@article{CabalarFandinnoSchaubetal.2019, author = {Cabalar, Pedro and Fandinno, Jorge and Schaub, Torsten H. and Schellhorn, Sebastian}, title = {Gelfond-Zhang aggregates as propositional formulas}, series = {Artificial intelligence}, volume = {274}, journal = {Artificial intelligence}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0004-3702}, doi = {10.1016/j.artint.2018.10.007}, pages = {26 -- 43}, year = {2019}, abstract = {Answer Set Programming (ASP) has become a popular and widespread paradigm for practical Knowledge Representation thanks to its expressiveness and the available enhancements of its input language. One of such enhancements is the use of aggregates, for which different semantic proposals have been made. In this paper, we show that any ASP aggregate interpreted under Gelfond and Zhang's (GZ) semantics can be replaced (under strong equivalence) by a propositional formula. Restricted to the original GZ syntax, the resulting formula is reducible to a disjunction of conjunctions of literals but the formulation is still applicable even when the syntax is extended to allow for arbitrary formulas (including nested aggregates) in the condition. Once GZ-aggregates are represented as formulas, we establish a formal comparison (in terms of the logic of Here-and-There) to Ferraris' (F) aggregates, which are defined by a different formula translation involving nested implications. In particular, we prove that if we replace an F-aggregate by a GZ-aggregate in a rule head, we do not lose answer sets (although more can be gained). This extends the previously known result that the opposite happens in rule bodies, i.e., replacing a GZ-aggregate by an F-aggregate in the body may yield more answer sets. Finally, we characterize a class of aggregates for which GZ- and F-semantics coincide.}, language = {en} } @article{JanhunenKaminskiOstrowskietal.2017, author = {Janhunen, Tomi and Kaminski, Roland and Ostrowski, Max and Schellhorn, Sebastian and Wanko, Philipp and Schaub, Torsten H.}, title = {Clingo goes linear constraints over reals and integers}, series = {Theory and practice of logic programming}, volume = {17}, journal = {Theory and practice of logic programming}, publisher = {Cambridge Univ. Press}, address = {New York}, issn = {1471-0684}, doi = {10.1017/S1471068417000242}, pages = {872 -- 888}, year = {2017}, abstract = {The recent series 5 of the Answer Set Programming (ASP) system clingo provides generic means to enhance basic ASP with theory reasoning capabilities. We instantiate this framework with different forms of linear constraints and elaborate upon its formal properties. Given this, we discuss the respective implementations, and present techniques for using these constraints in a reactive context. More precisely, we introduce extensions to clingo with difference and linear constraints over integers and reals, respectively, and realize them in complementary ways. Finally, we empirically evaluate the resulting clingo derivatives clingo[dl] and clingo[lp] on common language fragments and contrast them to related ASP systems.}, language = {en} } @article{GebserKaminskiKaufmannetal.2018, author = {Gebser, Martin and Kaminski, Roland and Kaufmann, Benjamin and L{\"u}hne, Patrick and Obermeier, Philipp and Ostrowski, Max and Romero Davila, Javier and Schaub, Torsten H. and Schellhorn, Sebastian and Wanko, Philipp}, title = {The Potsdam Answer Set Solving Collection 5.0}, series = {K{\"u}nstliche Intelligenz}, volume = {32}, journal = {K{\"u}nstliche Intelligenz}, number = {2-3}, publisher = {Springer}, address = {Heidelberg}, issn = {0933-1875}, doi = {10.1007/s13218-018-0528-x}, pages = {181 -- 182}, year = {2018}, abstract = {The Potsdam answer set solving collection, or Potassco for short, bundles various tools implementing and/or applying answer set programming. The article at hand succeeds an earlier description of the Potassco project published in Gebser et al. (AI Commun 24(2):107-124, 2011). Hence, we concentrate in what follows on the major features of the most recent, fifth generation of the ASP system clingo and highlight some recent resulting application systems.}, language = {en} } @misc{CabalarFandinnoSchaubetal.2019, author = {Cabalar, Pedro and Fandinno, Jorge and Schaub, Torsten H. and Schellhorn, Sebastian}, title = {Lower Bound Founded Logic of Here-and-There}, series = {Logics in Artificial Intelligence}, volume = {11468}, journal = {Logics in Artificial Intelligence}, publisher = {Springer}, address = {Cham}, isbn = {978-3-030-19570-0}, issn = {0302-9743}, doi = {10.1007/978-3-030-19570-0_34}, pages = {509 -- 525}, year = {2019}, abstract = {A distinguishing feature of Answer Set Programming is that all atoms belonging to a stable model must be founded. That is, an atom must not only be true but provably true. This can be made precise by means of the constructive logic of Here-and-There, whose equilibrium models correspond to stable models. One way of looking at foundedness is to regard Boolean truth values as ordered by letting true be greater than false. Then, each Boolean variable takes the smallest truth value that can be proven for it. This idea was generalized by Aziz to ordered domains and applied to constraint satisfaction problems. As before, the idea is that a, say integer, variable gets only assigned to the smallest integer that can be justified. In this paper, we present a logical reconstruction of Aziz' idea in the setting of the logic of Here-and-There. More precisely, we start by defining the logic of Here-and-There with lower bound founded variables along with its equilibrium models and elaborate upon its formal properties. Finally, we compare our approach with related ones and sketch future work.}, language = {en} } @article{FriouxSchaubSchellhornetal.2019, author = {Frioux, Cl{\´e}mence and Schaub, Torsten H. and Schellhorn, Sebastian and Siegel, Anne and Wanko, Philipp}, title = {Hybrid metabolic network completion}, series = {Theory and practice of logic programming}, volume = {19}, journal = {Theory and practice of logic programming}, number = {1}, publisher = {Cambridge University Press}, address = {New York}, issn = {1471-0684}, doi = {10.1017/S1471068418000455}, pages = {83 -- 108}, year = {2019}, abstract = {Metabolic networks play a crucial role in biology since they capture all chemical reactions in an organism. While there are networks of high quality for many model organisms, networks for less studied organisms are often of poor quality and suffer from incompleteness. To this end, we introduced in previous work an answer set programming (ASP)-based approach to metabolic network completion. Although this qualitative approach allows for restoring moderately degraded networks, it fails to restore highly degraded ones. This is because it ignores quantitative constraints capturing reaction rates. To address this problem, we propose a hybrid approach to metabolic network completion that integrates our qualitative ASP approach with quantitative means for capturing reaction rates. We begin by formally reconciling existing stoichiometric and topological approaches to network completion in a unified formalism. With it, we develop a hybrid ASP encoding and rely upon the theory reasoning capacities of the ASP system dingo for solving the resulting logic program with linear constraints over reals. We empirically evaluate our approach by means of the metabolic network of Escherichia coli. Our analysis shows that our novel approach yields greatly superior results than obtainable from purely qualitative or quantitative approaches.}, language = {en} } @article{SchellhornFrankKreitz2019, author = {Schellhorn, Sebastian and Frank, Mario and Kreitz, Christoph}, title = {Br{\"u}ckenkurse f{\"u}r mathematische und informatiknahe Studieng{\"a}nge}, series = {Alles auf Anfang! Befunde und Perspektiven zum Studieneingang}, journal = {Alles auf Anfang! Befunde und Perspektiven zum Studieneingang}, publisher = {Universit{\"a}tsverlag Potsdam}, address = {Potsdam}, isbn = {978-3-86956-452-4}, issn = {2192-1075}, doi = {10.25932/publishup-42853}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-428538}, pages = {257 -- 271}, year = {2019}, language = {de} } @book{FuhrmannSchubarthSchulzeReicheltetal.2019, author = {Fuhrmann, Michaela and Schubarth, Wilfried and Schulze-Reichelt, Friederike and Mauermeister, Sylvi and Seidel, Andreas and Hartmann, Nina and Erdmann, Melinda and Apostolow, Benjamin and Wagner, Laura and Berndt, Sarah and Wippermann, Melanie and Ratzlaff, Olaf and Lumpe, Matthias and Kirjuchina, Ljuba and Rost, Sophia and Zurek, Peter Paul and Faaß, Marcel and Schellhorn, Sebastian and Frank, Mario and Kreitz, Christoph and Wagner, Nelli and Jenneck, Julia and Kleemann, Katrin and Vock, Miriam and Schr{\"o}der, Christian and Erdmann, Kathrin and Koziol, Matthias and Meißner, Marlen and Dibiasi, Anna and Unger, Martin and Piskunova, Elena V. and Bahmutskiy, Andrey E. and Bessonova, Ekatarina A. and Borovik, Ludmila K.}, title = {Alles auf Anfang!}, series = {Potsdamer Beitr{\"a}ge zur Hochschulforschung}, journal = {Potsdamer Beitr{\"a}ge zur Hochschulforschung}, number = {4}, editor = {Schubarth, Wilfried and Mauermeister, Sylvi and Schulze-Reichelt, Friederike and Seidel, Andreas}, publisher = {Universit{\"a}tsverlag Potsdam}, address = {Potsdam}, isbn = {978-3-86956-452-4}, issn = {2192-1075}, doi = {10.25932/publishup-42296}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-422965}, publisher = {Universit{\"a}t Potsdam}, pages = {373}, year = {2019}, abstract = {Im Zuge der Bologna-Reform ist an Hochschulen vieles in Bewegung gekommen. Studium und Lehre sind st{\"a}rker ins Blickfeld ger{\"u}ckt. Dabei kommt der Studieneingangsphase besondere Bedeutung zu, werden doch hier die Weichen f{\"u}r ein erfolgreiches Studium gestellt. Deshalb ist es verst{\"a}ndlich, dass die Hauptanstrengungen der Hochschulen auf den Studieneingang gerichtet sind - ganz nach dem Motto: „Auf den Anfang kommt es an!". Konsens herrscht dahingehend, dass der Studieneingang neu zu gestalten ist, doch beim „Wie?" gibt es unterschiedliche Antworten. Zugleich wird immer deutlicher, dass eine wirksame Neugestaltung der Eingangsphase nur mit einer umfassenden Reform des Studiums gelingen kann. Ziel des vierten Bandes der Potsdamer Beitr{\"a}ge zur Hochschulforschung ist es, eine Zwischenbilanz der Debatte zum Studieneingang zu ziehen. Auf der Basis empirischer Studien werden unterschiedliche Perspektiven auf den Studieneingang eingenommen und Empfehlungen zur Optimierung des Studieneingangs abgeleitet. Die zahlreichen Untersuchungsergebnisse Potsdamer Forschergruppen werden durch weitere nationale sowie internationale Perspektiven erg{\"a}nzt. Der Band richtet sich an alle, die sich f{\"u}r die Entwicklung an Hochschulen interessieren.}, language = {de} }