Rule based systems (RBS) have been recognized as probably the best solution for knowledge based expert systems. This article tries to provide the overview of the architecture and basic characteristics of the RBS, focusing on both their weaknesses and strengths. Based on a theory, rule based expert system for web shop error detection has been proposed. The RBS builds on the available application knowledge base and focuses on a problem of detecting the possible error in the shortest possible timeframe. The formalization of the whole process has a potential to significantly reduce the time required to detect the possible error. |