### Abstract

In this paper we investigate the basic problem of Exploration of a graph by a group of identical mobile computational entities, called robots, operating autonomously and asynchronously. In particular we are concerned with what graphs can be explored, and how, if the robots do not remember the past and have no explicit means of communication. This model of robots is used when the spatial universe in which the robots operate is continuous (e.g., a curve, a polygonal region, a plane, etc.). The case when the spatial universe is discrete (i.e., a graph) has been also studied but only for the classes of acyclic graphs and of simple cycles. In this paper we consider networks of arbitrary topology modeled as connected graphs with local orientation (locally distinct edge labels). We concentrate on class H_{k} of asymmetric configurations with k robots. Our results indicate that the explorability of graphs in this class depends on the number k of robots participating in the exploration. In particular, exploration is impossible for k<3 robots. When there are only k=3 robots, only a subset of H_{3} can be explored; we provide a complete characterization of the networks that can be explored. When there are k=4 robots, we prove that all networks in H_{4} can be explored. Finally, we prove that for any odd k>4 all networks in H_{k} can be explored by presenting a general algorithm. The determination of which networks can be explored when k>4 is even, is still open but can be reduced to the existence of a gathering algorithm for H_{k}.

Original language | English |
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Title of host publication | Graph-Theoretic Concepts in Computer Science |

Subtitle of host publication | 36th International Workshop, WG 2010, Zarós, Crete, Greece, June 28-30, 2010, Revised Papers |

Editors | Dimitrios M. Thilikos |

Place of Publication | Berlin; Heidelberg |

Publisher | Springer, Springer Nature |

Pages | 208-219 |

Number of pages | 12 |

ISBN (Print) | 3642169252, 9783642169250 |

DOIs | |

Publication status | Published - 2010 |

Event | 36th International Workshop on Graph-Theoretic Concepts in Computer Science, WG 2010 - Zaros, Crete, Greece Duration: 28 Jun 2010 → 30 Jun 2010 |

### Publication series

Name | Lecture Notes in Computer Science |
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Volume | 6410 |

ISSN (Print) | 0302-9743 |

ISSN (Electronic) | 1611-3349 |

### Other

Other | 36th International Workshop on Graph-Theoretic Concepts in Computer Science, WG 2010 |
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Country | Greece |

City | Zaros, Crete |

Period | 28/06/10 → 30/06/10 |

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## Cite this

*Graph-Theoretic Concepts in Computer Science: 36th International Workshop, WG 2010, Zarós, Crete, Greece, June 28-30, 2010, Revised Papers*(pp. 208-219). (Lecture Notes in Computer Science; Vol. 6410). Berlin; Heidelberg: Springer, Springer Nature. https://doi.org/10.1007/978-3-642-16926-7_20