Lutz Priese

Fast and Robust Segmentation of Natural Color Scenes

We present a fast and robust system for color-based segmentation. The system is based on hierarchical region-growing on a special hexagonal topology. In contrast to common region-growing techniques it is independent of the starting point and the order of processing. It is generally applicable in natural color scenes and algorithmically efficient. The use of local and global information and a new color similarity measure contribute to the robust segmentation results. The system is successfully applied in two difficult applications from the field of autonomous vehicle guidance.

Traffic Sign Recognition Based On Color Image Evaluationion

This paper introduces some principles of an evaluation system, CSC (color structure code). The authors describe how to apply the CSC and its evaluation for a real-time traffic sign recognition (TSR) in vehicles. Several images are presented that provide an idea of the quality and reliability of this approach.

Ideogram identification in a realtime traffic sign recognition system

A robust system for the automatic detection of traffic signs has been developed at the Image Recognition Laboratory of the University of Koblenz. This traffic sign recognition (TSR) system was originally designed to localize traffic signs and to recognize their classes, e.g. prohibition signs, danger signs, beacons, etc. The exact identification of traffic signs is added. Traffic signs are identified by the interpretation of their ideograms realized by different modules in our TSR. The first module detects the position and direction of arrows. A second tool recognizes numerals and interprets them as reasonable speed limits. A third one is a general nearest neighbor classifier applied to three classes of ideograms (prohibition sign ideograms, speed limits, arrows on mandatory signs). The fourth module is based on neural nets and applied to two of these classes. Some of these components are used competitively in our realtime TSR. The use of several results from different tools increases the safety and provides high recognition rates.

Characterizing Behavioural Congruences for Petri Nets

We exploit a notion of interface for Petri nets in order to design a set of net combinators. For such a calculus of nets, we focus on the behavioural congruences arising from four simple notions of behaviour, viz., traces, maximal traces, step, and maximal step traces, and from the corresponding four notions of bisimulation, viz., weak and weak step bisimulation and their maximal versions. We characterize such congruences via universal contexts and via games, providing in such a way an understanding of their discerning powers.

On hierarchical color segmentation and applications

A hierarchical color segmentation technique is introduced. It combines the advantages of local (simplicity and quickness) and global (robustness, accuracy, avoidance of chaining mismatches) region growing methods. The method is implemented for a traffic sign recognition system.<<ETX>>

Automata and concurrency

Abstract The purpose of this paper is twofold: to give a precise notion of a realization for simulation of one concurrent system by another, and to study the relations of modular concurrent systems and non-persistent (i.e. with conflicts) concurrent systems in an automatatheoretical style. We will introduce a conception of realization that obeys three requirements: - it allows for proper hierarchies in certain classes of concurrent systems, - it allows for normal-form theorems, and the standard constructions of the literature remain realizations in our formal concept, - it clarifies some counter-intuitive examples. Further, although our realization conception is developed to translate the computational aspects of concurrent systems, it also gives a formal tool for the handling of synchronization problems. The investigated concept of APA-nets (asynchronous, parallel automata nets) is by definition a modular system of networks of (finite state) machines and seems to be quite reasonable for modelling asynchronous, distributed systems. This modular approach is in some contrast to the non-persistency of Petri-nets, as in APA-nets conflicts may arise only as some non-determinism within components of the nets but not in the structure of the nets. As a bv-product we also investigate the relation of conflicts and non-determinism in concurrent systems.

A uniform approach to true-concurrency and interleaving semantics for Petri nets

This paper continues a research on universal contexts and semantics for Petri nets started by Nielsen, Priese and Sassone (1995). We consider generalized, labelled Petri nets N where some transitions and places are distinguished as public. They form the interface of N that may communicate with a Petri net context. An elementary calculus, E, is introduced in which one can construct any Petri net with an interface from trivial constants (single places, single transitions) by drawing arcs, adding tokens, and hiding public places and transitions. We prove the existence of a universal context U such that two Petri nets behave the same in any context if their behaviour is equal in the universal context. Let B(U[N]) be the behaviour of N embedded in its universal context, where B may be the interleaving language, step-language, or true-concurrent pomset-language. In any of these cases, B(U[N]) (in contrast to B(N)) turns out to be a compositional semantics of N with respect to the algebra E. In addition, the interleavingand step-semantics are just special cases of the true-concurrency pomset-semantics.

ON A SIMPLE COMBINATORIAL STRUCTURE SUFFICIENT FOR SYBLYING NONTRIVIAL SELF-REPRODUCTION

Abstract An abstract research on self-reproduction from the viewpoint of systems theory is made, investigating the problem of how simple the combinatorial laws of formal systems can be chosen and to still ensure nontrivial self-reproduction. We take as a base the heuristic of the theory of cellular automata in the sense of von Neumann. We operate in a formal, microscopic, submolecular world as our patterns of cells shall represent some kind of artificial molecules. Computation- and construction-universal, self-reproducing systems are regarded as artificial living beings according to the common heuristic. A simple combinatorial system M of only four very simple dynamic laws is introduced and it can be shown that even in a world governed by this system M nontrivial self-reproduction can be established, thus illuminating what simple combinatorial structures allow for the handling of such logical somewhat difficult phenomenas as self-organization, self-reproduction, etc. To receive a model slightly more adapt...

A note on asynchronous cellular automata

Abstract Recently several different concepts of asynchronous cellular automata have been proposed where in these “two-dimensional calculi” the problem of overlapping arises. We will indicate in this Note how one may construct a computation and construction universal, concurrent, asynchronous, cellular automaton where no overlapping can possibly occur. In this cellular automaton a master-slave condition for the states is permitted: a cell in an active state may operate on a few neighboring cells.

A Combinatorial Approach to Self-Correction

Abstract We will introduce a concept of fault-implementation and combinatorial self-correction for networks of abstract automata. A universal class of networks will be examined for its self-correcting ability. Some simple automata will be introduced as component-machines, and it will be shown how self-correcting networks may be built up by simple components.