Interprocedural Reachability for Flat Integer Programs

We study programs with integer data, procedure calls and arbitrary call graphs. We show that, whenever the guards and updates are given by octagonal relations, the reachability problem along control flow paths within some language w1* ... wd* over program statements is decidable in Nexptime. To achieve this upper bound, we combine a program transformation into the same class of programs but without procedures, with an Np-completeness result for the reachability problem of procedure-less programs. Besides the program, the expression w1* ... wd* is also mapped onto an expression of a similar form but this time over the transformed program statements. Several arguments involving context-free grammars and their generative process enable us to give tight bounds on the size of the resulting expression. The currently existing gap between Np-hard and Nexptime can be closed to Np-complete when a certain parameter of the analysis is assumed to be constant.Comment: 38 pages, 1 figur

Refining Restriction Enzyme Genome Maps

A genome map is an ordering of a set of clones according to their believed position on a DNA string. Simple heuristics for genome map assembly based on single restriction enzyme with complete digestion data can lead to inaccuracies and ambiguities. This paper presents a method that adds additional constraint checking to the assembly process. An automaton is presented that for any genome map produces a refined genome map where both the clones and the restriction fragments in each clone are ordered satisfying natural constraints called step constraints. Any genome map that cannot be refined is highly likely to be inaccurate and can be eliminated as a possibility. 1 Introduction Deoxyribonucleic acid or DNA, the genetic material that encodes the blueprint of any living organism, is composed of a string of nucleotides that are adenine (A), thymine (T), cytosine (C), and guanine (G). Clones are copies of random substrings of a given DNA string. Clones may overlap in a clone database. Restr..

Assertional Removed Sets Merging of DL-Lite Knowledge Bases

International audienceDL-Lite is a tractable family of Description Logics that underlies the OWL-QL profile of the ontology web language, which is specifically tailored for query answering. In this paper, we consider the setting where the queried data are provided by several and potentially conflicting sources. We propose a merging approach, called "Assertional Removed Sets Fusion" (ARSF) for merging DL-Lite assertional bases. This approach stems from the inconsistency minimization principle and consists in determining the minimal subsets of assertions, called assertional removed sets, that need to be dropped from the original assertional bases in order to resolve conflicts between them. We give several merging strategies based on different definitions of minimality criteria, and we characterize the behaviour of these strategies with respect to rational properties. The last part of the paper shows how to use the notion of hitting sets for computing the assertional removed sets, and the merging outcome

Main Issues in Belief Revision, Belief Merging and Information Fusion

International audienceThis chapter focuses on the dynamics of information represented in logical or numerical formats, from pioneering works to recent developments. The logical approach to belief change is a topic that has been extensively studied in Artificial Intelligence, starting in the mid-seventies. In this problem, logical formulas represent beliefs held by an intelligent agent that must be revised upon receiving new information that conflicts with prior beliefs and usually has priority over them. In contrast, in the merging problem, the logical theories that must be combined have equal priority. Such logical approaches recalled here make sense for merging beliefs as well as goals, even if each of these problems cannot be reduced to the other. In the last part, we discuss a number of issues pertaining to the fusion and the revision of uncertainty functions representing epistemic states, such as probability measures, possibility measures and belief functions. The need to cope with logical inconsistency plays a major role in these problems. The ambition of this chapter is not to provide an exhaustive bibliography, but rather to propose an overview of basic notions, main results and new research issues in this area