Publikationen

2008

• A. Dermaku, T. Ganzow, G. Gottlob, B. J. McMahan, N. Musliu, and M. Samer. Heuristic Methods for Hypertree Decomposition. In Proceedings of the 7th Mexican International Conference on Artificial Intelligence, MICAI 2008, pp. 1–11, 2008.             
  BibTeX

  @inproceedings{DGGMMS08,
       author = {Artan Dermaku and Tobias Ganzow and Georg Gottlob and Benjamin J. McMahan and Nysret Musliu and Marko Samer},
       title = {Heuristic Methods for Hypertree Decomposition},
       booktitle = {Proceedings of the 7th Mexican International Conference on Artificial Intelligence, MICAI 2008},
       year = {2008},
       pages = {1–11},
       url = {http://dx.doi.org/10.1007/978-3-540-88636-5_1},
  }
  

• T. Ganzow and S. Rubin. Order-Invariant MSO is Stronger than Counting MSO in the Finite. In Proceedings of the 25th International Symposium on Theoretical Aspects of Computer Science, STACS 2008 (S. Albers and P. Weil, Eds.), pp. 313–324, 2008.                                 
  Abstract   BibTeX

  We compare the expressiveness of two extensions of monadic second-order logic (MSO) over the class of finite structures. The first, counting monadic second-order logic (CMSO), extends MSO with first-order modulo-counting quantifiers, allowing the expression of queries like “the number of elements in the structure is even''. The second extension allows the use of an additional binary predicate, not contained in the signature of the queried structure, that must be interpreted as an arbitrary linear order on its universe, obtaining order-invariant MSO. While it is straightforward that every CMSO formula can be translated into an equivalent order-invariant MSO formula, the converse had not yet been settled. Courcelle showed that for restricted classes of structures both order-invariant MSO and CMSO are equally expressive, but conjectured that, in general, order-invariant MSO is stronger than CMSO. We affirm this conjecture by presenting a class of structures that is order-invariantly definable in MSO but not definable in CMSO.

  @inproceedings{GR08,
       author = {Tobias Ganzow and Sasha Rubin},
       title = {Order-Invariant MSO is Stronger than Counting MSO in the Finite},
       booktitle = {Proceedings of the 25th International Symposium on Theoretical Aspects of Computer Science, STACS 2008},
       editor = {Susanne Albers and Pascal Weil},
       pages = {313–324},
       year = {2008},
       url = {http://www.logic.rwth-aachen.de/pub/ganzow/GR-STACS08.pdf},
  }