Assessing reliability at early stages of software development, such as at the level of software architecture, is desirable and can provide a cost-effective way of improving a software system’s quality. However, predicting a component’s reliability at the architectural level is challenging because of uncertainties associated with the system and its individual components due to the lack of information. This paper discusses representative uncertainties which we have identified at the level of a system’s components, and illustrates how to represent them in our reliability modeling framework. Our preliminary evaluation indicates promising results in our framework's ability to handle such uncertainties.