I have moved to a new position at Amazon Web Services.

Research Interests

databases; knowledge representation; information integration; data streaming; logic and its applications to computer science (in particular, finite model theory); complexity theory

Publications and Theses

  1. Horn-Rewritability vs PTime Query Evaluation in Ontology-Mediated Querying
    with Carsten Lutz, Fabio Papacchini, and Frank Wolter
    IJCAI-ECAI 2018, p. 1861-1867
  2. Dichotomies in Ontology-Mediated Querying with the Guarded Fragment
    with Carsten Lutz, Fabio Papacchini, and Frank Wolter
    PODS 2017, p. 185-199 (Best Paper Award)
  3. Horn Rewritability vs PTime Query Answering for Description Logic TBoxes
    with Carsten Lutz, Fabio Papacchini, and Frank Wolter
    DL 2017
  4. Foundations of information integration under bag semantics
    with Phokion G. Kolaitis
    LICS 2017, p. 1-12
  5. Query Answering in DL-Lite with Datatypes: A Non-Uniform Approach
    with Julio Lemos and Frank Wolter
    AAAI 2017, p. 1142-1148
  6. Constraint Patterns for Tractable Ontology-Mediated Queries with Datatypes
    with Julio Lemos and Frank Wolter
    DL 2016
  7. Schema.org As a Description Logic
    with Carsten Lutz, Ana Ozaki, and Frank Wolter
    IJCAI 2015, p. 3048-3054
  8. Stable Model Semantics for Guarded Existential Rules and Description Logics
    with Georg Gottlob, Clemens Kupke, and Thomas Lukasiewicz
    KR 2014
  9. Semantics for Non-Monotone Queries in Data Exchange and Data Integration
    Data Exchange, Integration, and Streams. DFU, Volume 5, p. 161-184, 2013
  10. Well-Founded Semantics for Extended Datalog and Ontological Reasoning
    with Georg Gottlob, Clemens Kupke, and Thomas Lukasiewicz
    PODS 2013, p. 225-236
  11. L-Recursion and a new Logic for Logarithmic Space
    with Martin Grohe, Berit Grußien, and Bastian Laubner
    Logical Methods in Computer Science 9(1), paper 11, 2013
    Also part of the Special Issue for CSL 2011
  12. Equality-Friendly Well-Founded Semantics and Applications to Description Logics
    with Georg Gottlob, Clemens Kupke, and Thomas Lukasiewicz
    AAAI 2012, p. 757-764. See here for the poster.
    This work was also presented at DL 2012.
  13. Computing Universal Models Under Guarded TGDs
    ICDT 2012, p. 222-235
  14. Answering Non-Monotonic Queries in Relational Data Exchange
    Logical Methods in Computer Science 7(3), paper 9, 2011
    Also part of the Special Issue for ICDT 2010
  15. L-Recursion and a new Logic for Logarithmic Space
    with Martin Grohe, Berit Grußien, and Bastian Laubner
    CSL 2011, p. 277-291
  16. Closed World Data Exchange
    with Leonid Libkin, and Nicole Schweikardt
    ACM Transactions on Database Systems 36(2), article 14, 2011
  17. Foundations of Query Answering in Relational Data Exchange
    PhD thesis, Goethe-Universität Frankfurt am Main, Germany, 2010
    Also published at Logos Verlag Berlin, ISBN 978-3-8325-2735-8
  18. Answering Non-Monotonic Queries in Relational Data Exchange
    ICDT 2010, p. 143-154 (Best Student Paper Award)
  19. Logic and Data Exchange: Which Solutions are "Good" Solutions?
    with Nicole Schweikardt
    Logic and the Foundations of Game and Decision Theory - LOFT 8, p. 61-85, 2010
  20. Lower Bounds for Processing Data with Few Random Accesses to External Memory
    with Martin Grohe, and Nicole Schweikardt
    Journal of the ACM 56(3), article 12, 2009, Special Section for PODS 2006
  21. Reversal Complexity Revisited
    with Nicole Schweikardt
    Theoretical Computer Science 401(1-3), p. 191-205, 2008
  22. CWA-Solutions for Data Exchange Settings with Target Dependencies
    with Nicole Schweikardt
    PODS 2007, p. 113-122
  23. Randomized Computations on Large Data Sets: Tight Lower Bounds
    with Martin Grohe, and Nicole Schweikardt
    PODS 2006, p. 243-252
  24. Combining Self-Reducibility and Partial Information Algorithms
    with Arfst Nickelsen
    MFCS 2005, p. 422-434
  25. Combining Self-Reducibility with Partial Information Algorithms
    Diploma Thesis (comparable to MSc thesis), Technische Universität Berlin, 2005

Teaching (at University of Liverpool)

See VITAL for information on the modules below.

2017-18: Previous years: