This volume contains papers selected for presentation at the 31st Annual C- ference on Current Trends in Theory and Practice of Informatics - SOFSEM 2005, held on January 22-28, 2005 in LiptovskyJ an, Slovakia. The series of SOFSEM conferences, organized alternately in the Czech - public and Slovakia since 1974, has a well-established tradition. The SOFSEM conferences were originally intended to break the Iron Curtain in scienti?c - change. After the velvet revolution SOFSEM changed to a regular broad-scope international conference. Nowadays, SOFSEM is focused each year on selected aspects of informatics. This year the conference was organized into four tracks, each of them complemented by two invited talks: - Foundations of Computer Science (Track Chair: Bernadette Charron-Bost) - Modeling and Searching Data in the Web-Era (Track Chair: Peter Vojt a? s) - Software Engineering (Track Chair: M aria Bielikova) - Graph Drawing (Track Chair: Ondrej Syk ora) The aim of SOFSEM 2005 was, as always, to promote cooperation among professionalsfromacademiaandindustryworkinginvariousareasofinformatics. Each track was complemented by two invited talks. The SOFSEM 2005 Program Committee members coming from 13 countries evaluated 144 submissions (128 contributed papers and 16 student research - rum papers). After a careful review process (counting at least 3 reviews per paper), followed by detailed discussions in the PC, and a co-chairs meeting held on October 8, 2005 in Bratislava, Slovakia, 44 papers (overall acceptance rate 34."

The Colloquium on Structural Information and Communication Complexity (SIROCCO) is an annual meeting focused on the relationship between comp- ing and communication. Over its 11 years of existence, SIROCCO has gained a considerable respect and has become an acknowledged forum bringing together specialists interested in the fundamental principles underlying all computing through communication. SIROCCO 2004 was the 11th in this series, held in Smolenice Castle, June 21 23,2004.PreviousSIROCCOcolloquiatookplaceinOttawa(1994), Olympia (1995), Siena (1996), Ascona (1997), Amal? (1998), Lacanau-Ocean (1999), L Aquila (2000), Val de Nuria (2001), Andros (2002), and Umea(2003). The colloquium in 2004 was special in the respect that, for the ?rst time, the p- ceedings were published in the Lecture Notes in Computer Science series of Springer Verlag. SIROCCO has alwaysencouragedhigh-quality researchfocused on the study of those factors which are signi?cant for the computability and the communi- tion complexity of problems, and onthe interplay betweenstructure, knowledge, and complexity. It covers topics as distributed computing, mobile computing, optical computing, parallel computing, communication complexity, information dissemination, routing protocols, distributed data-structures, models of com- nication, network topologies, high-speed interconnection networks, wireless n- works, sense of direction, structural properties, and topological awareness. The 56 contributions submitted to this year s SIROCCO were subject to a thorough refereeing process and 26 high quality submissions were selected for publication. WethanktheProgramCommitteemembersfortheirprofoundandcarefulwork. Our gratitude extends to the numerous subreferees for their valuable refereeing. We also acknowledgethe e?ort of all authors who submitted their contributions."

The International Workshop on Graph-Theoretic Concepts in Computer Science is one of the most traditional and high quality conferences in Computer Science. PreviousconferenceswereorganizedatvariousplacesinAustria, Germany, Italy, and the Netherlands. The workshop aims at uniting theory and practice by demonstrating how graph-theoretic concepts can be applied to various areas in computer science, or by extracting new problems from applications. The goal is to present recent research results and to identify and explore directions of future research. The workshop is well-balanced with respect to established researchers and young scientists. th The24 InternationalWorkshoponGraph-TheoreticConceptsinComputer Science(WG'98)washeldatSmoleniceCastle, nearBratislava, SlovakRepublic, June 18-20, 1998. It was organized by the Slovak Academy of Computer Science in cooperation with the Department of Computer Science I at RWTH Aachen (Germany) and with Slovak Society for Computer Science. For the ?rst time in its history, WG took place in a country of the former eastern block, in the Slovak Republic. The program committee of WG'98 consisted of: H. Bodlaender, Utrecht (NL) A. Brandst] adt, Rostock (D) M. Habib, Montpellier (F) J. Hromkovi? c, Aachen (D) L. Kirousis, Patras (GR) L. Ku? cera, Praha (CR) A. Marchetti-Spaccamela, Roma (I) E. Mayr, Munc ] hen (D) R. Moehring, Berlin (D) M. Nagl, Aachen (D) H. Noltemeier, Wurzburg ] (D) F. Parisi Presicce, Roma (I) O. Syk ora, Bratislava (SK) G. Tinhofer, Munc ] hen (D) D. Wagner, Konstanz (D) P."