Abstract
Straub, Boudreau and Gefen gave an important contribution in the critical scientific issue of the rigor in IS positivist research. They published an analysis of the state of the art of the research validation methods and heuristics. In an attempt to contribute to the debate on the rigor of IS positivist research, an application of their validation guidelines is practiced and discussed. The validation guidelines are applied to test IS success of a specific type of Information System: the Expert Recommender Service. The application point out some relevant issues regarding the method, such as: the importance of the practice of the expert panels and judges, the quality of the findings of a statistical analysis when the discriminant validity is doubtful, the relevance of the application of different methods altogether, the usefulness of complementary or alternative methods and heuristics and the interpretability of a model when one hypothesis lacks statistical significance.