A new software tool for web-server clusters development is presented. The tool consist of a set of predefined Hierarchical Timed Coloured Petri Net (HTCPN) structures-patterns. The patterns make it possible to naturally construct typical and experimental server-cluster structures. The preliminary patterns are executable queueing systems. A simulation based methodology of web-server model analysis and validation has been proposed. The paper focuses on presenting the construction of the software tool and the guidelines for applying it in cluster-based web-server development.

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Inconsistency, lacking values of attributes or parameters, as well as discrepancies between records caused by insufficient precision cannot always be managed in the initial phases of knowledge discovery, i.e., data preparation and refinement. The theory of rough sets aims to overcome problems that are caused by uncertainty and lack of precision within the gathered data sets. This approach is a useful tool that operates on a formal model using relational algebra, elementary operations on finite sets and first-order logic. In this paper, we present an analysis of existing rough set tools, namely: Rough Set Exploration System, Rough Sets Data Explorer, Rough Set Data Analysis Framework, Waikato Environment for Knowledge Analysis and Rough Set Toolkit for Analysis of Data. Our comparison is performed only theoretically and covers the available algorithms, preparation of input data, licensing, as well as installation requirements.