Researchers in databases, AI, and machine learning, have all proposed representations of probability distributions over relational databases (possible worlds). In a tuple-independent probabilistic database, the possible worlds all have distinct probabilities, because the tuple probabilities are distinct. In AI and machine learning, however, one typically learns highly symmetric distributions, w...

We investigate an approach to matroid complexity that involves describing a matroid via a list of independent sets, bases, circuits, or some other family of subsets of the ground set. The computational complexity of algorithmic problems under this scheme appears to be highly dependent on the choice of input-type. We define an order on the various methods of description, and we show how this ord...

Weak probabilistic bisimulation on probabilistic automata can be decided by an algorithm that needs to check a polynomial number of linear programming problems encoding weak transitions. It is hence polynomial, but not guaranteed to be strongly polynomial. In this paper we show that for polynomial rational probabilistic automata strong polynomial complexity can be ensured. We further discuss co...

For almost two decades, contradictory relativization has been a central theme in complexity theory. This concept was first introduced by Baker, Gill and Solovay [BGS75] in their ground breaking paper where they exhibited oracles A and B such that P = NP and P 6= NP. This result was startling because almost all results in recursion theory remain true in the presence of oracles and most technique...

In this paper we address ground logics, a family of nonmonotonic modal logics, and their usage in knowledge representation. In such a setting non-modal sentences are used to represent the knowledge of an agent about the world, while an epistemic operator provides the agent with autoepistemic or introspective knowledge. Ground logics are based on the idea of characterizing the knowledge of the a...

We investigate an approach to matroid complexity that involves describing a matroid via a list of independent sets, bases, circuits, or some other family of subsets of the ground set. The computational complexity of algorithmic problems under this scheme appears to be highly dependent on the choice of input type. We define an order on the various methods of description, and we show how this ord...

We describe two cases of open user experience (UX) design using the Firefox web browser and OpenOffice.org office suite as case studies. We analyze the social complexity of integrating UX practices into the two open source projects using activity awareness, a framework for understanding team performance in collective endeavors of significant scope, duration, and complexity. The facets of activi...

An AR model (= atomic representation of a Herbrand structure) is given through a set A = fA 1 ; : : : ; A n g of atoms over some Herbrand universe H with the following intended meaning: a ground atom over H evaluates to true, ii it is an instance of some atom A i 2 A. The applicability of AR models to automated model building has been demonstrated by recent publications in this eld (cf. FL 96])...

The theory of nite trees is the full rst-order theory of equality in the Herbrand universum (the set of ground terms) over a functional signature containing non-unary function symbols and constants. Albeit decidable, this theory turns out to be of the non-elementary complexity in the sense of Kalmar, i.e., it cannot be decided within time or space bounded by any nite xed tower of exponentials 2...