We investigate the computational complexity of several decision, enumeration and counting problems related to pseudo-intents. We show that given a formal context and a set of its pseudo-intents, checking whether this context has an additional pseudo-intent is in conp and it is at least as hard as checking whether a given simple hypergraph is saturated. We also show that recognizing the set of p...

The framework of consistent query answers and repairs has been introduced to alleviate the impact of inconsistent data on the answers to a query. A repair is a minimally different consistent instance and an answer is consistent if it is present in every repair. In this article we study the complexity of consistent query answers and repair checking in the presence of universal constraints. We pr...

Message sequence charts (MSCs) and high-level message sequence charts (HMSCs) are popular formalisms for the speciication of communication protocols between asynchronous processes. An important concept in this context is the size of the communication buuers used between processes. Since real systems impose limitations on the capacity (or speed) of communication links, we ask whether a given HMS...

Gopalan et al. studied in ICALP06 [17] connectivity properties of the solution-space of Boolean formulas, and investigated complexity issues on the connectivity problems in Schaefer’s framework. A set S of logical relations is Schaefer if all relations in S are either bijunctive, Horn, dual Horn, or affine. They conjectured that the connectivity problem for Schaefer is in P . We disprove their ...

a D epart ment of Radiol ogical Sciences, Ibara ki Pref ect ural U niversit y of H ealt h Sciences A mi, I baraki 300-0394, Japan b A tomic Physics Lab oratory , T he Institute of Physical and C hemical Research (RI K EN ) W ako, Saitama 351-0198, Japan c H igh Energy A ccelerator Research Organi zation (K EK ) T sukuba, I baraki 305-0801, Japan d Department of Physics, Tokyo Gakugei U niversit...

We prove that the class NP has Co-NP-immune sets relative to a random oracle. Moreover, we prove that, relative to a random oracle, there are L 2 P and NP-set L 1 L such that L 1 is Co-NP-immune and L n L 1 is NP-immune. The second theorem implies the theorem in 4] that Co-NP has NP-immune sets relative to a random oracle.

As a query language for navigating XML trees and selecting a set of element nodes, XPath is ubiquitous in XML applications. One important issue of XPath queries is containment checking, which is known as a co-NP complete. The homomorphism relationship between two XPath trees, which is a PTIME problem, is a sufficient but not necessary condition for the containment relationship. We propose a new...

Regular games provide a very useful model for the synthesis of controllers in reactive systems. The complexity of these games depends on the representation of the winning condition: if it is represented through a win-set, a coloured condition, a Zielonka-DAG or Emerson-Lei formulae, the winner problem is PSPACE-complete; if the winning condition is represented as a Zielonka tree, the winner pro...

The cyclability of a graph is the maximum integer k for which every k vertices lie on a cycle. The algorithmic version of the problem, given a graph G and a nonnegative integer k, decide whether the cyclability of G is at least k, is NP-hard. We study the parametrized complexity of this problem. We prove that this problem, parameterized by k, is co-W[1]-hard and that its does not admit a polyno...