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  • 151.
    Campano, Erik
    Umeå universitet, Samhällsvetenskapliga fakulteten, Institutionen för psykologi.
    Artificially Intelligent Black Boxes in Emergency Medicine: An Ethical Analysis2019Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [sv]

    Det blir allt vanligare att föreslå att icke-transparant artificiell intelligens, s.k. black boxes, används inom akutmedicinen. I denna uppsats används etisk analys för att härleda sju riktlinjer för utveckling och användning av black boxes i akutmedicin. Analysen är grundad på sju variationer av ett tankeexperiment som involverar en läkare, en black box och en patient med bröstsmärta på en akutavdelning. Grundläggande begrepp, inklusive artificiell intelligens, black boxes, metoder för transparens, akutmedicin och etisk analys behandlas detaljerat. Tre viktiga områden av etisk vikt identifieras: samtycke; kultur, agentskap och privatliv; och skyldigheter. Dessa områden ger upphov till de sju variationerna. För varje variation urskiljs en viktig etisk fråga som identifieras och analyseras. En riktlinje formuleras och dess etiska rimlighet testas utifrån konsekventialistiska och deontologiska metoder. Tillämpningen av riktlinjerna på medicin i allmänhet, och angelägenheten av fortsatt etiska analys av black boxes och artificiell intelligens inom akutmedicin klargörs.

  • 152. Canovas, Jose S.
    et al.
    Panchuk, Anastasiia
    Puu, Tönu
    Umeå universitet, Samhällsvetenskapliga fakulteten, Centrum för regionalvetenskap (CERUM).
    Asymptotic dynamics of a piecewise smooth map modelling a competitive market2015Inngår i: Mathematics and Computers in Simulation, ISSN 0378-4754, E-ISSN 1872-7166, Vol. 117, s. 20-38Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the present work we study asymptotic dynamics of a multi-dimensional piecewise smooth map which models an oligopoly market where competitors use adaptive scheme for reaction choice. Each competitor also defines the moment for renewing the capital equipment depending on how intensively the latter is used. Namely, the larger output is produced, the quicker the capital exhausts. It is shown then that the asymptotic dynamics of the map allows coexistence of different metric attractors in which case it is sensitive to initial conditions. We also investigate stability of trajectories representing Cournot equilibria which are here not fixed but periodic points. In particular, it is shown that several such Cournot equilibria, belonging to different invariant manifolds, may coexist some of them being locally asymptotically stable and some being unstable. (C) 2015 International Association for Mathematics and Computers in Simulation (IMACS).

  • 153. Carlsson, Christer
    et al.
    Ehrenberg, Dieter
    Eklund, Patrik
    Department of Computer Science, Åbo Akademi University, Åbo, Finland.
    Fedrizzi, Mario
    Gustafsson, Patrik
    Lindholm, Paul
    Merkuryeva, Galina
    Riissanen, Tony
    Ventre, Aldo
    Consensus in distributed soft environments1992Inngår i: European Journal of Operational Research, ISSN 0377-2217, E-ISSN 1872-6860, Vol. 61, nr 1-2, s. 165-185Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper studies the problem of formalizing consensus reaching within a set of decision makers trying to find and agree upon a mutual decision. Decision makers produce their individual rankings, using their own pet decision schemas. Thus consensus reaching relies only on the aggregation of individual decisions rather than on individual decision procedures. The aggregation of the individual rankings is supported by an advising monitor which tries to contract the decision makers into a mutual decision through soft enforcement. Convergence to consensus then depends upon the decision makers' willingness to compromise. We use a topological approach to consensus where we can measure distances between decision makers. Within the approach we can also model the trade-off between a degree of consensus and a strength of majority.

  • 154.
    Cavallin, Kristoffer
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Institutionen för datavetenskap.
    Svensson, Peter
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Institutionen för datavetenskap.
    Semi-Autonomous,Teleoperated Search and Rescue Robot2009Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The interest in robots in the urban search and rescue (USAR) field has increased the last two decades. The idea is to let robots move into places where human rescue workers cannot or, due to high personal risks, should not enter.In this thesis project, an application is constructed with the purpose of teleoperating a simple robot. This application contains a user interface that utilizes both autonomous and semi-autonomous functions, such as search, explore and point-and-go behaviours. The purpose of the application is to work with USAR principles in a refined and simplified environment, and thereby increase the understanding for these principles and how they interact with each other. Furthermore, the thesis project reviews the recent and the current status of robots in USAR applications and use of teleoperation and semi-autonomous robots in general. Some conclusions that are drawn towards the end of the thesis are that the use of robots, especially in USAR situations, will continue to increase. As robots and support technology both become more advanced and cheaper by the day, teleoperation and semi-autonomous robots will also be seen in more and more places.

     

  • 155. Chen, Ye
    et al.
    Wang, Aiguo
    Ding, Huitong
    Que, Xia
    Li, Yabo
    An, Ning
    Jiang, Lili
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    A global learning with local preservation method for microarray data imputation2016Inngår i: Computers in Biology and Medicine, ISSN 0010-4825, E-ISSN 1879-0534, Vol. 77, s. 76-89Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Microarray data suffer from missing values for various reasons, including insufficient resolution, image noise, and experimental errors. Because missing values can hinder downstream analysis steps that require complete data as input, it is crucial to be able to estimate the missing values. In this study, we propose a Global Learning with Local Preservation method (GL2P) for imputation of missing values in microarray data. GL2P consists of two components: a local similarity measurement module and a global weighted imputation module. The former uses a local structure preservation scheme to exploit as much information as possible from the observable data, and the latter is responsible for estimating the missing values of a target gene by considering all of its neighbors rather than a subset of them. Furthermore, GL2P imputes the missing values in ascending order according to the rate of missing data for each target gene to fully utilize previously estimated values. To validate the proposed method, we conducted extensive experiments on six benchmarked microarray datasets. We compared GL2P with eight state-of-the-art imputation methods in terms of four performance metrics. The experimental results indicate that GL2P outperforms its competitors in terms of imputation accuracy and better preserves the structure of differentially expressed genes. In addition, GL2P is less sensitive to the number of neighbors than other local learning-based imputation. methods.

  • 156.
    Chiang, David
    et al.
    University of Notre Dame.
    Drewes, Frank
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Gildea, Daniel
    University of Rochester.
    Lopez, Adam
    University of Edinburgh.
    Satta, Giorgio
    University of Padua.
    Weighted DAG automata for semantic graphs2018Inngår i: Computational linguistics - Association for Computational Linguistics (Print), ISSN 0891-2017, E-ISSN 1530-9312, Vol. 44, nr 1, s. 119-186Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Graphs have a variety of uses in natural language processing, particularly as representations of linguistic meaning. A deficit in this area of research is a formal framework for creating, combining, and using models involving graphs that parallels the frameworks of finite automata for strings and finite tree automata for trees. A possible starting point for such a framework is the formalism of directed acyclic graph (DAG) automata, defined by Kamimura and Slutzki and extended by Quernheim and Knight. In this article, we study the latter in depth, demonstrating several new results, including a practical recognition algorithm that can be used for inference and learning with models defined on DAG automata. We also propose an extension to graphs with unbounded node degree and show that our results carry over to the extended formalism.

  • 157.
    Chowdhury, Mabruk
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Institutionen för datavetenskap.
    Development of User Interfaces for Mobile, Context-aware Agenda Tools2010Independent thesis Advanced level (degree of Master (One Year)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Diverging from traditional agenda tools, comes Activity Ace which explores the closest vicinity of the hosting mobile device and responds the activity the user wants to be reminded of. In this thesis we investigate in and mobility means and moreover what evaluation methods exists Ace is used by typing down the activity you want to be reminded of and attaching to it a situational description built of metadata and Boolean conditions. The application will trigger the reminder i.e. the activity to be reminded of when the situational description matches with the device's closest vicinity. Amongst many, we found that core features of a contextaware applications consists of what contextawarenessfor these kinds of applications. Activitypresentation, automatic execution of a service  and misconceptions used in mobility rhetoric such as Furthermore we have learned that usability evaluation methods, therein cooperative evaluation methods provide qualitative information on the design and functionality thus prove to be suitable in evaluation of these kind of applications. By reflecting on these issues, we can better understand the role of contextawareness and mobility in an agenda tool such as Activity Ace. tagging of context to information for later retrieval. We have also clarified commonaccess, any time, anywhere.

  • 158.
    Ciegis, Raimondas
    et al.
    Vilnius Gediminas Technical University, Lithuania.
    Henty, David
    University of Edingburg, UK.
    Kågström, Bo
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Högpresterande beräkningscentrum norr (HPC2N).
    Zilinskas, Julius
    Vilnius Gediminas Technical University, Lithuania.
    Parallel Scientific Computing and Optimization: Advances with Applications2009Bok (Annet vitenskapelig)
  • 159.
    Cimiano, Philipp
    et al.
    Technical University of Karlsruhe.
    Minock, Michael
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Natural language interfaces: what's the problem? -a data-driven quantitative analysis2010Inngår i: Natural language processing and information systems: 14th International Conference on Applications of Natural Language to Information Systems, NLDB 2009 / [ed] Helmut Horacek, Elisabeth Métais, Rafael Muñoz and Magdalena Wolska, Springer Berlin/Heidelberg, 2010, s. 192-206Konferansepaper (Fagfellevurdert)
    Abstract [en]

    While qualitative analyses of the problems involved in building natural language interfaces (NLIs) have been available, a quantitative grounding in empirical data has been missing. We fill this gap by providing a quantitative analysis on the basis of the Geobase dataset. We hope that this analysis can guide further research in NLIs.

  • 160. Clodic, Aurélie
    et al.
    Vázquez-Salceda, Javier
    Dignum, Frank
    Mascarenhas, Samuel
    Dignum, Virginia
    Augello, Agnese
    Gentile, Manuel
    Alami, Rachid
    On the Pertinence of Social Practices for Social Robotics2018Inngår i: International Research Conference Robophilosophy 2018, Vienna, Austria, February 14-17, 2018, IOS Press , 2018, Vol. 311Konferansepaper (Fagfellevurdert)
    Abstract [en]

     In the area of consumer robots that need to have rich social interactions with humans, one of the challenges is the complexity of computing the appropriate interactions in a cognitive, social and physical context. We propose a novel approach for social robots based on the concept of Social Practices. By using social practices robots are able to be aware of their own social identities (given by the role in the social practice) and the identities of others and also be able to identify the different social contexts and the appropriate social interactions that go along with those contexts and identities.

  • 161. Cohen, Mika
    et al.
    Minock, Michael
    KTH Royal Institute of Technology, Stockholm, Sweden.
    Oskarsson, Daniel
    Pelzer, Björn
    Enterprise architecture with executable modelling rules: A case study at the Swedish Defence Materiel Administration2015Inngår i: Advanced Information Systems Engineering Workshops, CAiSE 2015 / [ed] Persson A.,Stirna J., Springer, 2015, Vol. 215, s. 339-350Konferansepaper (Fagfellevurdert)
  • 162. Cohen, Mika
    et al.
    Minock, Michael
    KTH Royal Institute of Technology, Stockholm.
    Oskarsson, Daniel
    Pelzer, Björn
    Natural Language Specification and Violation Reporting of Business Rules over ER-modeled Databases2015Inngår i: Proceedings of the 18th International Conference on Extending Database Technology, EDBT 2015, OpenProceedings.org, University of Konstanz, University Library , 2015, s. 541-544Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper presents our work on adapting and extending natural language interface (NLI) to database technology to support the specification and violation reporting of business rules. The resulting system allows non-technical users to author and manage a rulebook in controlled natural language - serving as a single point of definition that can be compiled into SQL to generate violation reports. To achieve this we represent business rules in tuple calculus, handle negation in our query re-writing algorithms and add support for natural language reflexives (e.g. 'its', 'themselves', etc.). Our results show a large class of business rules can be captured with these extensions. Although our approach is general, we present it applied to compliance checking of regulations over a materiel capability development information system at the Swedish Defence Materiel Administration. At EDBT we will also demonstrate this work over a more generic package delivery domain. While there has been recent effort in pursuing Semantics for Business Vocabulary and Business Rules (SBVR) in the semantic web and description logic communities, to our knowledge ours is the first attempt to provide this capability for ER-modeled relational databases.

  • 163. Conejero, Javier
    et al.
    Caminero, Blanca
    Carrion, Carmen
    Tomas, Luis
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    From volunteer to trustable computing: Providing QoS-aware scheduling mechanisms for multi-grid computing environments2014Inngår i: Future generations computer systems, ISSN 0167-739X, E-ISSN 1872-7115, Vol. 34, s. 76-93Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The exploitation of service oriented technologies, such as Grid computing, is being boosted by the current service oriented economy trend, leading to a growing need of Quality of Service (QoS) mechanisms. However, Grid computing was created to provide vast amounts of computational power but in a best effort way. Providing QoS guarantees is therefore a very difficult and complex task due to the distributed and heterogeneous nature of their resources, specially the volunteer computing resources (e.g., desktop resources). The scope of this paper is to empower an integrated multi QoS support suitable for Grid Computing environments made of either dedicated and volunteer resources, even taking advantage of that fact. The QoS is provided through SLAs by exploiting different available scheduling mechanisms in a coordinated way, and applying appropriate resource usage optimization techniques. It is based on the differentiated use of reservations and scheduling in advance techniques, enhanced with the integration of rescheduling techniques that improve the allocation decisions already made, achieving a higher resource utilization and still ensuring the agreed QoS. As a result, our proposal enhances best-effort Grid environments by providing QoS aware scheduling capabilities. This proposal has been validated by means of a set of experiments performed in a real Grid testbed. Results show how the proposed framework effectively harnesses the specific capabilities of the underlying resources to provide every user with the desired QoS level, while, at the same time, optimizing the resources' usage. (C) 2013 Elsevier B.V. All rights reserved.

  • 164. Confalonieri, Roberto
    et al.
    Nieves, Juan Carlos
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Osorio, Mauricio
    Vazquez-Salceda, Javier
    Dealing with explicit preferences and uncertainty in answer set programming2012Inngår i: Annals of Mathematics and Artificial Intelligence, ISSN 1012-2443, E-ISSN 1573-7470, Vol. 65, nr 2-3, s. 159-198Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, we show how the formalism of Logic Programs with Ordered Disjunction (LPODs) and Possibilistic Answer Set Programming (PASP) can be merged into the single framework of Logic Programs with Possibilistic Ordered Disjunction (LPPODs). The LPPODs framework embeds in a unified way several aspects of common-sense reasoning, nonmonotonocity, preferences, and uncertainty, where each part is underpinned by a well established formalism. On one hand, from LPODs it inherits the distinctive feature of expressing context-dependent qualitative preferences among different alternatives (modeled as the atoms of a logic program). On the other hand, PASP allows for qualitative certainty statements about the rules themselves (modeled as necessity values according to possibilistic logic) to be captured. In this way, the LPPODs framework supports a reasoning which is nonmonotonic, preference- and uncertainty-aware. The LPPODs syntax allows for the specification of (1) preferences among the exceptions to default rules, and (2) necessity values about the certainty of program rules. As a result, preferences and uncertainty can be used to select the preferred uncertain default rules of an LPPOD and, consequently, to order its possibilistic answer sets. Furthermore, we describe the implementation of an ASP-based solver able to compute the LPPODs semantics.

  • 165. Corradini, Andrea
    et al.
    Drewes, Frank
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Term graph rewriting and parallel term rewriting2011Inngår i: Proceedings of the 6th International Workshop on Computing with Terms and Graphs: Saarbrücken, Germany, 2nd April / [ed] Rachid Echahed, Open Publishing Association , 2011, s. 3-18Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The relationship between Term Graph Rewriting and Term Rewriting is well understood: a single term graph reduction may correspond to several term reductions, due to sharing. It is also known that if term graphs are allowed to contain cycles, then one term graph reduction may correspond to infinitely many term reductions. We stress that this fact can be interpreted in two ways. According to the "sequential interpretation", a term graph reduction corresponds to an infinite sequence of term reductions, as formalized by Kennaway et.al. using strongly converging derivations over the complete metric space of infinite terms. Instead according to the "parallel interpretation" a term graph reduction corresponds to the parallel reduction of an infinite set of redexes in a rational term. We formalize the latter notion by exploiting the complete partial order of infinite and possibly partial terms, and we stress that this interpretation allows to explain the result of reducing circular redexes in several approaches to term graph rewriting.

  • 166.
    Dahlberg, Emanuel
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Electricity in a 2D mechanicssimulator for education2011Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Electricity can be a difficult topic to grasp since it is abstract, it is e.g. not possible to see the current and the voltage in a circuit. If electricity can be simulated and visualized, it can become less abstract and easier to understand. This thesis covers the process of simulating electricity in real-time together with a mechanics simulator, called Algodoo.

    The process of analyzing electric circuits from a computers point of view is covered as well as different ways of simulating electric motors, generators and lasers. A large part of the thesis covers how to integrate the electricity and the mechanics simulators in a stable and accurate way. Furthermore, making the objects of the mechanics simulator able to conduct electricity is also covered.

    The thesis shows that it is possible to simulate electricity in real-time, and that physically correct conducting objects requires a lot of processing power, but can be simplified without losing too much correctness. The thesis also shows that the electrical and mechanics simulators preferably should be solved together to get a stable simulation.

    Simulating electricity opens up an endless number of interactive scenarios, e.g. mechanical

    switches, potentiometers, relays and even logic gates. It can be a helpful aid as an

    introduction to electronics and since the simulators are integrated, it can also provide an

    introduction to mechanical work. The amount of energy required to perform dierent tasks

    can be compared and analyzed.

  • 167.
    Desmeurs, David
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Simulation and analysis of bidding behaviours using agents in online auctions2014Inngår i: Proceedings of Umeå's 18th student conference in computing science: USCCS 2014.1 / [ed] Suna Bensch, Thomas Hellström, Umeå: Umeå universitet , 2014, s. 1-9Konferansepaper (Annet vitenskapelig)
  • 168. Dessouky, Ahmed M.
    et al.
    Taha, Taha E.
    Dessouky, Mohamed M.
    Eltholth, Ashraf A.
    Hassan, Emadeldeen
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap. Department of Electronics and Electrical Communication Engineering, Faculty of Electronic Engineering, Menoufia University, Menouf, Egypt.
    Abd El-Samie, Fathi E.
    Non-parametric spectral estimation techniques for DNA sequence analysis and exon region prediction2019Inngår i: Computers & electrical engineering, ISSN 0045-7906, E-ISSN 1879-0755, Vol. 73, s. 334-348Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Bioinformatics is the analysis of biological information using computers and statistical techniques. This paper presents non-parametric spectral estimation techniques based on the Discrete Fourier Transform (DFT) for the analysis of deoxyribonucleic acid (DNA) sequences. These techniques are efficient frequency-domain signal representation techniques, which improve the analysis of DNA sequences and enable the extraction of some desirable information that cannot be extracted from the time-domain representation of these sequences. The adopted techniques are the periodogram, average periodogram (Bartlett), modified average periodogram (Welch), and Blackman and Tukey spectral estimation techniques. The objective of these spectral estimation techniques is to investigate the locations of exons in DNA sequences for gene prediction. A comparison study is presented in this paper between the suggested spectral estimation techniques from the exon prediction perspective. The methods presented in this paper improve the detectability of peaks representing exon regions.

  • 169.
    Dignum, Virginia
    et al.
    Delft University of Technology, The Netherlands.
    Baldoni, Matteo
    Baroglio, Christina
    Caon, Maurizio
    Chatila, Raja
    Dennis, Louise
    Génova, Gonzalo
    Haim, Galit
    Kließ, Malte S
    Lopez-Sanchez, Maite
    Ethics by Design: necessity or curse?2018Inngår i: Proceedings of the 2018 AAAI/ACM Conference on AI, Ethics, and Society, New York: ACM Publications, 2018, s. 60-66Konferansepaper (Fagfellevurdert)
  • 170.
    Dignum, Virginia
    et al.
    Delft University of Technology, Netherlands .
    Dignum, Frank
    Vázquez-Salceda, Javier
    Clodic, Aurélie
    Gentile, Manuel
    Mascarenhas, Samuel
    Augello, Agnese
    Design for Values for Social Robot Architectures2018Inngår i: Envisioning Robots in Society: Power, Politics, and Public Space / [ed] Mark Coeckelbergh, Janina Loh, Michael Funk, Johanna Seibt, Marco Norskov, IOS Press , 2018, Vol. 311Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The integration of social robots in human societies requires that they are capable to take decisions that may affect the lives of people around them. In order to ensure that these robots will behave according to shared ethical principles, an important shift in the design and development of social robots is needed, one where the main goal is improving ethical transparency rather than technical performance, and placing human values at the core of robot designs. In this abstract, we discuss the concept of ethical decision making and how to achieve trust according to the principles of Autonomy, Responsibility and Transparency (ART).

  • 171.
    Dmytryshyn, Andrii
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Skew-symmetric matrix pencils: stratification theory and tools2014Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Investigating the properties, explaining, and predicting the behaviour of a physical system described by a system (matrix) pencil often require the understanding of how canonical structure information of the system pencil may change, e.g., how eigenvalues coalesce or split apart, due to perturbations in the matrix pencil elements. Often these system pencils have different block-partitioning and / or symmetries. We study changes of the congruence canonical form of a complex skew-symmetric matrix pencil under small perturbations. The problem of computing the congruence canonical form is known to be ill-posed: both the canonical form and the reduction transformation depend discontinuously on the entries of a pencil. Thus it is important to know the canonical forms of all such pencils that are close to the investigated pencil. One way to investigate this problem is to construct the stratification of orbits and bundles of the pencils. To be precise, for any problem dimension we construct the closure hierarchy graph for congruence orbits or bundles. Each node (vertex) of the graph represents an orbit (or a bundle) and each edge represents the cover/closure relation. Such a relation means that there is a path from one node to another node if and only if a skew-symmetric matrix pencil corresponding to the first node can be transformed by an arbitrarily small perturbation to a skew-symmetric matrix pencil corresponding to the second node. From the graph it is straightforward to identify more degenerate and more generic nearby canonical structures. A necessary (but not sufficient) condition for one orbit being in the closure of another is that the first orbit has larger codimension than the second one. Therefore we compute the codimensions of the congruence orbits (or bundles). It is done via the solutions of an associated homogeneous system of matrix equations. The complete stratification is done by proving the relation between equivalence and congruence for the skew-symmetric matrix pencils. This relation allows us to use the known result about the stratifications of general matrix pencils (under strict equivalence) in order to stratify skew-symmetric matrix pencils under congruence. Matlab functions to work with skew-symmetric matrix pencils and a number of other types of symmetries for matrices and matrix pencils are developed and included in the Matrix Canonical Structure (MCS) Toolbox.

  • 172.
    Dmytryshyn, Andrii
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Fonseca, Carlos
    Rybalkina, Tetiana
    Classification of pairs of linear mappings between two vector spaces and between their quotient space and subspace2016Inngår i: Linear Algebra and its Applications, ISSN 0024-3795, E-ISSN 1873-1856, Vol. 509, s. 228-246Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We classify pairs of linear mappings (U -> V, U/U' -> V') in which U, V are finite dimensional vector spaces over a field IF, and U', are their subspaces. (C) 2016 Elsevier Inc. All rights reserved.

  • 173.
    Dmytryshyn, Andrii
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Högpresterande beräkningscentrum norr (HPC2N).
    Johansson, Stefan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Högpresterande beräkningscentrum norr (HPC2N).
    Kågström, Bo
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Högpresterande beräkningscentrum norr (HPC2N).
    Codimension computations of congruence orbits of matrices, symmetric and skew-symmetric matrix pencils using Matlab2013Rapport (Annet vitenskapelig)
    Abstract [en]

    Matlab functions to work with the canonical structures for congru-ence and *congruence of matrices, and for congruence of symmetricand skew-symmetric matrix pencils are presented. A user can providethe canonical structure objects or create (random) matrix examplesetups with a desired canonical information, and compute the codi-mensions of the corresponding orbits: if the structural information(the canonical form) of a matrix or a matrix pencil is known it isused for the codimension computations, otherwise they are computednumerically. Some auxiliary functions are provided too. All thesefunctions extend the Matrix Canonical Structure Toolbox.

  • 174.
    Dmytryshyn, Andrii
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap. Umeå Univ, HPC2N, SE-90187 Umeå, Sweden.
    Kågstrom, Bo
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap. Umeå Univ, HPC2N, SE-90187 Umeå, Sweden.
    Coupled Sylvester-type Matrix Equations and Block Diagonalization2015Inngår i: SIAM Journal on Matrix Analysis and Applications, ISSN 0895-4798, E-ISSN 1095-7162, Vol. 36, nr 2, s. 580-593Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We prove Roth-type theorems for systems of matrix equations including an arbitrary mix of Sylvester and $\star$-Sylvester equations, in which the transpose or conjugate transpose of the unknown matrices also appear. In full generality, we derive consistency conditions by proving that such a system has a solution if and only if the associated set of $2 \times 2$ block matrix representations of the equations are block diagonalizable by (linked) equivalence transformations. Various applications leading to several particular cases have already been investigated in the literature, some recently and some long ago. Solvability of these cases follow immediately from our general consistency theory. We also show how to apply our main result to systems of Stein-type matrix equations.

  • 175.
    Dmytryshyn, Andrii
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Kågstrom, Bo
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Högpresterande beräkningscentrum norr (HPC2N).
    Orbit closure hierarchies of skew-symmetric matrix pencils2014Inngår i: SIAM Journal on Matrix Analysis and Applications, ISSN 0895-4798, E-ISSN 1095-7162, Vol. 35, nr 4, s. 1429-1443Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We study how small perturbations of a skew-symmetric matrix pencil may change its canonical form under congruence. This problem is also known as the stratification problem of skew-symmetric matrix pencil orbits and bundles. In other words, we investigate when the closure of the congruence orbit (or bundle) of a skew-symmetric matrix pencil contains the congruence orbit (or bundle) of another skew-symmetric matrix pencil. The developed theory relies on our main theorem stating that a skew-symmetric matrix pencil A - lambda B can be approximated by pencils strictly equivalent to a skew-symmetric matrix pencil C - lambda D if and only if A - lambda B can be approximated by pencils congruent to C - lambda D.

  • 176.
    Dmytryshyn, Andrii
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Högpresterande beräkningscentrum norr (HPC2N).
    Kågström, Bo
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Högpresterande beräkningscentrum norr (HPC2N).
    Orbit closure hierarchies of skew-symmetric matrix pencils2014Rapport (Annet vitenskapelig)
    Abstract [en]

    We study how small perturbations of a skew-symmetric matrix pencil may change its canonical form under congruence. This problem is also known as the stratification problem of skew-symmetric matrix pencil orbits and bundles. In other words, we investigate when the closure of the congruence orbit (or bundle) of a skew-symmetric matrix pencil contains the congruence orbit (or bundle) of another skew-symmetric matrix pencil. This theory relies on our main theorem stating that a skew-symmetric matrix pencil A-λB can be approximated by pencils strictly equivalent to a skew-symmetric matrix pencil C-λD if and only if A-λB can be approximated by pencils congruent to C-λD.

  • 177.
    Drewes, Frank
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    DAG automata for meaning representation2017Inngår i: Proceedings of the 15th Meeting on the Mathematics of Language (MoL 2017) / [ed] Makoto Kanazawa, Philippe de Groote, Mehrnoosh Sadrzadeh, 2017, Vol. W17-34, s. 88-99, artikkel-id W17-3409Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Languages of directed acyclic graphs (DAGs) are of interest in Natural Lanuage Processing because they can be used to capture the structure of semantic graphs like those of Abstract Meaning Representation. This paper gives an overview of recent results on a family of automata recognizing such DAG languages.

  • 178.
    Drewes, Frank
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Delegation Networks2007Rapport (Annet vitenskapelig)
    Abstract [en]

    We introduce a generalization of tree-based generators called delegation networks. These make it possible to generate objects such as strings, trees, graphs, and pictures in a modular way by combining tree-based generators of several types. Our main result states that, if all underlying tree generators generate regular tree languages (or finite tree languages), then the tree-generating power of delegation networks is the same as that of context-free tree grammars working in IO mode.

  • 179.
    Drewes, Frank
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Implementation and application of automata: 20th international conference, CIAA 2015, Umeå, Sweden, August 18-21, 2015, Proceedings2015Konferanseproceedings (Annet vitenskapelig)
  • 180.
    Drewes, Frank
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    On DAG Languages and DAG Transducers2017Inngår i: Bulletin of the European Association for Theoretical Computer Science, ISSN 0252-9742, Vol. 121, s. 78s. 142-163Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    We review recent results regarding DAG automata and regular DAG languages and point out some open problems that may be interesting to work on. Moreover, a notion of DAG transducers is suggested.

  • 181.
    Drewes, Frank
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Preface2017Inngår i: Theoretical Computer Science, ISSN 0304-3975, E-ISSN 1879-2294, Vol. 679, s. 1-1Artikkel i tidsskrift (Annet vitenskapelig)
  • 182.
    Drewes, Frank
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Selected Decision Problems for Square-Refinement Collage Grammars2011Inngår i: ALGEBRAIC FOUNDATIONS IN COMPUTER SCIENCE: ESSAYS DEDICATED TO SYMEON BOZAPALIDIS ON THE OCCASION OF HIS RETIREMENT, Berlin/Heidelberg: Springer Berlin/Heidelberg, 2011, Vol. 7020, s. 1-29Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We consider collage grammars whose rules subdivide the unit square into smaller and smaller rectangles. The decidability status of selected decision problems for this type of grammars is surveyed: the membership problem, the emptiness and finiteness problems, connectedness and disconnectedness of the generated pictures, and the question whether a generated collage contains a rectangle whose lower-left corner is a point on the diagonal.

  • 183.
    Drewes, Frank
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Towards the tree automata workbench marbles2010Inngår i: Electronic Communications of the EASST, ISSN 1863-2122, Vol. 16, s. 16-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The conceptual ideas that are intended to become the basis for the tree automata workbench Marbles are sketched. The goal is to design and implement an extensible system that facilitates experiments with virtually any kind of algorithm on tree automata. Moreover, the system will be released with a library and an application programmer's interface to make it accessible to anyone who wants to apply tree automata algorithms in research and development.

  • 184.
    Drewes, Frank
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Engelfriet, Joost
    Leiden Institute of Advanced Computer Science.
    Context-Free Tree Grammars are as Powerful as Context-Free Jungle Grammars2015Inngår i: Acta Cybernetica, ISSN 0324-721X, Vol. 22, nr 2, s. 78s. 373-392Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Jungles generalize trees by sharing subtrees and allowing garbage. It is shown that IO context-free tree grammars generate the same jungle languages as context-free jungle grammars. Also, they define the same subsets of any algebra. 

  • 185.
    Drewes, Frank
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Engelfriet, Joost
    Leiden Institute of Advanced Computer Science.
    The Generative Power of Delegation Networks2015Inngår i: Information and Computation, ISSN 0890-5401, E-ISSN 1090-2651, Vol. 245, s. 78s. 213-258Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A device that generates trees over a ranked alphabet, together with an interpretation of the symbols in that alphabet as functions or relations on some domain, generates subsets of that domain. This concept of tree-based generators is well known and essentially already present in the seminal paper by Mezei and Wright from 1967. A delegation network is a system consisting of a finite set of such generators that can "delegate" parts of the generation process to each other. It can be viewed as consisting of an (extended) IO context-free tree grammar and an interpretation. We investigate the language-theoretic properties of these systems and establish several characterizations of the generated languages. In particular, we obtain results in the style of Mezei and Wright. We also study the hierarchy of tree language classes obtained by iterating the concept of delegation, and show that this hierarchy is properly contained in the closure of the regular tree languages under nondeterministic macro tree transductions, but not contained in the IO-hierarchy.

  • 186.
    Drewes, Frank
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Engelfriet, Joost
    Leiden Institute of Advanced Computer Science.
    The Generative Power of Delegation Networks2012Rapport (Annet vitenskapelig)
    Abstract [en]

    A device that generates trees over a ranked alphabet ∑, together with an interpretation of the symbols in ∑ as functions or relations on a domain A, generates subsets of A. This concept of tree-based generators is well known and essentially already present in the seminal paper by Mezei and Wright from 1967. A delegation network is a system consisting of a finite set of such generators that can "delegate" parts of the generation process to each other. It can be viewed as consisting of an (extended) IO context-free tree grammar and an interpretation. We investigate the language-theoretic properties of these systems and establish several characterizations of the generated languages. In particular, we obtain results in the style of Mezei and Wright. We also study the hierarchy of tree language classes obtained by iterating the concept of delegation, and show that this hierarchy is properly contained in the closure of the regular tree languages under nondeterministic macro tree transductions, but not in the IO-hierarchy.

  • 187.
    Drewes, Frank
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Gebhardt, Kilian
    Technische Universität Dresden.
    Vogler, Heiko
    Technische Universität Dresden.
    EM-training for probabilistic aligned hypergraph bimorphisms2016Inngår i: Proceedings of the SIGFSM Workshop on Statistical NLP and Weighted Automata, Association for Computational Linguistics , 2016, s. 60-69Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We define the concept of probabilistic aligned hypergraph bimorphism. Each such bimorphism consists of a probabilistic regular tree grammar, two hypergraph algebras in which the generated trees are interpreted, and a family of alignments between the two interpretations. It generates a set of bihypergraphs each consisting of two hypergraphs and an alignment between them; for instance, discontinuous phrase structures and non-projective dependency structures are bihypergraphs. We show an EM-training algorithm which takes a corpus of bihypergraphs and an aligned hypergraph bimorphism as input and calculates a probability assignment to the rules of the regular tree grammar such that in the limit the maximum-likelihood of the corpus is approximated.

  • 188.
    Drewes, Frank
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Habel, Annegret
    University of Oldenburg.
    Hoffmann, Berthold
    University of Bremen.
    Plump, Detlef
    The University of York.
    Preface: Manipulation of graphs, algebras and pictures. Essays dedicated to Hans-Jörg Kreowski on the occasion of his 60th birthday2010Inngår i: Electronic Communications of the EASST, ISSN 1863-2122, Vol. 26, s. 2s. 2-Artikkel i tidsskrift (Fagfellevurdert)
  • 189.
    Drewes, Frank
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Hoffmann, Berthold
    University of Bremen.
    Contextual Hyperedge Replacement2015Inngår i: Acta Informatica, ISSN 0001-5903, E-ISSN 1432-0525, Vol. 52, nr 6, s. 497-524Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Contextual hyperedge-replacement grammars (contextual grammars, for short) are an extension of hyperedge replacement grammars.  They have recently been proposed as a grammatical method for capturing the structure of object-oriented programs, thus serving as an alternative to the use of meta-models like UML class diagrams in model-driven software design.

    In this paper, we study the properties of contextual grammars. Even though these grammars are not context-free, one can show that they inherit several of the nice properties of hyperedge replacement grammars. In particular, they possess useful normal forms and their membership problem is in NP.

  • 190.
    Drewes, Frank
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Hoffmann, Berthold
    Universität Bremen.
    Contextual Hyperedge Replacement2014Rapport (Annet vitenskapelig)
    Abstract [en]

    Contextual hyperedge-replacement grammars (contextual grammars, for short) are an extension of hyperedge replacement grammars. They have recently been proposed as a grammatical method for capturing the structure of object-oriented programs, thus serving as an alternative to the use of meta-models like UML class diagrams in model-driven software design.In this paper, we study the properties of contextual grammars. Even though these grammars are not context-free, one can show that they inherit several of the nice properties of hyperedge replacement grammars. In particular, they possess useful normal forms and their membership problem is in NP.

  • 191.
    Drewes, Frank
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Hoffmann, Berthold
    Minas, Mark
    Approximating Parikh images for generating deterministic graph parsers2016Inngår i: Software Technologies: Applications and Foundations: STAF 2016 Collocated Workshops: DataMod, GCM, HOFM, MELO, SEMS, VeryComp, Vienna Austria, July 4-8, 2016, Revised Selected Papers / [ed] Paolo Milazzo, Dániel Varró, Manuel Wimmer, Springer, 2016, s. 112-128Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The Parikh image of a word abstracts from the order of its letters. Parikh’s famous theorem states that the set of Parikh images of a context-free string language forms a semilinear set that can be effectively computed from its grammar. In this paper we study the computation of Parikh images for graph grammars defined by contextual hyperedge replacement (CHR). Our motivation is to generate efficient predictive top-down (PTD) parsers for a subclass of CHR grammars. We illustrate this by describing the subtask that identifies the nodes of the input graph that parsing starts with.

  • 192.
    Drewes, Frank
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Hoffmann, Berthold
    DFKI Bremen and Universität Bremen.
    Minas, Mark
    Universität der Bundeswehr München.
    Contextual Hyperedge Replacement2012Inngår i: Applications of Graph Transformations with Industrial Relevance: 4th International Symposium, AGTIVE 2011, Budapest, Hungary, October 4-7, 2011, Revised Selected and Invited Papers / [ed] Andy Schürr, Daniel Varro, Gergely Varro, Berlin: Springer Berlin/Heidelberg, 2012, s. 182-197Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In model-driven design, the structure of software is commonly specified by meta-models like uml class diagrams. In this paper we study how graph grammars can be used for this purpose, using statecharts as an example. We extend context-free hyperedge-replacement—which is not powerful enough for this application—so that rules may not only access the nodes attached to the variable on their left-hand side, but also nodes elsewhere in the graph. Although the resulting notion of contextual hyperedge replacement preserves many properties of the context-free case, it has considerably more generative power—enough to specify software models that cannot be specified by class diagrams. 

  • 193.
    Drewes, Frank
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Hoffmann, Berthold
    Minas, Mark
    Extending Predictive Shift-Reduce Parsing to Contextual Hyperedge Replacement Grammars2019Inngår i: Graph Transformation: 12th International Conference, ICGT 2019, Held as Part of STAF 2019, Eindhoven, The Netherlands, July 15–16, 2019, Proceedings / [ed] Esther Guerra, Fernando Orejas, Springer, 2019, s. 55-72Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Parsing with respect to grammars based on hyperedge replacement (HR) is NP-hard in general, even for some fixed grammars. In recent work, wehave devised predictive shift-reduce parsing (PSR), a very efficientalgorithm that applies to a wide subclass of HR grammars. In thispaper, we extend PSR parsing to contextual HR grammars, a moderateextension of HR grammars that have greater generative power, and aretherefore better suited for the practical specification of graph anddiagram languages. Although the extension requires considerablemodifications of the original algorithm, it turns out that theresulting parsers are still very efficient.

  • 194.
    Drewes, Frank
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Hoffmann, Berthold
    University of Bremen.
    Minas, Mark
    Universität der Bundeswehr München.
    Formalization and Correctness of Predictive Shift-Reduce Parsers for Graph Grammars Based on Hyperedge Replacement2019Inngår i: The Journal of logical and algebraic methods in programming, ISSN 2352-2208, E-ISSN 2352-2216, Vol. 104, s. 303-341Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Hyperedge replacement (HR) grammars can generate NP-complete graph languages, which makes parsing hard even for fixed HR languages. Therefore, we study predictive shift-reduce (PSR) parsing that yields efficient parsers for a subclass of HR grammars, by generalizing the concepts of SLR(1) string parsing to graphs. We formalize the construction of PSR parsers and show that it is correct. PSR parsers run in linear space and time, and are more efficient than the predictive top-down (PTD) parsers recently developed by the authors.

  • 195.
    Drewes, Frank
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Hoffmann, Berthold
    Minas, Mark
    Predictive Shift-Reduce Parsing for Hyperedge Replacement Grammars2017Inngår i: Graph Transformation: 10th International Conference, ICGT 2017, Held as Part of STAF 2017, Marburg, Germany, July 18-19, 2017, Proceedings / [ed] Detlef Plump, Juan de Lara, Cham: Springer, 2017, s. 106-122Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Graph languages defined by hyperedge replacement (HR) grammars can beNP-complete. We study predictive shift-reduce (PSR) parsing for a subclass ofthese grammars, which generalizes the concepts of SLR(1) string parsing tographs. PSR parsers run in linear space and time. In comparison to thepredictive top-down (PTD) parsers recently developed by the authors, PSRparsers are more efficient, and allow parsing for a wider class of HR grammars,while the analysis of PSR parsability is easier than for PTD parsing.

  • 196.
    Drewes, Frank
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Hoffmann, Berthold
    Minas, Mark
    Predictive Top-down Parsing for Hyperedge Replacement Grammars2015Inngår i: Graph Transformation (ICGT 2015): 8th International Conference, ICGT 2015, Held as Part of STAF 2015, L'Aquila, Italy, July 21-23, 2015. Proceedings / [ed] Francesco Parisi-Presicce, Bernhard Westfechtel, Springer Publishing Company, 2015, Vol. 9151, s. 19-34Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Graph languages defined by hyperedge replacement grammars can be NP-complete. We invent predictive top-down (PTD) parsers for a subclass of these grammars, similar to recursive descent parsers for string languages. The focus of this paper lies on the grammar analysis that computes neighbor edges of nonterminals, in analogy to the first and follow symbols used in SLL(1) parsing. The analysis checks whether a grammar is PTD parsable and yields all information for generating a parser that runs in linear space and quadratic time.

  • 197.
    Drewes, Frank
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Holzer, Markus
    Universität Giessen.
    Jakobi, Sebastian
    Universität Giessen.
    Merwe, Brink van der
    University of Stellenbosch.
    Tight Bounds for Cut-Operations on Deterministic Finite Automata2015Inngår i: Machines, Computations, and Universality: 7th International Conference, MCU 2015, Famagusta, North Cyprus, September 9-11, 2015, Proceedings / [ed] J. Durand-Lose and B. Nagy, Springer Publishing Company, 2015, Vol. 9288, s. 45-60Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We investigate the state complexity of the cut and iterated cut operation for deterministic finite automata (DFAs), answering an open question stated in [M. Berglund, et al.: Cuts in regular expressions. In Proc. DLT, LNCS 7907, 2011]. These operations can be seen as an alternative to ordinary concatenation and Kleene star modelling leftmost maximal string matching. We show that the cut operation has a matching upper and lower bound of (n−1)⋅m+n(n−1)⋅m+n states on DFAs accepting the cut of two individual languages that are accepted by n- and m-state DFAs, respectively. In the unary case we obtain max(2n−1,m+n−2)max(2n−1,m+n−2) states as a tight bound. For accepting the iterated cut of a language accepted by an n-state DFA we find a matching bound of 1+(n+1)⋅F(1,n+2,−n+2;n+1∣−1)1+(n+1)⋅F(1,n+2,−n+2;n+1∣−1) states on DFAs, where FF refers to the generalized hypergeometric function. This bound is in the order of magnitude Θ((n−1)!)Θ((n−1)!). Finally, the bound drops to 2n−12n−1 for unary DFAs accepting the iterated cut of an n-state DFA and thus is similar to the bound for the cut operation on unary DFAs.

  • 198.
    Drewes, Frank
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Holzer, Markus
    Universität Giessen.
    Jakobi, Sebastian
    Universität Giessen.
    Merwe, Brink van der
    University of Stellenbosch.
    Tight Bounds for Cut-Operations on Deterministic Finite Automata2017Inngår i: Fundamenta Informaticae, ISSN 0169-2968, E-ISSN 1875-8681, Vol. 155, s. 89-110Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We investigate the state complexity of the cut and iterated cut operation for determin- istic finite automata (DFAs), answering an open question stated in [M. BERGLUND, et al.: Cuts in regular expressions. In Proc. DLT, LNCS 7907, 2011]. These operations can be seen as an al- ternative to ordinary concatenation and Kleene star modelling leftmost maximal string matching. We show that the cut operation has a matching upper and lower bound of n states, if m = 1, and (n−1)·m+n states, otherwise, on DFAs accepting the cut of two individual languages that are ac- cepted by n- and m-state DFAs, respectively. In the unary case we obtain max(2n − 1, m + n − 2) states as a tight bound—notice that for m ≤ n the bound for unary DFAs only depends on the former automaton and not on the latter. For accepting the iterated cut of a language accepted by an n-state DFA we find a matching bound of 1+(n+1)·F(1,n+2,−n+2;n+1 | −1) states on DFAs, if n ≥ 4 and where F refers to the generalized hypergeometric function. This bound is in the order of magnitude Θ((n − 1)!). Finally, the bound drops to 2n − 1 for unary DFAs accepting the iterated cut of an n-state DFA, if n ≥ 3, and thus is similar to the bound for the cut operation on unary DFAs.

  • 199.
    Drewes, Frank
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Institutionen för datavetenskap.
    Högberg, Johanna
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Institutionen för datavetenskap.
    Maletti, Andreas
    Universitat Rovira i Virgili, Departament de Filologies Rom aniques.
    MAT Learners for Tree Series - an AbstractData Type and Two Realizations2009Rapport (Annet vitenskapelig)
    Abstract [en]

    We propose abstract observation tables, an abstract datatype for learning deterministic weighted tree automata in Angluin's minimal adequate teacher model. Besides the "classical" observation table,we show that abstract observation tables can also be implemented byobservation trees. The advantage of the latter is that they often requirefewer queries to the teacher.

  • 200.
    Drewes, Frank
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Högberg, Johanna
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Maletti, Andreas
    MAT learners for tree series: an abstract data type and two realizations2011Inngår i: Acta Informatica, ISSN 0001-5903, E-ISSN 1432-0525, Vol. 48, nr 3, s. 165-189Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We propose abstract observation tables, an abstract data type for learning deterministic weighted tree automata in Angluin’s minimal adequate teacher (MAT) model, and show that every correct implementation of abstract observation tables yields a correct MAT learner. Besides the “classical” observation table, we show that abstract observation tables can also be implemented by observation trees. The advantage of the latter is that they often require fewer queries to the teacher.

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