Université de Fribourg

Complementing Büchi automata with a subset-tuple construction

Allred, Joel ; Ultes-Nitsche, Ulrich

(Internal working papers DIUF ; 15-01)

Complementation of Büchi automata is well known for being difficult. In the worst case, a state-space growth of (0:76n)n is unavoidable. Recent studies suggest that “simpler” algorithms perform better than more involved ones on practical cases. In this paper, we present a simple “direct” algorithm for complementing Büchi automata. It involves a structured subset construction (using...

Université de Fribourg

Structure comparison of binary and weighted niche-overlap graphs

Sokhn, Nayla ; Baltensperger, Richard ; Bersier, Louis-Felix ; Ultes-Nitsche, Ulrich ; Hennebert, Jean

In: Complex Networks, 2014, vol. 5, p. 119–127

In ecological networks, niche-overlap graphs are considered as complex systems. They represent the competition between two predators that share common resources. The purpose of this paper is to investigate the structural properties of these graphs considered as weighted networks and compare their measures with the ones calculated for the binary networks. To conduct this study, we select four...

Université de Fribourg

Immune system based intrusion detection system

Ehret, Christoph ; Ultes-Nitsche, Ulrich

In: Innovative Minds (Information Systems Security Association - ISSA 2008), Johannesburg, South Africa, July 2008, 2008, p. -

The threats and intrusions in IT systems can basically be compared to human diseases with the difference that the human body has an effective way to deal with them, what still need to be designed for IT systems. The human immune system (HIS) can detect and defend against yet unseen intruders, is distributed, adaptive and multilayered to name only a few of its features. Our immune system...