirements, that captures the purpose of the facility and tracks the compliance of the facility with these requirements. Third, we need to model the lifecycle of the facility, allowing for an asset model and its requirements to evolve from conceptual design, through engineering, procurement, construction & commissioning, to operation, maintenance & decommissioning. This structuring of data and information provides a secure, scalable and foundation for all types of AI application. This paper presents examples of each of these types of semantic model. We also describe our plans for developing a new best practice for digital twins in collaboration with leading oil companies.

Cameron, David B.; Waaler, Arild; Skjæveland, Martin G; Gjerver, Anders & Hansen, Christian Mahesh (2019). The Whole Plant Digital Twin: What Can Semantic Technologies Contribute?.

Cameron, David B.; Waaler, Arild; Tungland, Knut Sebastian & Nøst, Elisabeth (2019). Using the Industry Collaboration Canvas in the MidTerm Review. Experience in applying the framework in the oil and gas industry.
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The SIRIUS Centre for Scalable Data Access in the Oil and Gas Domain is funded by the Research Council of Norway and hosted by the University of Oslo. It pursues fundamental research that drives innovations related to digitalisation of the oil & gas industry. The centre consists of researchers from four institutions (University of Oslo, NTNU, Simula Research Centre and University of Oxford) and fourteen companies in the oil and gas supply chain. It is funded for eight years from 2015 and is now undergoing a midterm review that assesses the centre’s progress and determines whether it will be funded for its full term. To prepare for the review, it was necessary to have a structured discussion with each industrial partner. This was done to determine how successful the partnership had been to date, see if any changes needed to be made and sketch a plan for the last half of the centre’s life. The assessment required a tool that was simple to use, easy to understand and flexible. We chose to use the Industry Collaboration Canvas of Frølund, Murray and Riedel (2018). This paper describes the process and results of this work, from the perspective of the centre management and two of the larger partner companies, Equinor and TechnipFMC. Two workers were trained in the use of the canvas in March 2018. The process was explained to the partners at the centre’s general assembly and it was agreed that we would conduct these workshops. The workshops were then held in the second half of 2018. SIRIUS management visited each partner’s site to hold the meeting. However, in some cases, videoconferencing had to be used due to the geographical factors. The use of the canvas was considered to be successful. Feedback from all participants was positive and the information gathered provided factual material for preparing the documents needed for the midterm review. In all cases, we identified concrete actions that will improve the value of collaboration between the researchers and each industrial partner. The canvas identified gaps and potential problems for collaboration. In these cases we were able to agree on necessary corrective actions. The canvas is now shared between centre management and the partner and is a defacto agreement on how the partnership will continue over the next 5 years. The canvas is an effective and powerful tool for assessing and planning interactions between researchers and industrial companies. It is simple to use, easy to understand and brings rigour and structure to the discussions around current and new collaborations. We are actively promoting the use of this tool in other parts of the University.

Cameron, David B.; Waaler, Arild & Komulainen, Tiina M. (2018). Oil and Gas digital twins after twenty years. How can they be made sustainable, maintainable and useful?.
Show summary
The digital twin offers a potentially powerful way of using simulation to support business and change the way industrial operations are done. The idea of the digital twin is not new but recent changes in information technology make implementation of digital twins a natural next step in the application of simulation technologies. Simulation practitioners will find that their models are increasingly embedded in complex systems that combine simulations with operational data to solve a business problem. However, the successful adoption of this approach is challenging. This paper asks the question: “How can digital twins be made sustainable, maintainable and useful?”. We focus primarily on the development of twins in the oil and gas industry. Most academic work in this area has been done in the manufacturing industries. We review this literature and propose a simple model of digital twins. This allows us to identify challenges with current implementations and propose a research agenda that will allow future twins to be sustainable, maintainable and usable.

Latif, Adnan; Waaler, Arild; Giese, Martin; Hovland, Dag & Skjæveland, Martin G (2018). OntologyBased Data Access in Exploration.

Cameron, David Bruce; Waaler, Arild; Hovland, Dag & Skjæveland, Martin G (2017). Practical Knowledge Representation for Data Access to Subsurface Data: The Achievements and Potential of the Optique Platform.

JimenezRuiz, Ernesto; Hovland, Dag; Slaughter, Laura; Håndstad, Tony & Waaler, Arild (2017). On adopting ontology alignment techniques within the phenotype acquisition process. CEUR Workshop Proceedings.
ISSN 16130073.
2042, s 1 2

Waaler, Arild (2017). Engineering Requirements: An Example of ResearchEnabled Digitalization.

Cameron, David B.; Skjæveland, Martin G; Giese, Martin; Hovland, Dag; Waaler, Arild; Bjørge, Eldar & Tungland, Knut Sebastian (2016). Optique: Simple, Oil & Gasoriented access to big data in exploration.

Giese, Martin & Waaler, Arild (2013). Optique  ￼Scalable Enduser Access to Big Data.

Kharlamov, Evgeny; Giese, Martin; Jimenezruiz, Ernesto; Skjæveland, Martin G; Soylu, Ahmet; Zheleznyakov, Dmitriy; Bagosi, Timea; Console, Marco; Haase, Peter; Horrocks, Ian; Marciuska, Sarunas; Pinkel, Christoph; Rodriguezmuro, Mariano; Ruzzi, Marco; Santarelli, Valerio; Fabio Savo, Domenico; Sengupta, Kunal; Schmidt, Michael; Thorstensen, Evgenij; Trame, Johannes & Waaler, Arild (2013). Optique 1.0: Semantic Access to Big Data: The Case of Norwegian Petroleum Directorate's FactPages.

Giese, Martin & Waaler, Arild (ed.) (2009). TABLEAUX 2009 Position Papers and Workshop Proceedings. Conference proceedings (Universitetet i Oslo. Institutt for informatikk). 387.

Hansen, Christian Mahesh; Antonsen, Roger & Waaler, Arild (2007). Incremental Closure of Variable Splitting Tableaux in TABLEAUX'07  Automated Reasoning with Analytic Tableaux and Related Methods: Position Papers. Editors: Nicola Olivetti, Camilla Schwind. LSIS.RR.2007.002.

Holen, Bjarne; Johnsen, Einar Broch & Waaler, Arild (2005). Representing Strategies for the Connection Calculus in Rewriting Logic.

Antonsen, Roger & Waaler, Arild (2005). Consistency of Variable Splitting in Free Variable Systems of FirstOrder Logic.

Holen, Bjarne; Johnsen, Einar Broch & Waaler, Arild (2005). Representing Strategies for the Connection Calculus in Rewriting Logic.

Kluwer, Johan & Waaler, Arild (2005). A default theory of trust.
Show summary
We present a framework for reasoning about information sources, with application to conflict resolution and belief formation at various degrees of reliability. On the basis of an assignment of relative trustworthiness to sets of information sources, a lattice of degrees of trustworthiness is constructed; from this, a priority structure is derived and applied to the problem of forming the right opinion. Consolidated with an unquestioned knowledge base, this provides an unambiguous account of what an agent should believe, conditionally on which information sources are trusted. Applications in multiagent doxastic logic are sketched.

Kluwer, Johan & Waaler, Arild (2005). Natural deduction for belief at most.
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We present a new approach to the logic of \emph{at most}, introducing the notion of \emph{parametric propositions} to modal natural deduction proofs. We apply the method with a natural deduction formulation of the doxastic logic \natded, a new system in the ``only knowing'' family. Using parametric proof rules, we give introduction and elimination rules for belief \emph{at most} that directly match the natural secondorder formulation of the concept. \natded is sound and complete with respect to the class of intended models. We conjecture that it weakly normalizes and that it satisfies the subformula property.

Kluwer, Johan & Waaler, Arild (2005). Relative trustworthiness.

Solhaug, Bjørnar & Waaler, Arild (2005). Logical Spaces in MultiAgent Only Knowing Systems.
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We present a weak multiagent language of Only knowing and an analysis of the logical spaces that can be defined in it. The logic complements the approach to generalizing Levesque`s All I Know system made by Halpern and Lakemeyer. A novel feature of our approach is that the logic is defined entirely at the object level with no reference to metaconcepts in the definition of the axiom system. We show that the logic of Halpern and Lakemeyer can be encoded in our system in the form of a particular logical space.

Solhaug, Bjørnar & Waaler, Arild (2005). Semantics for multiagent only knowing (extended abstract).

Waaler, Arild (2005). Bevissystemer og semantikk for multiagentsystemer.
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Jeg vil i dette foredraget presentere pågående arbeid innen formuleringer av systemer for automatisk deduksjon for klassiske og modale logikker og anvendelser av logikkene til analyse av kunnskapsrepresentasjon, tillit og defaultresonnering innen multiagent språk. Prosjektene som presenteres har for tiden knyttet til seg 4 stipendiater ved Universitetet i Oslo. Foruten å presentere de grunnleggende ideene og resultatene, vil jeg også skissere videre oppgaver og noen potensielle anvendelse.

Lian, Espen; Langholm, Tore & Waaler, Arild (2004). Only knowing with confidence levels  reductions and complexity.
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A new logic of belief (in the "Only knowing" family) withconfidence levels is presented. The logic allows a natural distinction between explicit and implicit belief representations, where the explicit form directly expresses its models. The explicit form can be found by applying a set ofequivalence preserving rewriting rules to the implicit form. The rewriting process is performed entirely within thelogic, on the object level. We prove that the problem of deciding whether there exists a consistent explicit form is

Waaler, Arild (2004). Consistency proofs for systems of multiagent only knowing.
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Various multimodal systems are proposed for the representation of belief states in a multiagent context. We introduce sequent calculi for these systems and prove cutelimination results. A corollary to these results is that a new and naturalmultimodal extension of Levesque's system of only knowing is consistent.

Waaler, Arild (2003). Trustwortiness by default.
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First, a new logic of belief is briefly presented and applied to the analysis of default inference. The logic allows a natural distinction between explicit and implicit belief representations, where the explicit form directly expresses its models. A novelty of the system is that the appeal to coherence intrinsic to the nature of defaults can be accommodated entirely within the object language. We will see that an implicit representation of a given set of defaults, in combination with situationspecific beliefs, can be reduced to a provably equivalent explicit form, and furthermore, that applying an order of precedence to a set of defaults can make such reduction possible where nonordered defaults do not yield explicit results.

Waaler, Arild (2003). Trustworthiness by default.

Waaler, Arild & Antonsen, Roger (2003). A Free Variable Sequent Calculus with Uniform Variable Splitting.
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En ny sekventkalkyle for første ordens logikk med frie variable som løser splitteproblemet. Reglene i kalkylen har ingen begrensninger mht. permutasjon. En ny sekventkalkyle for første ordens logikk med frie variable som løser splitteproblemet. Reglene i kalkylen har ingen begrensninger mht. permutasjon.

Waaler, Arild (2001). Proof search in intuitionistic logic.

Waaler, Arild (2001). Proof search in intuitionistic logic.

Waaler, Arild (2000). Den forventede Salomon Goldkalb.

Waaler, Arild (2000). Indicative conditionals.

Waaler, Arild (2000). Kierkegaard, Leibniz og modale kategorier.

Waaler, Arild & Storøy, S (2000). Proofsearch in intuitionistic logic.

Waaler, Arild (1999). Bevissøk i intuisjonistisk logikk.

Waaler, Arild (1999). Den forventede Salomon Goldkalb.

Waaler, Arild (1999). Indicative conditionals.
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Published Nov. 4, 2010 2:25 PM
 Last modified Nov. 25, 2014 10:20 AM