Information Sciences and Technologies Bulletin of the ACM Slovakia June 2011 Volume 3, Number 2 P. Kapec J. Sedláèková L. Holík M. Bieliková, P. Návrat F. Burda R. Èapla Knowledge-based Software Representation, Querying and Visualization Security Factors in Effort Estimation of Software Projects Abstract Regular Tree Model Checking with Nondeterministic Automata Preface to Special Section on Student Research in Informatics and Information Technologies Decreasing Packet Loss of VoIP Calls by Optimising Transport Network Improving Flexibility of the Bee Hive Metaphor for Web Search by Adding New Parameters and Modifying Dispatching Strategy continued on back cover 1 12 18 26 28 32 Special Section on Student Research in Informatics and Information Technologies