Jon Henrik Forssell

• Mathisen, Steinar; Sundtjønn, Trude & Forssell, Jon Henrik (2023). BlueBots and irrational numbers: Contingency moments in teaching mathematics and computational thinking in teacher education . I Drijvers, Paul; Csapodi, Csaba; Palmer, Hanna; Gosztonyi, Katalin & Kónya, Eszter (Red.), Proceedings of the thirteenth Congress of the European Society for Research in Mathematics Education (CERME13). European Society for Research in Mathematics Education. ISSN 978-963-7031-04-5. s. 2736–2743.
• Forssell, Henrik; Kharlamov, Evgeny & Thorstensen, Evgenij (2020). On equivalence and cores for incomplete databases in open and closed worlds. Leibniz International Proceedings in Informatics. ISSN 1868-8969. 155, s. 1–21. doi: 10.4230/LIPIcs.ICDT.2020.10. Fulltekst i vitenarkiv Vis sammendrag

  Data exchange heavily relies on the notion of incomplete database instances. Several semantics for such instances have been proposed and include open (OWA), closed (CWA), and open-closed (OCWA) world. For all these semantics important questions are: whether one incomplete instance semantically implies another; when two are semantically equivalent; and whether a smaller or smallest semantically equivalent instance exists. For OWA and CWA these questions are fully answered. For several variants of OCWA, however, they remain open. In this work we adress these questions for Closed Powerset semantics and the OCWA semantics of [24]. We define a new OCWA semantics, called OCWA*, in terms of homomorphic covers that subsumes both semantics, and characterize semantic implication and equivalence in terms of such covers. This characterization yields a guess-and-check algorithm to decide equivalence, and shows that the problem is NP-complete. For the minimization problem we show that for several common notions of minimality there is in general no unique minimal equivalent instance for Closed Powerset semantics, and consequently not for the more expressive OCWA* either. However, for Closed Powerset semantics we show that one can find, for any incomplete database, a unique finite set of its subinstances which are subinstances (up to renaming of nulls) of all instances semantically equivalent to the original incomplete one. We study properties of this set, and extend the analysis to OCWA*

• Forssell, Jon Henrik; Gylterud, Håkon Robbestad & Spivak, David I (2020). Type theoretical databases. Journal of Logic and Computation. ISSN 0955-792X. 30(1), s. 217–238. doi: 10.1093/logcom/exaa009. Fulltekst i vitenarkiv
• Forssell, Henrik & Lumsdaine, Peter Lefanu (2019). Constructive Reflectivity Principles for Regular Theories. Journal of Symbolic Logic (JSL). ISSN 0022-4812. 84(4), s. 1348–1367. doi: 10.1017/jsl.2019.70.
• Skjæveland, Martin G; Lupp, Daniel P.; Karlsen, Leif Harald & Forssell, Jon Henrik (2018). Practical Ontology Pattern Instantiation, Discovery, and Maintenance with Reasonable Ontology Templates. Lecture Notes in Computer Science (LNCS). ISSN 0302-9743. 11136, s. 477–494. doi: 10.1007/978-3-030-00671-6_28. Fulltekst i vitenarkiv
• 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 1613-0073. 1963, s. 1–4.
• Forssell, Jon Henrik; Lupp, Daniel Paul; Skjæveland, Martin G & Thorstensen, Evgenij (2017). Reasonable macros for ontology construction and maintenance. CEUR Workshop Proceedings. ISSN 1613-0073. 1879, s. 1–13.
• Skjæveland, Martin G; Forssell, Jon Henrik; Kluwer, Johan Wilhelm; Lupp, Daniel Paul; Thorstensen, Evgenij & Waaler, Arild (2017). Pattern-Based Ontology Design and Instantiation with Reasonable Ontology Templates. CEUR Workshop Proceedings. ISSN 1613-0073. 2043.
• Forssell, Jon Henrik; Gylterud, Håkon Robbestad & Spivak, David I (2016). Type theoretical databases. Lecture Notes in Computer Science (LNCS). ISSN 0302-9743. 9537, s. 117–129. doi: 10.1007/978-3-319-27683-0_9.
• Forssell, Henrik (2013). Subgroupoids and quotient theories . Theory and Applications of Categories. ISSN 1201-561X.
• Forssell, Henrik & Awodey, Steve (2013). First-order Logical Duality. Annals of Pure and Applied Logic. ISSN 0168-0072. doi: 10.1016/j.apal.2012.10.016.
• Forssell, Jon Henrik (2012). Topological representation of geometric theories. Mathematical logic quarterly. ISSN 0942-5616. 58(6), s. 380–393. doi: 10.1002/malq.201100080.
• Forssell, Henrik & Awodey, Steve (2005). Algebraic models of intuitionistic theories of sets and classes . Theory and Applications of Categories. ISSN 1201-561X.

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• Forssell, Jon Henrik & Briseid, Eyvind Martol (2020). Feilaktige bevis for sanne påstander.
• Forssell, Jon Henrik; Kharlamov, Evgeny & Thorstensen, Evgenij (2017). Towards characterising data exchange solutions in open and closedwords (extended abstract). CEUR Workshop Proceedings. ISSN 1613-0073. 1912, s. 1–2.
• Forssell, Jon Henrik; Kharlamov, Evgeny & Thorstensen, Evgenij (2017). Towards Characterising Data Exchange Solutions in Open and Closed Words. CEUR Workshop Proceedings. ISSN 1613-0073. 1912.

Se alle arbeider i Cristin