umu.sePublications
Change search
Refine search result
1234567 101 - 150 of 1920
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 101.
    Bensch, Suna
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Drewes, Frank
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Jürgensen, Helmut
    Middlesex College, The University of Western Ontario.
    van der Merwe, Brink
    Department of Mathematical Sciences, University of Stellenbosch.
    Incremental Construction of Millstream Configurations Using Graph Transformation2011In: Proceedings of the 9th International Workshop on Finite State Methods and Natural Language Processing, Stroudsburg: Association for Computational Linguistics , 2011, p. 93-97Conference paper (Refereed)
  • 102.
    Bensch, Suna
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Ewert, Sigrid
    University of the Witwatersrand, Johannesburg, South Africa.
    Describing resource allocation to dynamically formed groups with grammars2019In: Simulation and modeling methodologies, technologies and applications: 7th international conference, (SIMULTECH) 2017, Madrid, Spain, July 26-28, 2017 : revised selected papers / [ed] Mohammad S. Obaidat, Tuncer I. Ören and Floriano De Rango, Springer, 2019, , p. 23p. 153-176Chapter in book (Refereed)
    Abstract [en]

    In this paper we model dynamic group formation and resource allocation with grammars in order to gain a deeper understanding into the involved processes. Modelling with grammars allows us to describe resource allocation and group formation as generative processes that provide, at any given time, information about at what stage the process of group formation and resource allocation is. We divide our model into four phases: (1) resource supply, (2) candidate group formation, (3) final group formation, and (4) resource distribution. In particular, we show that we can use permitting random context grammars to describe the first two phases. For the third phase we introduce an algorithm that determines based on a resource allocation strategy the final group to which resources are distributed. The last phase is described with random context grammars under a specific leftmost derivation mode. Our model shows that if information about the available resource and candidate group formation is distributed and kept separate, then the synchronisation of this information at a later stage (i.e. resource distribution phase) needs a more powerful grammar model.

  • 103.
    Bensch, Suna
    et al.
    Umeå University. Department of Computing Science.
    Ewert, Sigrid
    Raborife, Mpho
    Modelling the Formation of Virtual Buying Cooperatives with Grammars of Regulated Rewriting2017In: Proceedings of the 7th International Conference on Simulation and Modeling Methodologies, Technologies and Applications - Volume 1: SIMULTECH, SciTePress, 2017, p. 45-55Conference paper (Refereed)
    Abstract [en]

    In this paper we model virtual buying cooperatives (VBC) with grammars of regulated rewriting and show that, if VBC relevant information is distributed over several successive VBC processes and must, in a later stage, be synchronised and co-ordinated, the formal grammar needs to be very powerful with respect to mode of derivation and thus generative capacity. In particular, we show how to model the supplier phase, invitation phase, and declaration phase of a VBC with random permitting context grammars and the VBC reservation phase with random context grammars under a special kind of leftmost derivation. If we use random permitting context grammars for all processes, we can only model a VBC formation during which information is introduced and processed locally and successively rather than being spread over different VBC processes.

  • 104.
    Bensch, Suna
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Freund, RudolfHirvensalo, MikaOtto, Friedrich
    Fundamenta Informaticae2016Collection (editor) (Refereed)
  • 105.
    Bensch, Suna
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Freund, Rudolf
    Hirvensalo, Mika
    Otto, Friedrich
    Non-Classical Models of Automata and Applications VI Preface2016In: Fundamenta Informaticae, ISSN 0169-2968, E-ISSN 1875-8681, Vol. 148, no 3-4, p. I-IIArticle in journal (Other academic)
  • 106.
    Bensch, Suna
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Freund, RudolfOtto, Friedrich
    Sixth Workshop on Non-Classical Models for Automata and Applications: NCMA 2014, Kassel, Germany, July 28-29, 2014. Proceedings2014Conference proceedings (editor) (Refereed)
  • 107.
    Bensch, Suna
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Hellström, ThomasUmeå University, Faculty of Science and Technology, Department of Computing Science.
    Proceedings of Umeå's 18th student conference in computing science: USCCS 2014.12014Conference proceedings (editor) (Other academic)
  • 108.
    Bensch, Suna
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Hellström, ThomasUmeå University, Faculty of Science and Technology, Department of Computing Science.
    Proceedings of Umeå's 20th student conference in computing science: USCCS 20162016Conference proceedings (editor) (Other academic)
  • 109.
    Bensch, Suna
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Hellström, ThomasUmeå University, Faculty of Science and Technology, Department of Computing Science.
    Proceedings of Umeå's 21st student conference in computing science: USCCS 20172017Conference proceedings (editor) (Other academic)
  • 110.
    Bensch, Suna
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science. Department of Computing Science.
    Hellström, ThomasUmeå University, Faculty of Science and Technology, Department of Computing Science. Department of Computing Science.
    Proceedings of Umeå's 22nd Student Conference in Computing Science (USCCS 2018)2018Conference proceedings (editor) (Other academic)
  • 111.
    Bensch, Suna
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Hellström, ThomasUmeå University, Faculty of Science and Technology, Department of Computing Science.
    Proceedings of Umeå's 23rd Student Conference in Computing Science: USCCS 20192019Conference proceedings (editor) (Other academic)
    Abstract [en]

    The Umeå Student Conference in Computing Science (USCCS) is organized annually as part of a course given by the Computing Science department at Umeå University. The objective of the course is to give the students a practical introduction to independent research, scientific writing, and oral presentation.

    A student who participates in the course first selects a topic and a research question that he or she is interested in. If the topic is accepted, the student outlines a paper and composes an annotated bibliography to give a survey of the research topic. The main work consists of conducting the actual research that answers the question asked, and convincingly and clearly reporting the results in a scientific paper. Another major part of the course is multiple internal peer review meetings in which groups of students read each others’ papers and give feedback to the author. This process gives valuable training in both giving and receiving criticism in a constructive manner. Altogether, the students learn to formulate and develop their own ideas in a scientific manner, in a process involving internal peer reviewing of each other’s work and under supervision of the teachers, and incremental development and refinement of a scientific paper.

    Each scientific paper is submitted to USCCS through an on-line submission system, and receives reviews written by members of the Computing Science department. Based on the review, the editors of the conference proceedings (the teachers of the course) issue a decision of preliminary acceptance of the paper to each author. If, after final revision, a paper is accepted, the student is given the opportunity to present the work at the conference. The review process and the conference format aims at mimicking realistic settings for publishing and participation at scientific conferences.

  • 112.
    Bensch, Suna
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Hellström, Thomas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Towards Proactive Robot Behavior Based on Incremental Language Analysis2014In: MMRWHRI '14 Proceedings of the 2014 Workshop on Multimodal, Multi-Party, Real-World Human-Robot Interaction / [ed] Mary Ellen Foster, Manuel Giuliani, Ronald P. A. Petrick, 2014, p. 21-22Conference paper (Refereed)
    Abstract [en]

    This paper describes ongoing and planned work on incremental language processing coupled to inference of expected robot actions. Utterances are processed word-by-word, simultaneously with inference of expected robot actions, thus enabling the robot to prepare and act proactively to human utterances. We believe that such a model results in more natural human-robot communication since proactive behavior is a feature of human-human communication.

  • 113.
    Bensch, Suna
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Hoeberechts, Maia
    Ocean Networks Canada and Department of Computer Science, University of Victoria, Victoria, Canada.
    On the Degree of Nondeterminism of Tree Adjoining Languages and Head Grammar Languages2017In: Descriptional Complexity of Formal Systems: 19th IFIP WG 1.02 International Conference, DCFS 2017, Milano, Italy, July 3-5, 2017, Proceedings / [ed] Giovanni Pighizzini, Cezar Câmpeanu, 2017, p. 65-76Conference paper (Refereed)
    Abstract [en]

    The degree of nondeterminism is a measure of syntactic complexity which was investigated for parallel and sequential rewriting systems. In this paper, we consider the degree of nondeterminsm for tree adjoining grammars and their languages and head grammars and their languages. We show that a degree of nondeterminism of 2 suffices for both formalisms in order to generate all languages in their respective language families. Furthermore, we show that deterministic tree adjoining grammars (those with degree of nondeterminism equal to 1), can generate non-context-free languages, in contrast to deterministic head grammars which can only generate languages containing a single word. 

  • 114.
    Bensch, Suna
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Holzer, Markus
    Institut für Informatik, Universität Giessen.
    Kutrib, Martin
    Institut für Informatik, Universität Giessen.
    Malcher, Andreas
    Institut für Informatik, Universität Giessen.
    Input-Driven Stack Automata2012In: IFIP TCS: Theoretical Computer Science - 7th IFIP TC 1/WG 2.2 International Conference, TCS 2012, Amsterdam, 2012. Proceedings / [ed] Jos C. M. Baeten, Thomas Ball, and Frank S. de Boer, 2012, p. 28-42Conference paper (Refereed)
    Abstract [en]

    We introduce and investigate input-driven stack automata, which are a generalization of input-driven pushdown automata that recently became popular under the name visibly pushdown automata. Basically, the idea is that the input letters uniquely determine the operations on the pushdown store. This can nicely be generalized to stack automata by further types of input letters which are responsible for moving the stack pointer up or down. While visibly pushdown languages share many desirable properties with regular languages, input-driven stack automata languages do not necessarily so. We prove that deterministic and non- deterministic input-driven stack automata have different computational power, which shows in passing that one cannot construct a deterministic input-driven stack automaton from a nondeterministic one. We study the computational capacity of these devices. Moreover, it is shown that the membership problem for nondeterministic input-driven stack automata languages is NP-complete.

  • 115.
    Berg, Mikaela
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Improving reading experience in digital newspapers2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Reading news on mobile devices has during the past decade transcended into an every- day activity, which induce greater demands on design and presentation of news. Several researchers have examined essential components in the area of digital newspapers, despite this, there are few newspapers that have switched to a reader-friendly format.

    The objective of this thesis is to evaluate how the reading experience in digital newspa- pers can be improved by abandoning the traditional structure of today’s printed newspapers. Based on numerous tests and studies, as well as support from literature, a set of guidelines has been produced as a result of this thesis.

    The design guidelines contain recommendations for optimal line size, typeface, point size, appearance, functionality, placement, recognition factor and packaging. To ensure quality, all guidelines were validated in order to prove that the reading experience had increased. An evaluation was performed that attempted to determine that.

    The statistic result of this thesis showed a significant difference in both reading speed and the subjective experience. However no significant difference could be seen regarding the reading comprehension. The conclusions made was that structure and design of content can influence both reading speed and reading experience.

    All design guidelines can be used as guidance when developing templates for digital newspapers. 

  • 116.
    Berggren, Martin
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    A unified discrete-continuous sensitivity analysis method for shape optimization2010In: Applied and Numerical Partial Differential Equations: Scientific Computing in Simulation, Optimization and Control in a Multidisciplinary Context / [ed] W. Fitzgibbon, Y.A. Kuznetsov, P. Neittaanmäki, J. Periaux, O. Pironneau, Springer, 2010, p. 25-39Conference paper (Refereed)
    Abstract [en]

    Boundary shape optimization problems for systems governed by partial differential equations involve a calculus of variation with respect to boundary modifications. As typically presented in the literature, the first-order necessary conditions of optimality are derived in a quite different manner for the problems before and after discretization, and the final directional-derivative expressions look very different. However, a systematic use of the material-derivative concept allows a unified treatment of the cases before and after discretization. The final expression when performing such a derivation includes the classical before-discretization (“continuous”) expression, which contains objects solely restricted to the design boundary, plus a number of “correction” terms that involve field variables inside the domain. Some or all of the correction terms vanish when the associated state and adjoint variables are smooth enough.

  • 117.
    Berggren, Martin
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Kasolis, Fotios
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Weak material approximation of holes with traction-free boundaries2012In: SIAM Journal on Numerical Analysis, ISSN 0036-1429, E-ISSN 1095-7170, Vol. 50, no 4, p. 1827-1848Article in journal (Refereed)
    Abstract [en]

    Consider the solution of a boundary-value problem for steady linear elasticity in which the computational domain contains one or several holes with traction-free boundaries. The presence of holes in the material can be approximated using a weak material; that is, the relative density of material rho is set to 0 < epsilon = rho << 1 in the hole region. The weak material approach is a standard technique in the so-called material distribution approach to topology optimization, in which the inhomogeneous relative density of material is designated as the design variable in order to optimize the spatial distribution of material. The use of a weak material ensures that the elasticity problem is uniquely solvable for each admissible value rho is an element of [epsilon, 1] of the design variable. A finite-element approximation of the boundary-value problem in which the weak material approximation is used in the hole regions can be viewed as a nonconforming but convergent approximation of a version of the original problem in which the solution is continuously and elastically extended into the holes. The error in this approximation can be bounded by two terms that depend on epsilon. One term scales linearly with epsilon with a constant that is independent of the mesh size parameter h but that depends on the surface traction required to fit elastic material in the deformed holes. The other term scales like epsilon(1/2) times the finite-element approximation error inside the hole. The condition number of the weak material stiffness matrix scales like epsilon(-1), but the use of a suitable left preconditioner yields a matrix with a condition number that is bounded independently of epsilon. Moreover, the preconditioned matrix admits the limit value epsilon -> 0, and the solution of corresponding system of equations yields in the limit a finite-element approximation of the continuously and elastically extended problem.

  • 118.
    Berglund, Ann-Charlotte
    et al.
    Linnaeus Centre for Bioinformatics, Uppsala Universitet.
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Hernández, Francisco
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Sandman, Björn
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Tordsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Combining local and grid resources in scientific workflows (for Bioinformatics)2009Conference paper (Refereed)
    Abstract [en]

    We examine some issues that arise when using both local and Gridresources in scientific workflows. Our previous work addresses and illustratesthe benefits of a light-weight and generic workflow engine that manages andoptimizes Grid resource usage. Extending on this effort, we hereillustrate how a client tool for bioinformatics applications employs the engine tointerface with Grid resources. We also explore how to define data flowsthat transparently integrates local and Grid subworkflows. In addition, the benefits of parameter sweep workflows are examined and a means for describing this type of workflows in an abstract and concise manner is introduced. Finally, the above mechanisms are employed to perform an orthology detection analysis.

  • 119.
    Berglund, Marianne
    et al.
    Umeå University, Faculty of Social Sciences, Department of Informatics.
    Demir, Carolina
    Umeå University, Faculty of Social Sciences, Department of Informatics.
    Vem är du på Flashback Forum?: En studie av identitetsskapande på ett forum.2012Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    With this study we aim to learn more about the process in creating an identity onFlashback Forum. We have observed four members of the forum to find what themesdefine thier way of making an identitity. Besides to our empirical material we foundearlier research that could support our study. The methods we used was qualitativesince we wanted to get a deep understandning for their behaviour. We found thattheese three themes were central: Language, Content and the feeling of beingAnonymous. Theese three themes combined show us how the process of creating anidentity works, but also we learned that the feeling of being anonymous is the maincore and that it effects the language and content.

  • 120.
    Berglund, Martin
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Analyzing Edit Distance on Trees: Tree Swap Distance is Intractable2011In: Proceedings of the Prague Stringology Conference 2011 / [ed] Jan Holub and Jan Žďárek, Prague: Prague Stringology Club, Czech Technical University , 2011, p. 59-73Conference paper (Refereed)
    Abstract [en]

    The string correction problem looks at minimal ways to modify one stringinto another using fixed operations, such as for example inserting a symbol, deleting asymbol and interchanging the positions of two symbols (a “swap”). This has been generalizedto trees in various ways, but unfortunately having operations to insert/deletenodes in the tree and operations that move subtrees, such as a “swap” of adjacent subtrees,makes the correction problem for trees intractable. In this paper we investigatewhat happens when we have a tree edit distance problem with only swaps. We callthis problem tree swap distance, and go on to prove that this correction problem isNP-complete. This suggests that the swap operation is fundamentally problematic inthe tree case, and other subtree movement models should be studied.

  • 121.
    Berglund, Martin
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Drewes, Frank (Contributor)
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Characterizing Non-Regularity2014Report (Other academic)
    Abstract [en]

    This paper considers a characterization of the context-free non-regular languages, conjecturing that there for all such languages exists a fixed string thatcan be pumped to exhibit infinitely many equivalence classes. A proof is given only for a special case, but the general statement is conjectured to hold. The conjecture is then shown to imply that the shuffle of two context-free languagesis not context-free.

  • 122.
    Berglund, Martin
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Complexities of Order-Related Formal Language Extensions2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The work presented in this thesis discusses various formal language formalisms that extend classical formalisms like regular expressions and context-free grammars with additional abilities, most relating to order. This is done while focusing on the impact these extensions have on the efficiency of parsing the languages generated. That is, rather than taking a step up on the Chomsky hierarchy to the context-sensitive languages, which makes parsing very difficult, a smaller step is taken, adding some mechanisms which permit interesting spatial (in)dependencies to be modeled.

    The most immediate example is shuffle formalisms, where existing language formalisms are extended by introducing operators which generate arbitrary interleavings of argument languages. For example, introducing a shuffle operator to the regular expressions does not make it possible to recognize context-free languages like anbn, but it does capture some non-context-free languages like the language of all strings containing the same number of as, bs and cs. The impact these additions have on parsing has many facets. Other than shuffle operators we also consider formalisms enforcing repeating substrings, formalisms moving substrings around, and formalisms that restrict which substrings may be concatenated. The formalisms studied here all have a number of properties in common.

    1. They are closely related to existing regular and context-free formalisms. They operate in a step-wise fashion, deriving strings by sequences of rule applications of individually limited power.
    2. Each step generates a constant number of symbols and does not modify parts that have already been generated. That is, strings are built in an additive fashion that does not explode in size (in contrast to e.g. Lindenmayer systems). All languages here will have a semi-linear Parikh image.
    3. They feature some interesting characteristic involving order or other spatial constraints. In the example of the shuffle multiple derivations are in a sense interspersed in a way that each is unaware of.
    4. All of the formalisms are intended to be limited enough to make an efficient parsing algorithm at least for some cases a reasonable goal.

    This thesis will give intuitive explanations of a number of formalisms fulfilling these requirements, and will sketch some results relating to the parsing problem for them. This should all be viewed as preparation for the more complete results and explanations featured in the papers given in the appendices.

  • 123.
    Berglund, Martin
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Complexities of Parsing in the Presence of Reordering2012Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The work presented in this thesis discusses various formalisms for representing the addition of order-controlling and order-relaxing mechanisms to existing formal language models. An immediate example is shuffle expressions, which can represent not only all regular languages (a regular expression is a shuffle expression), but also features additional operations that generate arbitrary interleavings of its argument strings. This defines a language class which, on the one hand, does not contain all context-free languages, but, on the other hand contains an infinite number of languages that are not context-free. Shuffle expressions are, however, not themselves the main interest of this thesis. Instead we consider several formalisms that share many of their properties, where some are direct generalisations of shuffle expressions, while others feature very different methods of controlling order. Notably all formalisms that are studied here

    • have a semi-linear Parikh image,
    • are structured so that each derivation step generates at most a constant number of symbols (as opposed to the parallel derivations in for example Lindenmayer systems),
    • feature interesting ordering characteristics, created either by derivation steps that may generate symbols in multiple places at once, or by multiple generating processes that produce output independently in an interleaved fashion, and
    • are all limited enough to make the question of efficient parsing an interesting and reasonable goal.

    This vague description already hints towards the formalisms considered; the different classes of mildly context-sensitive devices and concurrent finite-state automata.

    This thesis will first explain and discuss these formalisms, and will then primarily focus on the associated membership problem (or parsing problem). Several parsing results are discussed here, and the papers in the appendix give a more complete picture of these problems and some related ones.

  • 124.
    Berglund, Martin
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    The Membership Problem for the Shuffle of Two Deterministic Linear Context-Free Languages is NP-complete2012Report (Other academic)
    Abstract [en]

    Formal language models which employ shuffling, or interleaving, of strings are of interest in many areas of computer science. Notable examples include system verification, plan recognition, and natural language processing. Membership problems for the shuffle of languages are especially interesting. It is known that deciding membership for shuffles of regular languages can be done in polynomial time, and that deciding (non-uniform) membership in the shuffle of two deterministic context-free languages is NP-complete. In this paper we narrow the gap by showing that the non-uniform membership problem for the shuffle of two deterministic *linear* context-free languages is NP-complete.

  • 125.
    Berglund, Martin
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Björklund, Henrik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Björklund, Johanna
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Shuffled languages: representation and recognition2013In: Theoretical Computer Science, ISSN 0304-3975, E-ISSN 1879-2294, Vol. 489-490, p. 1-20Article in journal (Refereed)
    Abstract [en]

    Language models that use interleaving, or shuffle, operators have applications in various areas of computer science, including system verification, plan recognition, and natural language processing. We study the complexity of the membership problem for such models, in other words, how difficult it is to determine if a string belongs to a language or not. In particular, we investigate how interleaving can be introduced into models that capture the context-free languages.

  • 126.
    Berglund, Martin
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Björklund, Henrik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Drewes, Frank
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    On the Parameterized Complexity of Linear Context-Free Rewriting Systems2013In: Proceedings of the 13th Meeting on the Mathematics of Language (MoL 13), Association for Computational Linguistics, 2013, p. 21-29Conference paper (Other academic)
    Abstract [en]

    We study the complexity of uniform membership for Linear Context-Free RewritingSystems, i.e., the problem where we aregiven a string w and a grammar G and areasked whether w ∈ L(G). In particular,we use parameterized complexity theoryto investigate how the complexity dependson various parameters. While we focusprimarily on rank and fan-out, derivationlength is also considered.

  • 127.
    Berglund, Martin
    et al.
    Stellenbosch University.
    Björklund, Henrik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Drewes, Frank
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Single-Rooted DAGs in Regular DAG Languages: Parikh Image and Path Languages2017In: Proceedings of the 13th International Workshop on Tree Adjoining Grammars and Related Formalisms (TAG+13) / [ed] M. Kuhlmann, T. Scheffler, Association for Computational Linguistics , 2017, p. 94-101Conference paper (Refereed)
    Abstract [en]

    In a recent survey (Drewes, 2017) of results on DAG automata  some open problems are formulated for the case where the  DAG language accepted by a DAG automaton A is restricted to DAGs with a single root, denoted by L(A)u. Here we consider each of  those problems, demonstrating that: (i) the finiteness  of L(A)u is decidable, (ii) the path languages of L(A)u can be characterized in  terms of the string languages accepted by partially blind  multicounter automata, and  (iii) the Parikh image of L(A)u is semilinear.

  • 128.
    Berglund, Martin
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Björklund, Henrik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Drewes, Frank
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    van der Merwe, Brink
    Stellenbosch University, South Africa.
    Watson, Bruce
    Stellenbosch University, South Africa.
    Cuts in Regular Expressions2013In: Developments in Language Theory: 17th International Conference, DLT 2013, Marne-la-Vallée, France, June 18-21, 2013. Proceedings / [ed] Marie-Pierre Béal, Olivier Carton, Springer Berlin/Heidelberg, 2013, p. 70-81Conference paper (Refereed)
    Abstract [en]

    Most software packages with regular expression matching engines offer operators that extend the classical regular expressions, such as counting, intersection, complementation, and interleaving. Some of the most popular engines, for example those of Java and Perl, also provide operators that are intended to control the nondeterminism inherent in regular expressions. We formalize this notion in the form of the cut and iterated cut operators. They do not extend the class of languages that can be defined beyond the regular, but they allow for exponentially more succinct representation of some languages. Membership testing remains polynomial, but emptiness testing becomes PSPACE-hard. 

  • 129.
    Berglund, Martin
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Björklund, Henrik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Högberg, Johanna
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Recognizing shuffled languages2011In: Language and Automata Theory and Applications: 5th International Conference, LATA 2011, Tarragona, Spain, May 26-31, 2011. Proceedings / [ed] Adrian-Horia Dediu, Shunsuke Inenaga and Carlos Martín-Vide, Springer Berlin/Heidelberg, 2011, p. 142-154Conference paper (Refereed)
    Abstract [en]

    Language models that use interleaving, or shuffle, operators have applications in various areas of computer science, including system verification, plan recognition, and natural language processing. We study the complexity of the membership problem for such models, i.e., how difficult it is to determine if a string belongs to a language or not. In particular, we investigate how interleaving can be introduced into models that capture the context-free languages.

  • 130.
    Berglund, Martin
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Björklund, Henrik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Högberg, Johanna
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Recognizing Shuffled Languages2011Report (Other academic)
    Abstract [en]

    Language models that use interleaving, or shuffle, operators have applications in various areas of computer science, including system verification, plan recognition, and natural language processing. We study the complexity of the membership problem for such models, i.e., how difficult it is to determine if a string belongs to a language or not. In particular, we investigate how interleaving can be introduced into models that capture the context-free languages.

  • 131.
    Berglund, Martin
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Drewes, Frank
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    On the complexity of variants of the k best strings problem2010In: Proc. Prague Stringology Conference 2010 / [ed] M. Balík, J. Holub, 2010Conference paper (Refereed)
  • 132.
    Berglund, Martin
    et al.
    Stellenbosch University.
    Drewes, Frank
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Merwe, Brink van der
    University of Stellenbosch.
    On Regular Expressions with Backreferences and Transducers2018In: Tenth Workshop on Non-Classical Models of Automata and Applications (NCMA 2018) / [ed] Rudolf Freund, Michal Hospodár, Galina Jirásková, Giovanni Pighizzini, Österreichische Computer Gesellschaft , 2018, p. 49-64Conference paper (Refereed)
    Abstract [en]

    Modern regular expression matching software features many extensions, some general, while some are very narrowly specified. Here we consider the generalization of adding a class of operators which can be described by, e.g. finite-state transducers. Combined with backreferences, they enable new classes of languages to be matched. The addition of finite-state transducers is shown to make membership testing undecidable. Following this result, we study the complexity of membership testing for various restricted cases of the model.

  • 133.
    Berglund, Martin
    et al.
    Stellenbosch University.
    Drewes, Frank
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Merwe, Brink van der
    University of Stellenbosch.
    The output size problem for string-to-tree transducers2018In: Journal of Automata, Languages and Combinatorics, Vol. 23, no 1-3, p. 19-38Article in journal (Refereed)
    Abstract [en]

    The output size problem, for a string-to-tree transducer, is to determine the asymptotic behavior of the function describing the maximum size of output trees, with respect to the length of input strings. We show that the problem to determine, for a given regular expression, the worst-case matching time of a backtracking regular expression matcher, can be reduced to the output size problem. The latter can, in turn, be solved by determining the degree of ambiguity of a non-deterministic finite automaton.

  • 134.
    Berglund, Martin
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Drewes, Frank
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    van der Merwe, Brink
    University of Stellenbosch, South Africa.
    Analyzing Catastrophic Backtracking Behavior in Practical Regular Expression Matching2014Conference paper (Refereed)
    Abstract [en]

    We consider in some detail how regular expression matching happens in Java, as a popular representative of the category of regex-directed matching engines. We extract a slightly idealized algorithm for this scenario. Next we define an automata model which captures all the aspects needed to perform matching, of the Java style, in a formal way. Finally, two types of static analysis, which take a regular expression and tells whether there exists a family of strings which make Java-style matching run in exponential time, are done.

  • 135.
    Berglund, Martin
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    van der Merwe, Brink
    On the semantics of regular expression parsing in the wild2017In: Theoretical Computer Science, ISSN 0304-3975, E-ISSN 1879-2294, Vol. 679, p. 69-82Article in journal (Refereed)
    Abstract [en]

    We introduce prioritized transducers to formalize capturing groups in regular expression matching in a way that permits straightforward modeling of capturing in Java's 1 regular expression library. The broader questions of parsing semantics and performance are also considered. In addition, the complexity of deciding equivalence of regular expressions with capturing groups is investigated.

  • 136.
    Bergman, John
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Efficient fuzzy type-ahead search on big data using a ranked trie data structure2018Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The efficiency of modern search engines depends on how well they present typo-corrected results to a user while typing. So-called fuzzy type-ahead search combines fuzzy string matching and search-as-you-type functionality, and creates a powerful tool for exploring indexed data. Current fuzzy type-ahead search algorithms work well on small data sets, but for big data of social networking services such as Facebook, e-commerce sites such as Amazon, or media streaming services such as YouTube, responsive fuzzy type-ahead search remains a great challenge.

    This thesis describes a method that enables responsive type-ahead search combined with fuzzy string matching on big data by keeping the search time optimal for human interaction at the expense of lower accuracy for less popular records when a query contains typos. This makes the method effective for e-commerce and media services where the popularity of search terms is a result of human behaviour and thus often follow a power-law distribution.

  • 137.
    Bergqvist, Erik
    Umeå University, Faculty of Social Sciences, Department of Informatics.
    Varför diskutera formalisering.1985Report (Other (popular science, discussion, etc.))
  • 138.
    Bergström, Lars
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Syntaxbaserad författarigenkänning2010Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The writing style of a particular author can be divided into many subfeatures, for example use of words, language and syntax. Focusing on the latter, this study aims to show how well syntactic information alone can attribute the correct author to a document. Syntactic information is defined as overlapping syntactic subtrees of height one (1) for all sentences of all included documents. The performance is compared to that of the previously very successful method of comparing stop word frequencies. These are words normally excluded from search engine queries, because they are present in all sorts of texts regardless of topic. However, this property is a positive feature when it comes to authorship attribution, as it allows for context-free comparisons of texts. Training and test data is obtained from the icwsm 2009 corpus, containing some 200 igabyte of blog posts and news articles. This data is automatically filtered to create a reasonably large collection (about 250000 documents) while remaining manageable by an automatic natural language parser (Stanford nlp) within the constraints of time. The filtering process guarantees that all texts used for comparison has texts of the same author within the training portion of the data. Indexing and searching is done using Latent Semantic Indexing (lsi). All documents are represented by a vector in multidimensional space, thus creating a matrix of document vectors. Search documents are then matched with those in the matrix by calculating the angles between document vectors, returning those with the smallest angular difference to the query document. The process of creating a document matrix and search documents is repeated multiple times, creating a new document matrix of randomly selected authors  every time. The performance of the different methods are measured by comparing average scores for each created document matrix. The results show that by average the syntactic information is more successful in correct authorship recognition compared to both chance and stop word frequency analysis. These results hold true for all tested numbers of authors present within the index matrix, ranging from ten to one hundred unique authors.

  • 139.
    Bergström, Peter
    et al.
    Umeå University, Faculty of Social Sciences, Department of applied educational science, Interactive Media and Learning (IML).
    Årebrand, Stina
    Umeå University, Faculty of Social Sciences, Department of applied educational science.
    The student-role in the one-to-one computing classroom: tensions between teacher-centred learning and student-centred learning2013In: Scaling up Learning for Sustained Impact: 8th European Conference, on Technology Enhanced Learning, EC-TEL 2013, Paphos, Cyprus, September 17-21, 2013. Proceedings / [ed] Davinia Hernández-Leo, Tobias Ley, Ralf Klamma, Andreas Harrer, Berlin: Springer-Verlag New York, 2013, no 8, p. 424-429Conference paper (Refereed)
    Abstract [en]

    One-to-one (1:1) computing has recently been scaled up andintegrated into learning strategies, but there have been rather few studiesabout it so far. This explorative observation and interview studyaims to gain increased understanding about the student role in the 1:1computing classroom in upper secondary school. The results demonstratea media-rich classroom based on four categories of affordances:students’ note-taking; searching the Internet; social media; and laptopsfor duplication. The four categories of affordances delineate how teachers’behaviour is influencing students and their use of laptops in thedesigned learning activities. The designs of the 1:1 classrooms are basedon technology-enhanced consumption of media as opposed to designs fortechnology-enhanced learning. It is concluded that the student role is diverseand stretched between principles of both teacher-centred learningand student-centred learning.

  • 140.
    Bergvik, David
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Designing experiences for virtual reality, in virtual reality: A design process evaluation2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Creating immersive experiences for virtual reality (VR) presents new design opportunities and challenges that do not appear when creating experiences on a screen. Creating prototypes and exploring concepts in VR is today limited to professionals with previous knowledge in 3D application development, and testing 3D experiences requires the usage of an Head-Mounted Display (HMD), which forces professionals to switch medium from the computer to an HMD. With new advances in this field, there have to be new solutions to these challenges. The goal of this thesis is to explore how VR technology can be utilized in the experience design process for VR. This is achieved through a literature study and conducting expert interviews, followed by a hardware evaluation of different HMDs and concept creation using rapid prototyping. From the interviews, a number of issues could be identified that correlates with the research from the literature study. Based on these findings, two phases were identified as suitable for further improvements; Concept prototyping and testing/tweaking of a created experience. Lo-fi and hi-fi prototypes of a virtual design tool were developed for HTC Vive and Google Daydream, which were selected based on the hardware evaluation. The prototypes are designed and developed, then tested using a Wizard of Oz approach. The purpose of the prototypes is to solve some of the issues when designing immersive experiences for HMDs in the suitable experience design phases that were identified by analyzing the interview results. An interactive testing suite for HTC Vive was developed for testing and evaluation of the final prototype, to verify the validity of the concept. Using Virtual Reality as a medium for designing virtual experiences is a promising way of solving current issues within this technological field that are identified in this thesis. Tools for object creation and manipulation will aid professionals when exploring new concepts as well as editing and testing existing immersive experiences. Furthermore, using a Wizard of Oz approach to test VR prototypes significantly improves the prototype quality without compromising the user experience in this medium. 

  • 141.
    Bermell, Måns
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Identification of Problem Gambling via Recurrent Neural Networks: Predicting self-exclusion due to problem gambling within the remote gambling sector by means of recurrent neural networks2019Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Under recent years the gambling industry has been moving towards providing their customer the possibility to gamble online instead of visiting a physical location. Aggressive marketing, fast growth and a multitude of actors within the market have resulted in a spike of customers who have developed a gambling problem. Decision makers are trying to fight back by regulating markets in order to make the companies take responsibility and work towards preventing these problems. One method of working proactively in this regards is to identify vulnerable customers before they develop a destructive habit.

    In this work a novel method of predicting customers that have a higher risk in regards to gambling-related problems is explored. More concretely, a recurrent neural network with long short-term memory cells is created to process raw behaviour data that are aggregated on a daily basis to classify them as high-risk or not. Supervised training is used in order to learn from historical data, where the usage of permanent self-exclusions due to gambling related problems defines problem gamblers. The work consists of: obtain a local optimal configuration of the network which enhances the performance for identifying problem gam- blers who favour the casino section over sports section, and analyze the model to provide insights in the field.

    This project was carried out together with LeoVegas Mobile Gaming Group. The group offers both online casino games and sports booking in a number of countries in Europe. This collaboration made both data and expertise within the industry accessible to perform this work. The company currently have a model in production to perform these predictions, but want to explore other approaches.

    The model that has been developed showed a significant increase in performance compared to the one that is currently used at the company. Specifically, the precision and recall which are two metrics important for a two class classification model, increased by 37% and 21% respectively. Using raw time series data, instead of aggregated data increased the responsiveness regarding customers change in behaviour over time. The model also scaled better with more history compared to the current model, which could be a result of the nature of a recurrent network compared to the current model used.

  • 142.
    Bernland, Anders
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Wadbro, Eddie
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Berggren, Martin
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Acoustic shape optimization using cut finite elements2018In: International Journal for Numerical Methods in Engineering, ISSN 0029-5981, E-ISSN 1097-0207, Vol. 113, no 3, p. 432-449Article in journal (Refereed)
    Abstract [en]

    Fictitious domain methods are attractive for shape optimization applications, since they do not require deformed or regenerated meshes. A recently developed such method is the CutFEM approach, which allows crisp boundary representations and for which uniformly well-conditioned system matrices can be guaranteed. Here, we investigate the use of the CutFEM approach for acoustic shape optimization, using as test problem the design of an acoustic horn for favorable impedance-matching properties. The CutFEM approach is used to solve the Helmholtz equation, and the geometry of the horn is implicitly described by a level-set function. To promote smooth algorithmic updates of the geometry, we propose to use the nodal values of the Laplacian of the level-set function as design variables. This strategy also improves the algorithm's convergence rate, counteracts mesh dependence, and, in combination with Tikhonov regularization, controls small details in the optimized designs. An advantage with the proposed method is that the exact derivatives of the discrete objective function can be expressed as boundary integrals, as opposed to when using a traditional method that uses mesh deformations. The resulting horns possess excellent impedance-matching properties and exhibit surprising subwavelength structures, not previously seen, which are possible to capture due to the fixed mesh approach.

  • 143.
    Bertheim, Jane
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Designing Digital Nudges to Encourage Sustainable Decisions: Developing and Testing a Framework2018Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The awareness of environmental impacts lead to that organizations are starting to work towards UN's global sustainability goals. To influence customers into a more sustainable behaviour, organizations have the potential to look at nudging as a tool. A nudge is a way to alter peoples behaviour into taking a certain decision. However, since many organizations offer their service or product in the digital environment, such as websites or apps, increased knowledge of digital nudging is required. This thesis aims to establish a framework for how nudges should be designed and used on digital platforms to encourage sustainable decisions. The purpose is to enlighten designers of digital environment of the potential of nudges, pitfalls to avoid, and a general design process to follow. The framework is based on a literature study and interviews with people familiar with the concept of nudging. To examine how the framework works a case study is performed, this includes a workshop, performing a user research, developing prototypes and finally, conduct user tests. By testing the framework further methods could be found, this meant that more practical steps could be included in the framework. The result of this thesis shows that the framework proved to be useful and functional to use when designing digital nudges to encourage sustainable decisions.

  • 144.
    Bhuyan, Monowar H.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science. Umea University.
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science. Umea University.
    Multi-Scale Low-Rate DDoS Attack Detection Using the Generalized Total Variation Metric2018In: 17th IEEE International Conference on Machine Learning and Applications, IEEE, 2018, p. 1040-1047Conference paper (Refereed)
    Abstract [en]

    We propose a mechanism to detect multi-scale low-rate DDoS attacks which uses a generalized total variation metric. The proposed metric is highly sensitive towards detecting different variations in the network traffic and evoke more distance between legitimate and attack traffic as compared to the other detection mechanisms. Most low-rate attackers invade the security system by scale-in-and-out of periodic packet burst towards the bottleneck router which severely degrades the Quality of Service (QoS) of TCP applications. Our proposed mechanism can effectively identify attack traffic of this natures, despite its similarity to legitimate traffic, based on the spacing value of our metric. We evaluated our mechanism using datasets from CAIDA DDoS, MIT Lincoln Lab, and real-time testbed traffic. Our results demonstrate that our mechanism exhibits good accuracy and scalability in the detection of multi-scale low-rate DDoS attacks.

  • 145.
    Billing, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Cognition Rehearsed: Recognition and Reproduction of Demonstrated Behavior2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The work presented in this dissertation investigates techniques for robot Learning from Demonstration (LFD). LFD is a well established approach where the robot is to learn from a set of demonstrations. The dissertation focuses on LFD where a human teacher demonstrates a behavior by controlling the robot via teleoperation. After demonstration, the robot should be able to reproduce the demonstrated behavior under varying conditions. In particular, the dissertation investigates techniques where previous behavioral knowledge is used as bias for generalization of demonstrations.

    The primary contribution of this work is the development and evaluation of a semi-reactive approach to LFD called Predictive Sequence Learning (PSL). PSL has many interesting properties applied as a learning algorithm for robots. Few assumptions are introduced and little task-specific configuration is needed. PSL can be seen as a variable-order Markov model that progressively builds up the ability to predict or simulate future sensory-motor events, given a history of past events. The knowledge base generated during learning can be used to control the robot, such that the demonstrated behavior is reproduced. The same knowledge base can also be used to recognize an on-going behavior by comparing predicted sensor states with actual observations. Behavior recognition is an important part of LFD, both as a way to communicate with the human user and as a technique that allows the robot to use previous knowledge as parts of new, more complex, controllers.

    In addition to the work on PSL, this dissertation provides a broad discussion on representation, recognition, and learning of robot behavior. LFD-related concepts such as demonstration, repetition, goal, and behavior are defined and analyzed, with focus on how bias is introduced by the use of behavior primitives. This analysis results in a formalism where LFD is described as transitions between information spaces. Assuming that the behavior recognition problem is partly solved, ways to deal with remaining ambiguities in the interpretation of a demonstration are proposed.

    The evaluation of PSL shows that the algorithm can efficiently learn and reproduce simple behaviors. The algorithm is able to generalize to previously unseen situations while maintaining the reactive properties of the system. As the complexity of the demonstrated behavior increases, knowledge of one part of the behavior sometimes interferes with knowledge of another parts. As a result, different situations with similar sensory-motor interactions are sometimes confused and the robot fails to reproduce the behavior.

    One way to handle these issues is to introduce a context layer that can support PSL by providing bias for predictions. Parts of the knowledge base that appear to fit the present context are highlighted, while other parts are inhibited. Which context should be active is continually re-evaluated using behavior recognition. This technique takes inspiration from several neurocomputational models that describe parts of the human brain as a hierarchical prediction system. With behavior recognition active, continually selecting the most suitable context for the present situation, the problem of knowledge interference is significantly reduced and the robot can successfully reproduce also more complex behaviors.

  • 146.
    Billing, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Cognition reversed: Robot learning from demonstration2009Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The work presented in this thesis investigates techniques for learning from demonstration (LFD). LFD is a well established approach to robot learning, where a teacher demonstrates a behavior to a robot pupil. This thesis focuses on LFD where a human teacher demonstrates a behavior by controlling the robot via teleoperation. The robot should after demonstration be able to execute the demonstrated behavior under varying conditions.

    Several views on representation, recognition and learning of robot behavior are presented and discussed from a cognitive and computational perspective. LFD-related concepts such as behavior, goal, demonstration, and repetition are defined and analyzed, with focus on how bias is introduced by the use of behavior primitives. This analysis results in a formalism where LFD is described as transitions between information spaces. Assuming that the behavior recognition problem is partly solved, ways to deal with remaining ambiguities in the interpretation of a demonstration are proposed.

    A total of five algorithms for behavior recognition are proposed and evaluated, including the dynamic temporal difference algorithm Predictive Sequence Learning (PSL). PSL is model-free in the sense that it makes few assumptions of what is to be learned. One strength of PSL is that it can be used for both robot control and recognition of behavior. While many methods for behavior recognition are concerned with identifying invariants within a set of demonstrations, PSL takes a different approach by using purely predictive measures. This may be one way to reduce the need for bias in learning. PSL is, in its current form, subjected to combinatorial explosion as the input space grows, which makes it necessary to introduce some higher level coordination for learning of complex behaviors in real-world robots.

    The thesis also gives a broad introduction to computational models of the human brain, where a tight coupling between perception and action plays a central role. With the focus on generation of bias, typical features of existing attempts to explain humans' and other animals' ability to learn are presented and analyzed, from both a neurological and an information theoretic perspective. Based on this analysis, four requirements for implementing general learning ability in robots are proposed. These requirements provide guidance to how a coordinating structure around PSL and similar algorithms should be implemented in a model-free way.

  • 147.
    Billing, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Cognitive Perspectives on Robot Behavior2010In: Proceedings of the 2nd International Conference on Agents and Artificial Intelligence: Special Session on Computing Languages with Multi-Agent Systems and Bio-Inspired Devices / [ed] Joaquim Filipe, Ana Fred and Bernadette Sharp, Portugal: INSTICC , 2010, p. 373-382Conference paper (Refereed)
    Abstract [en]

    A growing body of research within the field of intelligent robotics argues for a view of intelligence drastically different from classical artificial intelligence and cognitive science. The holistic and embodied ideas expressed by this research promote the view that intelligence is an emergent phenomenon. Similar perspectives, where numerous interactions within the system lead to emergent properties and cognitive abilities beyond that of the individual parts, can be found within many scientific fields. With the goal of understanding how behavior may be represented in robots, the present review tries to grasp what this notion of emergence really means and compare it with a selection of theories developed for analysis of human cognition, including the extended mind, distributed cognition and situated action. These theories reveal a view of intelligence where common notions of objects, goals, language and reasoning have to be rethought. A view where behavior, as well as the agent as such, is defined by the observer rather than given by their nature. Structures in the environment emerge by interaction rather than recognized. In such a view, the fundamental question is how emergent systems appear and develop, and how they may be controlled.

  • 148.
    Billing, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Representing behavior: Distributed theories in a context of robotics2007Report (Other academic)
    Abstract [en]

    A growing body of research within the field of intelligent robotics argues for a view of intelligence drastically different from classical artificial intelligence and cognitive science. The holistic and embodied ideas expressed by this research sees emergence as the springing source for intelligence. Similar perspectives, where numerous interactions within the system lead to emergent properties and cognitive abilities beyond that of the individual parts, can be found within many scientific fields. With the goal of understanding how behavior may be represented in robots, the present review tries to grasp what this notion of emergence really means and compare it with a selection of theories developed for analysis of human cognition. These theories reveal a view of intelligence where common notions of objects, goals and reasoning have to be rethought. A view where behavior, as well as the agent as such, is in the eye of the observer rather than given. Structures in the environment is achieved by interaction rather than recognized. In such a view, the fundamental question is how emergent systems appear and develop, and how they may be controlled.

  • 149.
    Billing, Erik
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Hellström, Thomas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    A formalism for learning from demonstration2010In: Paladyn Journal of Behavioral Robotics, ISSN 2080-9778, 2081-4836 (e-version), Vol. 1, no 1, p. 1-13Article in journal (Refereed)
    Abstract [en]

    The paper describes and formalizes the concepts and assumptions involved in Learning from Demonstration (LFD), a common learning technique used in robotics. LFD-related concepts like goal, generalization, and repetition are here defined, analyzed, and put into context. Robot behaviors are described in terms of trajectories through information spaces and learning is formulated as mappings between some of these spaces. Finally, behavior primitives are introduced as one example of good bias in learning, dividing the learning process into the three stages of behavior segmentation, behavior recognition, and behavior coordination. The formalism is exemplified through a sequence learning task where a robot equipped with a gripper arm is to move objects to specific areas. The introduced concepts are illustrated with special focus on how bias of various kinds can be used to enable learning from a single demonstration, and how ambiguities in demonstrations can be identified and handled.

  • 150.
    Billing, Erik
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Hellström, Thomas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Behavior recognition for segmentation of demonstrated tasks2008In: IEEE SMC International Conference on Distributed Human-Machine Systems (DHMS), 2008Conference paper (Refereed)
    Abstract [en]

    One common approach to the robot learning technique Learning From Demonstration, is to use a set of pre-programmed skills as building blocks for more complex tasks. One important part of this approach is recognition of these skills in a demonstration comprising a stream of sensor and actuator data. In this paper, three novel techniques for behavior recognition are presented and compared. The first technique is function-oriented and compares actions for similar inputs. The second technique is based on auto-associative neural networks and compares reconstruction errors in sensory-motor space. The third technique is based on S-Learning and compares sequences of patterns in sensory-motor space. All three techniques compute an activity level which can be seen as an alternative to a pure classification approach. Performed tests show how the former approach allows a more informative interpretation of a demonstration, by not determining "correct" behaviors but rather a number of alternative interpretations.

1234567 101 - 150 of 1920
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf