arXiv subjects

Wolfgang Slany

Publications and source records attributed to Wolfgang Slany.

27 records · Page 2Linked to original sources

arXiv2012

Catroid: A Mobile Visual Programming System for Children

Catroid is a free and open source visual programming language, programming environment, image manipulation program, and website. Catroid allows casual and first-time users starting from age eight to develop their own animations and games solely using their Android phones or tablets. Catroid also allows to wirelessly control external hardware such as Lego Mindstorms robots via Bluetooth, Bluetooth Arduino boards, as well as Parrot's popular and inexpensive AR.Drone quadcopters via WiFi.

cs.PL↗

arXiv2012

Functional Magnetic Resonance Imaging and the Challenge of Balancing Human Security with State Security

Recent reports reveal that violent extremists are trying to obtain insider positions that may increase the impact of any attack on critical infrastructure and could potentially endanger state services, people's lives and even democracy. It is of utmost importance to be able to adopt extreme security measures in certain high-risk situations in order to secure critical infrastructure and thus lower the level of terrorist threats while preserving the rights of citizens. To counter these threats, our research is aiming for extreme measures to analyse and evaluate human threats related assessment methods for employee screening and evaluations using cognitive analysis technology, in particular functional Magnetic Resonance Imaging (fMRI). The development of fMRI has led some researchers to conclude that this technology has forensic potential and may be useful in investing personality traits, mental illness, psychopathology, racial prejudice and religious extremism. However, critics claim that this technology may present many new human rights and ethical dilemmas and could result in potentially disastrous outcomes. The main thrust of the research is to counter above concerns and harmful consequences by presenting a set of ethical and professional guidelines that will substantially reduce the risk of unethical use of this technology. The significance of this research is to ensure the limits of the state/organisation's right to peer into an individual's thought process with and without consent, to define the parameters of a person's right to ensure that fMRI scans do not pose more than an appropriate threat to cognitive liberty, and the proper use of such information in civil, forensic and security settings.

cs.CR↗

arXiv2006

On some winning strategies for the Iterated Prisoner's Dilemma or Mr. Nice Guy and the Cosa Nostra

We submitted two kinds of strategies to the iterated prisoner's dilemma (IPD) competitions organized by Graham Kendall, Paul Darwen and Xin Yao in 2004 and 2005. Our strategies performed exceedingly well in both years. One type is an intelligent and optimistic enhanced version of the well known TitForTat strategy which we named OmegaTitForTat. It recognizes common behaviour patterns and detects and recovers from repairable mutual defect deadlock situations, otherwise behaving much like TitForTat. The second type consists of a set of strategies working together as a team. These group strategies have one distinguished individual Godfather strategy that plays OmegaTitForTat against non-members while heavily profiting from the behaviour of the other members of his group, the Hitman. The Hitman willingly let themselves being abused by their Godfather while themselves lowering the scores of all other players as much as possible, thus further maximizing the performance of their Godfather in relation to other participants. The study of collusion in the simplified framework of the iterated prisoner's dilemma allows us to draw parallels to many common aspects of reality both in Nature as well as Human Society, and therefore further extends the scope of the iterated prisoner's dilemma as a metaphor for the study of cooperative behaviour in a new and natural direction. We further provide evidence that it will be unavoidable that such group strategies will dominate all future iterated prisoner's dilemma competitions as they can be stealthy camouflaged as non-group strategies with arbitrary subtlety. Moreover, we show that the general problem of recognizing stealth colluding strategies is undecidable in the theoretical sense.

cs.GT↗

arXiv2006

Efficient generation of rotating workforce schedules

Generating high-quality schedules for a rotating workforce is a critical task in all settings where a certain staffing level must be guaranteed beyond the capacity of single employees, such as for instance in industrial plants, hospitals, or airline companies. Results from ergonomics \cite{BEST91} indicate that rotating workforce schedules have a profound impact on the health and social life of employees as well as on their performance at work. Moreover, rotating workforce schedules must satisfy legal requirements and should also meet the objectives of the employing organization. We describe our solution to this problem. A basic design decision was to aim at quickly obtaining high-quality schedules for realistically sized problems while maintaining human control. The interaction between the decision maker and the algorithm therefore consists in four steps: (1) choosing a set of lengths of work blocks (a work block is a sequence of consecutive days of work shifts), (2) choosing a particular sequence of work and days-off blocks among those that have optimal weekend characteristics, (3) enumerating possible shift sequences for the chosen work blocks subject to shift change constraints and bounds on sequences of shifts, and (4) assignment of shift sequences to work blocks while fulfilling the staffing requirements. The combination of constraint satisfaction and problem-oriented intelligent backtracking algorithms in each of the four steps allows to find good solutions for real-world problems in acceptable time. Computational results from real-world problems and from benchmark examples found in the literature confirm the viability of our approach. The algorithms are now part of a commercial shift scheduling software package.

cs.OH↗

arXiv2005

On the Computational Complexity of the Forcing Chromatic Number

We consider vertex colorings of graphs in which adjacent vertices have distinct colors. A graph is $s$-chromatic if it is colorable in $s$ colors and any coloring of it uses at least $s$ colors. The forcing chromatic number $F(G)$ of an $s$-chromatic graph $G$ is the smallest number of vertices which must be colored so that, with the restriction that $s$ colors are used, every remaining vertex has its color determined uniquely. We estimate the computational complexity of $F(G)$ relating it to the complexity class US introduced by Blass and Gurevich. We prove that recognizing if $F(G)\le 2$ is US-hard with respect to polynomial-time many-one reductions. Moreover, this problem is coNP-hard even under the promises that $F(G)\le 3$ and $G$ is 3-chromatic. On the other hand, recognizing if $F(G)\le k$, for each constant $k$, is reducible to a problem in US via disjunctive truth-table reduction. Similar results are obtained also for forcing variants of the clique and the domination numbers of a graph.

cs.CC↗

arXiv2004

On the Lengths of Symmetry Breaking-Preserving Games on Graphs

Given a graph $G$, we consider a game where two players, $A$ and $B$, alternatingly color edges of $G$ in red and in blue respectively. Let $l(G)$ be the maximum number of moves in which $B$ is able to keep the red and the blue subgraphs isomorphic, if $A$ plays optimally to destroy the isomorphism. This value is a lower bound for the duration of any avoidance game on $G$ under the assumption that $B$ plays optimally. We prove that if $G$ is a path or a cycle of odd length $n$, then $Ω(\log n)\le l(G)\le O(\log^2 n)$. The lower bound is based on relations with Ehrenfeucht games from model theory. We also consider complete graphs and prove that $l(K_n)=O(1)$.

math.CO↗

arXiv2001

A Symmetric Strategy in Graph Avoidance Games

In the graph avoidance game two players alternatingly color edges of a graph G in red and in blue respectively. The player who first creates a monochromatic subgraph isomorphic to a forbidden graph F loses. A symmetric strategy of the second player ensures that, independently of the first player's strategy, the blue and the red subgraph are isomorphic after every round of the game. We address the class of those graphs G that admit a symmetric strategy for all F and discuss relevant graph-theoretic and complexity issues. We also show examples when, though a symmetric strategy on G generally does not exist, it is still available for a particular F.

cs.DM↗

arXiv1999

Graph Ramsey games

We consider combinatorial avoidance and achievement games based on graph Ramsey theory: The players take turns in coloring still uncolored edges of a graph G, each player being assigned a distinct color, choosing one edge per move. In avoidance games, completing a monochromatic subgraph isomorphic to another graph A leads to immediate defeat or is forbidden and the first player that cannot move loses. In the avoidance+ variants, both players are free to choose more than one edge per move. In achievement games, the first player that completes a monochromatic subgraph isomorphic to A wins. Erdos & Selfridge (1973) were the first to identify some tractable subcases of these games, followed by a large number of further studies. We complete these investigations by settling the complexity of all unrestricted cases: We prove that general graph Ramsey avoidance, avoidance+, and achievement games and several variants thereof are PSPACE-complete. We ultra-strongly solve some nontrivial instances of graph Ramsey avoidance games that are based on symmetric binary Ramsey numbers and provide strong evidence that all other cases based on symmetric binary Ramsey numbers are effectively intractable. Keywords: combinatorial games, graph Ramsey theory, Ramsey game, PSPACE-completeness, complexity, edge coloring, winning strategy, achievement game, avoidance game, the game of Sim, Polya's enumeration formula, probabilistic counting, machine learning, heuristics, Java applet

cs.CC↗

arXiv1998

A reusable iterative optimization software library to solve combinatorial problems with approximate reasoning

Real world combinatorial optimization problems such as scheduling are typically too complex to solve with exact methods. Additionally, the problems often have to observe vaguely specified constraints of different importance, the available data may be uncertain, and compromises between antagonistic criteria may be necessary. We present a combination of approximate reasoning based constraints and iterative optimization based heuristics that help to model and solve such problems in a framework of C++ software libraries called StarFLIP++. While initially developed to schedule continuous caster units in steel plants, we present in this paper results from reusing the library components in a shift scheduling system for the workforce of an industrial production plant.

cs.AI↗