data Peter Filzmoser, Karel Hron, Clemens Reimann Department of Statistics and Probability Theory, Vienna University of Technology, Wiedner Hauptstraße 8-10, A-1040 Vienna, Austria. Tel +43 1 58801 10733, FAX +43 1 58801 10799 Department of Mathematical Analysis and Applications of Mathematics, Palacký University, Faculty of Science, 17. listopadu 12, CZ-77146 Olomouc, Czech Republic Geological...

Compositional data need a special treatment prior to correlation analysis. In this paper we argue why standard transformations for compositional data are not suitable for computing correlations, and why the use of raw or log-transformed data is neither meaningful. As a solution, a procedure based on balances is outlined, leading to sensible correlation measures. The construction of the balances...

Prolog is widely used in prototyping, especially in artificial intelligence, but it has yet to gain widespread acceptance in application development. We think that the problems in this area result from the programming style enforced in existing Prolog systems. Zephyr is a new Prolog system refined and enhanced to help solve such problems. It allows users to do modular programming by always usin...

Access management for learning communities requires a unified theory, sustaining the implementation of instructional policies, for ‘social networks’. The management method we have reached is based on the integration of content-rich resources in ‘operations’ that model/control the access of those seeking to learn something by using them, with or without assistance. Activities may be sequenced em...